530
FXUS61 KLWX 202121
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
421 PM EST WED NOV 20 2024
SYNOPSIS
A STRONG COLD FRONT WILL MOVE THROUGH THE AREA TONIGHT. AN UPPER
LEVEL LOW WILL CIRCULATE OVERHEAD THROUGH SATURDAY. AN AREA OF
LOW PRESSURE WILL TRACK TO OUR NORTHWEST THROUGH THE GREAT
LAKES EARLY NEXT WEEK. HIGH PRESSURE WILL BUILD BACK IN FOR THE
MIDDLE OF THE WEEK.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
CURRENT WATER VAPOR IMAGERY SHOWS A SHARP UPPER TROUGH/CLOSED
LOW LOCATED OVER THE GREAT LAKES/OHIO VALLEY. A LEAD DISTURBANCE
EMBEDDED WITHIN THE MUCH BROADER CIRCULATION IS RAPIDLY
APPROACHING OUR AREA FROM THE WEST, AND WILL DRIVE A STRONG COLD
FRONT THROUGH THE AREA THIS EVENING. THE FRONT IS JUST
APPROACHING FAR WESTERN PORTIONS OF THE FORECAST AREA, AND WILL
MOVE THROUGH THE AREA FROM WEST TO EAST BETWEEN NOW AND 10-11
PM. A SQUALL LINE IS EXPECTED TO DEVELOP ALONG THE FRONT AS IT
SPREADS EASTWARD. MOST LOCATIONS WILL SEE A BRIEF BURST OF HEAVY
RAINFALL WITH THIS LINE, AND A RUMBLE OR TWO OF THUNDER CAN'T
EVEN BE RULED OUT. TRAILING THIS LINE, SHOWERS WILL CONTINUE FOR
A FEW HOURS BEHIND THE FRONT. AN ABRUPT WIND SHIFT WILL ALSO
ACCOMPANY THE FRONTAL PASSAGE. WINDS WILL SWITCH FROM LIGHT OUT
OF THE SOUTH TO SOUTHEAST TO STRONG OUT OF THE WEST. WINDS MAY
NEAR WIND ADVISORY CRITERIA FOR A 1-3 HOUR PERIOD THIS EVENING
IMMEDIATELY IN THE WAKE OF THE FRONT. A WIND ADVISORY IS IN
EFFECT FOR THE BLUE RIDGE AND ALLEGHENIES THIS EVENING. A
SPECIAL WEATHER STATEMENT HAS BEEN ISSUED FOR LOWER ELEVATIONS
TO ACCOUNT FOR THE POTENTIAL OF 40-50 MPH WIND GUSTS FOR A SHORT
TIME BEHIND THE FRONT. CONDITIONS WILL DRY OUT DURING THE
SECOND HALF OF THE NIGHT, BUT STRONG COLD ADVECTION WILL
CONTINUE. LOW TEMPERATURES WILL BE IN THE UPPER 30S TO NEAR 40
FOR MOST, WITH LOW TO MID 30S IN THE MOUNTAINS.
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
CONDITIONS SHOULD START OUT DRY TOMORROW, BUT THE BOUNDARY LAYER
WILL DESTABILIZE BY THE LATE MORNING TO EARLY AFTERNOON HOURS AS
THE CORE OF THE UPPER LOW APPROACHES FROM THE WEST. SNOW SHOWERS
WILL FORM WITHIN UPSLOPE FLOW TO THE WEST OF THE ALLEGHENIES
DURING THE LATE MORNING HOURS, WITH ADDITIONAL SHOWERS FORMING
TO THE EAST OF THE MOUNTAINS DURING THE AFTERNOON HOURS.
COVERAGE OF SHOWERS SHOULD REMAIN FAIRLY LOW TO THE EAST OF THE
MOUNTAINS, WITH THE BULK OF THE DAY REMAINING DRY. TEMPERATURES
WILL CLIMB UP INTO THE 40S TO NEAR 50 BY AFTERNOON, BUT
TEMPERATURES WILL DECREASE RAPIDLY WITH HEIGHT AS THE UPPER LOW
MOVES OVERHEAD, SO THESE SHOWERS WOULD LIKELY OCCUR AS A MIX OF
RAIN AND GRAUPEL TO THE EAST OF THE MOUNTAINS.
