Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 01/19/07

.SYNOPSIS...UPPER LEVEL LOW PRESSURE WILL BRING PERIODIC CHANCES OF SHOWERS THROUGH FRIDAY...MAINLY THIS EVENING AND AGAIN FRIDAY. THERE COULD BE THUNDERSTORMS NEAR THE COAST THIS AFTERNOON AND EVENING. LOCAL STRONG GUSTY WINDS THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES THURSDAY AND FRIDAY AND AGAIN DURING THE EARLY TO MIDDLE PART OF NEXT WEEK. HIGH PRESSURE WILL BRING MOSTLY CLEAR SKIES THIS WEEKEND THROUGH THE MIDDLE OF NEXT WEEK WITH GRADUALLY WARMER DAYS BUT COOL NIGHTS.

&&

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

.SHORT RANGE (TODAY-SATURDAY)...INCREASING CLOUDS IN THE NW AREAS AS A COLD FRONT APPROACHES THE COAST. ACARS SOUNDINGS INDICATED SLY WIND IN THE LOW LEVELS AND STRONG WSW WINDS ALOFT. WEAK GRADIENTS BUT TRENDING OFFSHORE FROM THE N.

THE COLD UPPER LOW IS EXPECTED TO DROP S TO JUST OFF THE SAN DIEGO COAST LATER TODAY AND SW OF SAN DIEGO THU THEN INTO AZ FRI. THIS COULD CAUSE SHOWERS W OF THE MOUNTAINS THIS AFTERNOON AND EVENING WITH A SLIGHT CHANCE IN THE HIGHER MOUNTAINS. THE SHOWERS WILL TAPER OFF AND MAINLY BE CONFINED TO SE AREAS THU. WRAP AROUND MOISTURE COULD BRING ANOTHER SHOT OF SHOWERS FRI. THE SNOW LEVEL WILL GENERALLY BE AROUND 3000-4000 FT BUT COULD BE LOCALLY LOWER. THERE COULD BE THUNDERSTORMS OVER THE COASTAL WATERS AND IN THE COASTAL AREAS THIS AFTERNOON AND EVENING AS THE COLD UPPER LOW MOVES OVER THE RELATIVELY WARM WATERS. PRECIP TOTALS SHOULD GENERALLY BE LIGHT AND LESS THAN A QUARTER OF AN INCH. HOWEVER...THERE COULD BE LOCAL LARGER AMOUNTS IN CONVECTION OR DUE TO OROGRAPHICS. OFFSHORE GRADIENTS AND WINDS ALOFT WILL CAUSE LOCAL GUSTY NE WINDS THU AND FRI...MAINLY THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES WITH WIND ADVISORIES FOR THE MOUNTAINS AND INLAND EMPIRE. WEAKER DRY OFFSHORE FLOW SAT FOR A MOSTLY SUNNY AND WARMER DAY. COOL AT NIGHT AT THE LOWER ELEVATIONS WHEN CLOUDS CLEAR AND WINDS SUBSIDE...BUT NOT AS COLD AS PREVIOUS NIGHTS.

.LONG RANGE (SUNDAY-WEDNESDAY)...DRY OFFSHORE FLOW WILL PREVAIL AND SHOULD BECOME STRONG TUE AND WED. WARMER DAYS IN MOST AREAS. COOL TO COLD AT NIGHT...ESPECIALLY IN AREAS PROTECTED FROM THE WINDS.

&&

.AVIATION... WEAK COLD FRONT PASSING THROUGH THIS AFTERNOON AND EARLY EVENING WILL BRING MULTIPLE CU AND STRATOCU LAYERS AND ISOLATED SHOWERS. LOWEST BASES AROUND 2500 TO 3000 FEET MSL WITH ANOTHER LAYER AROUND 5000 FEET. TOPS SHOULD BE AROUND 10000 FEET MSL. BEHIND THE FRONT...A COOL UNSTABLE AIR MASS WILL FOLLOW KEEPING SCATTERED TO BROKEN CU OVER THE AREA THROUGH THURSDAY WITH ISOLATED SHOWERS TONIGHT.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

WIND ADVISORY FOR THE MOUNTAINS AND INLAND EMPIRE FROM 6 AM THU THROUGH 4 PM FRI. SEE LAXNPWSGX.

$$

PUBLIC...DVA AVIATION...HORTON

.SYNOPSIS...UPPER LEVEL LOW PRESSURE WILL BRING PERIODIC CHANCE OF SHOWERS THROUGH FRIDAY. THERE COULD BE THUNDERSTORMS NEAR THE COAST THIS AFTERNOON AND EVENING. LOCAL STRONG GUSTY WINDS THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES AT THURSDAY AND FRIDAY AND AGAIN DURING THE EARLY TO MIDDLE PART OF NEXT WEEK. HIGH PRESSURE WILL BRING MOSTLY CLEAR SKIES THIS WEEKEND THROUGH THE MIDDLE OF NEXT WEEK WITH GRADUALLY WARMER DAYS BUT COOL NIGHTS.

&&

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

.SHORT RANGE (TODAY-SATURDAY)...INCREASING CLOUDS IN THE NW AREAS AS A COLD FRONT APPROACHES THE COAST. ACARS SOUNDINGS INDICATED WLY WINDS THROUGH MOST OF THE COLUMN...MODERATELY STRONG ALOFT. WEAK GRADIENTS BUT TRENDING OFFSHORE FROM THE N.

THE COLD UPPER LOW IS EXPECTED TO DROP S TO JUST OFF THE SAN DIEGO COAST LATER TODAY AND SW OF SAN DIEGO THU THEN INTO AZ FRI. THIS COULD CAUSE SHOWER OVER AND W OF THE MOUNTAINS THIS AFTERNOON AND EVENING...BECOMING MAINLY CONFINED TO SE AREAS THU AND TAPERING OFF. WRAP AROUND MOISTURE COULD BRING ANOTHER SHOT OF SHOWERS FRI. THE SNOW LEVEL WILL GENERALLY BE AROUND 3000-4000 FT BUT COULD BE LOCALLY LOWER. THERE COULD BE THUNDERSTORMS OVER THE COASTAL WATERS AND IN THE COASTAL AREAS THIS AFTERNOON AND EVENING AS THE COLD UPPER LOW MOVES OVER THE RELATIVELY WARM WATERS. PRECIP TOTALS SHOULD GENERALLY BE LIGHT AND LESS THAN A QUARTER OF AN INCH. HOWEVER...THERE COULD BE LOCAL LARGER AMOUNTS IN CONVECTION OR OROGRAPHICS. OFFSHORE GRADIENTS AND WINDS ALOFT WILL CAUSE LOCAL GUSTY NE WINDS THU AND FRI...MAINLY THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES WITH WIND ADVISORIES FOR THE MOUNTAINS AND INLAND EMPIRE. WEAKER DRY OFFSHORE FLOW SAT FOR A MOSTLY SUNNY AND WARMER DAY. COOL AT NIGHT AT THE LOWER ELEVATIONS BUT NOT AS COLD AS PREVIOUS NIGHTS.

.LONG RANGE (SUNDAY-WEDNESDAY)...DRY OFFSHORE FLOW WILL PREVAIL AND SHOULD BECOME STRONG TUE AND WED. WARMER DAYS IN MOST AREAS. COOL TO COLD AT NIGHT...ESPECIALLY IN AREAS PROTECTED FROM THE WINDS.

&&

.AVIATION... MARINE LAYER WAS QUITE SHALLOW THIS MORNING BASED ON THE 12Z NKX SOUNDING. SOME STRATOCU WAS DEVELOPING OVER THE COASTAL WATERS AHEAD OF A WEAK COLD FRONT APPROACHING FROM THE WEST. EXPECT THE STRATOCU TO CONTINUE TO DEVELOP AND FILL IN WEST OF THE MOUNTAINS THROUGH THE AFTERNOON. BASED ON UPSTREAM METARS...BASES OF THE LOWEST LAYER WAS AROUND 3000 TO 3500 FEET WITH ADDITIONAL LAYERS AROUND 5000 AND 8000 FEET. MOST OF THESE LAYERS WERE BROKEN. EXPECT BROKEN CEILINGS AT MOST AIRPORTS WEST OF THE MOUNTAINS THROUGH TONIGHT WITH ISOLATED SHOWERS. BASES SHOULD REMAIN ABOVE 2500 TO 3000 FEET MSL WITH TOPS OF THE LAYERS AROUND 9000 FEET MSL. VISIBILITIES SHOULD REMAIN UNRESTRICTED EXCEPT FOR SOME MVFR VISIBILITIES IN ISOLATED SHOWERS THROUGH THE NIGHT.

EXPECT CLOUDS TO SCATTER OUT ON THURSDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

WIND ADVISORY FOR THE MOUNTAINS AND INLAND EMPIRE FROM 6 AM THU THROUGH 4 PM FRI. SEE LAXNPWSGX.

$$

PUBLIC...DVA AVIATION...HORTON

.DISCUSSION FOR AFTERNOON GRIDS/ZONES... ZONE OF SHALLOW...BELOW 2500 FT..WARM ADVECTION CLOUDS ARE SURPRISINGLY EFFICIENT SNOW PRODUCERS TODAY. SCTD LIGHT SNOW SHOULD DECREASE WITH SUNSET BUT RESIDUAL LOW CLOUDS AND ADVANCING CLOUD DECK ACROSS MO AND SRN IOWA WILL MAINTAIN CLOUDY CONDS OVER THE FCST AREA THIS EVENING. ASSOCIATED SHORT WAVE WITH THIS SECOND BATCH EJECTING FROM CENTRAL NEBRASKA ATTM. WHILE LOW LEVEL MOISTURE IS LIMITED SYSTEM IS TRYING TO TAP THE BROAD STREAM OF TROPICAL CLOUDS RUNNING FROM WEST TEXAS TO CENTRAL ATLANTIC STATES. WHILE THIS PROCESS WILL BE LIMITED..MID LEVEL ISENTROPIC LIFT WITH APPROACHING SYSTEM SHOULD KICK OFF SCTD LIGHT SNOW OVER NRN IL LATER TONIGHT AND THUR MORNING. ANY SNOW AMTS SHOULD BE TRIVIAL BUT SITUATION WILL BE MONITORED.

ALL MODELS..GFS..WRF..EWCMF AND ENSEMBLES IN LINE MOVING THIS FIRST SHORT WAVE PAST LATER TONIGHT. SECOND SYSTEM EVIDENT ACROSS CENTRAL MONTANA THIS AFTERNOON WILL TRAIL THE NEBRASKA WAVE RAPDILY THROUGH REGION THURSDAY NIGHT AND EARLY FRIDAY WITH ANOTHER CHC FOR LIGHT SNOW. THIS SYSTEM WILL USHER IN THE NEXT ROUND OF COLDER AIR FOR THE FIRST PART OF THE WEEKEND.

