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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 171502
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1002 AM EST TUE DEC 17 2013

.SYNOPSIS...
A COLD FRONT AND UPPER TROUGH WILL MOVE THROUGH THIS AFTERNOON AND
TONIGHT. HIGH PRESSURE BUILDS BACK INTO THE AREA WEDNESDAY BEFORE
MOVING OFFSHORE THURSDAY. A SLOW-MOVING FRONTAL BOUNDARY WILL
APPROACH FROM THE NORTHWEST THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...

-- Changed Discussion --
A WARM FRONT CAN BE ANALYZED JUST NE OF CWFA...ASSOCD W/ LOPRES IN
WRN NYS. ATTENDENT CDFNT ACRS WRN WVA. A FEW BINOVC EVIDENT ON
VSBL SATPIX IN THE WARM /OR MORE ACCURATELY WARMER/ SECTOR...MAINLY
ACRS CENTRL VA UP INTO THE NRN SHEN VLY. THESE POTENTIALLY CUD
CROSS E OF THE BLURDG TDA. FOR MOST OF THE DAY THO...ENUF MSTR AND
MID LVL TROFFING WL LEAD TO CLDY CONDS.

THE CDFNT AND A POTENT SHORTWAVE OVER THE MIDWEST IS EXPECTED TO
MOVE THROUGH THE AREA THIS AFTERNOON AND EVENING. THIS WILL
RESULT IN A CHANCE OF SHOWERS...SPCLY COINCIDENT W/ FROPA. AN
UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW ALONG WITH COLDER
CONDITIONS WILL CAUSE SNOW OVER THE ALLEGHENY HIGHLANDS.
HWVR...THE SNOW WILL GET A LATER START...WHICH WL LIMIT ACCUMS
DURING THE DAYTIME HRS.

THE SHORTWAVE WILL CAUSE SURFACE LOW PRESSURE TO RAPIDLY INTENSIFY
AS IT MOVES TOWARD NEW ENGLAND TONIGHT. A COLD FRONT ASSOCIATED WITH
THIS SYSTEM WILL MOVE THROUGH THIS EVENING AND DRIER BUT COLDER
NORTHWEST WINDS ARE EXPECTED OVERNIGHT. AN UPSLOPE COMPONENT TO THE
LOW-LEVEL FLOW WILL TRIGGER SNOW SHOWERS ALONG AND WEST OF THE
ALLEGHENY FRONT. THINK IT/LL BE DURING THE EVNG HRS WHERE THE CHC
OF ACCUMS WL BE HIEST. AM CONSIDERING PSBL ADVY FOR THAT TIME
PD...PENDING LTST INFO.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
SURFACE HIGH PRESSURE WILL BUILD OVERHEAD WEDNESDAY...ALLOWING FOR
DRY AND CHILLY CONDITIONS. MAX TEMPS WILL REMAIN BELOW
CLIMO...RANGING FROM THE 20S IN THE MOUNTAINS TO THE LOWER 40S IN
CENTRAL VIRGINIA.

HIPRES CENTERED ALONG THE SE COAST WED NGT. WAA PATTERN DEVELOPS
ACROSS THE CWA WITH W-SW RETURN FLOW AROUND THE HIGH. 00Z GFS/NAM
SHOW H8 TEMPS WARMING 7-10C DURING THE 00Z-12Z THU PERIOD. DESPITE
WAA ALOFT...SFC WILL BE ABLE TO RADIATE EFFECTIVELY WITH THE SFC
RIDGE AXIS OVERHEAD. FCST MIN TEMPS GENERALLY IN THE 20S EXCEPT
LOWER 30S IN THE CITIES AND NEAR THE WRN SHORE OF THE BAY.

HIPRES MOVES OFFSHORE THU AND FRI. FLOW OVER THE MID ATLANTIC
BECOMES INCREASINGLY MERIDIONAL AROUND THE NWRN PERIPHERY OF
RIDGE...RESULTING IN ABOVE NORMAL TEMPS LATE IN THE WEEK. TEMPS MAY
REACH 60F BY FRI AFTN ACROSS CENTRAL VA AND SRN MD.