THE SNOW SHOWER ACTIVITY ALONG AND WEST OF THE ALLEGHENY FRONT
WILL BE INTERMITTENT, BUT SQUALLY IN NATURE, WITH MULTIPLE SHORT
DURATION HEAVY BURSTS OF SNOW AND THEN DRY PERIODS (AND EVEN
SOME SUN POSSIBLE) IN BETWEEN. THE SNOW IN THE MOUNTAINS WILL BE
RATHER LIGHT AND FLUFFY TOMORROW, AS INSTABILITY EXTENDS UP
INTO THE DENDRITIC SNOW GROWTH ZONE. A FEW INCHES WILL BE
POSSIBLE BY TOMORROW EVENING. THERE WILL BE A BIT OF A LULL IN
THE ACTIVITY TOMORROW NIGHT ONCE DAYTIME HEATING AND RESULTANT
BOUNDARY LAYER INSTABILITY IS LOST. LIGHT SNOW MAY CONTINUE ON
AND OFF THROUGH THE NIGHT, AND A COUPLE OF ADDITIONAL INCHES MAY
BE POSSIBLE BY FRIDAY MORNING.
ANOTHER DISTURBANCE EMBEDDED WITHIN THE MUCH LARGER UPPER LEVEL
LOW WILL ROTATE IN FROM THE NORTH ON FRIDAY. THE STEADIEST AND
LIKELY HEAVIEST SNOW IN THE MOUNTAINS WILL OCCUR LATE FRIDAY
MORNING THROUGH FRIDAY EVENING AS LOW-LEVEL WARM ADVECTION
OVERLAPS UPSLOPE FLOW INTERSECTING THE TERRAIN. SNOWFALL RATES
MAY APPROACH AN INCH PER HOUR AT TIMES FRIDAY AFTERNOON. THE
SNOW ON FRIDAY WILL BE A WETTER SNOW AS THE COLUMN STARTS TO
WARM.
SOME SNOW MAY ALSO OCCUR TO THE EAST OF THE MOUNTAINS FRIDAY
MORNING, WITH THE FIRST SNOWFLAKES OF THE YEAR POSSIBLE IN THE
DC AND BALTIMORE METRO AREAS. TEMPERATURES WILL LIKELY BE TOO
WARM FOR ACCUMULATIONS ALONG THE I-95 CORRIDOR, BUT SOME MINOR
ACCUMULATIONS MAY BE POSSIBLE ALONG PARR'S RIDGE IN NORTH-
CENTRAL MARYLAND AND IN THE CATOCTINS. ANY SNOW TO THE EAST OF
THE MOUNTAINS SHOULD SWITCH OVER TO RAIN DURING THE AFTERNOON AS
TEMPERATURES WARM.
