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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 081527
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1027 AM EST SUN DEC 8 2013

.SYNOPSIS...
-- Changed Discussion --
LOW PRESSURE WILL MOVE NORTHEAST ACROSS THE MID-ATLANTIC TODAY
THROUGH MONDAY. AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE
AREA TUESDAY. CANADIAN HIGH PRESSURE WILL BUILD OVERHEAD FOR THE
SECOND HALF OF THE WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

-- Changed Discussion --
AN 18Z BALLOON WL BE LAUNCHED TDA.

FCST SEEMS TO BE ON TRACK ATTM. PETERBURG WV HAS RCVD 4"...TOP
REPORT SO FAR. TRAFFIC CAMS SHOW LESSER AMTS FM I-81 TO I-95.
INSIDE THE DC BALTWAY FLAKES ARE FALLING BUT LTL ACCUM SO FAR. IN
BALT AREA ROADS APPEAR TO BE DRY...BUT RDR SHOWS ECHOES ARE MOVG
INTO THE AREA SO SNOW LKLY TO FALL THERE SOON.

PRVS DSCN...

NO DOUBT CAD EFFECT FROM THE HIGH TO OUR NORTH HAS BEEN
WORKING...WITH SURFACE TEMPS NEAR OR BELOW FREEZING ACROSS THE
REGION THIS MORNING. MEANWHILE...LAST EVENINGS 00Z RAOB FROM THE
BLACKBURG VA WFO INDICATED WARM NOSE IS IN PLACE AT 850. THIS WARM
AIR ALOFT WILL MOVE INTO THE REGION...SETTING THE STAGE FOR A
SLEET/FREEZING RAIN SCENARIO. IT IS QUITE POSSIBLE THAT SOUTHERN
COUNTIES...AROUND CHARLOTTESVILLE/STAUNTON AND SURROUNDING
AREAS...WILL SEE PRECIP START AS SLEET WITH WARM NOSE DEVELOPING.
ADJUSTED FORECAST HERE TO INCLUDE SLEET MIXED WITH SNOW AT THE
ONSET. FURTHER NORTH...STILL EXPECTING SNOW AT THE START WITH ALL
THE VERTICAL COLUMN BELOW FREEZING...THEN CHANGING TO FREEZING
RAIN/SLEET LATER. SNOW/SLEET ACCUMULATIONS EXPECTED TO BE AN INCH
OR LESS ALONG AND EAST OF I-95...THEN INCREASING TO THE NORTH AND
WEST...WITH 2-3 INCHES LIKELY OVER THE HIGHER ELEVATIONS AND THE
NORTHERN SHENANDOAH VALLEY.

WINTER STORM WARNING REMAINS IN EFFECT FOR MOST AREAS WEST OF
I-95...WITH WINTER WX ADVISORY TO THE EAST.

HIGHS TODAY NOT EXPECTED TO MAKE IT ABOVE FREEZING...EXCEPT FOR
AREAS RIGHT ALONG CHES BAY AND POTENTIALLY SRN MD NEAR THE
POTOMAC RIVER/BAY CONFLUENCE. MAV/MET BIAS CORRECTED GRIDS USED
FOR TEMPS TODAY.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...

