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000
FXUS61 KLWX 070247
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
947 PM EST FRI DEC 6 2013

.SYNOPSIS...
A COLD FRONT WILL CONTINUE TO DRIFT EAST ACROSS THE REGION THROUGH
THE REST OF TONIGHT. HIGH PRESSURE WILL BRIEFLY BUILD OVERHEAD
SATURDAY...THEN LOW PRESSURE WILL DEVELOP AND APPROACH FROM THE
SOUTHWEST SATURDAY NIGHT INTO EARLY SUNDAY. THIS SYSTEM WILL
IMPACT THE AREA WITH WINTRY PRECIPITATION SUNDAY INTO MONDAY. AN
UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE AREA TUESDAY AND
CANADIAN HIGH PRESSURE WILL BUILD OVERHEAD DURING THE MIDDLE OF
NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
WINTER WEATHER ADVISORY FOR WESTERN SEGMENTS OF ALLEGANY...
MINERAL...AND GRANT COUNTIES FOR FREEZING RAIN AMONGST THE WINTRY
MIX UP THERE UNTIL 4AM. RISK THERE IS FOR BRIDGES...OTW ICING IS
NOT EXPECTED TO BE GREAT ENOUGH TO CAUSE DAMAGE BEFORE PRECIP
TAPERS OFF LATE TONIGHT.

AS OF 02Z...1045MB SFC HIGH CENTERED OVER HAVRE MT...ALONG WITH
ABOUT A 1027MB MSLP BERMUDA HIGH. 1015MB TROUGH CENTERED OVER KROA
IS IN BETWEEN. WIDESCALE CONVERGENCE WILL CONTINUE TO PRODUCE
PRECIP ACROSS THE AREA. COLD DOME TO THE WEST IS SPREADING IN...
CAUSING POCKETS OF SLEET AND FREEZING RAIN WEST OF THE ALLEGHENY
FRONT. SLEET AND THEN SNOW WILL MIX WITH RAIN AT HIGHER ELEVATIONS
EAST OF THERE UNTIL THE PRECIP TAPERS OFF TONIGHT. WILL NEED TO
MONITOR FOR FURTHER FREEZING RAIN POCKETS AND A POSSIBLE WINTER
WEATHER ADVISORY EXPANSION. OTHERWISE SLEET/SNOW ACCUM OF UP TO
HALF INCH EXPECTED AT ELEVATIONS OVER 1000FT. THE GROUND IS STILL
FAIRLY WARM...SO ACCUM IS GOING TO BE QUITE LIMITED.

THE COLD DOME/COLD FRONT WILL PROGRESS EAST THROUGH THE CENTRAL
MID-ATLANTIC. PRECIP TAPERS OFF ESSENTIALLY BEFORE SUNRISE...WITH
LIGHT RAIN PERSISTING FOR SRN MD INTO THE MID-MORNING.

SATURDAY...
A BRIEF BREAK IN THE ACTION AS ONE SYSTEM LEAVES AND ANOTHER GEARS
UP TO OUR SOUTHWEST. TOWARD DAYBREAK SAT MRNG...AN UPPER SHORTWAVE
THAT IS CURRENTLY SLIDING OVER THE MID MS VLY WILL SWING BY TO OUR
NORTH AND PUSH THE REST OF THE PRECIP OFF THE MID ATLC COAST.
PRECIP WILL BE ENDING GRADUALLY FROM WEST TO EAST BUT FAIRLY
QUICKLY DURING THE POST-DAWN HRS. CLOUDS WILL BE A COUPLE OF HRS
BEHIND IN TERMS OF CLEARING OUT BUT THE PROCESS OF DRYING OUT AND
COOLING DOWN THE AREA WILL BE WELL UNDERWAY.