WE TRY THIS AGAIN LATER SUNDAY AND MONDAY AS A MORE POTENT SHORT WAVE WORKS OUT OF THE SRN ROCKIES INTO THE PLAINS. BY THEN THE RESIDUAL SFC RIDGE ALONG THE GULF COAST WILL HAVE DISSIPATED WITH MOISTURE RETURNING INTO THE LOWER MISS VLY. EARLIER GFS RUNS SUGGESTED THE CYCLONE EARLY NEXT WEEK WOULD BYPASS THE MIDWEST TO THE SOUTH BUT LATER RUNS SUGGEST A RESIDUAL BAROCLINIC ZONE...FRONT...WILL LINGER ACROSS THE MIDWEST AS COLDER AIR BUILDS OVER WESTERN CANADA AND SLOWLY EDGES SEWD. THIS PUTS FCST FOR SUN-MON IN THE LOW CONFIDENCE CAMP. AT THIS POINT WILL HOLD ONTO THREAT OF SNOW FOR THAT TIME PERIOD..SUN INTO EARLY TUE. IN SHORT TERM COLDEST ARCTIC AIR OF PAST TWO DAYS WILL ABATE OVER NEXT 24HRS BEFORE ANOTHER BATCH ARRIVES LATER FRIDAY. TEMPS TONIGHT SHOULD HOLD STEADY AND WL LKLY RISE LATER IN THE NIGHT AS SWLYS PICK UP. KML

&&

.AVIATION DISCUSSION

FOR 18Z TAFS...MAIN CONCERN IS SHALLOW LAYER OF STRATUS AND LIGHT SNOW MOVING INTO THE AREA THIS AFTERNOON. LOOKING AT SOUNDING FROM ILX AND ALSO ACARS DATA...INVERSION IS VERY SHALLOW. MOISTURE GOES UP TO ABOUT 1200 FEET...THEN VERY DRY ABOVE. SO WOULD EXPECT SOME MIXING OUT THIS AFTERNOON...THOUGH IT MIGHT BE DIFFICULT TO MIX MUCH WITH SHALLOW POLAR AIRMASS. LOOKING AT OBS AND RADAR IT APPEARS THAT THE SNOW IS FALLING MAINLY ON THE FRONT END OF THE STRATUS DECK. VISIBILITIES BRIEFLY IFR DOWN TO 2 MILES OR LESS AT A COUPLE SPOTS. WILL HAVE ABOUT A 2-3 HOUR WINDOW OF VISIBILITY FLUCTUATING BETWEEN 2 TO 5 MILES. WITH COLD DRY AIRMASS SNOW IS VERY LIGHT WITH VERY LITTLE WATER CONTENT. FLURRIES WILL PROBABLY NOT EVEN WET THE PAVEMENT IN MOST SPOTS. BY MID AFTERNOON EXPECT VISIBILITY TO IMPROVE TO 5 MILES OR BETTER. STRATUS EXTENDS ALL THE WAY THROUGH SOUTHERN ILLINOIS AND WITH SSW WINDS AND STRONG LOW LEVEL INVERSION...EXPECT STRATUS TO STAY WITH US FOR THE REST OF TODAY AND TONIGHT.

FOR LATER TONIGHT...UPPER SHORT WAVE TROF MOVING RAPIDLY OUT OF THE ROCKIES. SHOULD BE SUFFICIENT ISENTROPIC LIFT TO SQUEEZE OUT ANOTHER ROUND OF LIGHT SNOW BY AROUND DAYBREAK. WILL INTRODUCE A PROB30 GROUP FOR THE MORNING. DETAILS CAN BE REFINED IN LATER FORECASTS.

SSW WINDS AROUND 10 KNOTS THIS AFTERNOON. DESPITE INCREASING PRESSURE GRADIENT TONIGHT...DECOUPLING OF ATMOSPHERE WITH STRONG SHALLOW INVERSION SHOULD KEEP SURFACE WINDS AT OR BELOW 10 KNOTS OVERNIGHT. WINDS SHOULD PICK UP SOME DURING THE DAY THURSDAY WITH SOME GUSTINESS.

ALLSOPP

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...SMALL CRAFT ADVISORY THROUGH TUESDAY NIGHT.

&&

$$

.DISCUSSION FOR UPDATED MORNING GRIDS/ZONES... VERY SHALLOW BUT EFFECTIVE ZONE OF WARM ADVECTION CREATING STRATUS BAND AND SOME LIGHT SNOW OVER CENTRAL ILL AND HAS NOW MOVED AS FAR N AS I80 IN LASALLE CO. WINDS BELOW 10THSD FT ARE ALMOST DUE SOUTH AND EXPECT THESE CLOUS TO CONTINUE NWD DURING THE AFTERNOON BUT SLOWLY VEER TO THE WEST. ACARS SOUNDINGS FROM BMI INDICATE ARIMASS IS VERY DRY ABOVE THIS SHALLOW CLOUD DECK AND EXPECT AFTERNOON MXING TO ALSO HALP THIN CLOUDS A BIT. NO CHANGES MADE BEYOND EVENING WITH ANOTHER THREAT OF LIGHT SNOW FROM A MORE SYNOPTIC FEATURE LATER TONIGHT AND PART OF THURSDAY. KML

PREVIOUS DISCUSSION 345 AM CST

FOR THE VERY NEAR TERM...THE LAKE EFFECT SNOW POTENTIAL HAS ENDED ACROSS NWRN INDIANA AND THE FOCUS HAS SHIFTED TO MORNING LOW TEMPS AND THE PESKY PATCH OF STRATUS WORKING ITS WAY NWD THROUGH CNTRL IL. LOCATIONS OVR NCNTRL IL HAVE DROPPED TO 0F AND...UNDER CLEAR SKIES...LIGHT WINDS AND A LITTLE SNOW COVER TO AID RADIATIONAL COOLING...TEMPS SHOULD CONTINUE TO DROP A FEW MORE DEGREES BY SUNRISE. LATEST SATELLITE IMAGERY SHOWS A PATCH OF LOW STRATUS WORKING ITS WAY NWD THRU CNTRL IL. BASED ON THE LATEST OBSERVED TRENDS...MODEL GUIDANCE IS OF LITTLE USE HERE...DO NOT EXPECT THE CLOUDINESS TO GET ANY FARTHER NORTH THAN THE ILLINOIS/KANKAKEE RIVERS. OTHERWISE THE REMAINDER OF THE DAY IS STILL EXPECTED TO BE MOSTLY SUNNY AND COOL.

THE ONLY SGFNT CHANGE TO THE REMAINDER OF THE SHORT TERM FORECAST HAS BEEN TO INTRODUCE CHANCE POPS FOR SOME LIGHT SNOW OVER THE NWRN 2/3 OF THE CWA FOR THE EARLY MORNING HOURS THURSDAY MORNING. THE NAM AND GFS BOTH INITIALIZE A WEAK VORT MAX OVR NERN COLORADO THIS MORNING AND QUICKLY TRACK IT ENEWD ACROSS THE CENTRAL PLAINS AND OVR NWRN IL/SWRN WI BY THURSDAY MORNING. WHILE FORCING ASSD WITH THIS WAVE IS SOMEWHAT MARGINAL...FEEL THAT THE RETURN FLOW AROUND THE BACK SIDE OF THE EXITING SFC RIDGE SHOULD ALLOW FOR ADEQUATE MOISTURE TRANSPORT TO SUPPORT AT LEAST A DUSTING OF SNOW... PARTICULARLY FOR THE NWRN PORTIONS OF THE CWA.

BEYOND THURSDAY...HAVE NOT MADE ANY SGFNT CHANGES TO THE GOING FORECAST. STILL EXPECTING A LITTLE MORE LIGHT SNOW FOR THURSDAY NIGHT INTO FRIDAY MORNING AS THE NEXT NRN STREAM SHORT WAVE DROPS OUT OF THE NRN ROCKIES AND TRACKS ACROSS NRN IL. NOT A WHOLE LOT OF MOISTURE TO WORK WITH...SO HAVE LIMITED SNOWFALL AMOUNTS IN THE GRIDS TO ONLY A FEW TENTHS OF AN INCH. TEMPS SHOULD REMAIN AROUND SEASONAL NORMALS AS THE SYNOPTIC SCALE PATTERN IS DOMINATED BY BROAD TROUGHING OVER THE CNTRL AND ERN CONUS WITH NWLY FLOW ALOFT.

KREIN

&&

.AVIATION DISCUSSION

FOR 18Z TAFS...MAIN CONCERN IS SHALLOW LAYER OF STRATUS AND LIGHT SNOW MOVING INTO THE AREA THIS AFTERNOON. LOOKING AT SOUNDING FROM ILX AND ALSO ACARS DATA...INVERSION IS VERY SHALLOW. MOISTURE GOES UP TO ABOUT 1200 FEET...THEN VERY DRY ABOVE. SO WOULD EXPECT SOME MIXING OUT THIS AFTERNOON...THOUGH IT MIGHT BE DIFFICULT TO MIX MUCH WITH SHALLOW POLAR AIRMASS. LOOKING AT OBS AND RADAR IT APPEARS THAT THE SNOW IS FALLING MAINLY ON THE FRONT END OF THE STRATUS DECK. VISIBILITIES BRIEFLY IFR DOWN TO 2 MILES OR LESS AT A COUPLE SPOTS. WILL HAVE ABOUT A 2-3 HOUR WINDOW OF VISIBILITY FLUCTUATING BETWEEN 2 TO 5 MILES. WITH COLD DRY AIRMASS SNOW IS VERY LIGHT WITH VERY LITTLE WATER CONTENT. FLURRIES WILL PROBABLY NOT EVEN WET THE PAVEMENT IN MOST SPOTS. BY MID AFTERNOON EXPECT VISIBILITY TO IMPROVE TO 5 MILES OR BETTER. STRATUS EXTENDS ALL THE WAY THROUGH SOUTHERN ILLINOIS AND WITH SSW WINDS AND STRONG LOW LEVEL INVERSION...EXPECT STRATUS TO STAY WITH US FOR THE REST OF TODAY AND TONIGHT.

FOR LATER TONIGHT...UPPER SHORT WAVE TROF MOVING RAPIDLY OUT OF THE ROCKIES. SHOULD BE SUFFICIENT ISENTROPIC LIFT TO SQUEEZE OUT ANOTHER ROUND OF LIGHT SNOW BY AROUND DAYBREAK. WILL INTRODUCE A PROB30 GROUP FOR THE MORNING. DETAILS CAN BE REFINED IN LATER FORECASTS.

SSW WINDS AROUND 10 KNOTS THIS AFTERNOON. DESPITE INCREASING PRESSURE GRADIENT TONIGHT...DECOUPLING OF ATMOSPHERE WITH STRONG SHALLOW INVERSION SHOULD KEEP SURFACE WINDS AT OR BELOW 10 KNOTS OVERNIGHT. WINDS SHOULD PICK UP SOME DURING THE DAY THURSDAY WITH SOME GUSTINESS.

ALLSOPP

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...SMALL CRAFT ADVISORY THROUGH TUESDAY NIGHT.