TONIGHT...SURFACE LOW PRESSURE PUSHES NORTH INTO THE GREAT
LAKES...WITH A TRAILING COLD FRONT APPROACHING FROM THE WEST AND A
WARM FRONT TO THE SOUTH...WHILE ANOTHER LOW DEVELOPS OFFSHORE. PRECIP
CONTINUES TONIGHT...WITH PREDOMINANT P-TYPE AS FREEZING RAIN. WINTER
STORM WARNING REMAINS IN EFFECT...AND THE EVENING/OVERNIGHT PERIOD
IS WHERE WE WILL BE MOST LIKELY TO SEE QUARTER INCH ICE
ACCUMULATIONS OR MORE THAT WOULD VERIFY THE WARNING. 00Z GFS/ECMWF
AND 21Z SREF IS MORE AGGRESSIVE HEAVIER BANDS OF PRECIP TONIGHT
ASSOCIATED WITH 850MB JTST...WHEREAS THE 00Z NAM IS SOMEWHAT DRIER.
SOME CONCERN THAT ICING ACCUM COULD BE HIGHER THAN WHAT IS CURRENTLY
FCST...BUT WILL HAVE TO WAIT FOR MORE MODEL CONSISTENCY WITH REGARD
TO BANDED PRECIP AND TIMING OF THE WARM FRONT TO PUSH ACROSS THE
AREA...WHICH WOULD SUPPORT WARMER TEMPS. FOR NOW...LOWS STILL
EXPECTED TO STAY BELOW FREEZING BEFORE DAWN MONDAY.

WARMER AIR MOVES INTO THE REGION MONDAY...WITH FREEZING RAIN
CHANGING TO RAIN. MODELS ARE ALSO BACKING OFF ON QPF SOMEWHAT
MONDAY...WHICH COULD LESSEN A FLOOD THREAT FROM NEW
RAINFALL...ALTHOUGH MELTING OF FROZEN PRECIP WILL ALSO COME INTO THE
EQUATION. IN GENERAL...EXPECT PRECIP TO TAPER OFF WITH TEMPS WARMING
INTO THE LOW TO MID 40S.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...

THE SFC BNDRY WL REMAIN STALLED JUST SE OF CWFA MON NGT-TUE. THE
PTTN ALOFT WL BE CHARACTERIZED BY A BROAD RDG ACRS THE WRN ATLC/SERN
CONUS AND A L/WV TROF AXIS FM THE GRTLKS BACK TWD THE DESERT SW. A
TIGHT H5 HGT PTTN PROGGED SE OF THE TROF...HIGHLIGHTED BY A 160+ KT
UPR JET. WHILE S/WV ENERGY WL CROSS THE GRTLKS HEADED TWD NEW
ENGLAND TUE...RESULTING IN A MORE ZNL FLOW PTTN...CWFA WL RESIDE
IN RRQ OF THE JETMAX. HV BEEN HOPEFUL THAT THE BNDRY WUD PUSH FAR
ENUF SE TO NOT BE AN ISSUE TUE WHEN ANOTHER RIPPLE PROPAGATES
ALONG THE FNT...BUT AM BCMG MORE CONCERNED THAT WON/T BE THE CASE.
THERE/S PLENTY OF UPR LVL LIFT TO SUPPORT PCPN /EVEN THE DRY ECMWF
COMING ON BOARD/. THERMALLY...THE AMS WUD BE COLD ENUF TO SUPPORT
SNOW...EVEN THO BLYR TEMPS MAY BE MARGINAL. SUBFRZG DEWPTS WUD
SUPPORT MORE EVAP COOLING/WET BULB EFFECT...SO CANNOT DISCOUNT THE
POTL OF MORE SNOW. IF ANYTHING...MOS TEMPS MAY BE TOO WARM. HV
KEPT SAME FLAVOR IN GRIDS FOR MAX/MIN-T...BUT PLACED A LTL MORE
EMPHASIS ON SNOWY PTYPE. TOO FAR OUT TO TALK ABT ACCUMS...BUT HWO
ALREADY REFLECTS PSBLTY OF ADDTL SNFL...SO NO FURTHER ADJUSTMENTS
REQD.

HIPRES BLDS EWD FM CENTER OF CONUS...PROVIDING A CHILLY AMS FOR THE
2ND HALF OF THE WK. ITS ALSO REMARKABLE HOW QUICKLY SUBSIDENCE
ADVCS. DONT BELIEVE THERE WL BE MUCH OPPORTUNITY FOR UPSLP SHSN...
ALTHO WL BE ADDING A FEW CLDS WED.