PRECIPITATION WILL CONTINUE IN THE MOUNTAINS THROUGH FRIDAY
NIGHT. AS TEMPERATURES CONTINUE TO WARM, SOME OF THE LOWER
ELEVATIONS IN THE MOUNTAINS MAY SWITCH OVER TO RAIN BEFORE
ENDING, BUT THE HIGHEST ELEVATIONS (ABOVE 2500 FEET) SHOULD
STAY ALL SNOW THROUGH THE NIGHT. BY THE TIME ALL IS SAID AND
DONE, 6-12 INCHES IS EXPECTED ALONG AND WEST OF THE ALLEGHENY
FRONT, WITH ISOLATED TOTALS OF 12-18 INCHES POSSIBLE ALONG THE
HIGHEST RIDGETOPS. WINTER STORM WARNINGS ARE IN EFFECT FOR
GARRETT, WESTERN GRANT, WESTERN PENDLETON AND WESTERN HIGHLAND
COUNTIES STARTING AT 10 AM TOMORROW. THOSE WARNINGS CONTINUE
THROUGH FRIDAY NIGHT. A WINTER WEATHER ADVISORY IS ALSO IN
EFFECT FOR WESTERN MINERAL COUNTY FROM 10 AM TOMORROW THROUGH 10
PM TOMORROW NIGHT.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
SNOW SHOWERS WILL BEGIN TO TAPER OFF AFTER DAYBREAK ON SATURDAY AND
TRANSITION TO MORE OF A RAIN/SNOW MIX, AND PERHAPS EVEN OVER TO
FREEZING DRIZZLE AT THE HIGHEST ELEVATIONS. NOT EXPECTING MUCH
ADDITIONAL SNOW ACCUMULATION BEYOND EARLY SATURDAY MORNING, BUT
COULD SEE AT LEAST A FEW HUNDREDTHS OF AN INCH OF ICE ACCRETION ON
THE RIDGES. BY SATURDAY AFTERNOON THE SHORTWAVE WILL PIVOT EAST AND
HEIGHTS BEGIN TO RISE. THIS WILL RESULT IN PRETTY RAPID DRYING OUT
INTO THE AFTERNOON/EVENING. ELSEWHERE, SATURDAY REMAINS DRY WITH
GUSTY NORTHWESTERLY WINDS OF AROUND 25 TO 35 MPH, WITH GUSTS UP TO
40 MPH, MAINLY ON THE RIDGES AND OVER THE OPEN WATERS.
SUNDAY INTO MONDAY LOOK TO REMAIN MOSTLY DRY AS HIGH PRESSURE
RETURNS TO THE REGION. SUNDAY WILL SEE HIGHS AROUND THE MID 50S,
THEN INCREASING TO AROUND THE LOW 60S ON MONDAY.
MEANWHILE, LOW PRESSURE OVER THE CENTRAL U.S WILL TRACK NORTH AND
EAST INTO THE GREAT LAKES LATE MONDAY INTO TUESDAY. THIS WILL SEND
ANOTHER FRONT INTO OUR REGION FOR THE MIDDLE OF NEXT WEEK. AS IT
STANDS NOW, THE FRONT LOOKS TO STALL SOMEWHERE IN THE VICINITY OF
OUR REGION TUESDAY INTO WEDNESDAY. THIS WILL LEAD TO INCREASED
PRECIPITATION CHANCES DURING THIS TIME. ACTIVE WEATHER CONTINUES
THROUGH THE EXTENDED COULD POTENTIALLY CONTINUE INTO THANKSGIVING
AND TOWARDS NEXT WEEKEND.
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
VFR CONDITIONS AND LIGHT SOUTHEASTERLY WINDS ARE EXPECTED
THROUGH THE REMAINDER OF THE AFTERNOON. A STRONG COLD FRONT WILL
MOVE THROUGH THIS EVENING LEADING TO AN ABRUPT WIND SHIFT. WINDS
MAY GUST TO AROUND 30-40 KNOTS FOR A FEW HOURS IMMEDIATELY
BEHIND THE FRONT. A SQUALL LINE MAY ALSO ACCOMPANY THE FRONTAL
PASSAGE, LEADING TO A BRIEF PERIOD OF HEAVY RAIN, IFR
CONDITIONS, AND POTENTIALLY EVEN A RUMBLE OR TWO OF THUNDER.
SHOWERS MAY LINGER FOR A FEW HOURS BEHIND THE FRONT BEFORE
CONDITIONS DRY OUT DURING THE SECOND HALF OF THE NIGHT. LOW
LEVEL WIND SHEAR WILL ALSO BE POSSIBLE IMMEDIATELY IN THE WAKE
OF THE FRONT THIS EVENING.
PREVAILING VFR CONDITIONS ARE EXPECTED TOMORROW. A FEW MIXED
RAIN/SNOW/GRAUPEL SHOWERS MAY BE POSSIBLE TOMORROW AFTERNOON,
BUT THE VAST MAJORITY OF THE TIME SHOULD REMAIN DRY. WINDS WILL
REMAIN OUT OF THE WEST. MIXED RAIN AND SNOW MAY POTENTIALLY
IMPACT SOME OF THE TERMINALS FRIDAY MORNING. ANY PRECIPITATION
WOULD CHANGE OVER TO PLAIN RAIN BY FRIDAY AFTERNOON.
