AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 1010 PM EST FRI JAN 19 2007
.UPDATE...
MAIN FCST CONCERN OVERNIGHT IS LINGERING LES AND FATE OF ONGOING
HEADLINES.
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW NW FLOW INTO THE UPPER
GREAT LAKES REGION WITH 500MB HEIGHTS BEGINNING TO RISE AS SHORTWAVE
RIDGING SHIFTS E INTO THE NRN PLAINS/SCNTRL CANADA. APPROACHING
MIDLEVEL RIDGE IS SUPPORTING A SFC HIGH PRES RIDGE FROM IA ACROSS MN
INTO NW ONTARIO. THIS OBVIOUSLY FORESHADOWS A DIMINISHING TREND FOR
ONGOING LES. 00Z KINL SOUNDING SHOWED A HOSTILE ENVIRONMENT FOR
ANYTHING MORE THAN LIGHT LES WITH A NEAR ISOTHERMAL PROFILE FROM THE
SFC TO 800MB AND DWPT DEPRESSIONS OF 5 TO 10C.
AS AIRMASS CROSSING WRN LAKE SUPERIOR BECOMES MORE HOSTILE FOR
LES...LES WILL CONTINUE TO DIMINISH OVERNIGHT. WHILE THERE WILL BE
AN INCREASE IN LOW-LEVEL CONVERGENCE FROM THE PORCUPINE MOUNTAINS
TOWARD ROCKLAND DUE TO STRENGTHENING LAND BREEZE OFF WRN UPPER MI/NW
WI AND NNW WINDS PERSISTING OVER N HALF OF WRN LAKE SUPERIOR...THE
POOR TEMP/MOISTURE PROFILE OF AIRMASS CROSSING LAKE WILL KEEP LES IN
CHECK. THERE MIGHT BE A COUPLE OF INCHES OF NEW SNOW WHERE BEST
CONVERGENCE SETS UP. OTHERWISE...EXPECT ADDITIONAL ACCUMULATIONS OF
AN INCH OR LES. SO WILL CANCEL HEADLINES FOR THE W...WHICH WILL BE
EXPIRING SHORTLY ANYWAY. FOR THE NE FCST AREA...LOW-LEVEL
CONVERGENCE WILL ALSO IMPROVE OVER SCNTRL LAKE SUPERIOR DURING THE
NIGHT AS LAND BREEZES STRENGTHEN OFF ONTARIO AND NW/NCNTRL UPPER MI.
ALTHOUGH AIRMASS CROSSING THE LAKE WILL BECOME LES FAVORABLE FOR
LES...LONGER FETCH AND INCREASING CONVERGENCE SHOULD ALLOW FOR 2-4
INCH ACCUMULATIONS OVERNIGHT. ALGER COUNTY SHOULD SEE GREATEST
ACCUMULATIONS WITH MAX CONVERGENCE BECOMING FOCUSED THERE. WITH
850MB WINDS PROGGED TO HAVE A BIT MORE NRLY COMPONENT THAN 950MB
WINDS...BANDS WILL TEND TO TRANSLATE W...PREVENTING SIGNIFICANT
ACCUMULATIONS THAT WOULD OCCUR FROM STATIONARY BANDS. ALSO...BECAUSE
OF THE MORE NRLY COMPONENT TO THE 850MB WINDS...BANDS WILL IMPACT
PORTIONS OF MARQUETTE COUNTY AS WELL. AREAS AROUND BIG BAY AND E OF
MARQUETTE SHOULD SEE 2 MAYBE 3 INCHES OF ADDITIONAL SNOW DURING THE
REMAINDER OF THE NIGHT.
AS FOR TEMPS...LOWERED MINS TO -10F IN THE INTERIOR SW WHERE
SKIES HAVE CLEARED FOR THE MOST PART. WOULD GO LOWER...BUT WITH
850MB WINDS VEERING A BIT MORE NRLY...SOME LAKE CLOUDS MAY SPREAD
INTO THAT AREA AGAIN DURING THE NIGHT.
&&
.PREV DISCUSSION... ISSUED AT 430 PM EST
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 UNTIL 11 AM EST SAT MIZ006-007-085.
LAKE EFFECT SNOW ADVISORY UNTIL 9 AM EST SAT MIZ014.
&&
$$
ROLFSON (UPDATE)
JLA(SHORT TERM)
JLB(LONG TERM)
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 613 PM EST FRI JAN 19 2007
.AVIATION...
LAKE EFFECT SNOW SHOWERS WILL CONTINUE TO AFFECT KDTW/KDET THIS
EVENING WITH VISIBILITIES OF LESS THAN ONE MILE AT TIMES ESPECIALLY
AT KDTW. KFNT/KMBS WILL RECEIVE ONLY SCATTERED LIGHT SNOW SHOWERS.
MOST OF THIS ACTIVITY WILL BE FOCUSED DURING THE FIRST 2 TO 4 HOURS
OF THE FORECAST AS A SURFACE TROUGH MOVES THROUGH LOWER MICHIGAN.
STILL...COLD WEST/NORTHWEST FLOW OFF OF LAKE MICHIGAN WILL KEEP THE
STRATUS/STRATO-CU OVER THE AREA PRETTY MUCH THROUGH THE FORECAST W/
PASSING LIGHT SNOW SHOWERS EVEN INTO SATURDAY.
&&
.UPDATE...
UPDATED TO HONE IN ON HEAVIER SNOW BANDS THAT WILL BRING POSSIBLE
ACCUMULATIONS OF AN INCH OR TWO ALONG I-96/I-94. THIS ACTIVITY IS
SURVIVING THE TRIP FROM LAKE MICHIGAN NICELY...AND SHOULD REMAIN
LARGELY INTACT UNTIL A SURFACE TROUGH MOVES THROUGH THE AREA BY
BETWEEN 8 AND 10 PM. OTHER THAN THIS "CORRIDOR"...ACCUMULATIONS
SHOULD REMAIN BELOW AN INCH FOR THE MOST PART...WITH MOST AREAS
RECEIVING NO MORE THAN A DUSTING THE REST OF THE EVENING.
&&
.PREV DISCUSSION...ISSUED AT 356 PM
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.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING...ALL OPEN WATERS 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.
&&
$$
AVIATION.....DG
UPDATE.......DG
SHORT TERM...SF
LONG TERM....DWD
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 1205 PM EST THU JAN 18 2007
.UPDATE...
