Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 02/01/07

.UPDATE... LATEST SURFACE ANALYSIS CONTINUES TO SHOW HIGH PRESSURE BUILDING INTO THE STATE WITH SATELLITE IMAGERY SHOWING ADDITIONAL BATCH OF MID UPR LEVEL CLOUDS APPROACHING THE AREA. MAIN ISSUE FOR TODAY IS THE RED FLAG WARNING. ANALYZING THE 12Z SNDG DATA AND ASSUMING TEMPS WARM UP INTO AT LEAST THE UPPER 60S THERE SHOULD BE ENOUGH DRY AIR ABOVE THE SURFACE FOR AFTERNOON MINRHS TO PLUMMET AGAIN. HOWEVER...THE SNDG AS WELL AS LATEST ACARS DATA SHOW A NARROW LAYER OF ESE WINDS A FEW HUNDRED FEET ABOVE THE SFC. THIS IS INCREASING MOISTURE ABOVE THE SURFACE LAYER WHICH COULD PREVENT MIXING MECHANISMS FROM CAUSING THE EXPECTED DROP IN AFTERNOON RHS MAINLY ALONG THE EAST COAST. HOWEVER...WITH RIDGE BUILDING IN AND LOW LEVEL FLOW REMAINING LIGHT THROUGHOUT THE DAY...THE POTENTIAL IS STILL THERE SINCE IT IS POSSIBLE THIS LIGHT EASTERLY BREEZES WILL SHUT OFF BY THE AFTERNOON AS SHOWN BY FCST SNDGS. SO WILL LEAVE RFW AS IS GIVEN THE UNCERTAINTY.

.PREVIOUS DISCUSSION... HIGH PRESSURE WAS LOCATED OVER THE PANHANDLE OF FLORIDA EARLY THIS MORNING WHICH WAS ALLOWING FOR MOSTLY CALM WINDS OVER THE CWA. HOWEVER...THERE HAS BEEN SOME CIRRUS CLOUDS COMING INTO SOUTH FLORIDA EARLY THIS MORNING FROM THE GULF OF MEXICO WHICH WAS HELPING TO KEEP SOME OF THE HEAT FROM ESCAPING FROM THE GROUND. TEMPS EARLY THIS MORNING HAVE BEEN RUNNING IN THE MID 30S OVER THE FREEZE WARNING AREA WITH PALMDALE FAWN SITE REPORTING 32 DEGREES AT THE 2 FEET LEVEL. BECAUSE THE TEMPS ARE VERY CLOSE TO FREEZING...CALM WINDS...AND THE LOW TEMPS USUALLY OCCUR AT SUNRISE...PLAN ON KEEPING THE FREEZE WARNING UP FOR THE CENTRAL AND NORTHERN INTERIOR AREAS UNTIL 8 AM EST THIS MORNING.

THE HIGH WILL MOVE SLOWLY EAST TODAY AND INTO THE WESTERN ATLANTIC WATERS BY TONIGHT...AS A COLD FRONT OVER THE CENTRAL PLAINS STATES MOVES SOUTHEAST AND INTO NORTH FLORIDA BEFORE DISSIPATING ON WEDNESDAY. THIS WILL KEEP THE WX OVER THE CWA DRY WEDNESDAY...AND ALLOW FOR ANOTHER GOOD RADIATION COOLING NIGHT TONIGHT. TEMPS SHOULD GET DOWN INTO THE UPPER 30S TO AROUND 40 OVER THE INTERIOR AREAS TO MID 40S TO LOWER 50S ALONG THE COASTAL AREAS. THERE COULD EVEN BE SOME ISOLATED AREAS OF FROST OVER THE NORTHERN INTERIOR AREAS LATE TONIGHT IF THE LOW TEMPS FALL A LITTLE BIT LOWER THAN FORECAST. HOWEVER...WILL NOT MENTION THIS IN THE ZONES AT THIS TIME...AND LET THE DAY SHIFT TAKE A CLOSER LOOK AT THIS TO SEE IF THE PATCHY FROST NEEDS TO BE ADDED TO THE NORTHERN INTERIOR AREAS FOR TONIGHT.

LOW PRESSURE SHOULD THEN DEVELOP OVER THE NORTHWEST GULF OF MEXICO WEDNESDAY NIGHT AND MOVE NORTHEAST THROUGH THE SOUTHEAST UNITED STATES LATE THIS WEEK. THIS WILL ALLOW FOR THE WINDS OVER THE CWA TO SWING TO A SOUTHERLY DIRECTION AND INCREASE TO BREEZY TO WINDY CONDITIONS. SOME LOW LEVEL MOISTURE COULD ALSO WORK INTO THE AREA ON THE SOUTHERLY WIND FLOW. SO HAVE KEPT A SLIGHT CHANCE OF SHOWERS IN THE FORECAST FOR LATE THIS WEEK.

.EXTENDED FORECAST... THE COLD FRONT ASSOCIATED WITH THE LOW WILL MOVE SLOWLY DOWN THE SUNSHINE STATE AND THROUGH SOUTH FLORIDA LATE THIS WEEKEND...AS A STRONG HIGH PRESSURE SYSTEM WILL MOVE SOUTHEAST FROM CENTRAL CANADA INTO THE TENNESSEE VALLEY. THERE COULD BE SOME SHOWERS AHEAD OF THE FRONT...SO HAVE KEPT SOME SHOWERS IN THE FORECAST FOR THIS WEEKEND OVER SOUTH FLORIDA.

THE FRONT WILL THEN BE SOUTH OF THE AREA EARLY NEXT WEEK WITH BREEZY TO WINDY NORTHERLY WIND FLOW OVER THE CWA. THESE BREEZY TO WINDY CONDITIONS COULD HELP GENERATE A FEW SHOWERS OVER THE COASTAL WATERS THAT COULD MOVE INTO THE CWA EARLY NEXT WEEK. SO HAVE PUT A SLIGHT CHANCE OF SHOWERS IN FOR EARLY NEXT WEEK.

&&

.AVIATION... VFR CONDITIONS EXPECTED THROUGH THE FORECAST PERIOD.

&&

.MARINE... THE WINDS WILL BE FROM THE NORTHERLY DIRECTION TODAY INTO TONIGHT BEFORE SWING TO A SOUTHERLY DIRECTION BY LATE THIS WEEK. THE SPEEDS WILL REMAIN BELOW 10 KNOTS THROUGH TONIGHT BEFORE SLOWLY INCREASING TO 20 TO 25 KNOTS BY LATE THIS WEEK. THIS WILL KEEP THE SEAS BELOW 6 FEET THROUGH WEDNESDAY NIGHT BEFORE INCREASING THEM TO 7 FEET BY THURSDAY IN THE GULF STREAM. SO THE BOATING WEATHER LOOKS GOOD THROUGH WEDNESDAY.

&&

.FIRE WEATHER... AS MENTION ABOVE...THE WINDS WILL REMAIN MAINLY OUT OF THE NORTH TODAY AROUND 5 TO 10 MPH. THIS WILL ALLOW FOR SOME DRY AIR ALOFT TO MIX DOWN TO THE SURFACE. TEMPS SHOULD GET INTO THE LOWER 70S THIS AFTERNOON ALLOWING FOR THE RELATIVE HUMIDITIES TO FALL BELOW 35 PERCENT FOR 4 HOURS OR MORE THIS AFTERNOON. THEREFORE...WILL UPGRADE THE FIRE WEATHER WATCH TO A RED FLAG WARING FOR ALL OF THE CWA FROM NOON TO 6 PM EST TODAY.

&&

.PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 68 44 70 61 / - - 10 10 FORT LAUDERDALE 70 49 71 64 / - - 10 10 MIAMI 71 50 72 63 / - - 10 10 NAPLES 66 45 71 54 / - - 10 -

&&

.MFL WATCHES/WARNINGS/ADVISORIES... FL...RED FLAG WARNING FROM 11 AM THIS MORNING TO 6 PM EST THIS AFTERNOON FOR FLZ063-FLZ066-FLZ067-FLZ068-FLZ069-FLZ070- FLZ071-FLZ072-FLZ073-FLZ074-FLZ075.

FREEZE WARNING UNTIL 8 AM EST THIS MORNING FOR FLZ063-FLZ066- FLZ067-FLZ070-FLZ071.

AM...NONE. GM...NONE. &&

$$

LONG TERM...BAXTER SHORT TERM...BAXTER AVIATION...GREGORIA

.DAYS 1-2...

FOCUS THIS MORNING WILL BE ON PCPN CHANCES WEDNESDAY.

MAIN DIFFERENCES IN THE NAM/GFS AT 00Z WAS THE SFC FRONT AND 85H/7H BAROCLINIC ZONE WED WITH THE NAM FURTHER NORTH THAN THE GFS. ALSO THE SFC FEATURES FROM THE GFS THIS MORNING WERE SIMILAR TO THE ECMWF/UKMET AND CANADIAN MODELS. IT IS INTERESTING TO NOTE THAT DESPITE THE FURTHER NORTH SOLUTION OF THE NAM THE I285 SFC FROM THE NAM WAS VERY SIMILAR TO THE GFS AT 18Z WED WHICH ALSO SUPPORTED THE BETTER ISENTROPIC LIFT BEING FURTHER SOUTH. GIVEN THIS WILL BE TRENDING TOWARDS A FURTHER SOUTH SOLUTION OF PCPN THIS MORNING WHICH WOULD STILL FAVOR AREAS IN OUR SE CWA SEEING 1 TO 2 INCHES OF SNOW BY 12Z THURSDAY. WILL THEREFORE CONTINUE WITH LIKELY POPS IN THESE LOCATIONS WED AFTERNOON AND EARLY WEDNESDAY NIGHT. FURTHER NORTHWEST HOWEVER WILL TAPER POPS OFF DURING THE DAY ON WEDNESDAY AS ISENTROPIC DOWNGLIDE DEVELOPS AND 85H-7H BAROCLINIC ZONES MOVES SOUTH AND SOUTHEAST OF THE AREA. TEMPERATURES ON WEDNESDAY ARE NOT EXPECTED TO VARY MUCH FROM TONIGHTS LOWS AND KEPT DIURNAL CHANGE TO 10F OR LESS.

UNTIL THEN EXPECTING ONLY INCREASING CLOUDS LATER TODAY WITH TEMPS SOME 10F COOLER THAN YESTERDAY BASED ON 85H TEMPS.

.DAYS 3-7...

THE CURRENT GRIDS FOR THE EXTENDED PERIOD STILL LOOK VERY REASONABLE...AND ONLY MINOR ADJUSTMENTS WERE PERFORMED. THE NUMERICAL MODELS ARE IN SURPRISINGLY GOOD AGREEMENT THROUGH DAY FIVE AND DEMONSTRATE FAIRLY GOOD CONSISTENCY WITH PREVIOUS RUNS. THE GFS APPEARED TO INITIALIZE WELL THIS EVENING WITH AIRCRAFT AND SATELLITE WINDS OVER THE EASTERN PACIFIC AND LARGELY WAS FOLLOWED FOR THE GRIDS.

THE CLOSED UPPER LEVEL CYCLONE OFF THE CALIFORNIA COAST APPEARS TO BE OPENING SLOWLY AS THE UPPER LEVEL TROUGH EVIDENT ON SATELLITE IMAGERY OVER OREGON DROPS SOUTHWARD AND BEGINS TO INTERACT WITH THE OLD CYCLONE. A VORTICITY MAXIMUM THAT WAS APPROACHING BAJA CALIFORNIA EARLY THIS MORNING WILL RIPPLE EASTWARD THROUGH THE SOUTHERN BRANCH OF THE WESTERLIES, BUT MOST OF THE UPPER LEVEL CYCLONE WILL NOT EJECT UNTIL WEDNESDAY NIGHT AND THURSDAY WHEN IT PHASES WITH THE NEXT UPPER LEVEL TROUGH...CURRENTLY OVER NORTHERN ALBERTA...AS IT DIGS INTO THE LONG WAVE TROUGH POSITION OVER THE CENTRAL UNITED STATES. IT STILL APPEARS THAT THE BULK OF THE UVV AND PRECIPITATION WITH THE OLD CLOSED LOW WILL BE OVER THE SOUTHERN PLAINS WITH ONLY LIGHT PRECIPITATION SPREADING INTO SOUTH CENTRAL KANSAS LATE WEDNESDAY NIGHT AND THURSDAY MORNING. LOW POPS WERE CONTINUED OVER THE SOUTHEASTERN COUNTIES INTO THURSDAY MORNING.

A VIGOROUS UPPER LEVEL TROUGH ROTATING AROUND THE POLAR VORTEX OVER HUDSON BAY WILL DIG INTO THE NORTHERN PLAINS THURSDAY NIGHT, AND A STRONG SURGE OF ARCTIC AIR WILL INVADE KANSAS. THE ARCTIC AIR WILL ENTER NORTHERN KANSAS LATE THURSDAY AFTERNOON AND INVADE MOST OF THE STATE BY FRIDAY MORNING. GUIDANCE IS TRENDING DOWNWARD ON TEMPERATURES FOR THURSDAY NIGHT AND FRIDAY BUT STILL PROBABLY IS NOT SUFFICIENTLY COLD IN THE ARCTIC AIR. THERE MAY BE SOME FLURRIES BEHIND THE ARCTIC BOUNDARY AS IT PLUNGES SOUTHWARD THURSDAY NIGHT AND EARLY FRIDAY, BUT LITTLE SNOW ACCUMULATION IS EXPECTED IN SOUTHWESTERN KANSAS.

ONCE THE ARCTIC AIR BECOMES ENTRENCHED OVER THE GLACIER IN THE CENTRAL UNITED STATES, IT WILL BE VERY SLOW TO MODIFY. A SHARP MID LEVEL BAROCLINIC ZONE WILL PERSIST OVER THE CENTRAL PLAINS THROUGH THE WEEKEND, AND ANY MINOR JET STREAK ROTATING THROUGH THE FLOW MAY SUPPORT ENOUGH AGEOSTROPHIC CIRCULATION TO GENERATE SOME LIGHT SNOW. THE BEST OPPORTUNITY FOR ANYTHING MEASURABLE WILL BE ON THE WEST SIDE OF THE ARCTIC DOME. ALTHOUGH CERTAINTY IN DETAILS IS VERY LOW FOUR OR FIVE DAYS IN THE FUTURE, THE ECMWF, GFS AND CANADIAN ALL SUGGEST THAT AN UPPER LEVEL TROUGH WILL MOVE ACROSS COLORADO INTO THE TEXAS PANHANDLE LATE FRIDAY NIGHT AND SATURDAY. LIGHT SNOW WAS INTRODUCED OVER THE SOUTHWESTERN ZONES AFTER MIDNIGHT FRIDAY INTO SATURDAY MORNING IN THE MOST FAVORED AREA OF UPWARD VERTICAL MOTION.