&&

$$

.DISCUSSION FOR UPDATED MORNING GRIDS/ZONES... VERY SHALLOW BUT EFFECTIVE ZONE OF WARM ADVECTION CREATING STRATUS BAND AND SOME LIGHT SNOW OVER CENTRAL ILL AND HAS NOW MOVED AS FAR N AS I80 IN LASALLE CO. WINDS BELOW 10THSD FT ARE ALMOST DUE SOUTH AND EXPECT THESE CLOUS TO CONTINUE NWD DURING THE AFTERNOON BUT SLOWLY VEER TO THE WEST. ACARS SOUNDINGS FROM BMI INDICATE ARIMASS IS VERY DRY ABOVE THIS SHALLOW CLOUD DECK AND EXPECT AFTERNOON MXING TO ALSO HALP THIN CLOUDS A BIT. NO CHANGES MADE BEYOND EVENING WITH ANOTHER THREAT OF LIGHT SNOW FROM A MORE SYNOPTIC FEATURE LATER TONIGHT AND PART OF THURSDAY. KML

PREVIOUS DISCUSSION 345 AM CST

FOR THE VERY NEAR TERM...THE LAKE EFFECT SNOW POTENTIAL HAS ENDED ACROSS NWRN INDIANA AND THE FOCUS HAS SHIFTED TO MORNING LOW TEMPS AND THE PESKY PATCH OF STRATUS WORKING ITS WAY NWD THROUGH CNTRL IL. LOCATIONS OVR NCNTRL IL HAVE DROPPED TO 0F AND...UNDER CLEAR SKIES...LIGHT WINDS AND A LITTLE SNOW COVER TO AID RADIATIONAL COOLING...TEMPS SHOULD CONTINUE TO DROP A FEW MORE DEGREES BY SUNRISE. LATEST SATELLITE IMAGERY SHOWS A PATCH OF LOW STRATUS WORKING ITS WAY NWD THRU CNTRL IL. BASED ON THE LATEST OBSERVED TRENDS...MODEL GUIDANCE IS OF LITTLE USE HERE...DO NOT EXPECT THE CLOUDINESS TO GET ANY FARTHER NORTH THAN THE ILLINOIS/KANKAKEE RIVERS. OTHERWISE THE REMAINDER OF THE DAY IS STILL EXPECTED TO BE MOSTLY SUNNY AND COOL.

THE ONLY SGFNT CHANGE TO THE REMAINDER OF THE SHORT TERM FORECAST HAS BEEN TO INTRODUCE CHANCE POPS FOR SOME LIGHT SNOW OVER THE NWRN 2/3 OF THE CWA FOR THE EARLY MORNING HOURS THURSDAY MORNING. THE NAM AND GFS BOTH INITIALIZE A WEAK VORT MAX OVR NERN COLORADO THIS MORNING AND QUICKLY TRACK IT ENEWD ACROSS THE CENTRAL PLAINS AND OVR NWRN IL/SWRN WI BY THURSDAY MORNING. WHILE FORCING ASSD WITH THIS WAVE IS SOMEWHAT MARGINAL...FEEL THAT THE RETURN FLOW AROUND THE BACK SIDE OF THE EXITING SFC RIDGE SHOULD ALLOW FOR ADEQUATE MOISTURE TRANSPORT TO SUPPORT AT LEAST A DUSTING OF SNOW... PARTICULARLY FOR THE NWRN PORTIONS OF THE CWA.

BEYOND THURSDAY...HAVE NOT MADE ANY SGFNT CHANGES TO THE GOING FORECAST. STILL EXPECTING A LITTLE MORE LIGHT SNOW FOR THURSDAY NIGHT INTO FRIDAY MORNING AS THE NEXT NRN STREAM SHORT WAVE DROPS OUT OF THE NRN ROCKIES AND TRACKS ACROSS NRN IL. NOT A WHOLE LOT OF MOISTURE TO WORK WITH...SO HAVE LIMITED SNOWFALL AMOUNTS IN THE GRIDS TO ONLY A FEW TENTHS OF AN INCH. TEMPS SHOULD REMAIN AROUND SEASONAL NORMALS AS THE SYNOPTIC SCALE PATTERN IS DOMINATED BY BROAD TROUGHING OVER THE CNTRL AND ERN CONUS WITH NWLY FLOW ALOFT.

KREIN

&&

.AVIATION DISCUSSION REGARDING 12Z TAFS...

MAIN CONCERN THIS MRNG REGARDS FCST SKY COND. CURRENT LLVL IR SATLT IMAGERY SHOWS AREA OF MAINLY LOWER END MVFR CIGS OVR CNTRL/SRN IL WITH THE LEADING EDGE OF THIS AREA MOVG NWD. THIS IS IN RESPONSE TO RESIDUAL MOIST POCKET JUST ABV SFC INVERSION THAT HAS BEEN CIRCULATING BACK NWD/NWWD ON BACK SIDE OF RETREATING HI PRES CENTER OVR OH VLY. SATLT LOOPS HAVE ALSO SHOWN A TENDENCY TOWARD EROSION OF LEADING EDGE OF THIS DECK AS IT MOVES TWD NRN-E CNTRL IL. THIS MAKES ANY TIMING VERY TENUOUS. HAVE JUST GONE WITH ARRIVAL INTO NRN IL/NWRN IND ARND NOON CST...AND WILL JUST GO WITH SCT CLOUDS GIVEN THAT THIS DECK IS IN A VERY THIN LYR BASED ON SATLT IMAGERY. WILL BE ABLE TO TELL GET MUCH MORE DETAIL ABOUT THIS AREA WHEN 12Z SOUNDING DATA BECOMES AVBL. GIVEN INFORMATION AT HAND...EXPECT SOME OF THIS MOISTURE TO DRIFT NWD INTO TERMINAL AREA...BUT GIVEN TIME OF DAY AND INCRSG DRY SWLY FLOW ALF LATER THIS MRNG...WILL HOLD OFF ON ANY MENTION OF CIGS.

TNGT INCRSG LLVL SSWLY FLOW IS FCST TO MOISTEN UP SO WILL BRING LOW RANGE MVFR CIGS IN LATE THIS EVENING AND OVERNIGHT.

NO VIS RESTRICTIONS UNTIL LLVLS MOISTEN UP LATE TNGT. WITH OVC CONDS EXPECTED WILL ONLY GO WITH MVFR VIS IN LGT FOG.

WINDS HAVE TURNED SWLY AS HI PRES IS NOW OFF TO E. SPEEDS TO INCRS TDY TO 10-15 KT RANGE. STG LLVL INVERSION SHOULD PRECLUDE HIER SPPEDS OR ANY GUSTINESS.

MERZLOCK

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...SMALL CRAFT ADVISORY THROUGH TUESDAY NIGHT.

&&

$$

.DISCUSSION FOR AFTERNOON GRIDS/ZONES... 310 PM CST

LAKE EFFECT SNOW TRENDS MAIN SHORT TERM FOCUS FOR FIRST FEW HOURS TONIGHT.

WEAK VORT/POS TILT UPPER TROF AXIS MOVG EAST OF FCST AREA THIS AFTN. WEAKENING SFC PRES GRADIENT AS SFC HIGH APPRCHG FROM WEST...WITH MODEL TSECTS DEPICTING STRONG AND DEEP SUBSIDENCE DVLPG ATTM. RECENT ACARS SOUNDINGS OUT OF KORD SHOW DIRECTIONAL SHEAR INCREASING THRU ABOUT 750 HPA ALONG WITH DECREASING WIND SPEEDS...AND THIS LACK OF ORGANIZATION RESULTING IN DVLPMNT OF ONE TIME SINGLE BAND LES EVENT NOW TAKING ON MORE OF A THERMALLY FORCED MESO LOW STRUCTURE AS IT FADES. RADAR AND VIS SATELLITE IMGRY FROM LAST HOUR OR SO VERY IMPRESSIVE WITH THIS TRANSITION...LOOKING LIKE A MINI SNOW HURRICANE COMPLETE WITH AN EYE AT 1951Z. IT BEGS TO BE NAMED. WILL HAVE TO CONTEND WITH SNOW SHOWERS ACROSS NORTHERN LAKE/PORTER COUNTIES FOR REMAINDER OF AFTN HOURS AS THIS LES BAND CONTINUES TO DECAY...THOUGH ANTICIPATE THAT COMBINATION OF VERY DRY LOW LVLS...STRENGTHENING AND LOWERING SUBSIDENCE INVERSION AND LOSS OF LLVL CONVERGENCE WILL ALLOW PCPN TO COME TO AN END BY EARLY EVENING.

WITH SFC RIDGE BUILDING ACROSS FCST AREA TNGT...AND SNOW COVER IN PLACE MOST AREAS...SET UP FOR STRONG RADIATIONAL COOLING. LLVL PARCEL TRAJECTORIES FROM NERN IA...WHERE TEMPS DIPPED BLO ZERO THIS MRNG. WILL CONTINUE TO UNDERCUT ALL GUIDANCE NUMBERS FOR MINS OVRNGT...WITH CURRENT GRIDS ACTUALLY LOOKING QUITE GOOD RANGING FROM AROUND -3 NW WHERE DEEPEST SNOW COVER EXISTS...TO NEAR 10 ABOVE SOUTHEAST WHERE SNOW COVER MINIMAL.

MID LVL S/WV RDG MOVS ACROSS FCST AREA WED MORNING...WITH TSECTS AND FCST SOUNDINGS CONTINUING TO DEPICT VERY DRY AMS. SHOULD SEE PLENTY OF SUNSHINE...WITH A LITTLE REBOUND IN TEMPS AS WAA DVLPS IN SWLY FLOW ON BACK SIDE OF SFC RIDGE DURG AFTN. S/WV TROF THEN MOVG OUT OF HIGH PLAINS WED NGT EXPCTD TO GENERATE SOME MID CLOUD COVER AFTER MIDNIGHT AS IT APPROACHES UPPER MS VLY TOWARD MRNG. SWLY LLVL FLOW 10-15 MPH SHOULD HELP TEMPS KEEP FROM DROPPING TOO FAR WED EVENING...THOUGH HAVE STILL GONE A BIT BLO COLDEST FWC NUMBERS.

S/WV MOVES ACROSS FCST AREA THURSDAY...WITH MODELS IN AGREEMENT IN DROPPING SECOND WAVE IN BY LATE IN THE DAY. TSECTS INDICATE LOW LEVELS MOISTEN DURG THE AFTN HOURS AS LLVL COLD ADVECTION STARTS TO KICK IN...THOUGH MOISTURE FAIRLY SHALLOW AND LIFT FOCUSED MORE IN MID LEVELS. WRF/GFS DO ATTEMPT TO KICK OUT SOME VERY LIGHT QPF MAINLY NORTH OF THE FA HOWEVER...SO WILL MAINTAIN CHC OF FLURRIES DURG MAX LLVL CAA/SATURATION THURSDAY NIGHT.

FOR REMAINDER OF FCST...INCREASING SPREAD IN ENSEMBLE SOLUTIONS WITH PATTERN HEADING INTO NEXT WEEKEND. OVERALL TREND SUPPORTS MORE OF A TROUGHINESS ACROSS THE AREA...WITH PERHAPS BEST FOCUS FOR ORGANIZED PCPN ARRIVING SUN/SUN NGT. HPC FAVORING ECMWF/GEM HANDLING OF LATER PERIODS AND WILL NOT ARGUE AT THIS POINT. THUS WILL HAVE CHC LGT SNOW SUN/SUN NGT...THEN CHC SNOW SHOWERS/FLURRIES MONDAY/MON NGT. TEMPS REMAIN RELATIVELY COLD THRU PERIOD...ESPECIALLY IN WAKE OF COLD FRONT THURSDAY NIGHT/FRIDAY...AND WITH PASSAGE OF NEXT SFC HIGH PRES RIDGE FRI NGT/EARLY SAT.