DURING THIS TIME...A POTENT HIGH OVER THE NRN PLAINS/UPPER
MIDWEST - THE SAME ONE IN CONTROL OF THE WIDESPREAD FRIGID TEMPS
OVER A LARGE PART OF THE COUNTRY WILL BEGIN TO PUSH ITS EASTERN
PERIPHERY OVER THE CNTRL APLCNS AND FILTER DOWN INTO THE MID ATLC.
BREEZY NWLY WINDS WILL BE HELPING TO MIX OUT THE MOIST AND
RELATIVELY WARM CONDITIONS FROM TODAY...BRINGING IN DEWPOINTS
10-20 DEG LOWER THAN TODAY AND SETTING THE STAGE FOR THE NEXT WAVE
OF PRECIP AND WINTRY CONDITIONS. HIGHS ACROSS THE I-95 CORRIDOR
WILL PEAK NEAR THE 40 DEG MARK...BARELY ABOVE FREEZING FOR THE
MTNS AND GENERALLY M-U30S FOR THE REMAINDER OF THE CWA.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
ARCTIC HIGH PRESSURE WILL FILTER INTO THE AREA SATURDAY NIGHT. MIN
TEMPS IS THE MID 20S ARE EXPECTED SUNDAY MORNING WITH WARMER TEMPS
NEAR 30 DEGREES NEAR THE BAY AND POTOMAC RIVER. FURTHER
SOUTH...CYCLOGENESIS WILL FORM ALONG THE FRONT THAT MOVED THROUGH
OUR REGION TODAY AS AN UPPER LEVEL TROUGH MOVES EASTWARD FROM THE
ROCKIES. SHORTWAVE ENERGY WILL MOVE ACROSS THE REGION IN THE
MIDLEVELS AND A WARM 40-60KT JET WILL START TO NOSE INTO THE
CENTRAL FOOTHILLS...NRN VA AND NRN PIEDMONT SUNDAY MORNING. BEFORE
THE WARM NOSE REACHES THE MID ATLANTIC PRECIPITATION WILL BEGIN AS
ALL SNOW. THIS SNOW WILL ACCUMULATE AS SFC TEMPS WILL BE BELOW
FREEZING. AS THE WARM NOSE MOVES NORTHWARD SNOW WILL START TO MIX
WITH SLEET. SHORTWAVES WILL MOVE OVER THE REGION AND ENHANCE
PRECIPITATION AT TIMES. THE AXIS OF THE RIDGE ACROSS OUR AREA WILL
BE STRONG AND GFS AND ECMWF BOTH SHOW LOW PRESSURE SPLITTING
AROUND THE SFC RIDGE. LOW PRESSURE MOVING TO OUR EAST WILL ENHANCE
THE NORTHERLY FLOW INTO THE REGION AND ENHANCE THE COLD AIR.

WARM AIR ALOFT WILL INCREASE IN SIZE AND A SWITCH OVER TO FREEZING
RAIN IS EXPECTED. THE CONFIDENCE OF ALL FREEZING RAIN GOES FROM HIGH
TO MEDIUM CONFIDENCE MOVING FROM WEST TO EAST ACROSS THE LOOKOUT AREA.
TEMPERATURES WILL BE SUBFREEZING DUE TO THE FILTERING OF THE
NORTHERLY FLOW AROUND LOW PRESSURE TO OUR EAST AND THE HIGH TO OUR
NORTH. THE LOWER CONFIDENCE IS MAINLY ALONG AND EAST OF I-95 DUE TO
WARMER MARINE AIR MIXING IN TO THE AREA. WARM MOIST AIR ALOFT WILL
CONTINUE TO MOVE INTO THE REGION FROM THE S-SW SUNDAY AFTERNOON AND
EVENING AND FZRA IS EXPECTED TO CONTINUE. A WINTER STORM WATCH IS IN
EFFECT SUNDAY MORNING THROUGH MONDAY MORNING... PLEASE CHECK
WSWLWX FOR MORE DETAILS. AREAS WEST OF THE BLUE RIDGE INCLUDING
I-81 AND VALLEY LOCATIONS ARE EXPECTED TO SEE SIGNIFICANT ICE
ACCRETION OF A QUARTER INCH OR MORE SUNDAY AND SUNDAY NIGHT. THIS
WILL PRODUCE HAZARDOUS TRAVEL CONDITIONS...TREE DAMAGE AND POWER
OUTAGES.

SYNOPTIC FEATURES MOVE NORTHWARD INCLUDING LOW PRESSURE TO OUR WEST
AND EAST AND THE HIGH PRESSURE WEDGED ACROSS OUR REGION AS THE
TROUGH OVER THE ROCKIES MOVES EASTWARD. THE WARM NOSE WILL DESCEND TO
THE SFC SUNDAY NIGHT AND EVENTUALLY TAKE OVER THE SFC LATE MONDAY
MORNING. TEMPS BELOW FREEZING WILL LIFT NORTHWARD AND EXIT WEST
CENTRAL MD BY LATE MONDAY MORNING. TOTAL LIQUID FORECAST AMT OF
AROUND AN INCH ARE EXPECTED FOR THE EVENT.