FRESHENED UP WX/POPS/SNOW OVER FAR SE TIED TO SHORTWAVE TROUGH NOW
MOVING INTO NORTHERN LK MI. NORTHERN LK MI ON FAR NORTH FRINGE OF
DEEPER MOSITURE AND LIFT WITH THE SHORTWAVE. INCREASED POPS SLIGHTLY
NEAR LK MICHIGAN SHORE EAST OF KESC...BUT BLYR WINDS HAVE TOO MUCH
WESTERLY COMPONENT WITH 230-240 DIRECTIONS OBSERVED TO PROVIDE MUCH
LAKE ENHANCEMENT TO SOUTHERN SCHOOLCRAFT. OTHERWISE...A FEW FLURRIES
ARE AFFECTING OTHER PORTIONS OF CWA BTWN THE NORTHERN LK MICHIGAN
SHORTWAVE AND ANOTHER SHORTWAVE/SFC TROUGH/H85 FRONT OVR NORTHERN
MINNESOTA.
KDLH RADAR AND SFC OBS INDICATE TROUGH IS NEARING NE MN WITH LIGHT
SNOW SPREADING INTO FAR REACHES OF WEST LK SUPERIOR. TAMDAR
SOUNDINGS FM KSAW AND CYQT NOT VERY COLD AND DEEP WITH INVERSION
THIS MORNING IN MOIST LAYER...AS LOW AS -10C AT CYQT WITH INVERSION
AROUND H9. EVEN SO...LATEST VISIBLE SATELLITE LOOPS SHOW DEVELOPMENT
OF LK EFFECT BAND OVR WESTERN LK SUPERIOR ORIENTED WSW TO ENE WITH
STARTING POINT NEAR SILVER BAY MINNESOTA AND ENDING POINT JUST S OF
ISLE ROYALE. EXPECT THIS BAND TO SIGNAL ARRIVAL OF TROUGH THIS
EVENING WHILE DROPPING ACROSS KEWEENAW PENINSULA. SINCE IT IS
ALREADY LOOKING STRONG ON SATELLITE...IT MAY PROVIDE A QUICK FEW
INCHES OF SNOW THIS EVENING OVER THE KEWEENAW PENINSULA AND ADJACENT
PORTION OF ONTONAGON COUNTY. LIGHT SNOW FM MN WILL SPREAD EAST...
REACHING WEST HALF OF CWA BY THIS EVENING. NW WINDS BEHIND THE
TROUGH AND H9-H85 TEMPS FALLING TO NEAR -20C BY 12Z FRI WILL ALLOW
FOR INCREASE IN LK EFFECT IN NW FLOW AREAS AFTER MIDNIGHT. TWEAKED
WORDING IN WSW TO TRY AND GET HANDLE ON THESE TRENDS. NO CHANGES
WERE MADE TO GOING HEADLINES.
&&
.DISCUSSION (ISSUED AT 630 AM EST)...
MAIN FCST CONCERN IS POTENTIAL FOR HVY LES NEAR LAKE SUPERIOR
TONIGHT INTO FRI NIGHT.
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW SEVERAL SHORTWAVES OVER
THE CENTRAL AND WRN CONUS WITHIN TROF AMPLIFYING DOWNSTREAM OF RIDGE
OVER W COAST. FIRST SHORTWAVE IS LIFTING ENE THRU CENTRAL WI AND
DESPITE LIMITED MOISTURE TO WORK WITH...700-500 MB FGEN AND DPVA
ASSOC WITH THIS FEATURE HAS RESULTED IN LIGHT SNOW/FLURRIES OVER
SRN/CENTRAL WI. ANOTHER VORT MAX IS DIGGING INTO WRN NE INTO BASE OF
AMPLIFYING MID-LVL TROF AND WILL BRING A COLD FRONT ACROSS UPR MI
LATE TODAY AND TONIGHT. SEVERAL OTHER SHORTWAVES UPSTREAM OVER
CANADA ARE POISED TO DROP OVER THE WRN GREAT LAKES LATE TONIGHT INTO
FRI BRINGING REINFORCING SHOTS OF ARCTIC AIR AND INCREASED POTENTIAL
FOR HEAVY LES.
TODAY...GIVEN THAT THERE ARE ALREADY REPORTS OF LIGHT SNOW/FLURRIES
UPSTREAM OVER WI WITH SHORTWAVE LIFTING THROUGH THE AREA WILL KEEP
IN A LOW CHC POPS FOR LIGHT SNOW OVER SCNTRL AND ERN COUNTIES TODAY.
GENERALLY BETTER FORCING FROM THIS FEATURE WILL STAY SOUTH AND EAST
OF FCST AREA. AS SECOND SHORTWAVE CONTINUES TO DIG THROUGH THE
CENTRAL PLAINS INTO THE LOWER MIDWEST...AN ASSOCIATED COLD FRONT
WILL MOVE THROUGH WRN UPR MI LATE THIS AFTERNOON AND EVENING. WINDS
SHIFTING MORE WRLY BY LATE AFTERNOON ALONG WITH 850 MB TEMPS FALLING
TO AROUND -12C BY 00Z AND Q-VECT CONV AHEAD OF SHORTWAVE SHOULD
BRING UP TO 2 INCHES OF LES TO PORTIONS OF THE KEWEENAW PENINSULA.
TONIGHT INTO FRI NIGHT...CONDITIONS STILL LOOK GOOD FOR A MDT TO HVY LAKE
ENHANCED EVENT TRANSITIONING TO PURE LES AS MODELS INDICATE 850MB
TEMPS FALLING TO -20 TO -22C FRI. SHORTWAVE MOVING THROUGH IN THE
EVENING WILL BRING DEEPER MOISTURE AND Q-VECT CONV FOR ENHANCEMENT
TO LES AS 850 MB TEMPS BEGIN TO PLUMMET BEHIND THE SHORTWAVE LATE
FRI NIGHT. WITH DEEPER MOISTURE AND ENHANCEMENT POTENTIAL LASTING
LONGER OVER ERN COUNTIES HAVE DECIDED TO GO WITH AN LES WARNING FOR
ALGER-LUCE AND NRN SCHOOLCRAFT COUNTIES FOR TOTAL SNOW ACCUMS OF
MORE THAN A FOOT WITH AN LES ADVISORY FOR SRN SCHOOLCRAFT FOR LATE
TONIGHT INTO SAT MORNING. OVER THE WESTERN COUNTIES...MODELS NOW
INDICATE SHORTER WINDOW OF DEEPER MOISTURE/ENHANCEMENT (LATE
TONIGHT/EARLY FRI) WITH A QUICKER TRANSITION TO PURE LES AS
INVERSION HGTS LOWER TO AROUND 5 KFT IN THE AFTERNOON. THUS...HAVE
DECIDED TO GO WITH A HIGH END LES ADVISORY LATE TODAY/THIS EVENING
INTO FRI NIGHT FOR TOTAL ACCUMS OF 5 TO 11 INCHES. NW AND ERN MQT
COUNTY ALONG WITH NRN IRON COUNTY COULD ALSO SEE LOCAL ACCUMS
REACHING ADVISORY WITH FAIRLY STRONG NW FLOW. HIGH PRES RIDGE
PASSING ACROSS UPPER MI WILL BRING AN END TO LINGERING LES FROM W TO
E LATE FRI NIGHT INTO SAT MORNING.