RATZER

&&

.AVIATION... 1045 PM CST

RE 06Z TAFORS...SFC RDG CENTERED OVR LWR MO AMD MID MS VALLEYS LATE THIS EVE CONTS TO SETTLE SEWRD TO OH VALLEY OVRNITE. WITH WK GRADIENT...CLR SKY AND SNO COVER STG SFC BASED INVERSION IN PLACE. PRES GRADIENT INCREASES AHEAD OF SFC TROF MOVG E ACROSS THE NRN PLAINS ON WED BUT SFC TO REMAIN DECOUPLED FM INCREASED WINDS ALFT TIL MID TO LATE MORNING DUE TO INVERSION SLO TO MIX OUT. WITH RIDGE SFC AND ALFT SKC TO PREVAIL THRU REST OF NIGHT AND DAYTIME WED. BY WED EVE CI SPREADS OVRHEAD ON SW UPR FLO THICKENING TO A MID DECK WITH STG WAA AHEAD OF SHORT WAVE TROF APPROACHES MS VALLEY DURG THE EVE.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...SMALL CRAFT ADVISORY THROUGH TUESDAY NIGHT.

&&

$$

.UPDATE...FOR 12Z TAF CYCLE BELOW

&&

.PREV DISCUSSION... /ISSUED 330 AM CST WED JAN 17 2007/

DISCUSSION... TEMPERATURES HAVE BEEN ON THE RISE ACROSS ALL BUT IN WC WISCONSIN AS SOUTHERLY WINDS HAVE BEEN ON THE INCREASE BETWEEN COLD DEPARTING HIGH PRESSURE AND STRONG SURFACE LOW TRACKING ACROSS CENTRAL CANADA. WITH PUSH OF WARMER AIR AND FULL SUN TEMPERATURES SHOULD REBOUND AT LEAST INTO THE MID 20S ACROSS THE AREA. RATHER BREEZY BUT FEEL THAT ENUF OF AN INVERSION WILL REMAIN IN PLACE TO DAMPEN WINDS ENUF TO KEEP STRONG MIXING LIMITED. SHORTWAVE BEING EJECTED OUT OF THE 4-CORNERS BY STRONG TROF DIGGING ALONG CALIFORNIA COAST WILL BRING SOME UVV MAINLY IN SC MN AND WC WISCONSIN TONIGHT. THERE IS SOME SATURATION ON 290K SURFACE AND GFS PUMPS OUT SMALL QPF...LOWER LEVELS REMAIN DRY SO WON`T INTRODUCE THE 20% POPS BACK IN FORECAST. STRONGER WAVE MOVES THRU AREA ON THURSDAY. BUMPED UP POPS JUST A BIT ACROSS NORTHERN CWA AS RATHER STRONG DYNAMICS MOVE THRU. PASSAGE OF COLD FRONT WILL BRING A RETURN TO COOLER TEMPERATURES FOR A DAY OR TWO BEFORE APPROACH OF NEXT CLIPPER ON THE WEEKEND. NEW GFS IS TRENDING TOWARD A BIT MORE SOUTHERLY TRACK OF SUNDAY CLIPPER THAN EARLIER RUNS...MORE TOWARD SOUTHERN OR CENTRAL MN. &&

.AVIATION...FOR 12Z TAF CYCLE CONCERN FOR AVIATION ARE WINDS TODAY WHICH WILL BECOME GUSTY. A FAIRLY IMPRESSIVE PRESSURE GRADIENT WILL MOVE OVER REGION AHEAD OF SFC TROUGH. THE MIX DOWN POTENTIAL FOR GUSTS IS NOT THAT GREAT OVER SNOW COVERED AREAS NEAR MSP AND WI TAF SITES. WITH WARM AIR ADVECTION ALOFT OVER THESE GROUNDS THIS HAS CREATED QUITE THE INVERSION AS SEEN ON LATEST TAMDAR SOUNDINGS. MUCH BETTER CHANCE AT RWF WITH GUSTS ALREADY OF 30KT BEING SEEN ON BUFFALO RIDGE. NO MATTER WHAT...WITH 45-50KT SRLY FLOW AT 2K FT THERE WILL BE WIND SHEAR AS WELL ACROSS ALL OF TAF SITES. HAVE NOT INDICATED ANY SIGNIFICANT LLWS IN TAFS DUE TO HIGH SUSTAINED SURFACE SPEEDS. SKY CLEAR OR JUST SOME HIGH CIRRUS IS ALL THROUGH MID EVENING BEFORE SOME MID LEVEL CLOUDS COME IN. 06Z MODEL RUNS CONTINUE TO ADVERTISE MOIST MID-LEVEL UPGLIDE INTO SRN MN AND SW WI THIS EVE AND OVERNIGHT. LOW LEVEL DRY AIR STILL LOOKS ABUNDANT ENOUGH TO PREVENT ANY PROB GROUPS AT THIS TIME. BETTER LIGHT SNOW CHANCES ARRIVE THURS ACROSS THE TAF SITES.

&&

.MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. &&

$$

BAP/MTF

.SHORT TERM...TODAY THROUGH SATURDAY...UPPER PATTERN OVER STATE WILL SHIFT FROM NW FLOW TO A MORE WESTERLY PATTERN FOR SATURDAY AS RIDGE BUILDS IN. ONE MORE DISTURBANCE DROPPING SOUTHEAST. SEEN ON IMAGERY OVER EASTERN ND. BOTH MODELS BRING IT THROUGH STATE THIS AFTERNOON. FAVORABLE QG FORCING BETWEEN 5K AND 3K WITH BEST OMEGA OVER NORTHEAST CWA. FORECAST QUESTION IS PCPN CHANCE WITH FEATURE. FEATURE HAS MUCH LESS MOISTURE TO WORK WITH THAN PREVIOUS WAVES. IMAGERY SHOWING LOW CLOUDS OVER WI ERODING WITH CLEARING INTO WESTERN WI. SOME MID CLOUDS WITH WAVE MOVING SOUTHEAST. MODELS BOTH DEPICT LOW CLOUDS CONTINUING TO SCOUR OUT OVER THE WEST. HAVE TRIMMED BACK ON PCPN CHANCE TODAY...WITH FLURRIES SOUTH AND WEST AS SHORT WAVE PASSES THROUGH...STAYING WITH CHANCE POPS FURTHER NORTH WHERE MOISTURE BETTER. HAVE STAYED WITH MOSTLY CLOUDY WORDING...THOUGH SOME SUNNY BREAKS MORE THAN LIKELY...ESPECIALLY OVER CENTRAL WI.

LAKE EFFECT NOT OVERLY IMPRESSIVE AT THIS TIME WITH WINDS MORE WESTERLY AS DEPICTED IN EARLIER RUNS. LATE EVENING TAMDAR SOUNDINGS INDICATED INVERSIONS NR 6K FEET...THOUGH MODELS BOTH INDICATE THIS TO DROP TO NEAR 3K FEET LATE THIS AFTERNOON. WILL STAY WITH CURRENT TRENDS AND GO WITH MORE SCATTERED WORDING AND LIMIT ADDITIONAL ACCUMULATIONS TO AROUND AN INCH.

RIDGE TO BUILD IN TONIGHT AND SATURDAY WITH FURTHER CLEARING TREND. GUSTY WINDS/CAA PATTERN HAVE KEPT TEMPS UP OVER PREVIOUS THINKING. CONTINUED CAA TODAY WILL LIMIT DIURNAL RISE...WITH MANY MAXES LIKELY SEEN EARLY THIS MORNING. LIGHT WINDS OVERNIGHT WITH SFC HIGHS SHOULD ALLOW TEMPS TO FALL SIGNIFICANTLY...BELOW GUIDANCE TREND FROM PREVIOUS SHIFT CONTINUED.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY.

SNOW ASSOCIATED WITH A SURFACE SYSTEM AND MID LEVEL SHORT WAVE LIFTING NORTHEAST OUT OF THE PLAINS SHOULD REACH THE FORECAST AREA ON SUNDAY. NAM/WRF AND GFS KEEP SATURDAY NIGHT DRY SINCE IT IS LIKELY TO TAKE THAT LONG FOR SIGNIFICANT MOISTURE TO ARRIVE. HAVE LIKELY POPS GOING FOR MOST OF THE AREA BY AFTERNOON...BUT DID LOWER POPS INTO THE CHANCE CATEGORY OVER THE NORTH WHERE MOISTURE IS MORE LIMITED. LOOKS LIKE ABOUT 2 TO 3 INCHES ACROSS THE SOUTHERN HALF OF THE AREA WITH 1 TO 2 INCHES POSSIBLE OVER THE NORTH. THIS FITS FAIRLY WELL WITH SURROUNDING SNOWFALL GRIDS AND HPC GUIDANCE. A FRONTAL BOUNDARY MOVING SOUTH INTO THE STATE ON MONDAY WILL KEEP CHANCE POPS IN THROUGH 00Z TUESDAY. LEFT CHANCE POPS FOR SNOW SHOWERS IN THE NORTH MONDAY NIGHT...BUT WIND DIRECTION NOT REALLY FAVORABLE FOR LES. JUST WENT WITH SCATTERED FLURRIES ACROSS THE REST OF THE AREA. TUESDAY LOOKS LIKE A DRY DAY AS HIGH PRESSURE SLIDES ACROSS THE REGION. BUT AN APPROACHING SYSTEM WILL BRING A CHANCE OF SNOW BACK TO THE WESTERN HALF OF THE AREA TUESDAY NIGHT. &&

.GRB WATCHES/WARNINGS/ADVISORIES... NONE.

$$ TE/MG WEATHER.GOV/GREENBAY

.SYNOPSIS AND SHORT TERM (TONIGHT)...

UPPER LEVEL TROUGH WITH COLD AIRMASS SETTLING ACROSS UPR GREAT LAKES. H85 TEMPS AROUND -20C HAVE ARRIVED. THE COLD AIR ALONG WITH SHORTWAVES ROTATING ON WEST PERIPHERY OF TROUGH INTENSIFIED LK EFFECT SNOW BANDS BOTH LAST NIGHT AND AGAIN LATE THIS MORNING THROUGH THIS AFTN. IR SATELLITE LOOP SHOWS BACK EDGE OF DEEPER MOISTURE AND WEAK LIFT PRESSING INTO WESTERN LK SUPERIOR. 12Z RAOB FM KAPX AND 16Z TAMDAR SOUNDING FM KSAW IN MODIFIED AIR DOWNSTREAM OF LK SUPERIOR SHOWED INVERSION HEIGHTS AROUND 750MB WITH TEMPS AT TOP OF INVERSION AROUND -18C (KAPX) AND -24C (KSAW). UPSTREAM IN WAKE OF MOISTURE/SHORTWAVE...A 17Z TAMDAR FM KINL SHOWED INVERSION LOWERING TO LESS THAN H9. LOW LEVEL WINDS TO H85 ARE MOSTLY FM 310 DIRECTION IN BTWN LOW PRES EXITING OFF COAST OF ME AND HIGH PRES BUILDING ACROSS CNTRL CANADA INTO THE PLAINS. MUCH FARTHER UPSTREAM A SHORTWAVE TROUGH IS PRESENT OVR FAR SW CONUS WITH PCPN ADVANCING INTO WESTERN TX ATTM...WHILE ANOTHER SHORTWAVE COMPLEX IS DRIVING INTO BRITISH COLUMBIA.