A WAVE OF LOPRES WILL MOVE OVER THE SRN PLAINS LATE IN THE WEEK. THE
SYNOPTIC COLD FRONT IS FCST TO EXTEND NEWD FROM THIS LOW INTO THE
MIDWEST AND NORTHEAST STATES BY FRI. MOISTURE FROM THE GULF OF
MEXICO WILL STREAM NWD ALONG THE BOUNDARY. WITH THE LEADING EDGE OF
THIS DEEPER MOISTURE ANTICIPATED TO REACH THE CWA FRI NGT. THE BEST
CHANCE FOR SHOWERS WILL BE TO THE N AND W OF THE AREA ...BUT A FEW
SHOWERS AHEAD OF THE FRONT MAY BRUSH THE N/W TIER OF THE CWA LATE
FRI AFTN AND FRI NGT. POPS ARE LOW AND QPF LGT.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
THIS WEEKEND...THE REGION WILL BE SITUATED IN BETWEEN AN AMPLIFYING
UPPER TROUGH OVER THE CENTRAL CONUS AND THE RIDGE THAT WILL BE
PARKED OVER THE WRN ATLANTIC. THE WAVELENGTH BETWEEN THE UPSTREAM
TROUGH - DOWNSTREAM RIDGE WILL SHORTEN...YIELDING A STRENGTHENING
MERIDIONAL FLOW OVER THE ERN CONUS. THE SWLY STEERING FLOW WILL
BECOME ORIENTED PARALLEL TO THE FRONTAL BOUNDARY...CAUSING IT TO
STALL. 00Z MODELS HAVE COME INTO MUCH BETTER AGREEMENT WITH THE
BOUNDARY STALLING TO THE N AND W OF THE CWA THIS WEEKEND. THIS
WEEKEND WILL BE UNSETTLED WITH PERIODS OF SHOWERS. THE HEAVIEST/
STEADIEST PRECIP WOULD REMAIN WEST OF THE APPALACHIANS THROUGH
SUNDAY IF THE POSITION OF THE FRONT VERIFIES. A WAVE OF LOPRES OVER
THE SRN PLAINS IS FCST TO RIDE NWD ALONG THE FRONT...MOVING THRU THE
OH VLY AND NE STATES ON SUN. NW FLOW BEHIND THE LOW WILL ALLOW THE
FRONT TO FINALLY ADVANCE EWD ACROSS THE MID-ATLANTIC REGION SUN NGT.
MODELS ARE ALSO IN REASONABLE AGREEMENT WITH THE TIMING OF FROPA
OCCURRING SUN NGT ACROSS THE CWA. POPS WILL BE HIGHEST WITH FROPA.
ADDED SLGT CHANCE OF THUNDER FOR SUN AFTN AND NGT AS NOSE OF THE
PRE-FRONTAL WARM SECTOR BECOMES WELL DEFINED ALONG THE ERN SEABOARD.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
MVFR CIGS PREVAIL ACRS THE TERMINALS. THESE MAY BRIEFLY LIFT
DURING THE MIDDAY. HOWEVER...A POTENT SHORTWAVE WILL PASS THROUGH
THE TERMINALS THIS AFTERNOON AND EVENING. SHOWERS AND MVFR
CONDITIONS ARE ONCE AGAIN POSSIBLE DURING THIS TIME. NORTHWEST
WINDS WILL DEVELOP BEHIND A COLD FRONT LATER THIS EVENING THROUGH
WEDNESDAY. VFR CONDITIONS ARE EXPECTED WITH GUSTS AROUND 20 KNOTS.

VFR CONDITIONS UNDER THE CONTROL OF HIPRES WED NGT THRU FRI. LGT
SHOWERS AHEAD OF AN APPROACHING FRONTAL BOUNDARY MAY PASS THRU SOME
OF THE TERMINALS LATE FRI. THE FRONT WILL LIKELY STALL TO THE N AND
W OF THE AREA THIS WEEKEND. CHANCE FOR SHRA AND SUB-VFR CONDITIONS
INCREASE THIS WEEKEND WHEN DEEPER MOISTURE STREAMS NWD UP THE ERN
SEABOARD.
-- End Changed Discussion --

&&

.MARINE...
A COLD FRONT WILL PASS THROUGH THE WATERS LATE THIS AFTERNOON AND
EVENING. LOW PRESSURE WILL RAPIDLY DEVELOP TO OUR NORTHEAST
OVERNIGHT BEHIND THE COLD FRONT. NORTHWEST WINDS WILL INCREASE
DURING THIS TIME. A SMALL CRAFT ADVISORY IS IN EFFECT LATE TONIGHT
THROUGH WEDNESDAY.

SLY WINDS WILL INCREASE LATE IN THE WEEK ONCE HIPRES MOVES OFFSHORE.
WINDS COULD APPROACH SCA LVLS THU. CONFIDENCE IN A SCA BEING NEEDED
INCREASES FOR FRI AND THIS WEEKEND.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EST
     WEDNESDAY FOR ANZ530>543.

&&

$$
SYNOPSIS...
NEAR TERM...HTS/BJL
SHORT TERM...JRK
LONG TERM...JRK
AVIATION...HTS/BJL/JRK
MARINE...BJL/JRK