TEMPS WILL GET COLDER BEGINNING FRI AS THERE WILL BE VERY LTL
DIURNAL REBOUND FROM EARLY MORNING READINGS WITH A STRONG PUSH OF
(-20C TO -22C 850 MB TEMPS) ARCTIC AIR. WITH HIGH PRES RIDGE NEARING
LATE FRI NIGHT...TEMPS SHOULD PLUMMET TOWARD -10F OVER THE INTERIOR
W HALF AS LAKE EFFECT CLOUDS BREAK.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
HEAVY FREEZING SPRAY WARNING WRN LAKE SUPERIOR.
LAKE EFFECT SNOW WARNING LATE THIS AFTERNOON THROUGH FRI
NIGHT...MIZ001>003.
LAKE EFFECT SNOW WARNING TONIGHT THROUGH FRI EVENING...MIZ009.
LAKE EFFECT SNOW WARNING TONIGHT THROUGH FRI NIGHT...MI004.
LAKE EFFECT SNOW WARNING LATE TONIGHT INTO SAT
MORNING...MIZ006-007-085.
LAKE EFFECT SNOW ADVISORY TONIGHT THROUGH FRI NIGHT...MIZ084.
LAKE EFFECT SNOW ADVISORY LATE THIS EVENING THROUGH FRI
NIGHT...MIZ005.
LAKE EFFECT SNOW ADVISORY LATE TONIGHT THROUGH SAT
MORNING...MIZ014.
&&
$$
UPDATE...JLA
PREV DISCUSSION...VOSS
AREA FORECAST DISCUSSION
NWS RALEIGH NC
AFDRAH 1220 PM EST THU JAN 18 2007
.SHORT TERM /REST OF TODAY/...
RECENTLY UPDATED FORECAST TO ACCOUNT FOR DIMINISHING FREEZING RAIN
THREAT IN THE NE PIEDMONT AND TO DOWNPLAY ICE ACCRUAL AMOUNTS IN
THE NW PIEDMONT. APPEARS THAT BACK EDGE OF STEADY PRECIP OVER THE
WESTERN AND SOUTHERN PIEDMONT LIFTING E-NE. STILL EXPECT
WIDESPREAD DRIZZLE OVER THE PIEDMONT AND SANDHILLS /FREEZING
DRIZZLE IN THE NW PIEDMONT/ THROUGH THE AFTERNOON AND POSSIBLY
INTO THE EARLY EVENING HOURS. TEMPERATURES ON TRACK WITH JUST
SLIGHT ADJUSTMENT REQUIRED.
&&
.PREV DISCUSSION...
/ISSUED 1033 AM EST THU JAN 18 2007/
SHORT TERM /REST OF TODAY/...
12Z UPPER AIR ANALYSIS REVEALED TWO FEATURES THAT WILL [LAY MAJOR
ROLES IN P-TYPE THIS AFTERNOON. FIRST, DRIER AIR NOTED UPSTREAM
OF CENTRAL NC IN THE 700-500MB LAYER. THIS LAYER COINCIDES
IN FAVORED DENDRITE REGION. WITH MOISTURE DECREASING...EXPECT
SNOW TO DIMINISH NEXT FEW HOURS. ALSO NOTED WAS STRONG FETCH OF
WARMER AIR AROUND 850MB UPSTREAM. THIS WARM AIR SURGE ALSO NOTED
IN AIRCRAFT SOUNDINGS FROM CLT AND AREA VAD WIND PROFILES FROM
ACROSS AREA. THUS EXPECT PATCHES OF SNOW OVER THE NW PIEDMONT TO
TRANSITION TO FREEZING RAIN NEXT COUPLE HOURS WITH MAINLY LIGHT
PRECIP EXPECTED THROUGH THE AFTERNOON. DO NOT EXPECT THE TRIAD
REGION TO WARM TO AROUND FREEZING UNTIL LATE IN THE DAY. THE
PERSISTENT FREEZING PRECIP WILL LIKELY RESULT IN ICE ACCUMULATION
OF A TENTH OF AN INCH.
IN THE NE PIEDMONT...WIDESPREAD FREEZING RAIN WILL TRANSITION TO
RAIN AS SURFACE TEMPS RISE TO AROUND FREEZING WITH MUCH WARMER AIR
ALOFT. WILL MAINTAIN CATEGORICAL POPS FOR NOW. EXPECT PRECIP TO
DIMINISH SW-NE LATE TODAY AND EARLY TONIGHT.
FINALLY...ADJUSTED MAX TEMPS DOWN A DEGREE OR TWO...MAINLY IN THE
NORTHERN PIEDMONT.
PREV DISCUSSION...
/ISSUED 617 AM EST THU JAN 18 2007/
SHORT TERM /REST OF TODAY THROUGH SATURDAY NIGHT/...
THE WINTER WEATHER ADVISORY HAS BEEN EXPANDED TO INCLUDE THE
NORTHERN COASTAL PLAIN UNTIL NOON TODAY.
PREV DISCUSSION...
/ISSUED 412 AM EST THU JAN 18 2007/
CORRECTION TO WSW ENDING TIME NW PIEDMONT.
RFG
PREV DISCUSSION...
/ISSUED 339 AM EST THU JAN 18 2007/
UPDATE...
RADAR ECHOES ARE RAPIDLY SPREADING ACROSS CENTRAL NC. MOST PCPN
REMAINS ALOFT...BUT SOME IN THE FORM OF SNOW HAS BEEN REPORTED IN
THE SOUTHERN TIER COUNTIES. ADVISORIES HAVE REVERTED TO THEIR
EARLIER START TIMES OF 4 AM ACROSS THE SOUTH AND 6 AM ACROSS THE
NORTH TO MAKE PEOPLE AWARE THAT PCPN IS BEGINNING TO REACH THE
GROUND AS EARLIER PREDICTED. -RFG
PREV DISCUSSION...
/ISSUED 220 AM EST THU JAN 18 2007/
SHORT TERM /TODAY THROUGH SATURDAY NIGHT/...