THE ECMWF CONTINUES ITS TREND TO MAINTAIN MORE TROUGHING OVER THE CENTRAL UNITED STATES INTO EARLY NEXT WEEK, WHILE THE CANADIAN AND GFS ARE MORE PROGRESSIVE AND BREAK MORE FLOW THROUGH THE RIDGE NEAR 140W THAN THE ECMWF. SEVERAL OF THE CANADIAN ENSEMBLE MEMBERS SUGGEST A MORE PROGRESSIVE SOLUTION. THE MODELS HAVE A TENDENCY TO ATTEMPT TO SCOUR OUT ARCTIC AIR QUICKER THAN ACTUALLY OCCURS. MINOR UPPER LEVEL TROUGHS IN THE INCREASING MID LATITUDE FLOW WILL SERVE TO SLOSH THE WEST SIDE OF THE ARCTIC AIR BACK AND FORTH AS THEY MOVE OVER THE COLD DOME, RESULTING IN CONSIDERABLE UNCERTAINTY IN DAILY TEMPERATURES THE FIRST PART OF NEXT WEEK. THE GFS ENSEMBLE MEMBERS VARY WIDELY WITH SPEED OF EROSION OF THE ARCTIC AIR. FOR EXAMPLE, AT 00Z MONDAY, GFS ENSEMBLE H8 TEMPERATURES OVER SOUTHWEST KANSAS VARY FROM -15C TO +10C. GIVEN THE LEVEL OF UNCERTAINTY, THE CURRENT FORECAST OF BELOW AVERAGE TEMPERATURES IN THE 8 TO 10 DAY PERIOD STILL SEEMS REASONABLE.

&&

.AVIATION...

WINDS WILL BEGIN TO SHIFT TO A MORE NORTHERLY DIRECTION FROM 10-15KTS TODAY ACROSS SOUTHWEST KANSAS AND THE POSSIBILITY DOES EXITS FOR STRATUS NEAR THE BAROCLINIC ZONE IN CENTRAL KANSAS. CIGS ARE EXPECTED TO STAY ABOVE 030 SO VFR CONDITIONS ARE EXPECTED.

&&

.PRELIMINARY POINT TEMPS/POPS... DDC 32 20 30 15 / 0 30 40 30 GCK 29 18 27 13 / 0 20 30 10 EHA 30 21 28 16 / 0 30 30 30 LBL 34 21 30 16 / 0 30 40 30 HYS 26 15 28 13 / 0 10 30 10 P28 32 21 31 20 / 0 30 70 60

&&

.DDC WATCHES/WARNINGS/ADVISORIES... NONE. &&

$$

FN18/01/31

.AVIATION (18Z TAFS)...

GUSTY NORTHWEST WINDS TO 22KTS ARE EXPECTED IN THE WAKE OF A COLD FRONT WHICH HAS MOVED EAST OF THE TAF SITES. THESE GUSTY WINDS WILL DIMINISH AROUND 00Z. SCT TO BKN CU WILL BE POSSIBLE ACROSS SDF AND LEX THIS AFTERNOON AS AN UPPER TROUGH MOVES THROUGH THE LOWER OHIO VALLEY. CLEAR SKIES AND VFR VSBYS EXPECTED AFTER 02Z. --JA

.SHORT TERM (THIS AFTERNOON)...

AT 16Z A COLD FRONT WAS LOCATED EAST OF A LINE FROM WINCHESTER IN CENTRAL KY TO GLASGOW. TEMPERATURES HAD DROPPED 5 TO 10 DEGREES JUST AFTER THE FRONTAL PASSAGE AND LOOKING UP STREAM READINGS WERE IN THE TEENS. JUST LIKE SUNDAY... DEW POINTS HAVE DROPPED INTO THE SINGLE DIGITS ACROSS THE NORTHERN PORTION OF THE CWFA.

WILL CONTINUE TO MENTION ISOLATED TO LIGHT SNOW SHOWERS THIS AFTERNOON AS CU FIELD DEVELOPS BEHIND THE FRONT AND WITH STEEPENING LAPSE RATES. TEMPERATURES WILL CONTINUE THEIR SLOW DOWNWARD TREND EVEN WITH SOME SUNSHINE. UPDATED FORECAST OUT BY 1115. --JA

PREVIOUS DISCUSSION BELOW.

CLIPPER SHORT WAVE MOVING ESE THROUGH IOWA INTO IL/IN ATTM...WITH ASSOC SFC TROF/FRONT STRETCHING FROM NEAR IND TO PAH AS OF 6Z. MOISTURE POOLING ALONG THE FRONT...WITH DEWPOINTS RISING INTO THE MID 20S. SCT SHSN HAVE DEVELOPED ALONG/AHEAD OF THE SFC FRONT...WITH A FEW MOVING INTO THE LMK CWA AND AS FAR S AS NEAR LEITCHFIELD. RECENT ACARS DATA AT KSDF SHOW VERY STEEP LAPSE RATES TO 700MB... HELPING PROMOTE THIS PRECIP.

EXPECT ISLTD-SCT SHSN TO REMAIN POSSIBLE THROUGH THE MORNING HOURS...WITH HIGHEST CHCS OVER THE N 1/2 OF THE CWA...DECREASING SOUTHWARD. ANY SNOW AMTS SHOULD BE MINOR AT BEST THOUGH SOME OF THE SHSN HAVE BEEN INTENSE OVER IL/IN/OH BASED ON RADAR REFLECTIVITIES NEAR 35DBZ OR HIGHER...SO IF SOME OF THESE WERE TO AFFECT OUR CWA THERE COULD BE LOCALIZED ACCUMS OF A COUPLE TENTHS OF AN INCH IN A SHORT PERIOD OF TIME. WILL CONTINUE TO MONITOR AS WE GET CLOSER TO THE MORNING DRIVE.

BASED ON NAM/RUC...SFC FRONT WILL PASS THROUGH WRN COUNTIES AROUND 10-12Z...INTO ERN/SRN COUNTIES 12-14Z TIMEFRAME. THIS WILL BRING A ROUND OF GUSTY W/NW WINDS TODAY. BUFKIT DIAGNOSTICS INDICATE GUSTS TO 20-25KTS POSSIBLE AND THIS SEEMS REASONABLE BASED ON UPSTREAM OBSERVATIONS. THIS WILL ALSO BRING STEADY OR FALLING TEMPS (EXCEPT PERHAPS THE FAR SE COUNTIES). HAVE FOLLOWED A RUC/NAM BLEND FOR TEMPS TODAY INTO TONIGHT.

CHANCES FOR SHSN WILL CONTINUE INTO THE AFTN WITH STEEP LAPSE RATES...THOUGH FEEL THAT OVERALL THREAT WILL BE LOWER THAN IN THE MORNING DUE TO SIGNIFICANTLY DRIER AIR ADVECTING INTO THE LOWER OHIO VALLEY. DEWPOINTS WILL LIKELY FALL INTO THE SINGLE DIGITS THIS AFTN. WILL WORD AFTERNOON POPS AS CHANCE VERSUS MORNING COVERAGE WORDING.

GUSTY WINDS WILL LIGHTEN AFTER SUNSET...THOUGH BEFORE THAT OCCURS WIND CHILL VALUES THIS AFTN INTO THE EARLY EVENING WILL LIKELY DROP INTO THE SINGLE DIGITS WITH A FEW NEAR-ZERO VALUES POSSIBLE. HAVE ALLOWED SKIES TO CLEAR OVERNIGHT...THOUGH DID NOT GO WITH COMPLETE CLEARING SINCE NAM AND TO A LESSER EXTENT GFS SUGGEST AN AREA OF 3-5KFT CLOUDS SWEEPING ACROSS THE CWA BETWEEN 6-9Z/WED (OVERNIGHT).

CS

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. &&

$$

.SHORT TERM (THIS AFTERNOON)...

AT 16Z A COLD FRONT WAS LOCATED EAST OF A LINE FROM WINCHESTER IN CENTRAL KY TO GLASGOW. TEMPERATURES HAD DROPPED 5 TO 10 DEGREES JUST AFTER THE FRONTAL PASSAGE AND LOOKING UP STREAM READINGS WERE IN THE TEENS. JUST LIKE SUNDAY... DEW POINTS HAVE DROPPED INTO THE SINGLE DIGITS ACROSS THE NORTHERN PORTION OF THE CWFA.

WILL CONTINUE TO MENTION ISOLATED TO LIGHT SNOW SHOWERS THIS AFTERNOON AS CU FIELD DEVELOPS BEHIND THE FRONT AND WITH STEEPENING LAPSE RATES. TEMPERATURES WILL CONTINUE THEIR SLOW DOWNWARD TREND EVEN WITH SOME SUNSHINE. UPDATED FORECAST OUT BY 1115. --JA

PREVIOUS DISCUSSION BELOW.

CLIPPER SHORT WAVE MOVING ESE THROUGH IOWA INTO IL/IN ATTM...WITH ASSOC SFC TROF/FRONT STRETCHING FROM NEAR IND TO PAH AS OF 6Z. MOISTURE POOLING ALONG THE FRONT...WITH DEWPOINTS RISING INTO THE MID 20S. SCT SHSN HAVE DEVELOPED ALONG/AHEAD OF THE SFC FRONT...WITH A FEW MOVING INTO THE LMK CWA AND AS FAR S AS NEAR LEITCHFIELD. RECENT ACARS DATA AT KSDF SHOW VERY STEEP LAPSE RATES TO 700MB... HELPING PROMOTE THIS PRECIP.

EXPECT ISLTD-SCT SHSN TO REMAIN POSSIBLE THROUGH THE MORNING HOURS...WITH HIGHEST CHCS OVER THE N 1/2 OF THE CWA...DECREASING SOUTHWARD. ANY SNOW AMTS SHOULD BE MINOR AT BEST THOUGH SOME OF THE SHSN HAVE BEEN INTENSE OVER IL/IN/OH BASED ON RADAR REFLECTIVITIES NEAR 35DBZ OR HIGHER...SO IF SOME OF THESE WERE TO AFFECT OUR CWA THERE COULD BE LOCALIZED ACCUMS OF A COUPLE TENTHS OF AN INCH IN A SHORT PERIOD OF TIME. WILL CONTINUE TO MONITOR AS WE GET CLOSER TO THE MORNING DRIVE.

BASED ON NAM/RUC...SFC FRONT WILL PASS THROUGH WRN COUNTIES AROUND 10-12Z...INTO ERN/SRN COUNTIES 12-14Z TIMEFRAME. THIS WILL BRING A ROUND OF GUSTY W/NW WINDS TODAY. BUFKIT DIAGNOSTICS INDICATE GUSTS TO 20-25KTS POSSIBLE AND THIS SEEMS REASONABLE BASED ON UPSTREAM OBSERVATIONS. THIS WILL ALSO BRING STEADY OR FALLING TEMPS (EXCEPT PERHAPS THE FAR SE COUNTIES). HAVE FOLLOWED A RUC/NAM BLEND FOR TEMPS TODAY INTO TONIGHT.

CHANCES FOR SHSN WILL CONTINUE INTO THE AFTN WITH STEEP LAPSE RATES...THOUGH FEEL THAT OVERALL THREAT WILL BE LOWER THAN IN THE MORNING DUE TO SIGNIFICANTLY DRIER AIR ADVECTING INTO THE LOWER OHIO VALLEY. DEWPOINTS WILL LIKELY FALL INTO THE SINGLE DIGITS THIS AFTN. WILL WORD AFTERNOON POPS AS CHANCE VERSUS MORNING COVERAGE WORDING.

GUSTY WINDS WILL LIGHTEN AFTER SUNSET...THOUGH BEFORE THAT OCCURS WIND CHILL VALUES THIS AFTN INTO THE EARLY EVENING WILL LIKELY DROP INTO THE SINGLE DIGITS WITH A FEW NEAR-ZERO VALUES POSSIBLE. HAVE ALLOWED SKIES TO CLEAR OVERNIGHT...THOUGH DID NOT GO WITH COMPLETE CLEARING SINCE NAM AND TO A LESSER EXTENT GFS SUGGEST AN AREA OF 3-5KFT CLOUDS SWEEPING ACROSS THE CWA BETWEEN 6-9Z/WED (OVERNIGHT).

CS

.AVIATION (12Z TAFS)... COLD FRONT NOW ROLLING THROUGH THE LMK CWA AS OF 11Z...WITH WINDS AT HNB SOLIDLY NW WHILE DIRECTIONS AT SDF/FTK SWITCHING SOON. WITH FROPA...WE EXPECT WNW WINDS WILL INCREASE AND BECOME GUSTY. GUSTS TO 20-25KTS ARE LIKELY THROUGH AT LEAST MID-AFTERNOON TODAY. SHSN ARE WIDELY SCATTERED AT THIS POINT AND CIGS ARE VFR-MVFR UPSTREAM OVER SRN IL AND SW IN. LATEST NAM SHOWS CIGS DROPPING TO AROUND 3000 FEET THIS MORNING AT SDF/LEX...THEN RISING TO NEAR 5KFT WITH SKIES ACTUALLY GOING SCT (EVEN FEW OVER SRN KY).

-SHSN THREAT FOR THE TAF SITES SEEMS MINIMAL...WILL NOT MENTION IN PREVAILING GROUPS AND HANDLE ANY -SHSN WITH TEMPO GROUPS IF NECESSARY. GFS/NAM HAVE BEEN CONSISTENT IN BRINGING AN AREA OF LOWER CIGS (~2KFT) TONIGHT BETWEEN 0Z-6Z...AND WILL ACCOUNT FOR THIS. WINDS WILL SUBSIDE CONSIDERABLY AFTER 3Z AS SFC HIGH PRES SLIDES INTO THE REGION.

CS

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. &&

$$

.AVIATION (12Z TAFS)... COLD FRONT NOW ROLLING THROUGH THE LMK CWA AS OF 11Z...WITH WINDS AT HNB SOLIDLY NW WHILE DIRECTIONS AT SDF/FTK SWITCHING SOON. WITH FROPA...WE EXPECT WNW WINDS WILL INCREASE AND BECOME GUSTY. GUSTS TO 20-25KTS ARE LIKELY THROUGH AT LEAST MID-AFTERNOON TODAY. SHSN ARE WIDELY SCATTERED AT THIS POINT AND CIGS ARE VFR-MVFR UPSTREAM OVER SRN IL AND SW IN. LATEST NAM SHOWS CIGS DROPPING TO AROUND 3000 FEET THIS MORNING AT SDF/LEX...THEN RISING TO NEAR 5KFT WITH SKIES ACTUALLY GOING SCT (EVEN FEW OVER SRN KY).