RAIN WILL MOVE OUT OF THE REGION MONDAY NIGHT AND EVEN LINGER INTO
TUESDAY AS A COLD FRONT MOVES THROUGH AND HELPS SCOUR OUT MOISTURE.
COLD AIR WILL MOVE IN AND RAIN MAY SWITCH TO SNOW BUT NO
ACCUMULATION IS EXPECTED AT THIS TIME.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
A BRISK WEEK IS AHEAD AS HIGH PRESSURE MOVES INTO THE REGION AND
CANADIAN AIR CONTINUES TO FILTER INTO THE REGION. BELOW NORMAL
TEMPERATURES ARE EXPECTED. A SHORTWAVE TROUGH WILL PASS OVER THE
MID ATLANTIC THURSDAY AND MAY SQUEEZE OUT SOME SNOW SHOWERS. NO
HAZARDS EXPECTED THROUGH THE LONG TERM.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
MVFR/IFR IN RAIN PERSISTS THROUGH SUNRISE WITH PRECIP TAPERING OFF
GENERALLY BEFORE SUNRISE. AS THE PRECIP DISSIPATES...A FEW HRS OF
SUB- IFR CIGS SHOULD OCCUR ACROSS MUCH OF THE AREA AROUND THE
PREDAWN HRS SAT. THE CONDITIONS WILL QUICKLY IMPROVE AFTER
SUNRISE...W/ DRIER AIR SLIDING IN FROM THE NORTH AND MIXING OUT
THESE LOWER CIGS. BREEZY NW WINDS WILL TAKE OVER ON SAT
AFTN...CLEARING SKIES OUT FOR AT LEAST THE DAYTIME HRS.

SNOW AND SLEET ARE EXPECTED ACROSS THE TERMINALS SUNDAY MORNING
BEFORE CHANGING TO FZRA SUNDAY AFTERNOON. FZRA WILL CONTINUE THROUGH
SUNDAY NIGHT FOR CHO-MRB-IAD-DCA. LOWER CONFIDENCE IN CONSTANT FZRA
FOR BWI-MRB DUE TO TEMP MODERATING. MVFR/IFR CONDITIONS ARE POSSIBLE
DURING THIS TIME. HIGH PRESSURE MOVES INTO THE REGION TUESDAY AND
CONTINUES THROUGH THE MIDDLE OF THE WEEK.

&&

.MARINE...
NLY CHANNELING UP TO 25 KT ACROSS THE MD PORTION OF THE BAY...WITH
ALL WATERS UNDER SCA AFTER MIDNIGHT. THE COLD FRONT MOVES THRU AND
BEHIND IT WILL BE SEVERAL HRS OF SOLID SCA CONDITIONS DURING THE
DAYTIME HRS SAT.

SNOW AND SLEET ARE EXPECTED SUNDAY MORNING BEFORE CHANGING OVER A
MIX OF FZRA-SLEET-RAIN SUNDAY AFTERNOON. ICE ACCUMULATION IS
POSSIBLE MAINLY NEAR THE LAND AS WATER TEMPS ARE STILL IN THE MID
40S. NORTHERLY WINDS WILL BE 5 TO 10 KTS THROUGH THIS TIME. HIGH
PRESSURE MOVES OVER THE WATERS NEXT WEEK. SCA CONDITIONS POSSIBLE
MID WEEK WITH N-NW FLOW OVER THE WATERS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR DCZ001.
MD...WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR MDZ003-501-502.
     WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR MDZ004>007-009>011-013-014-016.
     WINTER WEATHER ADVISORY UNTIL 4 AM EST SATURDAY FOR MDZ501.
VA...WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR VAZ025>031-036>038-503-504.
     WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR VAZ039-040-042-050>057-501-502.
WV...WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR WVZ050>053-055-501>506.
     WINTER WEATHER ADVISORY UNTIL 4 AM EST SATURDAY FOR WVZ501-503.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST SUNDAY FOR ANZ530>534-537-
     539>541-543.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST SATURDAY FOR ANZ535-536-
     538-542.

&&

$$
UPDATE...JACKSON
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