TODAY...STRONG JET ALOFT WITH 160+ KTS OUT OF THE RED RIVER VALLEY
TOWARD NC IS HELPING TO DRAW WARMER MOIST AIR ALOFT FROM THE GULF
STATES TOWARD THE CAROLINAS. RADAR SHOWS DEVELOPING PCPN AREAS FROM
ALABAMA EASTWARD WITH JUST A SLIGHT NORTHWARD PROGRESSION. MOIST
SOUTHERLY FLOW ALOFT IS ENCOUNTERING AND BEGINNING TO OVERRUN MUCH
DRIER AIR OVER CENTRAL NC AND MOST PCPN IS LIKELY TO EVAP/SUBLIMATE
FOR SEVERAL HOURS BEFORE THE COLUMN SATURATES OVER THIS AREA.
CURRENT ALIGNMENT OF WINTER WEATHER ADVISORIES WILL BE KEPT IN PLACE
ACROSS CENTRAL NC...BUT ONSET DELAYED A COUPLE HOURS...AND POSSIBLY
ENDING EARLIER. AREAS OF PCPN IN THE FORM OF SLEET OR FRZG
RAIN SHOULD START IN THE SRN TIER TOWARD DAYBREAK...WITH MEASURABLE
PCPN AS FAR NORTH AS HIGHWAY 64 BY 10 AM AND AS FAR NORTH AS THE VA
BORDER AROUND NOON.
MODEL THICKNESS VALUES ARE SHOWING A MORE RAPID WARMUP DURING THE
DAY MEANING A QUICKER TRANSITION FROM SLEET TO FRZG RAIN TO RAIN.
DRYNESS IN THE DENDRITE GROWTH ZONE ALOFT SUGGESTS NEGLIGIBLE
CHANCES OF SNOW. PROGNOSES OF SURFACE WET BULB TEMPERATURES SHOWS
THE THREAT OF FREEZING RAIN RETREATING WEST OF U.S. ROUTE 1 BY 10 AM
AND LIMITED TO THE TRIAD AROUND NOON...ABOVE FREEZING THROUGHOUT THE
CWA AFTER 1 PM.
GIVEN THE TIGHT GRADIENT WESTERLY FLOW ALOFT...THERE IS LITTLE
OPPORTUNITY FOR WAVE AMPLIFICATION...EFFECTIVELY CUTTING OFF THE
NORTHWARD SURGE OF WARM MOIST AIR. THIS SHOULD MEAN RAPIDLY
DECREASING QPF NORTHWARD OVER THE NRN TIER OF CENTRAL NC. EXPECT QPF
OF .25-.50 IN THE SOUTHEAST THIRD TAPERING TO ONLY A FEW HUNDREDTHS
OF AN INCH IN THE NORTHERN TIER OF COUNTIES. MAX TEMPERATURES NEAR
34 IN THE TRIAD TO 43 IN SAMPSON CO.
TNGT..THE THREAT OF RAIN CONTINUES IN THE EASTERN HALF UNTIL AROUND
MIDNIGHT WITH SKIES REMAINING CLOUDY THROUGHOUT OVERNIGHT. THE RAIN
COOLED PIEDMONT AIRMASS SHOULD LINGER INTO FRI. LOWS OF 30 NW TO 37
SE MEANS SOME ICY PATCHES IN THE NW THIRD ARE POSSIBLE EARLY FRI.
-RFG
FRIDAY AND FRIDAY NIGHT...THE SFC CYCLONE WILL CONTINUE TO DEPART
THE REGION AS IT HEADS FURTHER NORTHEAST. THIS WILL LEAVE THE CWA IN
DRY NORTHWEST FLOW BOTH AT THE SFC AND ALOFT. FORECAST SOUNDINGS
INDICATE THAT MIXING SHOULD OCCUR TO NEAR 850 MB WHERE WINDS OF 40
TO 45 KTS WILL BE PRESENT. MEANWHILE...THE SFC PRESSURE GRADIENT
TIGHTENS OVER CENTRAL NORTH CAROLINA AS THE ATLANTIC LOW DEEPENS AND
HIGH PRESSURE MOVES INTO THE CENTRAL U.S. THESE FACTORS WILL RESULT
IN BREEZY CONDITIONS WITH WINDS POSSIBLY GUSTING TO 25 TO 30 MPH
DURING THE AFTERNOON. TEMPERATURES WILL ALSO CONTINUE TO BE ON THE
COOL SIDE AS LOW LEVEL THICKNESSES INDICATE HIGHS IN THE MID TO
UPPER 40S...WHICH ARE LOWER THAN THE CONSENSUS MOS. LOWS FRIDAY
NIGHT WILL DIP INTO THE MID 20S TO NEAR 30.
SATURDAY AND SATURDAY NIGHT...COOL DRY NORTHWEST FLOW WILL PERSIST
ACROSS THE FORECAST AREA. A REINFORCING SHOT OF COOLER AIR FILTERS
INTO THE AREA ON SATURDAY AFTERNOON...EVIDENT BY 850MB TEMPS
DROPPING TO AROUND -8C. HIGHS ARE ONCE AGAIN EXPECTED TO BE BELOW
MOS GUIDANCE...FROM AROUND 40 IN THE NE PIEDMONT TO MID 40S IN THE
COASTAL PLAIN. LOW LEVEL THICKNESS TECHNIQUE SUGGESTS IT MAY BE EVEN
COOLER THAN THIS...SO WILL CONTINUE TO MONITOR.
SFC HIGH PRESSURE SETTLES OVER CENTRAL NC BY SUNDAY MORNING. LIGHT
WINDS AND LOW DEWPOINTS POINT TO A VERY CHILLY NIGHT...BUT
INCREASING MID TO HIGH LEVEL CLOUDS WILL LIKELY HOLD TEMPS UP
SOMEWHAT. TEMPS STILL EXPECTED TO DROP INTO THE 20S. -JFB
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
NOT A LOT OF CONFIDENCE IN THE TIMING OF THE EVENT LATE THIS WEEKEND
AS MODEL EVOLUTION WAS FAST LAST NIGHT...AND HAS SPED UP EVEN
MORE TONIGHT. LOW PRESSURE RACES ACROSS THE SOUTHERN STATES AND THE
TRANSITORY COLD HIGH WILL BE REINFORCED AS PRECIP OVERSPREADS THE
AREA SUNDAY AFTERNOON/EVENING. WARM AIR ASSOCIATED WITH THE
OVERRUNNING WILL BE STRONG WITH A 50KT LLJ...THUS MIXED PRECIP IS A
FAIR BET AS EVAPORATIVE COOLING COULD EASILY LOCK TEMPS IN
THE CLIMATOLOGICALLY FAVORED AREA IN THE 30S ALL DAY. THERMAL
STRUCTURE AND TIMING OF THE ONSET IS STILL QUITE UNCERTAIN...WILL
ONLY MENTION R/S FOR NOW UNTIL THE TIMING MATTER IS RESOLVED.