GDNC AT ODDS BY THE END OF THE FCST. ECMWF REMAINS DRY...BUT GFS
SUGGESTING LOPRES TRACKS ACRS THE US/CNDN BRDR...DRAGGING A CDFNT
THRU AND ADVECTING MSTR NEWD AHD OF IT. IF THAT WERE TO OCCUR...
PTYPES WUD AGAIN BE AN ISSUE. TOO FAR OUT TO DRAW ANY CONCLUSIONS
YET...BUT DO HV POPS IN THE DATABASE SAT.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...

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A WINTRY MIX OF SNOW AND SLEET HAS DEVELOPED OVER ALL TERMINAL
SITES...WITH IFR VSBYS AND LOWERING CEILINGS. SNOW AND SLEET WILL
CHANGE TO ALL FREEZING RAIN THIS AFTERNOON AND EARLY EVENING.
PERIODS OF FREEZING RAIN WITH MVFR TO IFR CIGS AND VSBYS EXPECTED
INTO THE OVERNIGHT HOURS. SIGNIFICANT ICE ACCUMULATIONS WILL OCCUR
ESPECIALLY AT KIAD/KMRB AND KCHO. KBWI/KMTN AND KDCA WILL
GRADUALLY CHANGE OVER TO RAIN LATE TONIGHT OR EARLY MONDAY
MORNING. CIGS AND VSBY WILL REMAIN SUB VFR THROUGH MONDAY.

AN ADDTL WV OF LOPRES ALONG THE STALLED BNDRY OFFSHORE MAY LEAD
TO MORE PCPN TUE. CHO-DCA-BWI WL BE CLOSER TO SOURCE...AND STANDS
THE BETTER CHC AT SEEING SOMETHING. TEMPS WL BE COLD ENUF TO
SUPPORT SNOW. EVEN W/O PCPN...FLGT RESTRICTIONS A STRONG PSBLTY
DUE TO CIGS...W/ IFR LKLY IN ANY SNW.

VFR XPCTD WED-THU AS HIPRES BLDS.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
SMALL CRAFT ADVISORY IN EFFECT FOR PORTIONS OF THE CHES BAY AND
LOWER TIDAL PTMC.

AS THE CDFNT MVS OFFSHORE...NLY FLOW COMMENCES ARND BLDG HIPRES.
THAT WUD SUPPORT CHANNELING IN THE CHSPK BAY. SCA PSBL...PRIMARILY
FOR THE MID BAY. THE FLOW WUD BE INTERRUPTED AS A WAVE OF LOPRES MVS
ALONG THE SFC BNDRY TUE.
-- End Changed Discussion --

&&

.HYDROLOGY...

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QPF UP TO AN INCH SUN INTO ELY MON WL CAUSE ADDTL RIVER RISES MON
INTO TUE. HWVR...NOT ALL OF THAT QPF WL FALL AS RAIN...SO THERE/S
SOME UNCERTAINTY AS TO WHEN AND HOW QUICKLY THOSE RISES WL
OCCUR... OR HOW SGFNT THEY WL BE.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR DCZ001.
MD...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR MDZ007-011-
     013-014-016.
     WINTER STORM WARNING UNTIL 10 AM EST MONDAY FOR MDZ003>006-009-
     010-502.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST MONDAY FOR MDZ501.
     WINTER WEATHER ADVISORY UNTIL 8 PM EST THIS EVENING FOR MDZ017-
     018.
VA...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR VAZ054>057.
     WINTER STORM WARNING UNTIL 10 AM EST MONDAY FOR VAZ025>031-
     036>040-042-050>053-501>504.
WV...WINTER STORM WARNING UNTIL 10 AM EST MONDAY FOR WVZ050>053-055-
     502-504>506.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST MONDAY FOR WVZ501-503.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR
     ANZ532>534-536-537-540-541-543.
-- End Changed Discussion --

&&

$$
UPDATE...WOODY!
PRVS...KCS/HTS