-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 081937
AFDLWX

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

.SYNOPSIS...

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.

&&

.NEAR TERM /THROUGH TONIGHT/...

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18Z IAD BALLOON SHOWS SLT WRMG OVR 12Z...BUT ATMOSPHERIC COLUMN
RMNS BLO FRZG...ALTHO ARND 700 MB THE TEMP LN IS DRAWING CLOSE.
FURTHER SW...THE RNK SNDG SHOWS SIG WRMG SINCE 12Z W/ AN ABV-FRZG
LYR FM 850 TO 700MB...BUT THEN DROPPING BLO FRZG TO THE SFC. A
TEXT BOOK FZRA SNDG.

BUT THE STORY OF TDA WL BE THE SNOW TOTALS ACROSS NERN MD. 6-8"
HAS FALLEN FM FREDERICK TO HARFORD. ACROSS THE NRN HALF OF THE
FCST AREA DUAL POL CC NOW SHOWS RETURNS OF "NON MET UNIFORM" WHICH
IMPLIES THE SNOW IS NOW CHANGING TO SLEET...SO HIGHER SNOW TOTALS
NOT XPCTD. WE ARE NOW RCVG SPOTTER REPORTS OF PCPN CHANGING TO
SLEET AS WELL.

STLT W.V. IMGRY SHOWS THE WAVE CAUGHT UP IN THE SW-NE UPR WIND
FLOW ACROSS ERN W.V. AND NERN MD WHICH INTENSIFIED OVR MD. BUT THE
HEAVIEST PCPN IN ASSO W/ THIS BAND IS MOVG INTO SRN NJ. RDR AND
SFC OBS SHOW THE PCPN TO THE W HAS BECOME MORE SPOTTY...AND WL BE
LGT FOR THE RMDR OF THE AFTN. THE NEXT WV WL MOVE INTO THE AREA
THIS EVE. WE RMN CONCERNED ABT THE PSBLTY OF FZRA TNGT GIVEN THE
SUBFRZG TEMPS STILL XPCTD. THE WSW WL RMN IN EFFECT FOR THE OVRNGT
HRS.

LOWS IN THE U20S/L30S.
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY/...

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WARMER AIR MOVES INTO THE REGION MONDAY...WITH FREEZING RAIN
CHANGING TO RAIN. IN GENERAL...EXPECT PRECIP TO TAPER OFF WITH
TEMPS WARMING INTO THE LOW TO MID 40S.
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&&

.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 /19Z SUNDAY THROUGH FRIDAY/...

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SNOW AND SLEET WILL CHANGE TO ALL FREEZING RAIN THIS AFTERNOON
AND EARLY EVENING. PERIODS OF FREEZING RAIN WITH IFR CIGS AND
VSBYS EXPECTED INTO THE OVERNIGHT HOURS. SIGNIFICANT ICE
ACCUMULATIONS PSBL 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...
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SMALL CRAFT ADVISORY IN EFFECT FOR PORTIONS OF THE CHES BAY AND
LOWER TIDAL PTMC UNTIL 6 PM.

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...
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.

&&

.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 MDZ011-013-
     014-016.
     WINTER STORM WARNING UNTIL 10 AM EST MONDAY FOR MDZ003>007-009-
     010-501-502.
     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-
     501>506.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR
     ANZ532>534-536-537-540-541-543.
-- End Changed Discussion --

&&

$$

PRODUCTS...WOODY!/KCS/HTS