-SHSN THREAT FOR THE TAF SITES SEEMS MINIMAL...WILL NOT MENTION IN PREVAILING GROUPS AND HANDLE ANY -SHSN WITH TEMPO GROUPS IF NECESSARY. GFS/NAM HAVE BEEN CONSISTENT IN BRINGING AN AREA OF LOWER CIGS (~2KFT) TONIGHT BETWEEN 0Z-6Z...AND WILL ACCOUNT FOR THIS. WINDS WILL SUBSIDE CONSIDERABLY AFTER 3Z AS SFC HIGH PRES SLIDES INTO THE REGION.

CS

&&

.SHORT TERM (TODAY-TONIGHT)...

CLIPPER SHORT WAVE MOVING ESE THROUGH IOWA INTO IL/IN ATTM...WITH ASSOC SFC TROF/FRONT STRETCHING FROM NEAR IND TO PAH AS OF 6Z. MOISTURE POOLING ALONG THE FRONT...WITH DEWPOINTS RISING INTO THE MID 20S. SCT SHSN HAVE DEVELOPED ALONG/AHEAD OF THE SFC FRONT...WITH A FEW MOVING INTO THE LMK CWA AND AS FAR S AS NEAR LEITCHFIELD. RECENT ACARS DATA AT KSDF SHOW VERY STEEP LAPSE RATES TO 700MB... HELPING PROMOTE THIS PRECIP.

EXPECT ISLTD-SCT SHSN TO REMAIN POSSIBLE THROUGH THE MORNING HOURS...WITH HIGHEST CHCS OVER THE N 1/2 OF THE CWA...DECREASING SOUTHWARD. ANY SNOW AMTS SHOULD BE MINOR AT BEST THOUGH SOME OF THE SHSN HAVE BEEN INTENSE OVER IL/IN/OH BASED ON RADAR REFLECTIVITIES NEAR 35DBZ OR HIGHER...SO IF SOME OF THESE WERE TO AFFECT OUR CWA THERE COULD BE LOCALIZED ACCUMS OF A COUPLE TENTHS OF AN INCH IN A SHORT PERIOD OF TIME. WILL CONTINUE TO MONITOR AS WE GET CLOSER TO THE MORNING DRIVE.

BASED ON NAM/RUC...SFC FRONT WILL PASS THROUGH WRN COUNTIES AROUND 10-12Z...INTO ERN/SRN COUNTIES 12-14Z TIMEFRAME. THIS WILL BRING A ROUND OF GUSTY W/NW WINDS TODAY. BUFKIT DIAGNOSTICS INDICATE GUSTS TO 20-25KTS POSSIBLE AND THIS SEEMS REASONABLE BASED ON UPSTREAM OBSERVATIONS. THIS WILL ALSO BRING STEADY OR FALLING TEMPS (EXCEPT PERHAPS THE FAR SE COUNTIES). HAVE FOLLOWED A RUC/NAM BLEND FOR TEMPS TODAY INTO TONIGHT.

CHANCES FOR SHSN WILL CONTINUE INTO THE AFTN WITH STEEP LAPSE RATES...THOUGH FEEL THAT OVERALL THREAT WILL BE LOWER THAN IN THE MORNING DUE TO SIGNIFICANTLY DRIER AIR ADVECTING INTO THE LOWER OHIO VALLEY. DEWPOINTS WILL LIKELY FALL INTO THE SINGLE DIGITS THIS AFTN. WILL WORD AFTERNOON POPS AS CHANCE VERSUS MORNING COVERAGE WORDING.

GUSTY WINDS WILL LIGHTEN AFTER SUNSET...THOUGH BEFORE THAT OCCURS WIND CHILL VALUES THIS AFTN INTO THE EARLY EVENING WILL LIKELY DROP INTO THE SINGLE DIGITS WITH A FEW NEAR-ZERO VALUES POSSIBLE. HAVE ALLOWED SKIES TO CLEAR OVERNIGHT...THOUGH DID NOT GO WITH COMPLETE CLEARING SINCE NAM AND TO A LESSER EXTENT GFS SUGGEST AN AREA OF 3-5KFT CLOUDS SWEEPING ACROSS THE CWA BETWEEN 6-9Z/WED (OVERNIGHT).

CS

.LONG TERM (WEDNESDAY-MONDAY)...

...ACTIVE WEATHER PERIOD WITH POTENTIAL FOR ACCUMULATING SNOWS LATE WED THROUGH THURSDAY NIGHT...

WEDNESDAY THROUGH FRIDAY NIGHT...

FAIRLY ACTIVE AND CHALLENGING FORECAST PERIOD APPEARS TO BE IN STORE FOR THIS PART OF THE FORECAST PERIOD. LATE EVENING MODELS CONTINUE TO BE IN GENERAL AGREEMENT WITH SOUTHWESTERN U.S. UPPER LEVEL WAVE EJECTING EASTWARD DURING THE PERIOD. ALL THE MODELS INDUCE SFC CYCLOGENESIS ACROSS THE DEEP SOUTH AND BRING A SFC LOW EASTWARD ACROSS THE NORTHERN GULF STATES. THE PAST FEW RUNS OF THE MODELS HAVE BEEN TRENDING NORTHWARD WITH THE TRACK OF THE SFC LOW ACROSS THE SOUTHEAST U.S. WE STILL HAVE TWO CAMPS OF TRACKS TONIGHT...WITH THE CANADIAN GLOBAL AND NAM-WRF BEING THE FARTHEST NORTH WITH THE LOW COMING ACROSS THE FA...WHILE THE UKMET AND EURO ARE FURTHER SOUTH. THE 00Z OP GFS IS BETWEEN THESE TWO CAMPS AND OFFERS A PRETTY GOOD COMPROMISE.

USING A CONSENSUS OF THE MODEL DATA...WEDNESDAY WILL GENERALLY BE A DRY DAY WITH MID-HIGH LEVEL CLOUDS INCREASING FROM WEST TO EAST. ISENTROPIC UPGLIDE WILL INCREASE WEDNESDAY EVENING AS SFC LOW BEGINS ITS TREK TOWARDS THE NORTHEAST. ANTECEDENT DRY AIRMASS WILL TAKE SOME TIME TO MOISTEN UP WEDNESDAY NIGHT SO PRECIPITATION MAY NOT START UNTIL LATE WEDNESDAY NIGHT. NONETHELESS...IT DOES APPEAR PRECIPITATION WILL BE LIKELY AND THUS HAVE INCREASED POPS TO LIKELY FOR THIS PERIOD. MODEL PROFILES FROM THE GFS SUGGEST ALL SNOW AS THE PRECIPITATION TYPE FOR WEDNESDAY NIGHT.

MAIN BULK OF PRECIPITATION WILL FALL ON THURSDAY AS ISENTROPIC LIFT AND FRONTOGENETICAL FORCING WILL BE MAXIMIZED OVER KENTUCKY. BANDED PRECIPITATION WILL LIKELY LIFT NORTHWARD THROUGH THE DAY AND BE ORIENTED ALONG THE OHIO RIVER BY EVENING. HAVE GONE WITH LIKELY POPS HERE BUT PRECIPITATION TYPE WILL BE CHALLENGING. IN THE PAST SEVERAL EVENTS...WE HAVE SEEN STORMS SYSTEMS OUT IN THE LONG RANGE BEING FORECAST TO GO SOUTH...ONLY TO SEE A NORTHWARD TRACK VERIFY AS THE EVENT CAME CLOSER/UNFOLDED. IN ADDITION...THE NUMERICAL MODELS HAVE HAD A TOUGH TIME ESTIMATING THE AMOUNT OF WARM AIR ADVECTING IN ALOFT...WHICH HAS RESULTED IN MORE LIQUID PRECIPITATION OCCURRING. TONIGHT...WE ARE IN THE SAME DILEMMA.

BASED ON ALL THE AVAILABLE DATA...AND NOT COMPLETELY THROWING OUT THE NAM-WRF...AM INCLINED TO LEAVE A MIX OF RAIN/SLEET/SNOW IN ACROSS THE SOUTHERN FA SOUTH OF A LINE FROM NEAR HARTFORD TO JUST SOUTH OF RICHMOND. NORTH OF THAT LINE...FEEL THAT DOMINANT PRECIPITATION TYPE WILL BE SNOW. AS SFC LOW HEADS EAST THU NIGHT...SHOULD SEE ALL AREAS GO TO SNOW. ACCUMULATIONS OF SNOW APPEAR LIKELY AT THIS TIME WITH TWO TO FOUR INCHES ACROSS THE NORTHERN HALF OF THE FA WITH ONE TO TWO ACROSS SOUTHERN KY. HOWEVER...IF THE NORTHWARD TREND IN THE SURFACE TRACK OCCURS...LESS SNOW WILL BE LIKELY IN THE SOUTH AND THE 2-4 INCH BAND WOULD BE DISPLACED FURTHER NORTH...PROBABLY NORTH OF THE OHIO RIVER. GIVEN THIS EVENT IS SOME 60-72 HORUS...WILL ISSUE A SPECIAL WX STMT THIS MORNING HIGHLIGHT IMPACTS OF THE EVENT.

SNOW WILL LIKELY CONTINUE THURSDAY NIGHT AND DIMINISH SOME BY FRIDAY. SECONDARY CLIPPER TYPE SYSTEM IS FORECAST TO SWING THROUGH THE REGION FRIDAY AFTERNOON AND EVENING AND MAY BRING ANOTHER ROUND OF SNOW SHOWERS TO THE REGION. THUS...HAVE PRETTY MUCH LEFT ONGOING FORECAST INTACT FOR FRIDAY AND FRIDAY NIGHT. AS FOR TEMPERATURES THROUGH THE PERIOD...GENERALLY FOLLOWED A BLEND OF OP GFS RAW SFC TEMPS WITH A SPLASH OF THE MOS STAT GUIDANCE.

JARVIS

FORECAST FROM SATURDAY ONWARD WAS LEFT AS IS...PREVIOUS FORECAST DISCUSSION FOLLOWS...

WILL STAY CLOSE TO THE EURO THROUGH THE PERIOD...WITH SOME SUPPORT FROM THE GFS THROUGH THIS PERIOD AS WELL. INDICES (PNA/EPO/AO) STILL SUPPORT THE COLDER AIR TO CONTINUE TO REPLENISH ITSELF THROUGH THE NEXT FEW WEEKS. DEEP LONGWAVE TROUGH EXTENDS FROM HUDSON BAY POLAR VORTEX(PV) ROTATING FROM THE MS VALLEY THROUGH THE OHIO VALLEY OVER THE WEEKEND...WITH POSSIBLY THE COLDEST AIR OF THE WINTER TO DATE IN THIS PERIOD. SFC HI PRESSURE MOVES ACROSS THE REGION SATURDAY INTO SUNDAY...WEAK CLIPPER STILL LOOKS POSSIBLE SUNDAY EVENING INTO EARLY MONDAY BEFORE ANOTHER VERY COLD ARCTIC AIR MASS DROPS INTO THE CENTRAL US AND INTO THE OHIO VALLEY EARLY NEXT WEEK. AS MENTIONED EARLIER IF AN SNOW COVER ON THE GROUND DURING THIS PERIOD...MAY SEE TEMPS APPROACH ZERO FOR LOWS...WILL NOT ADJUST THAT WAY AS OF NOW...BUT HAVE TRENDED COLDER THRU THE PERIOD.

-SCHOTT

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. &&

$$

.SHORT TERM (TODAY-TONIGHT)...

CLIPPER SHORT WAVE MOVING ESE THROUGH IOWA INTO IL/IN ATTM...WITH ASSOC SFC TROF/FRONT STRETCHING FROM NEAR IND TO PAH AS OF 6Z. MOISTURE POOLING ALONG THE FRONT...WITH DEWPOINTS RISING INTO THE MID 20S. SCT SHSN HAVE DEVELOPED ALONG/AHEAD OF THE SFC FRONT...WITH A FEW MOVING INTO THE LMK CWA AND AS FAR S AS NEAR LEITCHFIELD. RECENT ACARS DATA AT KSDF SHOW VERY STEEP LAPSE RATES TO 700MB... HELPING PROMOTE THIS PRECIP.

EXPECT ISLTD-SCT SHSN TO REMAIN POSSIBLE THROUGH THE MORNING HOURS...WITH HIGHEST CHCS OVER THE N 1/2 OF THE CWA...DECREASING SOUTHWARD. ANY SNOW AMTS SHOULD BE MINOR AT BEST THOUGH SOME OF THE SHSN HAVE BEEN INTENSE OVER IL/IN/OH BASED ON RADAR REFLECTIVITIES NEAR 35DBZ OR HIGHER...SO IF SOME OF THESE WERE TO AFFECT OUR CWA THERE COULD BE LOCALIZED ACCUMS OF A COUPLE TENTHS OF AN INCH IN A SHORT PERIOD OF TIME. WILL CONTINUE TO MONITOR AS WE GET CLOSER TO THE MORNING DRIVE.

BASED ON NAM/RUC...SFC FRONT WILL PASS THROUGH WRN COUNTIES AROUND 10-12Z...INTO ERN/SRN COUNTIES 12-14Z TIMEFRAME. THIS WILL BRING A ROUND OF GUSTY W/NW WINDS TODAY. BUFKIT DIAGNOSTICS INDICATE GUSTS TO 20-25KTS POSSIBLE AND THIS SEEMS REASONABLE BASED ON UPSTREAM OBSERVATIONS. THIS WILL ALSO BRING STEADY OR FALLING TEMPS (EXCEPT PERHAPS THE FAR SE COUNTIES). HAVE FOLLOWED A RUC/NAM BLEND FOR TEMPS TODAY INTO TONIGHT.

CHANCES FOR SHSN WILL CONTINUE INTO THE AFTN WITH STEEP LAPSE RATES...THOUGH FEEL THAT OVERALL THREAT WILL BE LOWER THAN IN THE MORNING DUE TO SIGNIFICANTLY DRIER AIR ADVECTING INTO THE LOWER OHIO VALLEY. DEWPOINTS WILL LIKELY FALL INTO THE SINGLE DIGITS THIS AFTN. WILL WORD AFTERNOON POPS AS CHANCE VERSUS MORNING COVERAGE WORDING.