OTHERWISE...WILL BE ENDING THE PRECIP A LITTLE EARLIER AS ON
MONDAY...OTHERWISE NO CHANGES TO THE LATER EXTENDED. -MM
AVIATION /06Z-06Z/...
VFR CONDS EARLY IN THE TAF PERIOD WILL GIVE WAY TO MVFR/IFR CIGS AND
VIS FOR THE REMAINDER OF THE TAF PERIOD AS PRECIP DEVELOPS AND
ADVECTS INTO THE CWA FROM THE SOUTH BETWEEN 10-13Z THIS MORNING.
PRECIP IS EXPECTED TO BEGIN AS SNOW AT GSO...TRANSITIONING TO SN/PL
AND EVENTUALLY FZRA BY 18Z. FZRA AND EVENTUALLY RAIN ARE EXPECTED
FOR THE REMAINDER OF THE TAF PERIOD AT GSO. AT RDU/FAY...PRECIP IS
MORE APT TO BEGIN AS FZRA BEFORE TRANSITIONING TO RAIN BY
15-18Z...ALTHOUGH A BRIEF PERIOD OF SN/PL CANNOT BE RULED OUT AT
ONSET. AT RWI...PRECIP WILL LIKELY FALL AS RAIN WITH THE EXCEPTION
OF A BRIEF PERIOD OF FZRA AT ONSET. PRECIP ASSOC/W THE WEAK COASTAL
LOW WILL END FROM SOUTHWEST TO NORTHEAST NEAR THE END OF THE TAF
PERIOD. -VINCENT/MM
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
NCZ007-021>024-038-039.
&&
$$
SHORT TERM...WSS
AREA FORECAST DISCUSSION
NWS RALEIGH NC
AFDRAH 1033 AM EST THU JAN 18 2007
.SHORT TERM /REST OF TODAY/...
12Z UPPER AIR ANALYSIS REVEALED TWO FEATURES THAT WILL [LAY MAJOR
ROLES IN P-TYPE THIS AFTERNOON. FIRST, DRIER AIR NOTED UPSTREAM
OF CENTRAL NC IN THE 700-500MB LAYER. THIS LAYER COINCIDES
IN FAVORED DENDRITE REGION. WITH MOISTURE DECREASING...EXPECT
SNOW TO DIMINISH NEXT FEW HOURS. ALSO NOTED WAS STRONG FETCH OF
WARMER AIR AROUND 850MB UPSTREAM. THIS WARM AIR SURGE ALSO NOTED
IN AIRCRAFT SOUNDINGS FROM CLT AND AREA VAD WIND PROFILES FROM
ACROSS AREA. THUS EXPECT PATCHES OF SNOW OVER THE NW PIEDMONT TO
TRANSITION TO FREEZING RAIN NEXT COUPLE HOURS WITH MAINLY LIGHT
PRECIP EXPECTED THROUGH THE AFTERNOON. DO NOT EXPECT THE TRIAD
REGION TO WARM TO AROUND FREEZING UNTIL LATE IN THE DAY. THE
PERSISTENT FREEZING PRECIP WILL LIKELY RESULT IN ICE ACCUMULATION
OF A TENTH OF AN INCH.
IN THE NE PIEDMONT...WIDESPREAD FREEZING RAIN WILL TRANSITION TO
RAIN AS SURFACE TEMPS RISE TO AROUND FREEZING WITH MUCH WARMER AIR
ALOFT. WILL MAINTAIN CATEGORICAL POPS FOR NOW. EXPECT PRECIP TO
DIMINISH SW-NE LATE TODAY AND EARLY TONIGHT.
FINALLY...ADJUSTED MAX TEMPS DOWN A DEGREE OR TWO...MAINLY IN THE
NORTHERN PIEDMONT.
&&
.PREV DISCUSSION...
/ISSUED 617 AM EST THU JAN 18 2007/
SHORT TERM /REST OF TODAY THROUGH SATURDAY NIGHT/...
THE WINTER WEATHER ADVISORY HAS BEEN EXPANDED TO INCLUDE THE
NORTHERN COASTAL PLAIN UNTIL NOON TODAY.
PREV DISCUSSION...
/ISSUED 412 AM EST THU JAN 18 2007/
CORRECTION TO WSW ENDING TIME NW PIEDMONT.
RFG
PREV DISCUSSION...
/ISSUED 339 AM EST THU JAN 18 2007/
UPDATE...
RADAR ECHOES ARE RAPIDLY SPREADING ACROSS CENTRAL NC. MOST PCPN
REMAINS ALOFT...BUT SOME IN THE FORM OF SNOW HAS BEEN REPORTED IN
THE SOUTHERN TIER COUNTIES. ADVISORIES HAVE REVERTED TO THEIR
EARLIER START TIMES OF 4 AM ACROSS THE SOUTH AND 6 AM ACROSS THE
NORTH TO MAKE PEOPLE AWARE THAT PCPN IS BEGINNING TO REACH THE
GROUND AS EARLIER PREDICTED. -RFG
PREV DISCUSSION...
/ISSUED 220 AM EST THU JAN 18 2007/
SHORT TERM /TODAY THROUGH SATURDAY NIGHT/...
TODAY...STRONG JET ALOFT WITH 160+ KTS OUT OF THE RED RIVER VALLEY
TOWARD NC IS HELPING TO DRAW WARMER MOIST AIR ALOFT FROM THE GULF
STATES TOWARD THE CAROLINAS. RADAR SHOWS DEVELOPING PCPN AREAS FROM
ALABAMA EASTWARD WITH JUST A SLIGHT NORTHWARD PROGRESSION. MOIST
SOUTHERLY FLOW ALOFT IS ENCOUNTERING AND BEGINNING TO OVERRUN MUCH
DRIER AIR OVER CENTRAL NC AND MOST PCPN IS LIKELY TO EVAP/SUBLIMATE
FOR SEVERAL HOURS BEFORE THE COLUMN SATURATES OVER THIS AREA.
CURRENT ALIGNMENT OF WINTER WEATHER ADVISORIES WILL BE KEPT IN PLACE
ACROSS CENTRAL NC...BUT ONSET DELAYED A COUPLE HOURS...AND POSSIBLY
ENDING EARLIER. AREAS OF PCPN IN THE FORM OF SLEET OR FRZG
RAIN SHOULD START IN THE SRN TIER TOWARD DAYBREAK...WITH MEASURABLE
PCPN AS FAR NORTH AS HIGHWAY 64 BY 10 AM AND AS FAR NORTH AS THE VA
BORDER AROUND NOON.
MODEL THICKNESS VALUES ARE SHOWING A MORE RAPID WARMUP DURING THE
DAY MEANING A QUICKER TRANSITION FROM SLEET TO FRZG RAIN TO RAIN.
