424
FXUS61 KLWX 122107
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
407 PM EST FRI DEC 12 2025
SYNOPSIS
A WEAK AREA OF HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT. AN
UPPER LEVEL DISTURBANCE WILL MOVE THROUGH TOMORROW NIGHT,
PUSHING AN ARCTIC FRONT THROUGH THE AREA AT THE SURFACE. HIGH
PRESSURE WILL BUILD IN FOR THE FIRST HALF OF NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
WATER VAPOR IMAGERY SHOWS A WEAK DISTURBANCE EMBEDDED WITHIN
WEST-NORTHWESTERLY FLOW CURRENTLY LOCATED OVER WEST VIRGINIA.
LIFT AHEAD OF THIS FEATURE HAS PRODUCED CLOUDY SKIES THROUGH
MUCH OF THE DAY, BUT NO PRECIPITATION HAS BEEN OBSERVED.
WINDS ARE LIGHT, AND TEMPERATURES REMAIN CHILLY THIS AFTERNOON,
WITH TEMPERATURES NEAR THEIR DAYTIME HIGHS IN THE 30S (20S
MOUNTAINS).
AS WE MOVE INTO TONIGHT, THE AFOREMENTIONED UPPER LEVEL
DISTURBANCE WILL PASS OFF TO OUR EAST. SUBSIDENCE IN ITS WAKE
WILL CAUSE SKIES TO CLEAR OUT AT LEAST BRIEFLY. HIGH CLOUDS WILL
BEGIN TO MOVE BACK IN FROM THE WEST DURING THE LATTER HALF OF
THE NIGHT IN ADVANCE OF THE NEXT SYSTEM APPROACHING FROM THE
UPPER MIDWEST. SOME GUIDANCE HINTS THAT SOME FREEZING FOG COULD
FORM ACROSS THE CENTRAL SHENANDOAH VALLEY OR CENTRAL VIRGINIA
LATER TONIGHT, BUT CONFIDENCE WASN'T YET HIGH ENOUGH TO
DETERMINISTICALLY INTRODUCE THAT INTO THE FORECAST. OVERNIGHT
LOWS WILL BE IN THE 20S FOR MOST, WITH TEENS IN THE MOUNTAINS.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
A WEAK RIDGE OF HIGH PRESSURE WILL BECOME CENTERED OVER THE
REGION ON SATURDAY. MOSTLY CLOUDY SKIES AND DRY CONDITIONS ARE
EXPECTED TO THE EAST OF THE MOUNTAINS, WITH HIGHS IN THE UPPER
30S TO MID 40S FOR MOST. MEANWHILE, MUCH FURTHER TO THE WEST,
THE WAVEGUIDE ACROSS NORTH AMERICA WILL START TO AMPLIFY AS A
SYSTEM TRACKS TOWARD THE BRITISH COLUMBIA COAST. A RIDGE
BUILDING EVENT WILL ENSUE DOWNSTREAM OVER WESTERN CANADA, WHICH
WILL CAUSE A PRE- EXISTING UPPER LOW OVER THE UPPER GREAT LAKES
TO DROP SOUTHEASTWARD TOWARD THE MID- ATLANTIC AND AMPLIFY INTO
A SHORTER WAVELENGTH OPEN WAVE. AS THIS OCCURS, LARGE SCALE
FORCING FOR ASCENT WILL INCREASE ACROSS THE AREA LATE SATURDAY
AFTERNOON INTO SATURDAY NIGHT. SNOW NOW APPEARS AS THOUGH IT
WILL START DURING THE MID TO LATE AFTERNOON HOURS IN THE
ALLEGHENIES. THIS SNOW COULD BE MODERATE TO BRIEFLY HEAVY AT
TIMES DURING THE EVENING THROUGH THE FIRST HALF OF THE
OVERNIGHT. WINTER STORM WARNINGS HAVE BEEN ISSUED FOR WESTERN
GARRETT AND WESTERN GRANT COUNTIES, WHERE 4-8 INCHES OF SNOW IS
EXPECTED. WINTER WEATHER ADVISORIES HAVE BEEN ISSUED FOR EASTERN
GARRETT, WESTERN ALLEGANY, AND WESTERN PENDLETON COUNTIES,
WHERE 2-4 INCHES OF SNOW IS EXPECTED.