GUSTY WINDS WILL LIGHTEN AFTER SUNSET...THOUGH BEFORE THAT OCCURS WIND CHILL VALUES THIS AFTN INTO THE EARLY EVENING WILL LIKELY DROP INTO THE SINGLE DIGITS WITH A FEW NEAR-ZERO VALUES POSSIBLE. HAVE ALLOWED SKIES TO CLEAR OVERNIGHT...THOUGH DID NOT GO WITH COMPLETE CLEARING SINCE NAM AND TO A LESSER EXTENT GFS SUGGEST AN AREA OF 3-5KFT CLOUDS SWEEPING ACROSS THE CWA BETWEEN 6-9Z/WED (OVERNIGHT).

CS

.LONG TERM (WEDNESDAY-MONDAY)...

...ACTIVE WEATHER PERIOD WITH POTENTIAL FOR ACCUMULATING SNOWS LATE WED THROUGH THURSDAY NIGHT...

WEDNESDAY THROUGH FRIDAY NIGHT...

FAIRLY ACTIVE AND CHALLENGING FORECAST PERIOD APPEARS TO BE IN STORE FOR THIS PART OF THE FORECAST PERIOD. LATE EVENING MODELS CONTINUE TO BE IN GENERAL AGREEMENT WITH SOUTHWESTERN U.S. UPPER LEVEL WAVE EJECTING EASTWARD DURING THE PERIOD. ALL THE MODELS INDUCE SFC CYCLOGENESIS ACROSS THE DEEP SOUTH AND BRING A SFC LOW EASTWARD ACROSS THE NORTHERN GULF STATES. THE PAST FEW RUNS OF THE MODELS HAVE BEEN TRENDING NORTHWARD WITH THE TRACK OF THE SFC LOW ACROSS THE SOUTHEAST U.S. WE STILL HAVE TWO CAMPS OF TRACKS TONIGHT...WITH THE CANADIAN GLOBAL AND NAM-WRF BEING THE FARTHEST NORTH WITH THE LOW COMING ACROSS THE FA...WHILE THE UKMET AND EURO ARE FURTHER SOUTH. THE 00Z OP GFS IS BETWEEN THESE TWO CAMPS AND OFFERS A PRETTY GOOD COMPROMISE.

USING A CONSENSUS OF THE MODEL DATA...WEDNESDAY WILL GENERALLY BE A DRY DAY WITH MID-HIGH LEVEL CLOUDS INCREASING FROM WEST TO EAST. ISENTROPIC UPGLIDE WILL INCREASE WEDNESDAY EVENING AS SFC LOW BEGINS ITS TREK TOWARDS THE NORTHEAST. ANTECEDENT DRY AIRMASS WILL TAKE SOME TIME TO MOISTEN UP WEDNESDAY NIGHT SO PRECIPITATION MAY NOT START UNTIL LATE WEDNESDAY NIGHT. NONETHELESS...IT DOES APPEAR PRECIPITATION WILL BE LIKELY AND THUS HAVE INCREASED POPS TO LIKELY FOR THIS PERIOD. MODEL PROFILES FROM THE GFS SUGGEST ALL SNOW AS THE PRECIPITATION TYPE FOR WEDNESDAY NIGHT.

MAIN BULK OF PRECIPITATION WILL FALL ON THURSDAY AS ISENTROPIC LIFT AND FRONTOGENETICAL FORCING WILL BE MAXIMIZED OVER KENTUCKY. BANDED PRECIPITATION WILL LIKELY LIFT NORTHWARD THROUGH THE DAY AND BE ORIENTED ALONG THE OHIO RIVER BY EVENING. HAVE GONE WITH LIKELY POPS HERE BUT PRECIPITATION TYPE WILL BE CHALLENGING. IN THE PAST SEVERAL EVENTS...WE HAVE SEEN STORMS SYSTEMS OUT IN THE LONG RANGE BEING FORECAST TO GO SOUTH...ONLY TO SEE A NORTHWARD TRACK VERIFY AS THE EVENT CAME CLOSER/UNFOLDED. IN ADDITION...THE NUMERICAL MODELS HAVE HAD A TOUGH TIME ESTIMATING THE AMOUNT OF WARM AIR ADVECTING IN ALOFT...WHICH HAS RESULTED IN MORE LIQUID PRECIPITATION OCCURRING. TONIGHT...WE ARE IN THE SAME DILEMMA.

BASED ON ALL THE AVAILABLE DATA...AND NOT COMPLETELY THROWING OUT THE NAM-WRF...AM INCLINED TO LEAVE A MIX OF RAIN/SLEET/SNOW IN ACROSS THE SOUTHERN FA SOUTH OF A LINE FROM NEAR HARTFORD TO JUST SOUTH OF RICHMOND. NORTH OF THAT LINE...FEEL THAT DOMINANT PRECIPITATION TYPE WILL BE SNOW. AS SFC LOW HEADS EAST THU NIGHT...SHOULD SEE ALL AREAS GO TO SNOW. ACCUMULATIONS OF SNOW APPEAR LIKELY AT THIS TIME WITH TWO TO FOUR INCHES ACROSS THE NORTHERN HALF OF THE FA WITH ONE TO TWO ACROSS SOUTHERN KY. HOWEVER...IF THE NORTHWARD TREND IN THE SURFACE TRACK OCCURS...LESS SNOW WILL BE LIKELY IN THE SOUTH AND THE 2-4 INCH BAND WOULD BE DISPLACED FURTHER NORTH...PROBABLY NORTH OF THE OHIO RIVER. GIVEN THIS EVENT IS SOME 60-72 HORUS...WILL ISSUE A SPECIAL WX STMT THIS MORNING HIGHLIGHT IMPACTS OF THE EVENT.

SNOW WILL LIKELY CONTINUE THURSDAY NIGHT AND DIMINISH SOME BY FRIDAY. SECONDARY CLIPPER TYPE SYSTEM IS FORECAST TO SWING THROUGH THE REGION FRIDAY AFTERNOON AND EVENING AND MAY BRING ANOTHER ROUND OF SNOW SHOWERS TO THE REGION. THUS...HAVE PRETTY MUCH LEFT ONGOING FORECAST INTACT FOR FRIDAY AND FRIDAY NIGHT. AS FOR TEMPERATURES THROUGH THE PERIOD...GENERALLY FOLLOWED A BLEND OF OP GFS RAW SFC TEMPS WITH A SPLASH OF THE MOS STAT GUIDANCE.

JARVIS

FORECAST FROM SATURDAY ONWARD WAS LEFT AS IS...PREVIOUS FORECAST DISCUSSION FOLLOWS...

WILL STAY CLOSE TO THE EURO THROUGH THE PERIOD...WITH SOME SUPPORT FROM THE GFS THROUGH THIS PERIOD AS WELL. INDICES (PNA/EPO/AO) STILL SUPPORT THE COLDER AIR TO CONTINUE TO REPLENISH ITSELF THROUGH THE NEXT FEW WEEKS. DEEP LONGWAVE TROUGH EXTENDS FROM HUDSON BAY POLAR VORTEX(PV) ROTATING FROM THE MS VALLEY THROUGH THE OHIO VALLEY OVER THE WEEKEND...WITH POSSIBLY THE COLDEST AIR OF THE WINTER TO DATE IN THIS PERIOD. SFC HI PRESSURE MOVES ACROSS THE REGION SATURDAY INTO SUNDAY...WEAK CLIPPER STILL LOOKS POSSIBLE SUNDAY EVENING INTO EARLY MONDAY BEFORE ANOTHER VERY COLD ARCTIC AIR MASS DROPS INTO THE CENTRAL US AND INTO THE OHIO VALLEY EARLY NEXT WEEK. AS MENTIONED EARLIER IF AN SNOW COVER ON THE GROUND DURING THIS PERIOD...MAY SEE TEMPS APPROACH ZERO FOR LOWS...WILL NOT ADJUST THAT WAY AS OF NOW...BUT HAVE TRENDED COLDER THRU THE PERIOD.

-SCHOTT

&&

.AVIATION (06Z TAFS)... FOCUS FOR THE NEXT 6-12 HOURS IN THE TAFS CENTERS ON CHCS FOR SNOW SHOWERS ALONG WITH WIND SHIFT AS CLIPPER/COLD FRONT PASSES THROUGH THE REGION. AREA RADARS SHOW SCT SHSN OVER IL/IN...BASED ON TRENDS AND LATEST RUC/NAM DATA...A FEW OF THESE MAY AFFECT LEX/SDF TAF SITES THROUGH 15Z...THOUGH COVERAGE WILL LIKELY BE ISLTD SUCH THAT WE WILL NOT CARRY A PREVAILING SHSN GROUP IN THE TAFS...WILL RATHER HANDLE WITH TEMPOS AS NEEDED.

CIGS OVER THE REGION ARE NOT TERRIBLY LOW (GENERALLY MVFR-VFR) AND PLAN ON CONTINUING THAT BASED ON FCST SOUNDINGS. SOME CIGS CLOSE TO 1-1.5KFT AGL MAY DROP INTO SRN IND AND PARTS OF CNTRL KY NORTH OF I-64 BETWEEN 12-15Z (PER NAM)...BUT WILL NOT MENTION THOSE IN THE TAFS AT THIS TIME. WINDS WILL SHIFT TO THE W/NW AS COLD FRONT PUSHES THROUGH THE AREA THIS MORNING (11-14Z TIMEFRAME). WHEN THIS HAPPENS WINDS WILL GET GUSTY (GUSTS TO 20-23KTS OR SO) FOR THE BALANCE OF THE DAYLIGHT HOURS.

CS

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. &&

$$

...SEVERAL DAYS OF VERY COLD AIR EXPECTED THIS WEEKEND INTO NEXT WEEK...

.DISCUSSION... MAIN FCST ISSUES REVOLVE LES OVER THE NW FCST AREA TODAY/THIS EVENING....POSSIBLE SIGNIFICANT LAKE EFFECT/LAKE ENHANCED EVENT LATE TONIGHT/FRI WITH SHORTWAVE PASSAGE...AND THEN THE VERY COLD AIR TO SETTLE OVER THE AREA IN ITS WAKE.

WATER VAPOR IMAGERY AND GFS ANALYSIS CONTINUE TO SHOW A VERY PRONOUNCED RIDGE ALONG THE W COAST OF NAMERICA WITH 500MB HEIGHTS AROUND 5750M ALONG THE SHORE OF FAR SE ALASKA. IN THAT AREA...THE HEIGHT ANOMALY IS A WHOPPING 400M ABOVE THE AVERAGE FOR THIS TIME OF YEAR. DOWNSTREAM OF THIS HUGE POSITIVE ANOMALY...A TROF COVERS A GOOD PORTION OF CNTRL/ERN NAMERICA WITH CORE OF POLAR VORTEX CONTINUING TO DEEPEN OVER NRN HUDSON BAY WHERE HEIGHTS ARE AROUND 4780M. CLOSER TO HOME...ONE SHORTWAVE IS TRACKING E THRU THE GREAT LAKES REGION. SFC TROF ASSOCIATED WITH THIS FEATURE RUNS FROM A POSSIBLE MESOLOW OVER FAR NE LAKE SUPERIOR TO NEAR COPPER HARBOR THEN TO THE APOSTLES. MID EVENING TAMDAR SOUNDING FROM KDLH SHOWED INVERSION AT 840MB (5KFT MSL) WITH 850MB TEMP OF -18C. PROFILE WAS MOIST THRU 600MB. WITH FOCUSED CONVERGENCE...CONDITIONS ARE FAVORABLE FOR MDT/HVY LES...ESPECIALLY CONSIDERING RELATIVELY DEEP LAYER OF FAVORABLE DENDRITIC SNOW GROWTH TEMPS BLO INVERSION. KEWEENAW COUNTY SHERIFF AT EAGLE RIVER IN FACT DID REPORT A PERIOD OF HVY SNOW WITH 4-6 INCHES OF ACCUMULATION BTWN 530Z AND 08Z AS LES BAND SHIFTED SE. BAND APPEARS TO BE SOMEWHERE BETWEEN HOUGHTON AND COPPER HARBOR AT 0930Z. NEXT SHORTWAVE TROF OF INTEREST WAS HEADING S THRU NW ONTARIO/MANITOBA/SASKATCHEWAN. IT IS THIS SYSTEM THAT WILL BRING THE ARCTIC AIR S INTO THE GREAT LAKES AND MIDWEST. ARCTIC COLD FRONT ASSOCIATED WITH SHORTWAVE IS CLEARLY EVIDENT IN SFC OBS AS THERE IS A SHARP WIND SHIFT FROM NW ONTARIO TO ND/SASKATCHEWAN BORDER

FCST TODAY IS EXTREMELY COMPLICATED FOR THE KEWEENAW DUE TO SFC TROFFING ACROSS THE LAKE AND UNCERTAIN SFC WIND FIELD EVOLUTION. RUC13 WHICH HAS FREQUENTLY HAD SUPERIOR PERFORMANCE WITH WIND FIELDS OVER LAKE SUPERIOR/NRN LAKE MICHIGAN SHOWS TROF HANGING UP OVER NW UPPER MI FROM JUST OFFSHORE OF ONTONAGON NE ACROSS THE KEWEENAW. IT WOULD POINT TO PERSISTENT LES FROM JUST S OF HOUGHTON NORTHWARD. NAM BRINGS TROF ACROSS THE KEWEENAW THIS MORNING...BUT IT THEN DEVELOPS CONVERGENT WRLY WINDS INTO THE KEWEENAW IN THE AFTN. LOCAL HIGH RESOLUTION WRF-ARW LOOKS LIKE THE RUC13 THIS MORNING...BUT THEN IT SHIFTS CONVERGENCE N OF THE KEWEENAW THIS AFTN. DIFFICULT TO SAY WHICH IF ANY OF THESE SOLUTIONS WILL WORK OUT...BUT THE RUC13 DOES HAVE RECENT HISTORY OF OUTSTANDING PERFORMANCE. WILL LEAN IN ITS DIRECTION...SO NEXT QUESTION IS SNOW INTENSITY. UPSTREAM 00Z KINL SOUNDING SHOWED INVERSION AT 880MB (3.3KFT MSL) WITH SHARP DRYING ABOVE. THIS IS A SIGNIFICANT DIFFERENCE FROM MID EVENING KDLH TAMDAR SOUNDING WHICH WAS MUCH MORE FAVORABLE FOR LES. NAM/GFS FCST SOUNDINGS SOMEWHAT REFLECT THIS DRYING AND LOWERING OF INVERSION AT KCMX DURING THE MORNING. SO...ONE WOULD EXPECT A DIMINISHING OF LES THAT IS OCCURRING OVER THE KEWEENAW RIGHT NOW. GIVEN REPORT AT EAGLE RIVER...WILL GO WITH AN ADVY THIS MORNING FOR NRN HOUGHTON/KEWEENAW WITH EXPECTATION THAT MAIN SNOW BAND WILL DIMINISH BY LATE MORNING DUE TO DRYING AND LOWERING OF INVERSION. IT`S POSSIBLE MAIN SNOW BAND MAY BE JUST ABOUT OUT OF KEWEENAW COUNTY...BUT THERE IS NO WAY TO KNOW FOR SURE RIGHT NOW. OTHERWISE...EXPECT DRY WEATHER ELSEWHERE TODAY AFTER A FEW FLURRIES EARLY. THE TROF OVER LAKE SUPERIOR MAY SAG S TOWARD THE SRN PORTION OF THE ERN LAKE TODAY...BUT IT APPEARS WIND DIRECTION OVER UPPER MI WILL RETAIN ENOUGH OF A SRLY COMPONENT TO KEEP LES OFFSHORE OF THE ERN FCST AREA.