DRYNESS IN THE DENDRITE GROWTH ZONE ALOFT SUGGESTS NEGLIGIBLE
CHANCES OF SNOW. PROGNOSES OF SURFACE WET BULB TEMPERATURES SHOWS
THE THREAT OF FREEZING RAIN RETREATING WEST OF U.S. ROUTE 1 BY 10 AM
AND LIMITED TO THE TRIAD AROUND NOON...ABOVE FREEZING THROUGHOUT THE
CWA AFTER 1 PM.
GIVEN THE TIGHT GRADIENT WESTERLY FLOW ALOFT...THERE IS LITTLE
OPPORTUNITY FOR WAVE AMPLIFICATION...EFFECTIVELY CUTTING OFF THE
NORTHWARD SURGE OF WARM MOIST AIR. THIS SHOULD MEAN RAPIDLY
DECREASING QPF NORTHWARD OVER THE NRN TIER OF CENTRAL NC. EXPECT QPF
OF .25-.50 IN THE SOUTHEAST THIRD TAPERING TO ONLY A FEW HUNDREDTHS
OF AN INCH IN THE NORTHERN TIER OF COUNTIES. MAX TEMPERATURES NEAR
34 IN THE TRIAD TO 43 IN SAMPSON CO.
TNGT..THE THREAT OF RAIN CONTINUES IN THE EASTERN HALF UNTIL AROUND
MIDNIGHT WITH SKIES REMAINING CLOUDY THROUGHOUT OVERNIGHT. THE RAIN
COOLED PIEDMONT AIRMASS SHOULD LINGER INTO FRI. LOWS OF 30 NW TO 37
SE MEANS SOME ICY PATCHES IN THE NW THIRD ARE POSSIBLE EARLY FRI.
-RFG
FRIDAY AND FRIDAY NIGHT...THE SFC CYCLONE WILL CONTINUE TO DEPART
THE REGION AS IT HEADS FURTHER NORTHEAST. THIS WILL LEAVE THE CWA IN
DRY NORTHWEST FLOW BOTH AT THE SFC AND ALOFT. FORECAST SOUNDINGS
INDICATE THAT MIXING SHOULD OCCUR TO NEAR 850 MB WHERE WINDS OF 40
TO 45 KTS WILL BE PRESENT. MEANWHILE...THE SFC PRESSURE GRADIENT
TIGHTENS OVER CENTRAL NORTH CAROLINA AS THE ATLANTIC LOW DEEPENS AND
HIGH PRESSURE MOVES INTO THE CENTRAL U.S. THESE FACTORS WILL RESULT
IN BREEZY CONDITIONS WITH WINDS POSSIBLY GUSTING TO 25 TO 30 MPH
DURING THE AFTERNOON. TEMPERATURES WILL ALSO CONTINUE TO BE ON THE
COOL SIDE AS LOW LEVEL THICKNESSES INDICATE HIGHS IN THE MID TO
UPPER 40S...WHICH ARE LOWER THAN THE CONSENSUS MOS. LOWS FRIDAY
NIGHT WILL DIP INTO THE MID 20S TO NEAR 30.
SATURDAY AND SATURDAY NIGHT...COOL DRY NORTHWEST FLOW WILL PERSIST
ACROSS THE FORECAST AREA. A REINFORCING SHOT OF COOLER AIR FILTERS
INTO THE AREA ON SATURDAY AFTERNOON...EVIDENT BY 850MB TEMPS
DROPPING TO AROUND -8C. HIGHS ARE ONCE AGAIN EXPECTED TO BE BELOW
MOS GUIDANCE...FROM AROUND 40 IN THE NE PIEDMONT TO MID 40S IN THE
COASTAL PLAIN. LOW LEVEL THICKNESS TECHNIQUE SUGGESTS IT MAY BE EVEN
COOLER THAN THIS...SO WILL CONTINUE TO MONITOR.
SFC HIGH PRESSURE SETTLES OVER CENTRAL NC BY SUNDAY MORNING. LIGHT
WINDS AND LOW DEWPOINTS POINT TO A VERY CHILLY NIGHT...BUT
INCREASING MID TO HIGH LEVEL CLOUDS WILL LIKELY HOLD TEMPS UP
SOMEWHAT. TEMPS STILL EXPECTED TO DROP INTO THE 20S. -JFB
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
NOT A LOT OF CONFIDENCE IN THE TIMING OF THE EVENT LATE THIS WEEKEND
AS MODEL EVOLUTION WAS FAST LAST NIGHT...AND HAS SPED UP EVEN
MORE TONIGHT. LOW PRESSURE RACES ACROSS THE SOUTHERN STATES AND THE
TRANSITORY COLD HIGH WILL BE REINFORCED AS PRECIP OVERSPREADS THE
AREA SUNDAY AFTERNOON/EVENING. WARM AIR ASSOCIATED WITH THE
OVERRUNNING WILL BE STRONG WITH A 50KT LLJ...THUS MIXED PRECIP IS A
FAIR BET AS EVAPORATIVE COOLING COULD EASILY LOCK TEMPS IN
THE CLIMATOLOGICALLY FAVORED AREA IN THE 30S ALL DAY. THERMAL
STRUCTURE AND TIMING OF THE ONSET IS STILL QUITE UNCERTAIN...WILL
ONLY MENTION R/S FOR NOW UNTIL THE TIMING MATTER IS RESOLVED.
OTHERWISE...WILL BE ENDING THE PRECIP A LITTLE EARLIER AS ON
MONDAY...OTHERWISE NO CHANGES TO THE LATER EXTENDED. -MM
AVIATION /06Z-06Z/...
VFR CONDS EARLY IN THE TAF PERIOD WILL GIVE WAY TO MVFR/IFR CIGS AND
VIS FOR THE REMAINDER OF THE TAF PERIOD AS PRECIP DEVELOPS AND
ADVECTS INTO THE CWA FROM THE SOUTH BETWEEN 10-13Z THIS MORNING.
PRECIP IS EXPECTED TO BEGIN AS SNOW AT GSO...TRANSITIONING TO SN/PL
AND EVENTUALLY FZRA BY 18Z. FZRA AND EVENTUALLY RAIN ARE EXPECTED
FOR THE REMAINDER OF THE TAF PERIOD AT GSO. AT RDU/FAY...PRECIP IS
MORE APT TO BEGIN AS FZRA BEFORE TRANSITIONING TO RAIN BY
15-18Z...ALTHOUGH A BRIEF PERIOD OF SN/PL CANNOT BE RULED OUT AT
ONSET. AT RWI...PRECIP WILL LIKELY FALL AS RAIN WITH THE EXCEPTION
OF A BRIEF PERIOD OF FZRA AT ONSET. PRECIP ASSOC/W THE WEAK COASTAL
LOW WILL END FROM SOUTHWEST TO NORTHEAST NEAR THE END OF THE TAF
PERIOD. -VINCENT/MM
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ008>011-
025>028-040-041-043-073>076-083-084.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
NCZ007-021>024-038-039.