WITH WESTERLY LOW-LEVEL FLOW DOWNSLOPING OFF OF THE
APPALACHIANS, PRECIPITATION WILL STRUGGLE TO MAKE PROGRESS TO
THE EAST OF THE ALLEGHENY FRONT FOR SEVERAL HOURS. AS THE WAVE
AMPLIFIES AND APPROACHES FROM THE WEST, MOST MODELS SHOW A JET
STEAK DEVELOPING DOWNSTREAM, WITH FORCING FOR ASCENT INCREASING
WITHIN THE EQUATORWARD ENTRANCE OF THE JET STREAK. MOST
SOLUTIONS SHOW THE JET ENTRANCE REGION LINING UP RIGHT ALONG
I-95. ASCENT WITHIN THE JET ENTRANCE REGION MAY CAUSE
PRECIPITATION TO JUMP EASTWARD AND DEVELOP IN-SITU ALONG THE
I-95 CORRIDOR, LARGELY SKIPPING LOCATIONS BETWEEN THE ALLEGHENY
FRONT AND BLUE RIDGE.
PRECIPITATION WITHIN THE JET ENTRANCE REGION TO THE EAST OF THE
BLUE RIDGE IS EXPECTED TO BLOSSOM DURING THE MID-LATE EVENING
HOURS, AND THEN SLOWLY DRIFT SOUTHEASTWARD THROUGH THE REMAINDER
OF THE NIGHT. THE PRECIPITATION MAY BEGIN AS A BRIEF PERIOD OF
RAIN OR MIXED RAIN AND SNOW, ESPECIALLY ALONG AND SOUTHEAST OF THE
I-95 CORRIDOR. THIS MIX SHOULD BE SHORT-LIVED HOWEVER, AS MUCH
COLDER AIR RUSHES IN BEHIND AN ARCTIC FRONT THAT WILL MOVE
THROUGH OVER THE COURSE OF THE NIGHT. IN TERMS OF TIMING, SOME
LIGHT PRECIPITATION COULD BEGIN AS EARLY AS THE MID-LATE EVENING
HOURS, BUT THE BULK OF THE PRECIPITATION ALONG THE I-95
CORRIDOR IS EXPECTED TO OCCUR BETWEEN ROUGHLY 11 PM AND 7 AM.
THE BAND THAT WILL DEVELOP WILL BE A RELATIVELY NARROW FEATURE,
AND WILL FEATURE MODERATE TO HEAVY SNOW AT TIMES. SNOWFALL RATES
WITHIN THE BAND COULD NEAR OR POTENTIALLY BRIEFLY EXCEED ONE
INCH PER HOUR AT TIMES LATE SATURDAY NIGHT. WITH A NARROW
FEATURE PRODUCING HEAVY PRECIPITATION, SNOW TOTALS WILL BE
HEAVILY DEPENDENT ON THE ULTIMATE PLACEMENT OF THIS BAND. THIS,
COMBINED WITH THE POTENTIAL FOR A BIT OF MIXING WITH RAIN AT
ONSET MAKES FOR A CHALLENGING SNOWFALL FORECAST.
PROBABILISTICALLY SPEAKING, 12Z GUIDANCE HAS FOCUSED IN ON THE
I-95 CORRIDOR FROM DC NORTHEASTWARD, AND THEN EASTWARD ALONG
US-50 TOWARD THE CHESAPEAKE, WITH NORTHEAST MARYLAND SOUTHWARD
TOWARD ANNAPOLIS HAVING THE GREATEST PROBABILITIES FOR HIGHER
TOTALS. AS OF THIS MOMENT, A BROAD 1-4 INCHES FROM THE VICINITY
OF THE I-95 CORRIDOR EASTWARD APPEARS LIKE THE MOST LIKELY
SCENARIO, WITH EMBEDDED MAXES OF 4-7 INCHES POSSIBLE WHERE THE
BAND RESIDES FOR THE LONGEST TIME PERIOD. SINCE THERE WILL BE
VERY SHARP SNOWFALL GRADIENTS ON THE EDGES OF THIS BAND, AND
THERE'S STILL A BIT OF UNCERTAINTY WITH RESPECT TO WHERE THIS
BAND WILL BE, WE'VE DECIDED TO HOLD OFF ON ISSUING HEADLINES TO
THE EAST OF THE BLUE RIDGE FOR THE TIME BEING. HEADLINES WILL
ALMOST CERTAINLY BE NEEDED EVENTUALLY, AND WE'LL CONTINUE TO
ASSESS TRENDS AND REFINE THE FORECAST THROUGH THE REMAINDER OF
THE DAY. SNOW WILL END FROM NORTHWEST TO SOUTHEAST A FEW HOURS
EITHER SIDE OF DAYBREAK, WITH THE BACK EDGE OF THE SNOW CLEARING
SOUTHERN MARYLAND BY AROUND MID-MORNING.