FCST DOES NOT GET ANY EASIER TONIGHT/FRI. AGAIN...ALL THE COMPLICATIONS REVOLVE AROUND THE WIND FIELDS. SHORTWAVE TROF OVER SRN CANADA APPROACHES TONIGHT...BUT ENERGY TENDS TO FOCUS IN SW END OF TROF WITH TIME. THE RESULT TONIGHT IS THAT THE ARCTIC FRONT WILL MOVE OVER LAKE SUPERIOR...AND THEN BECOME NEARLY STATIONARY UNTIL THE CONSOLIDATING ENERGY IN SHORTWAVE TROF TRACKS THRU THE UPPER LAKES FRI. DESPITE THE DIFFERENCES IN WIND FIELDS TODAY...THE RUC13 AND NAM LOOK SIMILAR BY THE 06Z-12Z TIME FRAME. ARCTIC FRONT WILL REACH THE KEWEENAW AT SOME POINT THIS EVENING AND THEN IT SHOULD SLOW OR HANG UP FROM NEAR OR SE OF THE APOSTLES TO NEAR HOUGHTON AND TO SE LAKE SUPERIOR WHERE MAIN SFC LOW WILL BEGIN TO ORGANIZE/DEEPEN. LOW-LEVEL CONVERGENCE/GRADUAL INCREASE IN DEEP LAYER FORCING AND DEEP MOISTENING OF COLUMN STRONGLY ARGUE FOR THE DEVELOPMENT OF HVY LAKE ENHANCED SNOW (ESPECIALLY ALONG ARCTIC FRONT) SINCE 850MB TEMPS ARE ALREADY LOW AROUND -18C. ALTHOUGH THERE IS A BIT MORE CONFIDENCE IN PLACEMENT OF ARCTIC FRONT OVERNIGHT... WIND FIELDS WILL STILL BE TROUBLESOME FOR PINPOINTING LOCATIONS OF HEAVIEST SNOW. RUC13 HAS MESOLOW DEVELOPMENT OVERNIGHT ALONG FRONT BTWN APOSTLES AND PORCUPINE MTNS. THIS COMBINED WITH SFC LOW DEVELOPMENT OVER SE LAKE SUPERIOR RESULTS IN DIVERGENT WIND FLOW DEVELOPING IN VCNTY OF FRONT OVER THE KEWEENAW. ALTHOUGH THAT`S POSSIBLE...STILL THINK THE VERY FAVORABLE LAKE ENHANCEMENT CONDITIONS WILL LEAD TO HVY SNOW THERE. HAVE OPTED TO RETAIN WATCH...BUT DID START TIMING EARLY THIS EVENING AND CARRIED WATCH THRU SAT MORNING (MORE ON THAT LATER). FOLLOWING NAM/RUC13 SOLUTIONS...HEAVIER SNOW WILL NOT START OVER ONTONAGON/GOGEBIC COUNTIES UNTIL AFTER MIDNIGHT WHEN WINDS FINALLY SHIFT AROUND TO THE N OR NW. LAKE ENHANCMENT PERIOD WILL BE SHORT FOR GOGEBIC COUNTY AS WINDS BACK W OR EVEN SW FRI. STILL...MIGHT BE ABLE TO PICK UP A QUICK 8 INCHES GIVEN SUCH FAVORABLE LAKE ENHANCEMENT CONDITIONS. AT LEAST A BRIEF PERIOD OF VERY HVY SNOW WILL SWEEP ACROSS MARQUETTE/ALGER/LUCE COUNTIES FRI AS DEEPENING LOW SHIFTS E OF LAKE SUPERIOR AND ARCTIC FRONT HEADS SE. SHOULD EASILY BE AN ADVY TYPE EVENT.

ANOTHER SHORTWAVE WILL ROTATE SE INTO THE UPPER LAKES FRI NIGHT AS POLAR VORTEX HEADS S. THIS WILL BRING ANOTHER ROUND OF HVY LAKE ENHANCED SNOW...AND ANOTHER SFC LOW WILL LIKELY DEVELOP OVER ERN LAKE SUPERIOR. THIS WILL RESULT IN CONVERGENT LOW-LEVEL WIND FLOW INTO NW UPPER MI. AIRMASS WILL NOT QUITE BE TOO COLD YET TO PRECLUDE DECENT SNOW GROWTH MICROPHYSICS...SO SNOW ACCUMULATIONS COULD BE HVY...ESPECIALLY CONSIDERING THE LOW-LEVEL CONVERGENCE. DEVELOPMENT OF ERN LAKE SUPERIOR LOW PRES AND STRENGTHENING LAND BREEZE WILL LIKELY RESULT IN WINDS BACKING ENOUGH TO KEEP HEAVIEST LES OFFSHORE OF THE NE FCST AREA FRI NIGHT. OVER THE WEEKEND AND INTO EARLY NEXT WEEK...THE COLDEST AIR OF THE SEASON WILL SETTLE OVER THE AREA. CONSENSUS OF THE LAST FEW DAYS OF ECWMF/GFS RUNS IS THAT 850MB TEMPS WILL BOTTOM OUT IN THE -28 TO -32C RANGE. NOGAPS AND SEVERAL RECENT LOCAL HEMISPHERIC WRF-ARW RUNS HAVE INDICATED 850MB TEMPS A FEW DEGREES LWR. IN ANYCASE...IT IS POSSIBLE THAT A FEW LOCATIONS OVER THE W HALF OF UPPER MI AWAY FROM LAKE SUPERIOR INFLUENCE MAY SEE TEMPS REMAIN BLO ZERO FROM FRI NIGHT UNTIL TUE AFTN. MIN TEMPS WILL DEPEND ON CLOUD COVER/WINDS...BUT -10F TO -20F SHOULD BE THE RULE AWAY FROM LAKE SUPERIOR INFLUENCE. AS FOR LAKE EFFECT...GFS FCST SOUNDINGS INDICATE AIRMASS REMAINING FAIRLY MOIST WITH HIGH INVERSIONS 8KFT TO AS MUCH AS 15KFT. HOWEVER...AN OVERWHELMING NEGATIVE FOR SIGNIFICANT SNOW IS THE VERY COLD AIR WHICH WILL SEVERELY LIMIT SNOWFLAKE GROWTH AND THUS ACCUMULATIONS. IT WILL BE INTERESTING THOUGH TO SEE IF LOCAL CONVERGENCE ZONES STRENGTHENED BY LAND BREEZES WILL BE ABLE TO YIELD HEAVIER LES BANDS AND SIGNIFICANT SNOW IN SUCH A COLD AIRMASS. ALTHOUGH ACCUMULATIONS ARE EXPECTED TO BE FAIRLY LIGHT EACH DAY...DURING SNOW SHOWERS THE AIR WILL BE THICK WITH SMALL SNOWFLAKES WHICH WILL BE EXTREMELY EFFECTIVE AT REDUCING VISIBILITY TO NEAR ZERO.

&&

.MQT WATCHES/WARNINGS/ADVISORIES... LAKE EFFECT SNOW ADVISORY UNTIL NOON EST MIZ001-003. WINTER STORM WATCH THIS EVENING THRU SAT MORNING MIZ001-003. WINTER STORM WATCH LATE TONIGHT THRU FRI AFTN MIZ002-004-009-084. HEAVY FREEZING SPRAY WARNING W HALF OF LAKE SUPERIOR.

&&

$$

ROLFSON

.UPDATE...

&&

.SHORT TERM /REST OF TODAY/...

THE INITIAL HEAVY BURST OF SNOW HAS RESULTED IN HEAVIEST SNOWFALL TOTALS ACROSS THE SOUTHERN HALF OF CWA...SEEN CLEARLY EARLIER ON THE KRAX RADAR IMAGERY WITH THE BRIGHT BAND REFLECTIVITY EXTENDING OVER THE SOUTHERN SECTOR. REPORTS INDICATE THE HIGHEST AMOUNTS ACROSS THE SOUTHWEST PIEDMONT...STANLY...ANSON...AND MONTGOMERY AND MOORE COUNTIES. 1 TO 1.5 INCHES WAS REPORTED IN THE SANDHILLS AND SOUTHERN COASTAL PLAIN...WHICH PROMPTED RAISING A WINTER WX ADVISORY THROUGH NOON. MEANWHILE ACROSS THE NORTHERN HALF...SNOW AMOUNTS ARE LESS THAN AN INCH WITH THE TRIAD AND COUNTIES ALONG THE VA BORDER REPORTING ONLY A TRACE.

CURRENTLY... REAL TIME REPORTS...AIRCRAFT(AMDAR)SOUNDINGS...AND THE MRR-VERTICALLY POINTING RADAR...ARE ALL SHOWING THE ADVERTISED WARMING NOSE ALOFT ADVANCING NORTH WITH THE MELTING LAYER STARTING TO DESCEND DOWN TO THE SURFACE. REPORTS EXTENDING FROM ALBEMARLE...MOORE... FAYETTEVILLE HAVE CHANGED OVER TO SLEET OR FREEZING RAIN. THE LATEST RUC IS MODELING THE THERMAL PROFILE FAIRLY WELL WHEN COMPARED TO THE LATEST AMDAR SOUNDING FROM GSO...WITH IT A LITTLE TOO COOL ALOFT AND SLIGHTLY TOO WARM NEAR THE SURFACE SURFACE.

WITH THE MAIN WARM/MOIST AIR CONVEYOR BELT DIRECTED IN A MORE SW TO NE FASHION AND TRANSLATING IN A MORE EASTERLY DIRECTION...RADARS RETURNS HAVE BEEN HARD TO COME BY ACROSS THE TRIAD. IT APPEARS THAT THE PREDICTED SNOWFALL OF 1 TO 2 INCHES WILL NOT BE REALIZED. HOWEVER...PRECIP WILL SPREAD BACK NORTH THIS AFTERNOON AS THE WELL-DEFINED WAVE OVER ALABAMA TRANSLATES NE TOWARDS CENTRAL NC. BY THAT TIME...THE THERMAL PROFILE WILL BE WARMING TO SUPPORT A TRANSITION TO SLEET AND THE ANTICIPATED FREEZING RAIN. THERE IS STILL YET ANOTHER WAVE OVER THE TEXAS AND OKLAHOMA THIS IS PROGGED TO APPROACH THE AREA BETWEEN 00Z TO 06Z. SO BY NO MEANS IS THE TRIAD OUT OF THE WOODS...WITH A QUARTER OF AN INCH ICE STILL VERY POSSIBLE. WILL BE KEEPING ALL WARNINGS AND ADVISORIES UP...BUT LOWER THE SNOWFALL AMOUNTS AND POPS. OTHERWISE...MINOR ADJUSTMENTS TO FORECAST OF P-TYPE AND TIMING OF CHANGEOVER.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... THE FLOW ALOFT IS DOMINATED BY A BROAD LARGE SCALE TROUGH OVER THE EASTERN TWO-THIRDS OF THE CONUS WITH A TROUGH AXIS THAT STEEPENS OVER THE APPALACHIANS AROUND TUE NIGHT...THEN FLATTENS AS THE TROUGH LOSES AMPLITUDE BY THU. SURFACE FEATURES SHOW WEAK HIGH PRESSURE DRIFTING ACROSS THE AREA SUN NGT AND MON AHEAD OF A COLD FRONT MON NIGHT THAT USHERS ANOTHER ARCTIC AIRMASS SOUTHEASTWARD OUT OF THE NORTHERN PLAINS. THE OVERNIGHT GFS SHOWS A WEAK LOW FORMATION IN THE LEE OF THE APPALACHIANS WITH THE COLD FRONT LATE MON... SUGGESTING SOME MOISTURE CONVERGENCE IN LOWER TO MID LEVELS. OTHER MODELS DO NOT RESOLVE THIS FEATURE. THE SURFACE LAYER IS EXPECTED TO BE VERY DRY WITH DEW POINTS OF 10-15 DEGREES AND CHANCES OF PRECIPITATION HITTING THE GROUND REMAIN LESS THAN 15 PERCENT IN THE RAH CWA. TEMPERATURES DROP TO BETWEEN 10 AND 20 DEGREES BELOW NORMAL FOLLOWING THE ARCTIC COLD FRONT FOR TUE AND WED MODERATING BUT STILL BELOW NORMAL ON THU.