FOR THE VERY SHORT TERM...SNOW AMOUNTS AND STATUS OF HEADLINES ARE MAIN CONCERNS. LK EFFECT SNOW SHOULD CONTINUE DESPITE INVERSION LOWERING TO BLO 5 KFT AFTER MIDNIGHT AS TEMPS AT INVERSION TOP STAY -15C TO -18C. HOWEVER...DUE TO THE DRIER AIR ADVECTING IN BENEATH INVERSION (SUB ZERO SFC DEWPOINTS UPSTREAM) AND STRONG SUBSIDENCE ...EXPECT HEAVIER SNOW BANDS WILL BECOME FEWER IN NUMBER. WINDS VEER A BIT LATE EVENING-EARLY OVERNIGHT IN WAKE OF SHORTWAVE PASSING BY BUT OVERALL THE GREATEST CONVERGENCE AND BETTER CHANCE FOR DOMINANT BANDING REMAINS EAST OF MARQUETTE FM SHOT POINT TO MUNISING AND EAST TO KERY. SOME CONVERGENCE ALSO WILL SET UP OVR HIGHER TERRAIN OVR ONTONAGON THROUGH BARAGA COUNTIES. SINCE STRONGER LK EFFECT IN WEST IS EXPECTED TO DIMINISH WILL KEEP WARNINGS UNTIL ORIGINAL LATE EVENING EXPIRATION. 3-6" OF ACCUMS SEEM LIKELY EAST OF MARQUETTE TO NEWBERRY...ESPECIALLY IF ANOTHER ENHANCED DOMINANT BAND CAN DEVELOP AS OCCURRED LATE LAST NIGHT NEAR MUNISING. IN THE WEST...ACCUMS SHOULD TOP OUT AT 4" AND THAT WOULD BE MAINLY THIS EVENING BEFORE SNOW SHOWERS DIMINISH IN INTENSITY. TEMPS...SW INTERIOR WILL HAVE BEST CHANCE OF FALLING BLO ZERO AS WINDS IN FAR WEST ARE ALREADY DECREASING AND SFC TD NEAR ZERO ARE MOVING IN. SOME CLEARING OVERNIGHT AS WELL WILL ALSO AID TEMP DROP. SOME FALL IN TEMPS FARTHER N AND E BUT SOME WIND OFF LK SUPERIOR WILL KEEP TEMPS MOSTLY FM 5 TO 15 ABOVE ZERO.

&&

.LONG TERM...(SAT THROUGH FRI) MAIN FCST CONCERNS ARE LES TRENDS SAT AND AGAIN NEXT WEEK.

SAT...12Z NAM/GFS FCST SOUNDINGS SHOW INVERSION HEIGHTS IN THE 4K-5K FT RANGE OVER THE EAST WILL DROP TO NEAR 3K FT AS THE RDG BUILDS INTO THE AREA. SO...LES...MAINLY BTWN KP53-KERY WITH BEST 950 MB CONVERGENCE...WILL CONTINUE DURING THE MORNING BUT QUICKLY WIND DOWN IN THE AFTERNOON TO MAINLY LIGHT SNOW SHOWERS OR FLURRIES AND END LATE AS WINDS BECOME VARIABLE AND BACK SW. OVER THE NW CWA...ONLY SCT LIGHT SNOW SHOWERS OR FLURRIES ARE EXPECTED AS THE ACYC FLOW AND DRY AIR BUILD IN DURING THE MORNING. OTHERWISE...MDLS RH SUGGEST SOME MID/HIGH CLOUDS MAY MOVE THROUGH BUT SHOULD BE THIN ENOUGH FOR AT LEAST PARTLY SUNNY SKIES.

SAT NIGHT AND SUN...THE DEVELOPING WAA PATTERN INTO THE WESTERN GREAT LAKES AS THE PLAINS SHRTWV LIFTS TO THE NE WILL BRING THICKENING MID/HIGH CLOUDS OVER THE AREA LATE SAT AND SAT NIGHT...PER NAM/GFS 290K-295K PROGS. LINGERING SFC RIDGING WITH LOW LVL ACYC FLOW AS THE SHRTWV MOVES TO THE SRN LAKES WILL LIMIT LIGHT SNOW CHANCES INTO UPPER MI. THE 18Z NAM HAS ALSO FINALLY COME INTO BETTER AGREEMENT WITH THE MORE SRLY TRACK OF THE MORE CONSISTENT GFS BUT STILL REMAINED SLOWER AND A BIT FARTHER N WITH ITS INCREASINGLY SHEARED 500 MB LOW. SO...POPS WERE REDUCED TO SLIGHT CHANCE EXCEPT OVER THE SOUTH.

SUN NIGHT INTO MON...LIGHT SNOW CHANCES STILL REMAIN WITH AS A SFC TROF AND WEAK NRN STREAM SHRTWV MOVE THROUGH THE UPPER GREAT LAKES. 850 MB TEMPS FALLING ONLY TO AROUND -12C WILL BE MARGINAL FOR LES BUT COULD SUPPORT SOME LAKE ENHANCEMENT INTO NRN UPPER MI AS WINDS VEER NW. WITH THE LACK OF SIGNIFICANTLY COLDER AIR...OVERALL ONLY LIGHT SNOW AMOUNTS IF ANY EXPECTED.

TUE-FRI...GENERAL MODEL TREND IS TOWARD A MORE AMPLIFIED POSITIVE PNA PATTERN(WRN NOAM RDG AND TROF IN THE EAST). HOWEVER...DIFFERENCES REMAIN IN TIMING OF THE ARRIVAL OF THE COLD AIR AND ITS POSSIBLE DEPARTURE LATE IN THE WEEK. ANY LINGERING SNOW SHOWERS WOULD LIKELY END EARLY TUE WITH WAA AND BACKING WINDS AHEAD OF A CLIPPER SHRTWV. BY TUE NIGHT INTO WED...ADDITIONAL CLIPPER SHRTWVS FROM CNTRL CANADA SHOULD HELP USHER IN MUCH COLDER AIR WITH 850 TEMPS DROPPING AOB -20C. THE GFS AND ITS ENSEMBLES ALONG WITH THE UKMET SHOW MORE AMPLIFIED SOLUTIONS THAT PERSIST LATER INTO THE WEEK COMPARED TO THE ECMWF/CANADIAN WHICH ALLOW A GLF AK TO HELP PUSH OUT THE ERN TROF. FOLLOWING THE HPC PREFERENCE FOR THE GFS WOULD LEAD TO MODERATE OR EVEN HEAVY LES AT TIMES FOR N TO NW FLOW FAVORED AREAS WED INTO THU. SOME MODERATING MAY BE POSSIBLE BY FRI WITH LES DIMINISHING AS THE GFS AND ENSEMBLES HINT AT DECENT WAA AHEAD OF A CLIPPER LOW PASSING THROUGH NRN ONTARIO.

&&

.MQT WATCHES/WARNINGS/ADVISORIES... LAKE EFFECT SNOW WARNING THROUGH 11 AM EST SAT MIZ006-007-085. LAKE EFFECT SNOW WARNING UNTIL 11 PM EST FRI MIZ002-004-084. LAKE EFFECT SNOW WARNING UNTIL 11 PM EST FRI MIZ003. LAKE EFFECT SNOW ADVISORY UNTIL 1 AM EST SAT MIZ001. LAKE EFFECT SNOW ADVISORY UNTIL 9 AM EST SAT MIZ014. LAKE EFFECT SNOW ADVISORY UNTIL 10 PM CST FRI MIZ009.

&&

$$

JLA(SHORT TERM) JLB(LONG TERM)

.SHORT TERM...TONIGHT AND SATURDAY

SCATTERED TO NUMEROUS SNOW SHOWER ACTIVITY TO CONTINUE AT LEAST INTO THE EVENING HOURS AS UPPER LEVEL TROUGH AXIS PUSHES INTO THE CENTRAL GREAT LAKES REGION. WITH THE LACK OF ORGANIZED BANDING (ALTHOUGH THERE IS A HINT OF AN I-94 BAND) AND INVERSION HEIGHTS AROUND 6000 FEET AT THE PRESENT TIME (PER DTW TAMDAR)...ACCUMULATIONS SHOULD BE LESS THAN AN INCH FOR THE MOST PART. WITH SOME SEMBLANCE OF AN I-94 BAND...WASHTENAW COUNTY STANDS TO SEE THE MOST...PROBABLY AN INCH OR SLIGHTLY BETTER.

BOTH 12Z GFS/NAM INDICATING SATURATION AT 850 MB WITH TEMPS FALLING TO -18C BY 6Z SATURDAY. INVERSION HEIGHTS THEN FALL BELOW 5000 FEET LATE TONIGHT. HOWEVER...WITH THE AIRMASS AS COLD AS IT IS...MOISTURE AT 925 MB COULD BE ENOUGH TO PRODUCE A FEW FLURRIES ON SATURDAY. SURFACE RIDGE WILL SLOWLY BUILD INTO SOUTHEAST MICHIGAN DURING SATURDAY AND ARRIVE BY EVENING...WITH CLEARING TAKING PLACE OVER THE CWA. JUST NOT SURE HOW QUICK THE CLEARING WILL OCCUR...AS WE COULD EASILY START THE DAY OUT MOSTLY CLOUDY WITH MOISTURE TRAPPED UNDERNEATH THE INVERSION. OR...WE COULD START OUT WITH A FAIR AMOUNT OF SUN...CU UP LATE MORNING...BEFORE MIXING OUT THE REMAINING LOW LEVEL MOISTURE DURING THE AFTERNOON. EITHER WAY...THE DAY SHOULD AVERAGE OUT TO AT LEAST PARTLY SUNNY. BLENDED THE NEW MAV GUIDANCE AND PREVIOUSLY FORECASTED TEMPS FOR TONIGHT AND TOMORROW.

&&

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

SATURDAY NIGHT THROUGH MONDAY...

MODELS QUITE SIMILAR. SURFACE RIDGE ON TAP TO PASS THROUGH SATURDAY NIGHT...BEFORE MOVING OFF TO THE EAST SUNDAY. ON ITS HEELS...A BROAD DIFFUSE INVERTED TROUGH TO PROGRESS EAST ACROSS THE AREA SUNDAY THROUGH SUNDAY NIGHT. AT 500 MB...SHORTWAVE RIDGE BUILDING IN SATURDAY NIGHT...BEFORE IT GETS DISPLACED EAST SUNDAY AS A SHORTWAVE TROUGH FROM THE SOUTHWEST SHEARS NORTHEAST INTO THE SOUTHERN LAKES REGION AND CONTINUES EAST SUNDAY NIGHT. MORE MID LEVEL TROUGHINESS APPROACHING MONDAY FROM THE WEST.

850 TO 500 MB MOISTURE RAPIDLY INCREASES SUNDAY AS PER GOOD MODEL CONSENSUS...THEN TREND TOWARD SLIGHT LESSENING SUNDAY NIGHT AND MONDAY. AT 925 MB...DRIER SATURDAY NIGHT IN PRESENCE OF LOW LEVEL RIDGE...MOISTENING BY SUNDAY AFTERNOON AND CONTINUING MOIST THROUGH MONDAY. GFS...NAM...AND LOCAL WRFHEMI ALL SHOW 700 MB THETA E RIDGE NUDGING SOUTHERN LOWER MI SUNDAY.

A FEW UBAR/SEC OF OMEGA ASCENT SEEN SUNDAY AFTERNOON AS PER MODEL CONSENSUS...THOUGH STRONGER GFS CLOSER TO 10 UBAR/SEC ASCENT DESPITE LOWER MOS POPS. 850 TO 500 MB QVECTOR CONVERGENCE QUITE ROBUST SUNDAY AFTERNOON...OTHERWISE LITTLE TO NONE FOR THIS PERIOD. DURING SUNDAY...TOO...MAINLY IN THE AFTERNOON...MODELS ADVERTISE SLIGHT SURFACE WIND CONVERGENCE...MODEST 850 TO 700 MB FRONTOGENESIS AND DEFORMATION...AND PRETTY GOOD 250 MB DIVERGENCE/850 MB CONVERGENCE COUPLING. FINALLY...A FEW UBAR/SEC ASCENT SEEN BY SUNDAY AFTERNOON ON 280K SURFACE...AS CONDENSATION PRESSURE DEFICITS LOWER TO AROUND 10 MB IN MOST AREAS.