&&
$$
SHORT TERM...WSS
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 310 AM PST THU JAN 18 2007
.SYNOPSIS...RAIN WILL DECREASE BY THIS AFTERNOON AS THE WEAK WARM
FRONT OVER WESTERN WASHINGTON MOVES NORTH INTO BRITISH COLUMBIA.
RAIN WILL SPREAD IN FROM THE WEST TONIGHT AND FRIDAY AS THE
ASSOCIATED WEAK COLD FRONT MOVES INLAND. COOLER NORTHWEST FLOW WILL
BRING MORE SHOWERY WEATHER FRIDAY NIGHT AND SATURDAY. ANOTHER WARM
FRONT WILL CROSS THE AREA SATURDAY NIGHT AND SUNDAY. AN UPPER LEVEL
RIDGE ALONG THE COAST MAY BRING DRIER WEATHER EARLY NEXT WEEK.
&&
.SHORT TERM...LIGHT RAIN CONTINUES OVER MOST OF THE AREA THIS
MORNING WITH SOME LIGHT SNOW BEING REPORTED ABOVE ABOUT 500 FEET.
ACARS SOUNDINGS AROUND MIDNIGHT POINT TO A FREEZING LEVEL AROUND
1500 FEET. 06Z MODELS AND LATEST IR SATELLITE IMAGERY SUPPORT
CONTINUED WARM ADVECTION THROUGH THIS MORNING...THEN FINALLY LIFTING
MOSTLY UP INTO B.C. THIS AFTERNOON. WITH LOW FREEZING LEVELS HAVE
KEPT THE MENTION OF SNOW THIS MORNING AND WORDED IT ABOVE 500 FEET.
HAVE BACKED OFF TO A CHANCE OF RAIN FOR MUCH OF SOUTH PART OF THE
AREA THIS AFTERNOON AS THE WARM FRONT LIFTS NORTH. THE TRAILING WEAK
COLD FRONT COMES THROUGH LATE TONIGHT AND FRIDAY AS EXPECTED...POPS
CATEGORICAL.
NONDESCRIPT POST FRONTAL WNW FLOW FRIDAY NIGHT-SATURDAY BUT GFS
SHOWS A NICE COLD POOL MOVING OVER THE AREA. MOS POPS REMAIN UP SO
HAVE KEPT HIGH CHANCE POPS FOR SHOWERS MOST OF THE LOWLANDS...LIKELY
COAST AND OROGRAPHIC AREAS. SNOW LEVELS ONLY MAKE IT TO 1000-1500
FEET IN ONSHORE FLOW SO NO SNOW WORDING FOR THE LOWLANDS.
BIGGEST CHANGE IS THE MODELS GOING BACK TO A WARM ADVECTION LIGHT
RAIN PATTERN SATURDAY NIGHT-SUNDAY. THE `OPEN DOOR` RIDGE AXIS ALONG
130W AT THAT TIME LOOKS ALMOST EXACTLY LIKE THE ONE OUT THERE RIGHT
NOW. 500 MB HEIGHTS OVER W WA JUST ABOUT THE SAME AT 564 DM. BOTH
ECMWF AND CANADIAN SUPPORT THE GFS WARM ADVECTION SOLUTION. KAM
.LONG TERM...GFS IS STILL BEING A TEASE SHOWING MAYBE SOME DRY
WEATHER FOR PARTS OF MONDAY-THURSDAY OR MAYBE PART OF THE FORECAST
AREA. THE PATTERN REMAINS ABOUT THE SAME MONDAY-TUESDAY WITH THE
UPPER LEVEL RIDGE AXIS ALONG THE COAST AND WEAK SYSTEMS BEING
DIRECTED UP OVER THE RIDGE AND ACROSS VANCOUVER ISLAND. GFS ACTUALLY
SHOWS SOME LIGHT QPF OVER THE NORTHERN ZONES OR ALONG THE BORDER
BOTH DAYS. WILL DEFER CHANGES TO THE DAY SHIFT...BUT WITH THE MODELS
STILL BEING SHAKY...THE DRY FORECAST MAY BE AS WELL. KAM
&&
.AVIATION...WARM FRONT PUSHING TO THE COAST WITH CIGS RISING THERE
AS AREA OF SIGNIFICANT LIFT IS INLAND AND MOVING EAST. SAT IMAGERY
INDICATES ANOTHER SURGE OF LIFT MAY BE HEADED OUR WAY. PRECIP HAS
BEEN HEAVY ENOUGH IN THIS COOL AIRMASS TO DRAG SNOW LEVELS VERY
LOW...TO THE SURFACE ACROSS HIGHER TERRAIN. SO KSEA/KPWT HAVE A
THREAT OF SOME LIGHT SNOW MUCH LIKE KPAE WHERE IT IS ALREADY
SNOWING. NOT EXPECTING ANY ACCUMULATION OF CONCERN AND PRECIP SHOULD
BE BACK TO JUST RAIN LATER THIS MORNING. CIGS ARE ABOUT AS BAD AS
THEY WILL GET AND SHOULD IMPROVE SOME OVER INLAND AREAS TODAY.
KSEA...CIGS DROPPED INTO IFR...SOMEWHAT LOWER THAN EARLIER
EXPECTED...GENERALLY DUE TO LOWERING SNOW LEVELS. EXPECT IFR TO LOW
MVFR CIGS THROUGH MID MORNING WITH IMPROVEMENT TO 2000-5000 FT
CEILINGS THEREAFTER. UNTIL ABOUT 14-16Z COULD GET SOME LIGHT SNOW
WITH THE RAIN...BUT NOT EXPECTING PAVEMENT ACCUMULATIONS. WIND
REMAINING S-SE 5-10 KTS TODAY. CERNIGLIA
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY ALL WATERS EXCEPT CENTRAL STRAIT.
$$
WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 925 PM PST WED JAN 17 2007
.SYNOPSIS...A FRONT WILL BRUSHING WESTERN WASHINGTON TONIGHT AND
THURSDAY WILL BRING PRECIPITATION TO MAINLY THE COAST AND NORTHWEST
INTERIOR. THE WEATHER PATTERN WILL REMAIN UNSETTLED THROUGH SATURDAY
FOR A CONTINUED CHANCE OF PRECIPITATION. HIGH PRESSURE ALOFT AND LOW
LEVEL OFFSHORE FLOW WILL RESULT IN DRY WEATHER EARLY NEXT WEEK.
&&
.SHORT TERM...