&&

.PREV DISCUSSION... /ISSUED 312 AM EST THU FEB 1 2007/

SHORT TERM /TODAY THROUGH SATURDAY NIGHT/... TODAY THROUGH FRIDAY... INTERESTING AND SOMEWHAT TRICKY FORECAST FOR THE NEXT 24 HOURS OVER A LARGE PORTION OF CENTRAL NORTH CAROLINA. MID/HIGH LEVEL CLOUDS SPREADING INTO AREA RESULTING IN TEMPERATURES BOUNCING AROUND SHOWING RISES WHICH MAKES FORECAST ALL THE MORE TRICKY. BUT DEWPOINTS ARE QUITE LOW...STILL SINGLE DIGITS IN NORTHWEST BUT A SLIGHT RISE OVER SOUTH/SOUTHWEST SECTIONS. HOWEVER EXPECT TEMPERATURES TO FALL ONCE PRECIP STARTS. ONSET TIMING AND QPF AMOUNTS ARE THE KEY FACTORS. PRECIPITATION CURRENTLY OVER DEEP SOUTH HANDLED QUITE WELL BY GFS. LATEST RADAR TRENDS SHOW AREA ADVANCING NORTHEAST/EAST FAIRLY QUICKLY. HEAVIER MIX PRECIP CURRENTLY INTO NORTH AND NORTH CENTRAL GEORGIA WITH SOME LIGHTER ECHOES ALOFT NOW OVER CENTRAL CWA. SOME DIFFERENCES EXIST BETWEEN NAM/GFS WHILE THERE ARE SIMILARITIES. NAM IS THE COLDEST AND WETTEST. NAM BRINGS CORE OF HIGHEST PRECIP ACROSS THE CWA WHILE GFS MOVES ACROSS MAINLY SOUTHERN SECTIONS. ALSO NAM HAS MORE PRONOUNCED INSITU WEDGE AND PROFILES FOR GSO/RDU BELOW FREEZING THROUGH 18Z INDICATING A LONGER PERIOD OF SNOW. GFS WEAKER ON INSITU WEDGE AND PROFILES INDICATE PRECIP TRANSITIONING OVER SLEET/FREEZING RAIN BY THE AFTERNOON. TOUGH CALL AS GFS HAS BEEN FAIRLY CONSISTENT AND PERFORMANCE GOOD SO FAR THIS WINTER. GFS PARTIALS ARE MORE IN LINE WITH LATEST GSO RAOB (06Z). 06Z GSO SOUNDING SHOWING QUITE A BIT OF MID LEVEL DRY AIR. PER GFS GOOD ISENTROPIC LIFT COMMENCES OVER CWA AT 12Z WHILE NAM FURTHER SOUTH AND SOUTHWEST. BOTH NAM/GFS SHOWING TWO ROUNDS OF PRECIP MOVING ACROSS THE AREA...ONE DURING THE DAY...THEN ANOTHER WITH SECOND WAVE 00Z-06Z. OVERALL WILL LEAN TOWARD GFS WITH MODIFICATION. WILL HOLD ON TO ALL SNOW LONGER IN NORTHWEST PIEDMONT. ALSO SLOWER TREND ON TRANSITION OF PRECIP IN EASTERN PIEDMONT TO ALL RAIN. ADDITIONALLY WILL ADJUST TEMPERATURE TRENDS TO KEEP COLDER THROUGH 00Z. FOR FRIDAY WILL KEEP DRIZZLE MENTIONED THROUGH MID MORNING. --RA

FRIDAY NIGHT THROUGH SATURDAY NIGHT... AT THIS POINT WILL CONTINUE CURRENT FORECAST TREND. DRY AND COLD.

LONG TERM /SUNDAY THROUGH WEDNESDAY/... BROAD UPPER LEVEL TROUGH REMAIN ANCHORED OVER THE AREA THROUGH THE PERIOD TO REINFORCE COLD AIR OVER THE AREA. AT THE SURFACE HIGH PRESSURE BUILDS OVER THE AREA SUNDAY. SUNDAY NIGHT...A BOUNDARY DEVELOPS ALONG THE VIRGINIA/NORTH CAROLINA BORDER AND EXTENDS WEST AND SOUTHWEST TO TENNESSEE...THEN TO A LOW OVER EASTERN TEXAS. THERE IS SOME MOISTURE AND WEAK UPPER SUPPORT ASSOCIATED WITH THIS FEATURE ..HOWEVER WILL LEAVE FORECAST DRY AT THE PRESENT TIME. THIS SYSTEM WILL BE PUSHED TO THE SOUTHEAST LATE MONDAY AND EARLY TUESDAY AS ARCTIC HIGH PRESSURE BUILDS OVER THE AREA...AND REMAINS OVER THE REGION THROUGH WEDNESDAY. THE RESULT OF THIS ARCTIC AIRMASS WILL BE BELOW TO MUCH BELOW NORMAL TEMPERATURES. -RHJ

AVIATION /07Z-06Z/... ALTOCUMULUS BEGINNING TO MOVE INTO THE FOOTHILLS AT THIS TIME. CLOUDS WILL LOWER OVERNIGHT AND LIKELY DROP BELOW VFR A COUPLE OF HOURS AFTER SUNRISE AT THE TAF LOCATIONS. CEILINGS BELOW 1000 FEET ONCE PRECIPITATION BEGINS WITH MVFR VISIBILITIES IN GENERAL. CEILINGS BELOW 600 FEET MOST OF THE AFTERNOON AND INTO THE NIGHT.

ALL TAF SITES EXPECTING SOME NON-LIQUID PRECIPITATION THURSDAY WITH FAYETTEVILLE HAVING THE LEAST IMPACT AND SHORTEST DURATION...AND GREENSBORO AND WINSTON-SALEM MOST IMPACTED BY WINTER WEATHER. ACCUMULATING SNOW THURSDAY MORNING WILL MIX WITH SLEET AND CHANGE TO FREEZING RAIN IN THE AFTERNOON. LESSER AMOUNTS OF SNOW AND SLEET AS ONE MOVES EAST BUT FREEZING RAIN WILL BE A CONCERN. -RLH/VINCENT

&&

.RAH WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ078-085- 086-088-089.

WINTER STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR NCZ007>010- 021>025-038>040-073-074.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ011- 026>028-041>043-075>077-083-084.

&&

$$

SHORT TERM...CBL

.SYNOPSIS...A DEEP MARINE LAYER WILL CAUSE VARIABLE CLOUDINESS WEST OF THE MOUNTAINS THROUGH FRIDAY MORNING WITH A FEW SPRINKLES THIS EVENING. OTHERWISE...FAIR AND A LITTLE WARMER FRIDAY. MOSTLY CLEAR AND MUCH WARMER THIS WEEKEND THROUGH EARLY NEXT WEEK UNDER HIGH PRESSURE. UPPER LEVEL LOW PRESSURE WILL BRING MORE CLOUDS AND COOLING TOWARD THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

.SHORT TERM (TODAY-SUN)...THERE WAS A DEEP MOIST LAYER WITH PARTLY TO MOSTLY CLOUDY SKIES WITH A FEW LIGHT SHOWERS OVER AND W OF THE MOUNTAINS TODAY. ACARS SOUNDINGS INDICATED AN INVERSION BASED NEAR 6000 FT WITH STRONG NW WINDS ALOFT. ONSHORE GRADIENTS WITH ABOUT 4 MB SAN-IPL.

RESIDUAL MOISTURE AND A DEVELOPING DEEP MARINE LAYER WILL CAUSE LOW CLOUDS AND PATCHY FOG W OF THE MOUNTAINS TONIGHT AND FRI MORNING. THERE COULD STILL BE A FEW SPRINKLES OR LIGHT SHOWERS FROM THE W OF THE MOUNTAIN RIDGES THIS EVENING. GOOD CLEARING FRI AFTERNOON AS OFFSHORE FLOW BEGINS TO DEVELOP. A LITTLE WARMER FRI. DRY NW FLOW ALOFT THROUGH FRI WITH A HIGH AMPLITUDE RIDGE OFF THE W COAST. THIS RIDGE WILL SLOWLY SHIFTS E SAT AND SUN AND OFFSHORE GRADIENTS CONTINUE. THIS WILL BRING MOSTLY CLEAR SKIES AND MUCH WARMER DAYS...ESPECIALLY SUN. LOCALLY BREEZY IN THE MOUNTAINS AND DESERTS TODAY DUE TO ONSHORE FLOW AND WINDS ALOFT...THEN LOCAL GUSTY OFFSHORE WINDS FRI THROUGH SUN. MOST WINDS SHOULD REMAIN BELOW ADVISORY STRENGTH BUT THERE COULD BE LOCAL STRONGER GUSTS THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES...ESPECIALLY BELOW THE CAJON PASS AND IN THE SANTA ANA MOUNTAINS. LARGE W SWELL WILL CAUSE ABOVE NORMAL SURF THROUGH SAT MORNING.

&&

.LONG TERM (MON-THU)...CONTINUED MOSTLY CLEAR AND WARM MON WITH HIGH PRESSURE ALOFT AND WEAK OFFSHORE FLOW. SLIGHTLY COOLER IN MOST AREAS TUE AS THE HIGH WEAKENS. A PAC TROUGH WILL APPROACH THE W COAST WED AND MOVE THROUGH THU FOR MORE CLOUDS AND COOLING. MODELS HAVE BEEN INCONSISTENT ON THE STRENGTH OF THIS TROUGH AND CANNOT COMPLETELY RULE OUT THE POSSIBILITY OF PRECIP THU.

&&

.AVIATION... A DEEP MARINE LAYER WILL CONTINUE THROUGH TONIGHT KEEPING LAYERS OF STRATOCU OVER MOST OF THE AREA FROM THE MOUNTAINS TO THE COASTAL WATERS. THE LOWEST SCATTERED TO BROKEN LAYER SHOULD BE AROUND 3000 FEET MSL WITH ADDITIONAL LAYERS AROUND 4500 FEET AND 6000 FEET MSL. TOPS SHOULD BE AROUND 7000 FEET. THE MARINE LAYER SHOULD BEGIN TO LOWER FRIDAY MORNING WITH BETTER CLEARING EXPECTED BY FRIDAY AFTERNOON.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

HIGH SURF ADVISORY UNTIL 2 AM PST SATURDAY FOR SAN DIEGO COUNTY COASTAL AREAS. SEE LAXCFWSGX.

&&

$$

PUBLIC...DVA AVIATION...HORTON

...SEVERAL DAYS OF VERY COLD AIR EXPECTED THIS WEEKEND INTO NEXT WEEK...

.DISCUSSION... MAIN CONCERN WITH THE UPDATE THIS MORNING IS HANDLING OF CURRENT HEADLINES ACROSS THE CWFA. A VERY COMPLICATED SCENARIO IS SHAPING UP FOR THE NEXT SEVERAL DAYS...WITH PERIODIC SURGES OF ARCTIC AIR ACCOMPANYING SHORT WAVE PASSAGES. IN THE SHORT TERM...WHICH WAS THE PERIOD OF FOCUS FOR THE UPDATE...THE SHORTWAVE MOVING EASTWARD FROM THE NORTHERN PLAINS WILL SWEEP THROUGH THE AREA TONIGHT THROUGH EARLY FRIDAY. THE ARCTIC BOUNDARY IS CURRENTLY SAGGING SOUTH ACROSS LAKE SUPERIOR...AND THIS BOUNDARY WILL SURGE A BIT FARTHER SOUTH TONIGHT THROUGH EARLY FRIDAY AS THE SHORTWAVE SWINGS THROUGH...BUT WILL THEN DRIFT BACK TO THE NORTH LATE FRIDAY AFTERNOON INTO FRIDAY NIGHT...BEFORE IT IS DEPRESSED SOUTHWARD AGAIN BY ANOTHER SHORTWAVE FRIDAY NIGHT AND SATURDAY. THAT SECOND SHORTWAVE IS CURRENTLY ROTATING AROUND THE WESTERN PERIPHERY OF THE EASTERN CANADA UPPER LOW AND CAN BE SEEN DROPPING SOUTHWARD THROUGH CENTRAL CANADA.

LOCATIONS THAT WILL BE IMPACTED BY SIGNIFICANT LAKE ENHANCED SNOW TONIGHT AND FRIDAY IS TOUGH TO PIN DOWN SINCE MUCH WILL DEPEND ON THE BOUNDARY LAYER WIND FLOW. OTHER FACTORS ARE ALL SUGGESTING THE POTENTIAL OF A GOOD LAKE ENHANCED EVENT...WITH DECENT Q-VECTOR CONVERGENCE...DEEP MOISTURE (APPARENT ON 12Z KINL SOUNDING)...GOOD SNOW GROWTH POTENTIAL IN THE POSITIVE AREA OF THE CBL...AND SIGNIFICANT LOW LEVEL CONVERGENCE OWING TO THE ARCTIC FRONTAL BOUNDARY AND SIGNIFICANTLY BACKED LOW LEVEL WINDS SOUTH OF THE FRONT GIVEN THE SHARP TEMPERATURE CONTRAST FROM LAKE TO LAKE. THE WESTERN CWFA SEEMS SOMEWHAT STRAIGHTFORWARD...WITH CONVERGENCE ALONG THE FRONTAL BOUNDARY GIVING DECENT SNOW SHOWERS TO THE KEWEENAW THIS AFTERNOON...THEN DROPPING SOUTH THROUGH ONTONAGON AND INTO GOGEBIC COUNTY THIS EVENING. BEHIND THE FRONT...NORTHERLY WINDS SHOULD STILL HAVE ENOUGH FETCH GIVEN THE OTHER FAVORABLE CONDITIONS TO KEEP SNOW SHOWERS GOING OVER THE KEWEENAW. THE BOUNDARY WILL LIFT BACK TO THE NORTH ON FRIDAY...BRINGING THINGS TO AN END OVER GOGEBIC AND ONTONAGON COUNTIES...BUT THEN IT APPEARS THE CONVERGENCE AXIS MAY STALL OVER THE KEWEENAW AND LINGER THERE UNTIL THE NEXT SHORTWAVE ARRIVES. WITH THESE IDEAS...UPGRADED THE WATCHES TO WARNINGS OVER THE WEST...AND KEPT IT GOING FOR AN EXTENDED PERIOD OVER THE KEWEENAW SINCE ALTHOUGH THERE MAY BE LULLS IN THE ACTIVITY...GENERALLY POOR CONDITIONS WILL PERSIST THROUGH SATURDAY.