AFTER A DRY SATURDAY NIGHT...DYNAMICS AND MOISTURE JUSTIFY LIKELY POPS SUNDAY...WHEN SNOWFALL AMOUNTS FROM AROUND AN INCH TO 2 INCHES ARE ANTICIPATED...WITH HEAVIEST AMOUNTS EXPECTED NEAR THE SOUTHERN BORDER.

AFTER MONDAY...

SURFACE LOW LEVEL CYCLONIC FLOW EXPECTED TO PREVAIL EARLY IN WEEK...AHEAD OF A CLIPPER LIKE SYSTEM ARRIVING MID WEEK. CONSIDERABLE MODEL TIMING VARIATION SEEN WITH THIS MID WEEK SYSTEM AMONG MODELS AND GFS ENSEMBLE MEMBERS. AT ANY RATE...MODELS ARE IN OVERALL AGREEMENT...WITH THE MID WEEK SYSTEM INTRODUCING A FRESH REINFORCEMENT OF ARCTIC AIR BEHIND IT. 12Z MEX TEMPERATURES FOR THURSDAY ARE ABOUT 10 DEGREES F COLDER THAN THE 00Z GUIDANCE... REFLECTING A FASTER PROGRESSION AS PER THE 12Z GFS. HAVE LOWERED TEMPERATURES A FEW DEGREES FOR THURSDAY...BUT THEY MAY NEED EVEN MORE LOWERING IF LATER RUNS CONTINUE THIS TREND.

AT 500 MB...A LOOSELY PHASED HIGH AMPLITUDE SHORTWAVE TROUGH EXPECTED TO SLOWLY ADVANCE EAST ACROSS THE AREA EARLY IN WEEK...WITH COLD NORTHWEST FLOW IN ITS WAKE PERTURBED BY STRONG MID WEEK IMPULSE.

AS IN PREVIOUS FORECAST...CHANCE OF SNOW OR SNOW SHOWERS EACH DAY IS HARD TO DISPUTE IN THIS TYPE OF PATTERN...GIVEN LAKE EFFECT COMBINED WITH SYNOPTIC SCALE BOOST FROM TIME TO TIME.

&&

.PREV DISCUSSION...ISSUED 1205 PM EST FRI JAN 19 2007

AVIATION...

VFR CONDITIONS WITH PERIODS OF MVFR SNOW SHOWERS WILL CONTINUE TO IMPACT SOUTHEAST MICHIGAN THROUGH TONIGHT. IN FACT...WITH THE UPPER LEVEL TROUGH AXIS AND SURFACE TROUGH SWINGING INTO SOUTHEAST MICHIGAN LATE TODAY/THIS EVENING...THERE WILL LIKELY BE SOME ENHANCEMENT TO THE ACTIVITY...WITH POCKETS OF IFR SNOW SHOWERS EXPECTED. HOWEVER...UNCERTAINTY WITH THE EXACT TIMING...LOCATION...AND DURATION PRECLUDES THE MENTION AT TAF SITES DURING THIS ISSUANCE. TAFS WILL BE AMENDED AS SHORT TERM TRENDS DICTATE. TOMORROW MORNING WE ARE EITHER GOING TO CLEAR OUT OR MOISTURE TRAPPED UNDERNEATH LOWERING SUBSIDENCE INVERSION WILL KEEP MVFR CEILINGS LOCKED IN. FAVOR THE LATTER AT THIS POINT BASED ON THE 12Z NAM.

&&

.DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...GALE WARNING...NORTH HALFGALE WARNING...SOUTH HALF UNTIL 11 AM SATURDAY.

SMALL CRAFT ADVISORY...LHZ422 UNTIL 7 AM SATURDAY.

SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON UNTIL 7 PM SATURDAY.

SMALL CRAFT ADVISORY...LHZ421 UNTIL 11 AM SATURDAY.

LAKE ST CLAIR...SMALL CRAFT ADVISORY...LCZ460 UNTIL 7 AM SATURDAY.

MI WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY...UNTIL 7 AM SATURDAY.

&&

$$

SHORT TERM...SF LONG TERM....DG

YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

.SHORT TERM(TONIGHT-MONDAY)... NO CHANGES ARE PLANNED TO CURRENT HEADLINES. A LITTLE LULL IN LAKE EFFECT JUST IN TIME FOR THE EVENING RUSH HOUR AS THE SHORT WAVE RESPONSIBLE FOR ENHANCING THE LAKE EFFECTS BANDS LATE THIS MORNING INTO THIS AFTERNOON HAS EXITED EAST CAUSING SOME DRYING AND WK SYNOPTIC DOWNWARD MOTION. HOWEVER...WATER VAPOR AND RUC ANALYSIS INDICATE A SHEARED SHORT WAVE FROM WI TO LOWER MI WHICH IS FCST TO MOVE ACROSS THE AREA AROUND OR AFTER 00Z THIS EVENING. THIS SHORT WAVE WILL SERVE TWO PURPOSES. IT WILL FIRST ALLOW FOR THE LAKE EFFECT SNOW TO BE ENHANCED AGAIN THIS EVENING WITH WK MID LVL Q-VECTOR CONVERGENCE...AND SECONDLY THIS SHORT WAVE WILL ALLOW FOR THE WINDS TO VEER TO A MORE NWLY DIRECTION WHICH SHOULD ALLOW THE SNOW BANDS TO MOVE FURTHER INLAND. SEE NO REASON TO MAKE MAJOR CHANGES TO THE FCST SNOW AMOUNTS TONIGHT...WITH 4 TO 8 INCHES POSSIBLE IN THE SNOWBELT...AND 2-5 INCHES NEAR THE LAKESHORE AND INTO EASTERN CUYAHOGA COUNTY. I AM NOT SURE IF ANYWHERE CAN SEE A FOOT TONIGHT GIVEN THE SLOWLY VEERING WINDS AND THE SHORT NW FETCH THAT WILL DEVELOP OVERNIGHT WITHOUT ANY LAKE HURON SUPPORT UNTIL LATE. WITH NW FLOW DEVELOPING...THERE IS A CONCERN THAT THE SECONDARY BELTS IN NRN SUMMIT AND PORTAGE COUNTIES MAY BE ABLE TO SEE ADVY CRITERIA. THIS WILL NEED TO BE WATCHED...BUT IT SEEMS LIKE WHEN THE WINDS TURN ENOUGH TO ALLOW FOR STRONG BANDS INTO THE SECONDARY BELT...THE INVERSION WILL ALSO START TO LOWER SO IT SEEMS REASONABLE TO CONTINUE WITH A 1 TO 3 INCH FORECAST FOR THE SECONDARY BELTS. SHOULD ALSO SEE SOME BLOWING AND DRIFTING THIS EVENING WITH GUSTS TO 30 MPH ESPECIALLY IN THE WARNING AREA.

STRONG RIDGING AND DRYING BUILDS INTO THE AREA FOR THE DAY SATURDAY. MODEL GUIDANCE SHOWS A LAKE HURON FETCH...BUT A WEAKER ONE WITH THE INVERSION AROUND 5000 FT AND DRY AIR MOVING IN. WILL CONTINUE WITH CATEGORICAL WORDING IN THE SNOWBELT...WITH 3-6 INCHES ADDITIONAL ACCUMULATION. MAY BE A LITTLE HIGHER IF A STRONGER LAKE HURON BAND SETS UP BUT MOST 3-6 SHOULD COVER THE MAJORITY OF THE SNOWBELT.

SOME MODEL DIFFS STARTING SAT NIGHT AND CONTINUING INTO SUNDAY WITH THE SRN STREAM SYSTEM. GFS IS FASTER BY ABOUT 6 HOURS AND FURTHER EAST WITH THE SHORT WAVE ENERGY ON SUNDAY. PREFER THE GFS PRIMARILY DUE TO THE FAST AND CONFLUENT FLOW ACROSS THE EASTERN PART OF THE COUNTRY. THE GFS SHOWS A FAIRLY POTENT SHORT WAVE AND ASSOCIATED INVERTED TROUGH MOVING THRU THE AREA SUNDAY AFTERNOON INTO THE EVENING. THIS SYSTEM HAS SOME FAVORABLE DYNAMICS FOR A PERIOD OF SNOW...STRONG DUAL UPPER JETS...AN AREA OF STRONG ISENTROPIC UPGLIDE...AND AN AREA OF FRONTOGENESIS MOVING THRU THE AREA. WILL GO WITH SNOW LIKELY OVER THE WEST SUN AFTN WITH HIGH CHANCE POPS SUN EVENING FOR THE ENTIRE REGION. WILL NEED TO MONITOR THIS SYSTEM AS INVERTED TROUGHS ARE NOTORIOUS FOR CREATING MORE PCPN THAN THE MODELS PREDICT. DRYING BEHIND THE SYSTEM SUN NIGHT INTO MON MAY ALLOW FOR FREEZING DRIZZLE...BUT FOR NOW HAVE OPTED TO KEEP JUST LOW CHC POPS FOR SNOW INTO MONDAY.

TEMPS WILL CONTINUE BELOW NORMAL THRU SUNDAY. WILL GENERALLY GO WITH A BLEND OF GUIDANCE THRU THE PERIOD.

.LONG TERM(TUE-FRI)... NO SIGNIFICANT CHANGES TO GOING FORECAST... WITH NORTHWEST FLOW ALOFT STILL THE RULE THROUGH THE PERIOD. LOW LEVEL FLOW OFF THE LAKES CONTINUES TO HANG ON THROUGH TUESDAY AS RIDGING PUSHES INTO THE AREA FROM THE SOUTH. EXPECT CLOUDS AND SOME SNOW TO CONTINUE IN THE SNOWBELT AREAS AT LEAST THROUGH TUESDAY NIGHT BEFORE WEAK RETURN FLOW BEGINS WEDNESDAY MORNING AHEAD OF A FAST MOVING CLIPPER SYSTEM. NOT MUCH MOISTURE AVAILABLE FOR THIS SYSTEM... BUT PLENTY OF COLD AIR BEHIND IT. THE GFS IS CONSIDERABLY COLDER THAN YESTERDAYS RUN... WITH 850 TEMPS FROM THIS MORNINGS RUN HITTING -20 OVER THE AREA BY FRIDAY MORNING. BUT THIS COLDER SOLUTION IS IN BETTER AGREEMENT WITH THE ECMWF... AND I TRENDED THE TEMPS COLDER ON DAYS 6-7 TO REFLECT THIS. COLDEST TEMPS OF THE SEASON ARE NOT OUT OF THE QUESTION TOWARDS NEXT WEEKEND... AND A SOLID SHOT OF LAKE EFFECT SNOW IS LOOKING PRETTY GOOD FOR THE END OF THE WEEK AS THIS AIR MOVES OVER THE STILL WARM LAKES.