LIGHT PRECIP AHEAD OF A WMFNT OFF THE WA COAST HAD OVERSPREAD MUCH
OF THE CWA THIS EVENING. EXPECT THE PRECIP TO PERSIST THE REMAINDER
OF THE NIGHT AS THE WMFNT CONTINUES TO MOVE SLOWLY E.
MEANWHILE...WARM AIR ADVECTION WAS OCCURRING AHEAD OF THE FRONT...
WITH ACARS DATA INDICATING THE FREEZING LEVEL BETWEEN 1500 AND 2000
FT OVER THE INTERIOR. ON THE COAST...THE FREEZING LEVEL WAS NEAR
2300 FT EARLIER THIS EVENING. SURFACE DEW POINTS WERE ALSO UP...
MOSTLY IN THE LOWER TO MID 30S...AND NOT MUCH CHANGE IN THE DEW
POINTS IS EXPECTED OVERNIGHT. THEREFORE THE THREAT OF SNOW HAS ENDED
FOR THE LOWLANDS...ALTHOUGH THE RAIN WILL LIKELY BE MIXED WITH SNOW
AT TIMES AT OR ABOVE THE 500 FOOT LEVEL. OTHERWISE THE AREAS MOST
LIKELY TO SEE SNOW WILL BE THE HOOD CANAL ZONE AND THE EAST PUGET
SOUND LOWLANDS...HOWEVER ANY ACCUMULATION WILL BE LESS THAN AN INCH.
THE FORECAST WAS UPDATED ACCORDINGLY.
THE WEAKENING WMFNT WILL MOVE ACROSS THE NW PORTION OF THE CWA
DURING THE DAY THU AND THEN DISSIPATE AS IT MOVES INTO BRITISH
COLUMBIA. THE PRECIP THREAT SHOULD THEN BECOME CONFINED TO MOSTLY
THE COAST AND FAR NW INTERIOR BY THE END OF THE DAY. THE LATEST
NAM/WRF AND GFS INDICATED THAT MUCH OF THE INTERIOR WILL BE DRY THU
NIGHT.
.LONG TERM...FROM THE PREV DISCUSSION...12Z GFS PRETTY UNEQUIVOCAL
ABOUT OFFSHORE FLOW DEVELOPING SUNDAY AND CONTINUING INTO NEXT WEEK.
UPPER RIDGE ALSO BUILDS. DETAILS FLUCTUATE FROM RUN TO RUN BUT FOR
NOW AM SATISFIED TREND IS TOWARD DRIER WEATHER. HAVE REMOVED PCPN
FROM SUNDAY ON. TEMPS SHOULD BE CLOSE TO CLIMATOLOGICAL
AVERAGES...45 TO 50 FOR HIGHS AND 35 TO 40 FOR LOWS. BURKE
&&
.AVIATION...WITH WEAK WARM ADVECTION AND LIGHT OFFSHORE
GRADIENTS...CEILINGS WILL BE HIGHLY VARIABLE WITH BASICALLY A MIX OF
LOW AND MID CLOUDS. RAIN WILL CONTINUE TO SPREAD OVER THE AREA...NOT
VERY HEAVY OR STEADY HOWEVER. LOWEST CEILINGS SHOULD BE TOWARD THE
COAST AND NORTH PART WHERE RAIN WILL BE MORE PREVALENT.
KSEA...2000-5000 FT CEILINGS THROUGH THE NIGHT WITH LIGHT RAIN. NOT
EXPECTING ANY SIGNIFICANT VISIBILITY RESTRICTIONS...GENERALLY
GREATER THAN 5 MILES. CERNIGLIA
&&
.SEW WATCHES/WARNINGS/ADVISORIES...SMALL CRAFT ADVISORY COASTAL
WATERS AND WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.
$$
WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
AFDARX 1100 AM CST THU JAN 18 2007
.UPDATE...MADE SOME CHANGES TO THE FORECAST FOR TODAY BASED ON A FEW
ITEMS. BY MID-MORNING...KARX RADAR HAD REALLY INCREASED THE ECHO
COVERAGE EAST OF A LINE FROM KCCY-KONA-KMDZ. WITHIN THAT ECHO...A
BROAD WEST-EAST BAND OF MORE ENHANCED ECHO /15-20 DBZ/ HAS BEEN
ACTIVE FROM KCCY-KMSN ROUGHLY. THIS HAS BEEN ALL SNOW. LATEST NCEP
RUC SHOWS A WEAK FRONTOGENETICAL FORCING REGION IN THE 850-700 MB
LAYER IN THIS EXACT LOCATION. THIS LIFT AND FRONTAL CIRCULATION HAS
PRODUCED 1-2 MI SNOW IN THAT AREA. THE RUC DOES SHIFT THIS AREA EAST
WITH TIME THIS AFTERNOON. CALLS DOWN TO KPDC SAY AROUND ONE-HALF INCH
HAS FALLEN SINCE MORNING...WITH BOAZ /NRN RICHLAND/ ONLY IN THE
TENTH AREA.
SECOND AREA OF FORCING IS ALONG THE COLD FRONT ALONG A KFSD-KDLH
LINE ROUGHLY AT 16Z. RADAR ECHOES ARE ALONG THAT BOUNDARY. THIS
SHOULD ARRIVE AROUND MID-AFTERNOON IN THE WESTERN FORECAST AREA
/KRST/. AT THE SAME TIME...A STRONG SHORTWAVE TROUGH AND POTENTIAL
VORTICITY /PV/ ANOMALY OVER KSUX AT 16Z IS SHIFTING EAST AND WILL
PROVIDE VERY GOOD FORCING ALOFT THIS AFTERNOON AND EARLY EVENING.
THIS IS ALSO ENHANCING THE FRONTOGENETICAL CIRCULATION DISCUSSED
ABOVE AT THIS TIME IN SWRN WI AND NERN IA.
SO...BOTTOM LINE IS UPDATED TO HAVE MORE WEATHER IN THE FORECAST
TODAY AND ALL SN. KALO TAMDAR AT 16Z INDICATED PROBAIBLITIES ARE
MORE TOWARD ICE INTORDUCTION RATHER THAN LIQUID /FZDZ/. WILL LIKELY
NEED TO UPDATE THE GRIDS TONIGHT TO INCREASE THE SNOW CHANCES TOO.
WOULD EXPECT AN INCH OR SO DOWN SOUTH IN THE BAND TODAY. THE FRONT
LOOKS TO PROVIDE A QUICK ONE-HALF INCH AS IT MOVES THROUGH WITH THE
PV ANOMALY. UPDATES ARE OUT FOR TODAY...WILL LOOK INTO EVENING
UPDATES AND TRY TO SHIP PRIOR TO NOON.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
BAUMGARDT