FARTHER EAST...THINGS ARE MORE DIFFICULT TO ASSESS...SINCE BOUNDARY LAYER WIND DIRECTIONS LOOK PARTICULARY TROUBLING. USED A VARIETY OF GUIDANCE...INCLUDING THE 12Z NAM...RUC13...LOCAL 20KM AND 5KM WRF-ARW...AND REGIONAL GEM TO HELP DETERMINE HOW THINGS WILL EVOLVE OVER NORTH CENTRAL UPPER MICHIGAN. THERE IS GENERAL AGREEMENT THAT THE BOUNDARY AND ASSOCIATED CONVERGENCE AXIS WILL MOVE INTO THE AREA LATE TONIGHT AND LINGER INTO FRIDAY AFTERNOON. HOWEVER...WITH ALL OF THE MODELS SUGGESTING A CLOSED LOW OVER SOUTHEAST LAKE SUPERIOR...THE BL WIND DIRECTIONS VARY CONSIDERABLY DEPENDING ON EXACTLY WHERE THAT LOW WILL BE LOCATED. THE NAM IS FARTHEST WEST...AND WOULD PRODUCE THE MOST PROLONGED PERIOD OF FAVORABLE CONDITIONS AND CONVERGENCE OVER NORTHERN AND EASTERN MARQUETTE COUNTIES...WHILE MOST OF THE OTHER GUIDANCE IS FARTHER EAST AND WOULD ONLY GIVE THE FAR NORTHEAST PORTION OF MARQUETTE COUNTY A BRIEF BOUT OF HEAVIER SNOW SHOWER ACTIVITY. THE RUC13 HAS DONE EXCEPTIONALLY WELL WITH BL WINDS OF LATE...SO LEANED MORE HEAVILY TOWARD ITS SLIGHTLY FARTHER EAST SOLUTION...WHICH NEVER REALLY BRINGS NE 925-850MB WINDS INTO MARQUETTE COUNTY AS THE NAM DOES. IF THE NAM VERIFIES...THEN FAR NORTHERN AND EASTERN MARQUETTE COUNTY...INCLUDING THE CITY...COULD SEE WARNING SNOWFALL AMOUNTS WITH 3 TO 4 INCH PER HOUR RATES FRIDAY MORNING. GIVEN THE UNCERTAINTY AND GENERALLY FARTHER EAST SOLUTIONS OF THE OTHER MODELS...WILL JUST ISSUE AND ADVISORY FOR MARQUETTE COUNTY AT THIS TIME...PARTICULARLY SINCE ONLY A SMALL PORTION OF THE COUNTY WILL BE SIGNIFICANTLY IMPACTED IN EITHER SCENARIO. ALSO PUT UP AN ADVISORY FOR ALGER COUNTY. ALTHOUGH CONDITIONS WILL BE MORE FAVORABLE FOR ALGER...THE PROGRESSIVELY BACKING WINDS FRIDAY INTO FRIDAY EVENING THROUGH KEEP ANY SPECIFIC LOCATION FROM BEING IMPACTED BY HEAVIER SNOW FOR AN EXTENDED PERIOD. LATER SHIFTS WILL DEFINITELY NEED TO KEEP AN EYE ON THINGS...SINCE SUBTLE DIFFERENCES IN THE SURFACE LOW LOCATION AND WIND FIELD WILL HAVE A BIG IMPACT ON THE LOCATIONS IMPACTED. ADVISORIES MAY EVENTUALLY BE NEEDED FOR NORTHERN SCHOOLCRAFT AND LUCE COUNTIES AS WELL...BUT SINCE THEY WILL NOT BE IMPACTED UNTIL LATER IN THE DAY ON FRIDAY...LEFT THEM OUT OF THE HEADLINE SCENARIO FOR NOW.

TRH

&&

.PREV DISCUSSION... MAIN FCST ISSUES REVOLVE LES OVER THE NW FCST AREA TODAY/THIS EVENING....POSSIBLE SIGNIFICANT LAKE EFFECT/LAKE ENHANCED EVENT LATE TONIGHT/FRI WITH SHORTWAVE PASSAGE...AND THEN THE VERY COLD AIR TO SETTLE OVER THE AREA IN ITS WAKE.

WATER VAPOR IMAGERY AND GFS ANALYSIS CONTINUE TO SHOW A VERY PRONOUNCED RIDGE ALONG THE W COAST OF NAMERICA WITH 500MB HEIGHTS AROUND 5750M ALONG THE SHORE OF FAR SE ALASKA. IN THAT AREA...THE HEIGHT ANOMALY IS A WHOPPING 400M ABOVE THE AVERAGE FOR THIS TIME OF YEAR. DOWNSTREAM OF THIS HUGE POSITIVE ANOMALY...A TROF COVERS A GOOD PORTION OF CNTRL/ERN NAMERICA WITH CORE OF POLAR VORTEX CONTINUING TO DEEPEN OVER NRN HUDSON BAY WHERE HEIGHTS ARE AROUND 4780M. CLOSER TO HOME...ONE SHORTWAVE IS TRACKING E THRU THE GREAT LAKES REGION. SFC TROF ASSOCIATED WITH THIS FEATURE RUNS FROM A POSSIBLE MESOLOW OVER FAR NE LAKE SUPERIOR TO NEAR COPPER HARBOR THEN TO THE APOSTLES. MID EVENING TAMDAR SOUNDING FROM KDLH SHOWED INVERSION AT 840MB (5KFT MSL) WITH 850MB TEMP OF -18C. PROFILE WAS MOIST THRU 600MB. WITH FOCUSED CONVERGENCE...CONDITIONS ARE FAVORABLE FOR MDT/HVY LES...ESPECIALLY CONSIDERING RELATIVELY DEEP LAYER OF FAVORABLE DENDRITIC SNOW GROWTH TEMPS BLO INVERSION. KEWEENAW COUNTY SHERIFF AT EAGLE RIVER IN FACT DID REPORT A PERIOD OF HVY SNOW WITH 4-6 INCHES OF ACCUMULATION BTWN 530Z AND 08Z AS LES BAND SHIFTED SE. BAND APPEARS TO BE SOMEWHERE BETWEEN HOUGHTON AND COPPER HARBOR AT 0930Z. NEXT SHORTWAVE TROF OF INTEREST WAS HEADING S THRU NW ONTARIO/MANITOBA/SASKATCHEWAN. IT IS THIS SYSTEM THAT WILL BRING THE ARCTIC AIR S INTO THE GREAT LAKES AND MIDWEST. ARCTIC COLD FRONT ASSOCIATED WITH SHORTWAVE IS CLEARLY EVIDENT IN SFC OBS AS THERE IS A SHARP WIND SHIFT FROM NW ONTARIO TO ND/SASKATCHEWAN BORDER

FCST TODAY IS EXTREMELY COMPLICATED FOR THE KEWEENAW DUE TO SFC TROFFING ACROSS THE LAKE AND UNCERTAIN SFC WIND FIELD EVOLUTION. RUC13 WHICH HAS FREQUENTLY HAD SUPERIOR PERFORMANCE WITH WIND FIELDS OVER LAKE SUPERIOR/NRN LAKE MICHIGAN SHOWS TROF HANGING UP OVER NW UPPER MI FROM JUST OFFSHORE OF ONTONAGON NE ACROSS THE KEWEENAW. IT WOULD POINT TO PERSISTENT LES FROM JUST S OF HOUGHTON NORTHWARD. NAM BRINGS TROF ACROSS THE KEWEENAW THIS MORNING...BUT IT THEN DEVELOPS CONVERGENT WRLY WINDS INTO THE KEWEENAW IN THE AFTN. LOCAL HIGH RESOLUTION WRF-ARW LOOKS LIKE THE RUC13 THIS MORNING...BUT THEN IT SHIFTS CONVERGENCE N OF THE KEWEENAW THIS AFTN. DIFFICULT TO SAY WHICH IF ANY OF THESE SOLUTIONS WILL WORK OUT...BUT THE RUC13 DOES HAVE RECENT HISTORY OF OUTSTANDING PERFORMANCE. WILL LEAN IN ITS DIRECTION...SO NEXT QUESTION IS SNOW INTENSITY. UPSTREAM 00Z KINL SOUNDING SHOWED INVERSION AT 880MB (3.3KFT MSL) WITH SHARP DRYING ABOVE. THIS IS A SIGNIFICANT DIFFERENCE FROM MID EVENING KDLH TAMDAR SOUNDING WHICH WAS MUCH MORE FAVORABLE FOR LES. NAM/GFS FCST SOUNDINGS SOMEWHAT REFLECT THIS DRYING AND LOWERING OF INVERSION AT KCMX DURING THE MORNING. SO...ONE WOULD EXPECT A DIMINISHING OF LES THAT IS OCCURRING OVER THE KEWEENAW RIGHT NOW. GIVEN REPORT AT EAGLE RIVER...WILL GO WITH AN ADVY THIS MORNING FOR NRN HOUGHTON/KEWEENAW WITH EXPECTATION THAT MAIN SNOW BAND WILL DIMINISH BY LATE MORNING DUE TO DRYING AND LOWERING OF INVERSION. IT`S POSSIBLE MAIN SNOW BAND MAY BE JUST ABOUT OUT OF KEWEENAW COUNTY...BUT THERE IS NO WAY TO KNOW FOR SURE RIGHT NOW. OTHERWISE...EXPECT DRY WEATHER ELSEWHERE TODAY AFTER A FEW FLURRIES EARLY. THE TROF OVER LAKE SUPERIOR MAY SAG S TOWARD THE SRN PORTION OF THE ERN LAKE TODAY...BUT IT APPEARS WIND DIRECTION OVER UPPER MI WILL RETAIN ENOUGH OF A SRLY COMPONENT TO KEEP LES OFFSHORE OF THE ERN FCST AREA.

FCST DOES NOT GET ANY EASIER TONIGHT/FRI. AGAIN...ALL THE COMPLICATIONS REVOLVE AROUND THE WIND FIELDS. SHORTWAVE TROF OVER SRN CANADA APPROACHES TONIGHT...BUT ENERGY TENDS TO FOCUS IN SW END OF TROF WITH TIME. THE RESULT TONIGHT IS THAT THE ARCTIC FRONT WILL MOVE OVER LAKE SUPERIOR...AND THEN BECOME NEARLY STATIONARY UNTIL THE CONSOLIDATING ENERGY IN SHORTWAVE TROF TRACKS THRU THE UPPER LAKES FRI. DESPITE THE DIFFERENCES IN WIND FIELDS TODAY...THE RUC13 AND NAM LOOK SIMILAR BY THE 06Z-12Z TIME FRAME. ARCTIC FRONT WILL REACH THE KEWEENAW AT SOME POINT THIS EVENING AND THEN IT SHOULD SLOW OR HANG UP FROM NEAR OR SE OF THE APOSTLES TO NEAR HOUGHTON AND TO SE LAKE SUPERIOR WHERE MAIN SFC LOW WILL BEGIN TO ORGANIZE/DEEPEN. LOW-LEVEL CONVERGENCE/GRADUAL INCREASE IN DEEP LAYER FORCING AND DEEP MOISTENING OF COLUMN STRONGLY ARGUE FOR THE DEVELOPMENT OF HVY LAKE ENHANCED SNOW (ESPECIALLY ALONG ARCTIC FRONT) SINCE 850MB TEMPS ARE ALREADY LOW AROUND -18C. ALTHOUGH THERE IS A BIT MORE CONFIDENCE IN PLACEMENT OF ARCTIC FRONT OVERNIGHT... WIND FIELDS WILL STILL BE TROUBLESOME FOR PINPOINTING LOCATIONS OF HEAVIEST SNOW. RUC13 HAS MESOLOW DEVELOPMENT OVERNIGHT ALONG FRONT BTWN APOSTLES AND PORCUPINE MTNS. THIS COMBINED WITH SFC LOW DEVELOPMENT OVER SE LAKE SUPERIOR RESULTS IN DIVERGENT WIND FLOW DEVELOPING IN VCNTY OF FRONT OVER THE KEWEENAW. ALTHOUGH THAT`S POSSIBLE...STILL THINK THE VERY FAVORABLE LAKE ENHANCEMENT CONDITIONS WILL LEAD TO HVY SNOW THERE. HAVE OPTED TO RETAIN WATCH...BUT DID START TIMING EARLY THIS EVENING AND CARRIED WATCH THRU SAT MORNING (MORE ON THAT LATER). FOLLOWING NAM/RUC13 SOLUTIONS...HEAVIER SNOW WILL NOT START OVER ONTONAGON/GOGEBIC COUNTIES UNTIL AFTER MIDNIGHT WHEN WINDS FINALLY SHIFT AROUND TO THE N OR NW. LAKE ENHANCMENT PERIOD WILL BE SHORT FOR GOGEBIC COUNTY AS WINDS BACK W OR EVEN SW FRI. STILL...MIGHT BE ABLE TO PICK UP A QUICK 8 INCHES GIVEN SUCH FAVORABLE LAKE ENHANCEMENT CONDITIONS. AT LEAST A BRIEF PERIOD OF VERY HVY SNOW WILL SWEEP ACROSS MARQUETTE/ALGER/LUCE COUNTIES FRI AS DEEPENING LOW SHIFTS E OF LAKE SUPERIOR AND ARCTIC FRONT HEADS SE. SHOULD EASILY BE AN ADVY TYPE EVENT.

ANOTHER SHORTWAVE WILL ROTATE SE INTO THE UPPER LAKES FRI NIGHT AS POLAR VORTEX HEADS S. THIS WILL BRING ANOTHER ROUND OF HVY LAKE ENHANCED SNOW...AND ANOTHER SFC LOW WILL LIKELY DEVELOP OVER ERN LAKE SUPERIOR. THIS WILL RESULT IN CONVERGENT LOW-LEVEL WIND FLOW INTO NW UPPER MI. AIRMASS WILL NOT QUITE BE TOO COLD YET TO PRECLUDE DECENT SNOW GROWTH MICROPHYSICS...SO SNOW ACCUMULATIONS COULD BE HVY...ESPECIALLY CONSIDERING THE LOW-LEVEL CONVERGENCE. DEVELOPMENT OF ERN LAKE SUPERIOR LOW PRES AND STRENGTHENING LAND BREEZE WILL LIKELY RESULT IN WINDS BACKING ENOUGH TO KEEP HEAVIEST LES OFFSHORE OF THE NE FCST AREA FRI NIGHT. OVER THE WEEKEND AND INTO EARLY NEXT WEEK...THE COLDEST AIR OF THE SEASON WILL SETTLE OVER THE AREA. CONSENSUS OF THE LAST FEW DAYS OF ECWMF/GFS RUNS IS THAT 850MB TEMPS WILL BOTTOM OUT IN THE -28 TO -32C RANGE. NOGAPS AND SEVERAL RECENT LOCAL HEMISPHERIC WRF-ARW RUNS HAVE INDICATED 850MB TEMPS A FEW DEGREES LWR. IN ANYCASE...IT IS POSSIBLE THAT A FEW LOCATIONS OVER THE W HALF OF UPPER MI AWAY FROM LAKE SUPERIOR INFLUENCE MAY SEE TEMPS REMAIN BLO ZERO FROM FRI NIGHT UNTIL TUE AFTN. MIN TEMPS WILL DEPEND ON CLOUD COVER/WINDS...BUT -10F TO -20F SHOULD BE THE RULE AWAY FROM LAKE SUPERIOR INFLUENCE. AS FOR LAKE EFFECT...GFS FCST SOUNDINGS INDICATE AIRMASS REMAINING FAIRLY MOIST WITH HIGH INVERSIONS 8KFT TO AS MUCH AS 15KFT. HOWEVER...AN OVERWHELMING NEGATIVE FOR SIGNIFICANT SNOW IS THE VERY COLD AIR WHICH WILL SEVERELY LIMIT SNOWFLAKE GROWTH AND THUS ACCUMULATIONS. IT WILL BE INTERESTING THOUGH TO SEE IF LOCAL CONVERGENCE ZONES STRENGTHENED BY LAND BREEZES WILL BE ABLE TO YIELD HEAVIER LES BANDS AND SIGNIFICANT SNOW IN SUCH A COLD AIRMASS. ALTHOUGH ACCUMULATIONS ARE EXPECTED TO BE FAIRLY LIGHT EACH DAY...DURING SNOW SHOWERS THE AIR WILL BE THICK WITH SMALL SNOWFLAKES WHICH WILL BE EXTREMELY EFFECTIVE AT REDUCING VISIBILITY TO NEAR ZERO.