GUSTY WNW WINDS AROUND 20 TO 30 KTS WILL BE THE MAIN THREAT TO THE
TERMINALS ON SATURDAY AT THE TERMINALS. OTHERWISE, VFR CONDITIONS
ARE EXPECTED AS WE TRANSITION INTO A PERIOD OF HIGH PRESSURE THAT
WILL THEN CONTINUE INTO SUNDAY. WINDS TURN MORE WESTERLY ON SUNDAY
AND WILL BE AROUND 10 TO 20 KTS.
MARINE
WINDS REMAIN LIGHT OUT OF THE EAST TO SOUTHEAST THIS AFTERNOON.
A COLD FRONT WILL MOVE THROUGH THE AREA THIS EVENING. WINDS WILL
ABRUPTLY SHIFT TO WESTERLY BEHIND THE FRONT, AND INCREASE TO
GALE LEVELS. A FEW STORM FORCE GUSTS CAN'T EVEN BE RULED OUT
ACROSS THE WIDEST WATERS. A SPECIAL MARINE WARNING WILL LIKELY
BE NEEDED THIS EVENING AS THE FRONT MOVES THROUGH WITH A SQUALL
LINE, GIVEN THE ABRUPT WIND SHIFT. SOME THUNDER MAY BE POSSIBLE
IN ASSOCIATION WITH THE SQUALL LINE. WINDS GRADUALLY DECREASE
LATE TONIGHT INTO TOMORROW MORNING, BUT SMALL CRAFT ADVISORY
CONDITIONS WILL CONTINUE THROUGH THURSDAY AND FRIDAY. GUSTS MAY
NEAR LOW- END GALE LEVELS FRIDAY AFTERNOON INTO FRIDAY NIGHT.
IN THE WAKE OF A STRONG COLD FRONT, HIGH-END SCAS WILL CONTINUE
THROUGH MUCH OF THE DAY SATURDAY. GALE CONDITIONS MAY EVEN BRIEFLY
BE POSSIBLE EARLY SATURDAY.
WINDS TAPER OFF INTO SUNDAY, BUT SCAS SEEM LIKELY TO CONTINUE,
ALBEIT CLOSER TO THE LOW END.
TIDES/COASTAL FLOODING
MINOR COASTAL FLOODING IS POSSIBLE AT THE MORE SENSITIVE TIDAL
SITES LIKE ANNAPOLIS AND DC SW WATERFRONT WITH THE TIDE CYCLE
THIS EVENING. WATER LEVELS WILL DECREASE TONIGHT THROUGH THE
UPCOMING WEEKEND AS WINDS TURN WESTERLY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...GALE WARNING UNTIL 6 AM EST THURSDAY FOR MDZ008.
WIND ADVISORY UNTIL 1 AM EST THURSDAY FOR MDZ001-501.
WINTER STORM WARNING FROM 10 AM THURSDAY TO MIDNIGHT EST
FRIDAY NIGHT FOR MDZ001.
VA...WIND ADVISORY UNTIL 1 AM EST THURSDAY FOR VAZ503-507-508.
WINTER STORM WARNING FROM 10 AM THURSDAY TO 6 AM EST SATURDAY
FOR VAZ503.
WV...WIND ADVISORY UNTIL 1 AM EST THURSDAY FOR WVZ501-503-505.
WINTER STORM WARNING FROM 10 AM THURSDAY TO 6 AM EST SATURDAY
FOR WVZ501-505.
WINTER WEATHER ADVISORY FROM 10 AM TO 10 PM EST THURSDAY FOR
WVZ503.
MARINE...GALE WARNING UNTIL 6 AM EST THURSDAY FOR ANZ530>543.
SYNOPSIS...KJP
NEAR TERM...KJP
SHORT TERM...KJP
LONG TERM...CJL
AVIATION...CJL/KJP
MARINE...CJL/KJP
TIDES/COASTAL FLOODING...LWX
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