.AVIATION (18Z-18Z)... SCATTERED RATHER INTENSE SNOW SHOWERS HAVE PREVAILED ACROSS NORTHERN OHIO AT MIDDAY WITH THE HEAVIEST ACTIVITY FROM THE LAKE ERIE ISLANDS EAST TO CAK AND YNG. VSBYS FREQUENTLY DROP TO BELOW 1 MILE WITH CIGS BELOW 1000 FEET IN THE MORE INTENSE SHOWERS NEAR THE LAKE. EXPECT THE SNOW SHOWER ACTIVITY TO PERSIST INTO THE EVENING HOURS AND THEN DIMINISH SLOWLY AFTER MIDNIGHT. CURRENT ACARS SOUNDINGS SHOW THE INVERSION HEIGHT NEAR CLE AROUND 7900 FEET AT 16Z WITH MOIST CONDITIONS BELOW THE INVERSION. THIS IS A RATHER DEEP MIXED BOUNDARY LAYER WHICH SHOULD CONTINUE TO SUPPORT INTENSE SCATTERED SNOW SHOWERS. THE INVERSION BASE IS EXPECTED TO LOWER AFTER MIDNIGHT AND THIS SHOULD HELP TO SUPPRESS SNOW SHOWERS. &&

.CLE WATCHES/WARNINGS/ADVISORIES... OH...LAKE EFFECT SNOW WARNING FROM FRIDAY AFTERNOON THROUGH SATURDAY AFTERNOON FOR OHZ011>014-023-089.

PA...LAKE EFFECT SNOW WARNING FROM FRIDAY AFTERNOON THROUGH SATURDAY AFTERNOON FOR PAZ001>003.

&&

$$

SHORT TERM...MRD LONG TERM...ASTIFAN AVIATION...REL

.AVIATION (18Z-18Z)... SCATTERED RATHER INTENSE SNOW SHOWERS HAVE PREVAILED ACROSS NORTHERN OHIO AT MIDDAY WITH THE HEAVIEST ACTIVITY FROM THE LAKE ERIE ISLANDS EAST TO CAK AND YNG. VSBYS FREQUENTLY DROP TO BELOW 1 MILE WITH CIGS BELOW 1000 FEET IN THE MORE INTENSE SHOWERS NEAR THE LAKE. EXPECT THE SNOW SHOWER ACTIVITY TO PERSIST INTO THE EVENING HOURS AND THEN DIMINISH SLOWLY AFTER MIDNIGHT. CURRENT ACARS SOUNDINGS SHOW THE INVERSION HEIGHT NEAR CLE AROUND 7900 FEET AT 16Z WITH MOIST CONDITIONS BELOW THE INVERSION. THIS IS A RATHER DEEP MIXED BOUNDARY LAYER WHICH SHOULD CONTINUE TO SUPPORT INTENSE SCATTERED SNOW SHOWERS. THE INVERSION BASE IS EXPECTED TO LOWER AFTER MIDNIGHT AND THIS SHOULD HELP TO SUPPRESS SNOW SHOWERS. &&

.SHORT TERM (TODAY THROUGH SUNDAY)... COLD FRONT MOVED THROUGH OVERNIGHT. LACK OF ICE CRYSTALS CAUSED SOME FREEZING DRIZZLE FOR SHORT TIME. MOST AREAS HAVE SWITCHED OVER TO LIGHT SNOW...OR SHOULD DO SO SHORTLY. OTHERWISE COLD ARCTIC AIR MOVING IN BEHIND FRONT. WILL TRANSITIONING FROM LIGHT SYNOPTIC SNOW TO PRIMAIRLY LAKE EFFECT SNOW LATER TODAY AND CONTINUING INTO PART OF SATURDAY. WILL ISSUE LAKE EFFECT SNOW WARNING FROM NOON TODAY UNTIL 4 PM SATURDAY. MAY BE SOMEWHAT OF A BREAK THIS MORNING BEFORE THE LAKE EFFECT GETS GOING BUT WITH THE WESTERLY FLOW AND 8H TEMPS DROPPING TO ARND -13C BY EVENING FELT THE LAKE EFFECT SNOW WARNING SHOULD START AT NOON THOUGH THE THE HEAVIEST MAY NOT GET GOING UNTIL THIS EVENING. PREVIOUS FORECAST OF 6 TO 12 FOR THE SNOW BELT LOOKS OK. WESTERLY FLOW THIS AFTERNOON AND EARLY TONIGHT GRADUALLY BECOMES WELL AROUND TO NW AND MAY ADD LAKE HURON FETCH AFFECTING NW INLAND PA WHICH COULD RAISE SNOW AMOUNTS. HIGH PRESSURE BUILDING IN ON SATURDAY WILL CUT OFF LAKE EFFECT IN MORNING ARND CLEVELAND BUT SHOULD LINGER IN THE EAST UNTIL AFTERNOON. THEN FLURRIES FAR EAST SATURDAY EVENING THEN HIGH MOVES QUICKLY ACROSS SATURDAY NIGHT. THEN LOW MOVES INTO MID MISSISSIPPI VALLEY SUNDAY BRINGING ANOTHER CHANCE FOR SOME SNOW.

&&

.LONG TERM (SUNDAY NIGHT THROUGH THURSDAY)... NW FLOW GENERALLY CONTINUES THROUGH THE PERIOD. FLOW IS FAIRLY FAST SO PINNING DOWN INDIVIDUAL DETAILS TRICKY. NO BIG STORMS...MOSTLY JUST CLIPPER TYPE SYSTEMS BUT EACH ONE OPENS THE DOOR TO AT LEAST SOME SNOW SHOWERS AS WELL AS LAKE EFFECT SNOWS. TROUGH ALOFT AND SECONDARY COLD FRONT AT SURFACE DROP SOUTH ACROSS THE LOWER LAKES BY LATE MONDAY. I THINK THE MAJORITY OF THE COLDER AIR WILL SLIDE OFF TO THE NORTH BUT SOME COLDER AIR WILL TRICKLE SOUTHWARD AND WITH NNW FLOW SOME LAKE EFFECT POSSIBLE BY TUESDAY. ELSEWHERE THERE SHOULD BE SOME CLEARING. LOOKS LIKE A BIT OF A BREAK LATER TUE NGT INTO WEDNESDAY. STILL NOT SURE WITH A FAST FLOW THAT THERE MIGHT BE A SMALL CHANCE OF SNOW SHOWERS BUT IT LOOKS UNTIL LATER WED/WED NGT THAT NEXT SHORT WAVE DROPS ACROSS FCST AREA WITH SOME LAKE EFFECT BY THURSDAY AS SOME COLDER AIR RETURNS. LAKE EFFECT WILL CONTINUE INTO FRIDAY WITH DRIER AND COLDER CONDITIONS ELSEWHERE. ECMWF COLDER BY THE END OF THE WEEK AS GFS SHOWS A BIT OF A CHINOOK FLOW DEVELOPING BY FRIDAY WHERE AS ECMWF BRINGS A MORE SIGNIFICANT CHUNK OF COLDER AIR SOUTHWARD. CONSENSUS THINKING IS THAT COLDER SOLUTION MIGHT BE BETTER.

&&

.CLE WATCHES/WARNINGS/ADVISORIES... OH...LAKE EFFECT SNOW WARNING FROM FRIDAY AFTERNOON THROUGH SATURDAY AFTERNOON FOR OHZ011>014-023-089.

PA...LAKE EFFECT SNOW WARNING FROM FRIDAY AFTERNOON THROUGH SATURDAY AFTERNOON FOR PAZ001>003.

&&

$$

SHORT TERM...WCR LONG TERM...KOSARIK/ASTIFAN AVIATION...REL

.DISCUSSION...A WINTER STORM OF MAINLY SNOW AND SLEET CONTINUES TO COME TOGETHER. THE UPPER LEVEL CYCLONE HAS BEEN STALLED OVER THE BAJA PENINSULA BENEATH SHORTWAVE RIDGING FARTHER NORTH. THIS RIDGING SHOULD CONTINUE TO MOVE EAST...OWING TO ITS SHORT WAVELENGTH...AND SATELLITE SHOWED A KICKER TROUGH APPROACHING THE WEST COAST. THEREFORE...HAVE GOOD CONFIDENCE IN THE UNANIMOUS COMPUTER MODEL FORECASTS THAT SHOW THE LOW KICKING OUT INTO THE PLAINS VERY QUICKLY FROM SATURDAY INTO SATURDAY NIGHT.

MOISTURE ADVECTION AND ISENTROPIC UPGLIDE ALREADY EVIDENT AHEAD OF THE LOW...WITH A LOT OF VIRGA AND LIGHT PRECIPITATION FROM WEST TEXAS TOWARD THE RED RIVER. MORNING SOUNDINGS INDICATED A LOT OF DRY AIR THAT WILL NEED TO BE COOLED BY EVAPORATION BEFORE PRECIPITATION REACHES THE GROUND...BUT ONCE PRECIPITATION BEGINS IT SHOULD BE STEADY AND WIDESPREAD. ALL ALONG...THERE HAS BEEN SUBSTANTIAL UNCERTAINTY AS TO THE TYPE OF PRECIP THAT WILL BE OBSERVED FROM CENTRAL OKLAHOMA SOUTHWARD...AS TEMPERATURE PROFILES HOVER CLOSE TO FREEZING THROUGH A GREAT VERTICAL DEPTH. THE LATEST THINKING IS THAT THE EVENT APPEARS SLIGHTLY COLDER...AND MORE LIKELY TO SUPPORT SNOW FOR A LONGER TIME BEFORE BECOMING MIXED WITH SLEET OR RAIN. THE EVIDENCE LIES MAINLY IN THE WET BULB PROFILE IN THE NORMAN SOUNDING...COLDER NAM AND GFS FORECAST SOUNDINGS...AND A FEW TEMPERATURE PROFILES OBTAINED FROM THE TAMDAR AIRCRAFT ASCENT DATA.

BECAUSE OF THE COLDER PROFILES AND AN EARLIER ONSET NOW AGREED UPON BY THE MODELS...WENT AHEAD AND PULLED THE WINTER STORM WARNING FARTHER SOUTH. ALSO WILL HAVE A WINTER WEATHER ADVISORY IN THE FAR SOUTHEAST. THE MAIN CONCERN IS FOR TONIGHT INTO SATURDAY MORNING FOR SOUTHERN OKLAHOMA...WITH A FEW INCHES OF ACCUMULATION BEFORE CHANGING TO RAIN TOMORROW AFTERNOON.

MEANWHILE...THE MODELS HAVE ALSO CONTINUE TO TREND TOWARD A DEEPER LOW TRACKING SLIGHTLY FARTHER SOUTH THAN IN PREVIOUS FORECAST CYCLES. THE LOW IS QUITE IMPRESSIVE ON SATELLITE...AND WILL HAVE A FAIRLY SHORT WAVELENGTH AND FAST MOTION AS IT COMES OUT...TO GENERATE VERY DEEP AND STRONG LIFT OVER THE REGION. THIS ALSO FAVORS MORE SNOW...ESPECIALLY NEAR AND NORTH OF THE UPPER LOW TRACK. MOST OF THE PRECIPITATION IS EXPECTED TO BE SNOW TO THE NORTH OF A LINE FROM VERNON TEXAS TO LAWTON...NORMAN...AND SHAWNEE.