STRONG COLD AIR ADVECTION IS EXPECTED BEHIND THE ARCTIC FRONT
THROUGH THE DAY SUNDAY, WITH 850 HPA TEMPERATURES CRASHING TO
AROUND -15 TO -20 C BY PEAK HEATING. THIS WILL CAUSE
TEMPERATURES TO DROP THROUGH THE 20S OVER THE COURSE OF THE DAY.
NORTHWESTERLY WIND GUSTS TO AROUND 35 MPH WILL MAKE IT FEEL EVEN
COLDER, PUSHING WIND CHILLS INTO THE SINGLE DIGITS AND TEENS.
AFTER THE SNOW MOVES OUT, DRY CONDITIONS ARE EXPECTED TO THE
EAST OF THE MOUNTAINS. UPSLOPE SNOW SHOWERS WILL LINGER IN THE
ALLEGHENIES OVER THE COURSE OF THE DAY. COLD AND WINDY
CONDITIONS WILL CONTINUE THROUGH SUNDAY NIGHT, WITH COLD WEATHER
HEADLINES LIKELY BEING NEEDED FOR PORTIONS OF THE AREA.
LONG TERM /MONDAY THROUGH FRIDAY/
STILL VERY COLD MONDAY, BUT NOT AS WINDY WITH GUSTS UP TO 25 MPH.
ARCTIC HIGH PRESSURE SETTLES OVER THE AREA MONDAY NIGHT.
DEEP TROUGH PATTERN LIFTS OUT EARLY NEXT WEEK AND REPLACED BY
LARGELY ZONAL FLOW LEADING TO A WELCOME MODERATING TREND IN
TEMPERATURES MID WEEK. AN AREA OF LOW PRESSURE TRACKING NORTH OF THE
GREAT LKS WILL PUSH A COLD FRONT THROUGH THE AREA THU NIGHT BRINGING
A RISK OF RAIN SHOWERS AND MOUNTAIN RAIN/SNOW SHOWERS. HIGH PRESSURE
BUILDS AGAIN OVER THE AREA TO END THE WEEK. OVERALL, MUCH WARMER AND
TRANQUIL WEATHER MIDDLE AND SECOND HALF OF NEXT WEEK THAN IT HAD
BEEN THE FIRST TWO WEEKS OF DECEMBER.
AVIATION /19Z FRIDAY THROUGH WEDNESDAY/
VFR CONDITIONS ARE EXPECTED AT THE TERMINALS THROUGH THE DAY
TODAY, WITH LIGHT WINDS. VFR CONDITIONS WILL LIKELY PERSIST
THROUGH THE NIGHT AT MOST OF THE TERMINALS, ALTHOUGH SOME LOW
CLOUDS OR FREEZING FOG CAN'T BE COMPLETELY RULED OUT NEAR CHO.
VFR CONDITIONS AND SOUTHWESTERLY WINDS ARE EXPECTED AT ALL
TERMINALS DURING THE DAY TOMORROW.