ROLFSON

&&

.MQT WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING THROUGH 6PM EST SATURDAY MIZ001-003. WINTER STORM WARNING 10 PM EST THIS EVENING THROUGH 4 PM EST FRIDAY MIZ002. WINTER STORM WARNING 9 PM CST THIS EVENING THROUGH 9 AM CST FRIDAY MIZ009. WINTER STORM WARNING MIDNIGHT EST TONIGHT THROUGH 4 PM EST FRIDAY MIZ084. WINTER WEATHER ADVISORY MIDNIGHT EST TONIGHT THROUGH 4 PM EST FRIDAY MIZ004. WINTER WEATHER ADVISORY 1 AM EST TONIGHT THROUGH 4 PM EST FRIDAY MIZ005. WINTER WEATHER ADVISORY 7 AM EST THROUGH 10 PM EST FRIDAY MIZ006. HEAVY FREEZING SPRAY WARNING W HALF OF LAKE SUPERIOR.

&&

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...SEVERAL DAYS OF VERY COLD AIR EXPECTED THIS WEEKEND INTO NEXT WEEK... .DISCUSSION... MAIN FCST ISSUES REVOLVE LES OVER THE NW FCST AREA TODAY/THIS EVENING....POSSIBLE SIGNIFICANT LAKE EFFECT/LAKE ENHANCED EVENT LATE TONIGHT/FRI WITH SHORTWAVE PASSAGE...AND THEN THE VERY COLD AIR TO SETTLE OVER THE AREA IN ITS WAKE. WATER VAPOR IMAGERY AND GFS ANALYSIS CONTINUE TO SHOW A VERY PRONOUNCED RIDGE ALONG THE W COAST OF NAMERICA WITH 500MB HEIGHTS AROUND 5750M ALONG THE SHORE OF FAR SE ALASKA. IN THAT AREA...THE HEIGHT ANOMALY IS A WHOPPING 400M ABOVE THE AVERAGE FOR THIS TIME OF YEAR. DOWNSTREAM OF THIS HUGE POSITIVE ANOMALY...A TROF COVERS A GOOD PORTION OF CNTRL/ERN NAMERICA WITH CORE OF POLAR VORTEX CONTINUING TO DEEPEN OVER NRN HUDSON BAY WHERE HEIGHTS ARE AROUND 4780M. CLOSER TO HOME...ONE SHORTWAVE IS TRACKING E THRU THE GREAT LAKES REGION. SFC TROF ASSOCIATED WITH THIS FEATURE RUNS FROM A POSSIBLE MESOLOW OVER FAR NE LAKE SUPERIOR TO NEAR COPPER HARBOR THEN TO THE APOSTLES. MID EVENING TAMDAR SOUNDING FROM KDLH SHOWED INVERSION AT 840MB (5KFT MSL) WITH 850MB TEMP OF -18C. PROFILE WAS MOIST THRU 600MB. WITH FOCUSED CONVERGENCE...CONDITIONS ARE FAVORABLE FOR MDT/HVY LES...ESPECIALLY CONSIDERING RELATIVELY DEEP LAYER OF FAVORABLE DENDRITIC SNOW GROWTH TEMPS BLO INVERSION. KEWEENAW COUNTY SHERIFF AT EAGLE RIVER IN FACT DID REPORT A PERIOD OF HVY SNOW WITH 4-6 INCHES OF ACCUMULATION BTWN 530Z AND 08Z AS LES BAND SHIFTED SE. BAND APPEARS TO BE SOMEWHERE BETWEEN HOUGHTON AND COPPER HARBOR AT 0930Z. NEXT SHORTWAVE TROF OF INTEREST WAS HEADING S THRU NW ONTARIO/MANITOBA/SASKATCHEWAN. IT IS THIS SYSTEM THAT WILL BRING THE ARCTIC AIR S INTO THE GREAT LAKES AND MIDWEST. ARCTIC COLD FRONT ASSOCIATED WITH SHORTWAVE IS CLEARLY EVIDENT IN SFC OBS AS THERE IS A SHARP WIND SHIFT FROM NW ONTARIO TO ND/SASKATCHEWAN BORDER FCST TODAY IS EXTREMELY COMPLICATED FOR THE KEWEENAW DUE TO SFC TROFFING ACROSS THE LAKE AND UNCERTAIN SFC WIND FIELD EVOLUTION. RUC13 WHICH HAS FREQUENTLY HAD SUPERIOR PERFORMANCE WITH WIND FIELDS OVER LAKE SUPERIOR/NRN LAKE MICHIGAN SHOWS TROF HANGING UP OVER NW UPPER MI FROM JUST OFFSHORE OF ONTONAGON NE ACROSS THE KEWEENAW. IT WOULD POINT TO PERSISTENT LES FROM JUST S OF HOUGHTON NORTHWARD. NAM BRINGS TROF ACROSS THE KEWEENAW THIS MORNING...BUT IT THEN DEVELOPS CONVERGENT WRLY WINDS INTO THE KEWEENAW IN THE AFTN. LOCAL HIGH RESOLUTION WRF-ARW LOOKS LIKE THE RUC13 THIS MORNING...BUT THEN IT SHIFTS CONVERGENCE N OF THE KEWEENAW THIS AFTN. DIFFICULT TO SAY WHICH IF ANY OF THESE SOLUTIONS WILL WORK OUT...BUT THE RUC13 DOES HAVE RECENT HISTORY OF OUTSTANDING PERFORMANCE. WILL LEAN IN ITS DIRECTION...SO NEXT QUESTION IS SNOW INTENSITY. UPSTREAM 00Z KINL SOUNDING SHOWED INVERSION AT 880MB (3.3KFT MSL) WITH SHARP DRYING ABOVE. THIS IS A SIGNIFICANT DIFFERENCE FROM MID EVENING KDLH TAMDAR SOUNDING WHICH WAS MUCH MORE FAVORABLE FOR LES. NAM/GFS FCST SOUNDINGS SOMEWHAT REFLECT THIS DRYING AND LOWERING OF INVERSION AT KCMX DURING THE MORNING. SO...ONE WOULD EXPECT A DIMINISHING OF LES THAT IS OCCURRING OVER THE KEWEENAW RIGHT NOW. GIVEN REPORT AT EAGLE RIVER...WILL GO WITH AN ADVY THIS MORNING FOR NRN HOUGHTON/KEWEENAW WITH EXPECTATION THAT MAIN SNOW BAND WILL DIMINISH BY LATE MORNING DUE TO DRYING AND LOWERING OF INVERSION. IT`S POSSIBLE MAIN SNOW BAND MAY BE JUST ABOUT OUT OF KEWEENAW COUNTY...BUT THERE IS NO WAY TO KNOW FOR SURE RIGHT NOW. OTHERWISE...EXPECT DRY WEATHER ELSEWHERE TODAY AFTER A FEW FLURRIES EARLY. THE TROF OVER LAKE SUPERIOR MAY SAG S TOWARD THE SRN PORTION OF THE ERN LAKE TODAY...BUT IT APPEARS WIND DIRECTION OVER UPPER MI WILL RETAIN ENOUGH OF A SRLY COMPONENT TO KEEP LES OFFSHORE OF THE ERN FCST AREA. FCST DOES NOT GET ANY EASIER TONIGHT/FRI. AGAIN...ALL THE COMPLICATIONS REVOLVE AROUND THE WIND FIELDS. SHORTWAVE TROF OVER SRN CANADA APPROACHES TONIGHT...BUT ENERGY TENDS TO FOCUS IN SW END OF TROF WITH TIME. THE RESULT TONIGHT IS THAT THE ARCTIC FRONT WILL MOVE OVER LAKE SUPERIOR...AND THEN BECOME NEARLY STATIONARY UNTIL THE CONSOLIDATING ENERGY IN SHORTWAVE TROF TRACKS THRU THE UPPER LAKES FRI. DESPITE THE DIFFERENCES IN WIND FIELDS TODAY...THE RUC13 AND NAM LOOK SIMILAR BY THE 06Z-12Z TIME FRAME. ARCTIC FRONT WILL REACH THE KEWEENAW AT SOME POINT THIS EVENING AND THEN IT SHOULD SLOW OR HANG UP FROM NEAR OR SE OF THE APOSTLES TO NEAR HOUGHTON AND TO SE LAKE SUPERIOR WHERE MAIN SFC LOW WILL BEGIN TO ORGANIZE/DEEPEN. LOW-LEVEL CONVERGENCE/GRADUAL INCREASE IN DEEP LAYER FORCING AND DEEP MOISTENING OF COLUMN STRONGLY ARGUE FOR THE DEVELOPMENT OF HVY LAKE ENHANCED SNOW (ESPECIALLY ALONG ARCTIC FRONT) SINCE 850MB TEMPS ARE ALREADY LOW AROUND -18C. ALTHOUGH THERE IS A BIT MORE CONFIDENCE IN PLACEMENT OF ARCTIC FRONT OVERNIGHT... WIND FIELDS WILL STILL BE TROUBLESOME FOR PINPOINTING LOCATIONS OF HEAVIEST SNOW. RUC13 HAS MESOLOW DEVELOPMENT OVERNIGHT ALONG FRONT BTWN APOSTLES AND PORCUPINE MTNS. THIS COMBINED WITH SFC LOW DEVELOPMENT OVER SE LAKE SUPERIOR RESULTS IN DIVERGENT WIND FLOW DEVELOPING IN VCNTY OF FRONT OVER THE KEWEENAW. ALTHOUGH THAT`S POSSIBLE...STILL THINK THE VERY FAVORABLE LAKE ENHANCEMENT CONDITIONS WILL LEAD TO HVY SNOW THERE. HAVE OPTED TO RETAIN WATCH...BUT DID START TIMING EARLY THIS EVENING AND CARRIED WATCH THRU SAT MORNING (MORE ON THAT LATER). FOLLOWING NAM/RUC13 SOLUTIONS...HEAVIER SNOW WILL NOT START OVER ONTONAGON/GOGEBIC COUNTIES UNTIL AFTER MIDNIGHT WHEN WINDS FINALLY SHIFT AROUND TO THE N OR NW. LAKE ENHANCMENT PERIOD WILL BE SHORT FOR GOGEBIC COUNTY AS WINDS BACK W OR EVEN SW FRI. STILL...MIGHT BE ABLE TO PICK UP A QUICK 8 INCHES GIVEN SUCH FAVORABLE LAKE ENHANCEMENT CONDITIONS. AT LEAST A BRIEF PERIOD OF VERY HVY SNOW WILL SWEEP ACROSS MARQUETTE/ALGER/LUCE COUNTIES FRI AS DEEPENING LOW SHIFTS E OF LAKE SUPERIOR AND ARCTIC FRONT HEADS SE. SHOULD EASILY BE AN ADVY TYPE EVENT. ANOTHER SHORTWAVE WILL ROTATE SE INTO THE UPPER LAKES FRI NIGHT AS POLAR VORTEX HEADS S. THIS WILL BRING ANOTHER ROUND OF HVY LAKE ENHANCED SNOW...AND ANOTHER SFC LOW WILL LIKELY DEVELOP OVER ERN LAKE SUPERIOR. THIS WILL RESULT IN CONVERGENT LOW-LEVEL WIND FLOW INTO NW UPPER MI. AIRMASS WILL NOT QUITE BE TOO COLD YET TO PRECLUDE DECENT SNOW GROWTH MICROPHYSICS...SO SNOW ACCUMULATIONS COULD BE HVY...ESPECIALLY CONSIDERING THE LOW-LEVEL CONVERGENCE. DEVELOPMENT OF ERN LAKE SUPERIOR LOW PRES AND STRENGTHENING LAND BREEZE WILL LIKELY RESULT IN WINDS BACKING ENOUGH TO KEEP HEAVIEST LES OFFSHORE OF THE NE FCST AREA FRI NIGHT. OVER THE WEEKEND AND INTO EARLY NEXT WEEK...THE COLDEST AIR OF THE SEASON WILL SETTLE OVER THE AREA. CONSENSUS OF THE LAST FEW DAYS OF ECWMF/GFS RUNS IS THAT 850MB TEMPS WILL BOTTOM OUT IN THE -28 TO -32C RANGE. NOGAPS AND SEVERAL RECENT LOCAL HEMISPHERIC WRF-ARW RUNS HAVE INDICATED 850MB TEMPS A FEW DEGREES LWR. IN ANYCASE...IT IS POSSIBLE THAT A FEW LOCATIONS OVER THE W HALF OF UPPER MI AWAY FROM LAKE SUPERIOR INFLUENCE MAY SEE TEMPS REMAIN BLO ZERO FROM FRI NIGHT UNTIL TUE AFTN. MIN TEMPS WILL DEPEND ON CLOUD COVER/WINDS...BUT -10F TO -20F SHOULD BE THE RULE AWAY FROM LAKE SUPERIOR INFLUENCE. AS FOR LAKE EFFECT...GFS FCST SOUNDINGS INDICATE AIRMASS REMAINING FAIRLY MOIST WITH HIGH INVERSIONS 8KFT TO AS MUCH AS 15KFT. HOWEVER...AN OVERWHELMING NEGATIVE FOR SIGNIFICANT SNOW IS THE VERY COLD AIR WHICH WILL SEVERELY LIMIT SNOWFLAKE GROWTH AND THUS ACCUMULATIONS. IT WILL BE INTERESTING THOUGH TO SEE IF LOCAL CONVERGENCE ZONES STRENGTHENED BY LAND BREEZES WILL BE ABLE TO YIELD HEAVIER LES BANDS AND SIGNIFICANT SNOW IN SUCH A COLD AIRMASS. ALTHOUGH ACCUMULATIONS ARE EXPECTED TO BE FAIRLY LIGHT EACH DAY...DURING SNOW SHOWERS THE AIR WILL BE THICK WITH SMALL SNOWFLAKES WHICH WILL BE EXTREMELY EFFECTIVE AT REDUCING VISIBILITY TO NEAR ZERO. && .MQT WATCHES/WARNINGS/ADVISORIES... LAKE EFFECT SNOW ADVISORY UNTIL NOON EST MIZ001-003. WINTER STORM WATCH THIS EVENING THRU SAT MORNING MIZ001-003. WINTER STORM WATCH LATE TONIGHT THRU FRI AFTN MIZ002-004-009-084. HEAVY FREEZING SPRAY WARNING W HALF OF LAKE SUPERIOR. && $$ ROLFSON