SOME OF THE SNOW IS EXPECTED TO BE QUITE HEAVY AROUND MIDDAY SATURDAY INTO THE AFTERNOON. CROSS SECTIONS INDICATE STRONG LIFT THROUGH THE DENDRITIC ICE CRYSTAL LAYER OVER A FAIRLY BROAD REGION OF WEST CENTRAL...CENTRAL...AND NORTH CENTRAL OKLAHOMA. THIS COUPLED WITH TEMPERATURES PROFILES JUST A FEW DEGREES BELOW FREEZING THROUGH A GREAT DEPTH...MAY RESULT IN SOME HEAVY FALLS OF LARGE WET SNOWFLAKES. THIS MAXIMUM IN SNOWFALL RATES MAY NOT LAST LONG...BUT COULD PUSH STORM TOTAL ACCUMULATIONS TOWARD 10 INCHES IN SOME AREAS. ELSEWHERE...A RANGE OF 4 TO 8 INCHES SEEMS LIKELY...AND SOME OF THAT WILL BE SLEET TO THE SOUTH OF THE UPPER STORM TRACK.

AS A FURTHER COMPLICATION...FAR SOUTHEAST OKLAHOMA MAY SEE SOME FAIRLY HEAVY RAIN SATURDAY AFTERNOON AND EVENING...WHERE LOW LEVEL FRONTOGENESIS IS MAXIMIZED...AND THERE IS SOME INDICATION OF MID LEVEL INSTABILITY. THIS WOULD BE MAINLY THE COUNTIES THAT ARE IN THE WINTER WEATHER ADVISORY. WILL LET THE ADVISORY RUN THROUGH SATURDAY NIGHT...HOWEVER...AS THERE IS POTENTIAL FOR TEMPERATURES TO FALL AGAIN OVERNIGHT AND RESULT IN FREEZING DRIZZLE. THE SAME COULD BE SAID FOR OTHER PARTS OF OKLAHOMA...WHERE FREEZING DRIZZLE MAY BECOME A CONCERN BEHIND THE UPPER LOW...WHERE MOISTURE DEPTH BECOMES SHALLOW.

IN THE EXTENDED...WILL MAINTAIN A CHANCE FOR LIGHT SNOW IN NORTH TEXAS AND SOUTHERN OKLAHOMA MONDAY. OTHERWISE...CONTINUED IN A COLD BUT DRY NORTHERLY FLOW ALOFT...WITH COOL BUT NOT BITTERLY COLD SURFACE HIGH PRESSURE ENTRENCHED OVER THE PLAINS.

&&

.PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 26 32 29 33 / 70 100 60 10 HOBART OK 24 31 27 32 / 90 100 40 10 WICHITA FALLS TX 29 33 31 37 / 100 100 40 10 GAGE OK 23 30 25 31 / 70 90 50 10 PONCA CITY OK 23 32 28 32 / 30 100 80 20 DURANT OK 31 37 33 40 / 90 100 70 10

&&

.OUN WATCHES/WARNINGS/ADVISORIES... OK...WINTER STORM WARNING UNTIL 6 AM CST SUNDAY FOR OKZ004>020- 022>032-039>042-045-046.

WINTER STORM WARNING UNTIL 6 AM CST SUNDAY FOR OKZ021-033>038- 044.

WINTER WEATHER ADVISORY UNTIL 6 AM CST SUNDAY FOR OKZ043-047-048- 050>052.

TX...WINTER STORM WARNING UNTIL 6 AM CST SUNDAY FOR TXZ086-088>090.

WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR TXZ086- 088>090.

WINTER STORM WARNING UNTIL 6 AM CST SUNDAY FOR TXZ083>085-087.

&&

$$

BURKE/07

.SYNOPSIS...A WEAKENING COLD FRONT IS SPREADING RAIN ACROSS THE FORECAST AREA THIS MORNING WITH RAIN IN THE VALLEYS AND SNOW IN THE CASCADES. THERE MAY BE ISOLATED POCKETS OF FREEZING RAIN IN THE COLDER VALLEYS OF THE COAST RANGE AND ALONG THE LOWER COLUMBIA RIVER AND NEAR HILLSBORO THIS MORNING TILL AROUND 930 AM BUT EXPECT THAT SHALLOW COLD AIR TO MIX OUT QUICKLY. SHOWERS WILL CONTINUE BEHIND THE FRONT TONIGHT AND SATURDAY AS WEAK PACIFIC WEATHER SYSTEMS BRUSH OUR FAR NORTHERN ZONES. HIGH PRESSURE BUILDS OVER THE PAC NW EARLY NEXT WEEK...WITH DRY WEATHER FOR MONDAY THROUGH AT LEAST WEDNESDAY.

&&

.SHORT TERM...A SHEARED PACIFIC COLD FRONT NEAR THE COAST WILL MOVE INLAND SHORTLY. THE FRONT HAS A WIDE MOISTURE SHIELD AND IT APPEARS ON SATELLITE THAT THE MID AND UPPER PORTIONS SHEARED EASTWARD AHEAD OF THE SURFACE FEATURE UNDER THE INFLUENCE OF A STRONG WESTERLY JET APPROACHING THE PACNW. ALTHOUGH THAT WEAKENS THE FRONT IT ALSO SPED UP THE ONSET OF PRECIPITATION A FEW HOURS AHEAD OF THE MODELS. SINCE THE PRECIPITATION ARRIVED IN THE MORNING WITH WEAKER DYNAMICS IT PRECEDED THE MIX OUT OF ALL THE COLDER AIR AND LEFT SOME SHALLOW POOLS OF COLD AIR WITH SOME FREEZING PRECIPITATION AND FOG DURING THE MORNING HOURS OVER THE COAST RANGE...LOWER COLUMBIA RIVER WEST OF PORTLAND...AND POSSIBLY TO WESTERN WASHINGTON COUNTY WHERE POCKETS OF FREEZING TEMPERATURES EXIST. OBSERVATIONS AT SCAPPOOSE AND HILLSBORO SHOWED SOME FREEZING RAIN THIS MORNING...THAT WILL BE BRIEF WITHOUT ANY SIGNIFICANT ACCUMULATION AND EXPECT IT WILL NOT BE INCLUDED IN THE FORECAST PACKAGE ISSUED AT 940 AM. THE AIRCRAFT SOUNDINGS OVER THE PORTLAND AIRPORT ARE ALL ABOVE FREEZING AND THE SURFACE TEMPERATURE THERE THIS MORNING AT 8 AM IS 35 DEGREES. WITH A SHEARED FRONT EXPECT PRECIPITATION AMOUNTS IN GENERAL TO BE LOW. ANOTHER CONCERN IS IN THE COLUMBIA RIVER GORGE AROUND HOOD RIVER WHERE AREAS OF FREEZING TEMPERATURES EXIST. ROOSTER ROCK SHOWED 35 DEGREES AND BONNEVILLE 33 AT 8 AM AND CASCADE LOCKS WAS ABOVE FREEZING BUT HOOD RIVER AIRPORT WAS STILL 28 DEGREES AND HOOD RIVER AGRIMET SHOWED 27 DEGREES THIS MORNING. MODELS ARE NOT HANDLING THIS SHEARED SYSTEM WELL AT ALL AND i LIKE THE PREVIOUS FORECAST IDEA TO MENTION POSSIBILITY OF FREEZING PRECIPITATION IN THE HOOD RIVER AND PARKDALE AREA AS PRECIPITATION ARRIVES. A SPECIAL WEATHER STATEMENT HIGHLIGHTS THE POSSIBILITY OF FREEZING PRECIPITATION IN THESE AREAS. ONCE THE COLD FRONT IS THROUGH TONIGHT ONSHORE FLOW WILL FINALLY PUSH THE SHALLOW COLD AIR ALL THE WAY OUT. WEAK WARM ADVECTION OVERRUNNING MOISTURE WILL GIVE A CHANCE OF LIGHT PRECIPITATION TO THE NORTHWEST PART OF THE FORECAST AREA SATURDAY NIGHT AND SUN AS THE OFFSHORE UPPER LEVEL RIDGE BUILDS AND PUSHES PRECIPITATION AREAS BACK NORTH OF THE AREA...MODELS VARY RUN TO RUN ON AREAL COVERAGE OF THIS PRECIP EVENT WITH BEST PROSPECTS FOR RAIN OVER THE NORTHWEST CORNER OF THE FORECAST AREA. WILLSON.

&&

.LONG TERM...A STRONG UPPER RIDGE WILL REMAIN OVER THE PACIFIC NW THROUGH THE MIDDLE OF NEXT WEEK WITH DRY WEATHER. MODELS INDICATING A WEAK FRONT WILL RUN INTO THE RIDGE AND WEAKEN LATE WEDNESDAY/ THURSDAY. MODELS IMPLY THAT MAY BE THE BEGINNING OF A CHANGE FROM THE RIDGE/DRY PATTERN...BUT SOLUTIONS DIVERGE QUITE A BIT. WILL CONTINUE CHANCE POPS FOR THE END OF THE EXTENDED PERIOD. BOHL &&

&&

.AVIATION...THE BACK EDGE OF THE FRONT WILL MOVE INLAND OVER THE COAST WITHIN THE NEXT HOUR OR TWO. TEMPERATURES THIS MORNING ARE GENERALLY IN THE 30S. PRECIPITATION IS MAINLY STARTING AS RAIN WITH A FEW PATCHES OF FREEZING RAIN IN AREAS SUCH AS HILLSBORO WHERE SURFACE TEMPERATURES ARE STILL BELOW FREEZING. THIS COLD AIR WILL MIX OUT QUICKLY AS THE FRONT MOVES INLAND. NON LIQUID PRECIPITATION WILL REMAIN A PROBLEM LONGER IN THE COLUMBIA RIVER GORGE WHERE MORE COLD AIR IS ENTRENCHED. A TRAILING UPPER LEVEL DISTURBANCE CURRENTLY ALONG THE BRITISH COLUMBIA COAST WILL BRING ANOTHER SHOT OF RAIN AND LOWER CEILINGS THIS EVENING AND TONIGHT. RUTHFORD. &&

.MARINE...SOUTHERLY WINDS OFFSHORE ARE CURRENTLY GUSTING TO AROUND 25 KNOTS AT BUOYS 29 AND 50 WITH SEAS OF 10 FEET AND 8 FT RESPECTIVELY. WINDS WILL TURN TO THE WEST AND DROP INTO THE TEENS THIS AFTERNOON ONCE THE FRONT MOVES THROUGH. SEAS ARE EXPECTED TO BUILD TO 11 FEET TODAY THEN CONTINUE AROUND 10 FEET THROUGH SATURDAY. WINDS IN THE NORTHERN WATERS WILL INCREASE TO 20 OR 25 KNOTS AGAIN TONIGHT AS AN UPPER LEVEL DISTURBANCE MOVES THROUGH THE AREA. RUTHFORD.

&&

.PQR WATCHES/WARNINGS/ADVISORIES .OR/WA...SMALL CRAFT ADVISORY FOR WINDS THROUGH TONIGHT FOR THE COASTAL WATERS FROM CAPE SHOALWATER TO CASCADE HEAD. SMALL CRAFT ADVISORY FOR WINDS TODAY FOR THE COASTAL WATERS FROM CASCADE HEAD TO FLORENCE. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FOR TODAY AND TONIGHT FOR COASTAL WATERS FROM CAPE SHOALWATER TO CASCADE HEAD. SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR TODAY AND TONIGHT.

&&

.PRELIMINARY POINT POPS... AST 97355 PDX 87311 SLE 76311 EUG 66311

$$

MORE WEATHER INFORMATION ONLINE AT... Http://weather.gov/portland

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY REFERRED TO AS THE FORECAST AREA.