LOWER CEILINGS AND SNOW ARE EXPECTED TO DEVELOP IN PLACE ACROSS
MUCH OF THE FORECAST AREA TOMORROW NIGHT. BWI, MTN, DCA, AND
IAD ARE MOST LIKELY TO EXPERIENCE THE GREATEST IMPACTS FROM
SNOW, WITH A COUPLE INCHES OF ACCUMULATION POSSIBLE DURING THE
SECOND HALF OF THE NIGHT. THE PRECIPITATION COULD ALSO BRIEFLY
MIX WITH RAIN AT ONSET. CHANCES FOR SNOWFALL ARE A BIT LESSER AT
MRB, AND THE SNOW APPEARS AS THOUGH IT WILL LIKELY AVOID CHO
ALTOGETHER.
CONDITIONS ARE EXPECTED TO IMPROVE BACK TO VFR BY MID-MORNING
SUNDAY AT ALL TERMINALS. NORTHWESTERLY GUSTS TO AROUND 25-30
KNOTS ARE EXPECTED THROUGHOUT THE DAY IN THE WAKE OF A STRONG
ARCTIC FRONT.
MONDAY...NW WIND GUSTS UP TO 25 KT. LIGHT WINDS 10 KT OR LESS
TUE.
MARINE
SUB-SCA LEVEL SOUTHERLY WINDS ARE EXPECTED OVER THE WATERS THE
REMAINDER OF THE AFTERNOON THROUGH TONIGHT. THERE COULD BE A
BRIEF 2-3 HOUR WINDOW WHERE GUSTS APPROACH LOW-END SCA LEVELS
AROUND DAYBREAK. SUB-SCA LEVEL SOUTHWESTERLY WINDS ARE EXPECTED
DURING THE DAY TOMORROW. WINDS WILL GO LIGHT TOMORROW EVENING,
BEFORE TURNING OUT OF THE NORTHWEST AND PICKING UP IN MAGNITUDE
DURING THE SECOND HALF OF THE NIGHT AS AN ARCTIC FRONT MOVES
OVER THE WATERS. SCAS WILL LIKELY BE NEEDED OVER THE WATERS LATE
SUNDAY NIGHT. SNOW MAY ALSO BE POSSIBLE OVER THE WATERS THE
SECOND HALF OF THE NIGHT INTO THE FIRST COUPLE HOURS OF SUNDAY
MORNING.
WINDS WILL FURTHER STRENGTHEN DURING THE DAYLIGHT HOURS SUNDAY.
GALE WATCHES ARE IN EFFECT FOR ALL WATERS FROM 11 AM SUNDAY
THROUGH 6 AM MONDAY MORNING. FREEZING SPRAY MAY ALSO BE POSSIBLE
AT TIMES DURING THE DAY SUNDAY.
SCA CONDITIONS EXPECTED MONDAY WITH GUSTS UP TO 25 KT, DIMINISHING
GRADUALLY THROUGH THE DAY AND NIGHT, AND DROPPING BELOW SCA
THRESHOLD BY DAYBREAK TUESDAY. FREEZING SPRAY CONDITIONS ARE STILL
POSSIBLE MONDAY, BUT ARE MORE LIKELY TO OCCUR SUNDAY WITH THE
STRONGER WINDS AND COLDER TEMPERATURES.
LIGHTER WINDS TUE AND WED. WINDS STRENGTHEN AGAIN DURING THE SECOND
HALF OF NEXT WEEK.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...GALE WATCH FROM SUNDAY MORNING THROUGH LATE SUNDAY NIGHT FOR
MDZ008.
WINTER WEATHER ADVISORY FROM 4 PM SATURDAY TO 1 PM EST SUNDAY
FOR MDZ501-510.
WINTER STORM WARNING FROM 1 PM SATURDAY TO 4 PM EST SUNDAY FOR
MDZ509.
VA...NONE.
WV...WINTER WEATHER ADVISORY FROM 4 PM SATURDAY TO 1 PM EST SUNDAY
FOR WVZ503-505.
WINTER STORM WARNING FROM 1 PM SATURDAY TO 4 PM EST SUNDAY FOR
WVZ501.
MARINE...GALE WATCH FROM SUNDAY MORNING THROUGH LATE SUNDAY NIGHT FOR
ANZ530>543.
SYNOPSIS...KJP
NEAR TERM...KJP
SHORT TERM...KJP
LONG TERM...LFR
AVIATION...LFR/KJP
MARINE...LFR/KJP
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