942
FXUS61 KLWX 021400
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
900 AM EST TUE DEC 2 2025
SYNOPSIS
HIGH PRESSURE OVER NEW ENGLAND WILL STEADILY RETREAT THROUGH THE
CANADIAN MARITIMES AS LOW PRESSURE MOVES UP THE EAST COAST
THROUGH TODAY. HIGH PRESSURE WILL BRIEFLY RETURN WEDNESDAY,
THEN A REINFORCING COLD FRONT WILL CROSS THURSDAY. LOW PRESSURE
LIKELY PASSES TO THE SOUTH FRIDAY INTO SATURDAY, THEN ANOTHER
FRONTAL SYSTEM MAY APPROACH BY EARLY NEXT WEEK.
KEY MESSAGES:
- QUICK HITTING WINTER SYSTEM WILL EXIT THE AREA THROUGH EARLY
THIS AFTERNOON.
- WINTER WEATHER ADVISORIES REMAIN IN EFFECT NEAR AND WEST OF
US-15 AND NEAR AND NORTH OF I-70.
- LOCALIZED FREEZING RAIN (ICE) AMOUNTS OF NEAR ONE-QUARTER
INCH ARE POSSIBLE OVER THE HIGHER TERRAIN OF HIGHLAND,
PENDLETON, ROCKINGHAM, AND AUGUSTA COUNTIES AS WELL AS THE
CENTRAL AND NORTHERN VIRGINIA BLUE RIDGE MOUNTAINS.
NEAR TERM /THROUGH TONIGHT/
AS OF MID MORNING (14Z/9 AM EST), WIDESPREAD PRECIPITATION WAS
MOVING ACROSS THE MID-ATLANTIC. SOME BREAKS IN THE STEADY PRECIP
WERE BEGINNING TO DEVELOP WEST OF I-81. HOWEVER, AT LEAST A FEW
MORE HOURS OF PRECIP IS EXPECTED AREAWIDE.
PRECIP IS IN THE FORM OF FREEZING RAIN WHERE THE WINTER WEATHER
ADVISORY IS IN EFFECT, THOUGH SOME LOWER ELEVATIONS HAVE WARMED
TO 34-36 F IN LOCALIZED SPOTS. GIVEN NUMEROUS LOCATIONS STILL AT
OR BELOW 32 F, WILL MAINTAIN THE ADVISORY AS IS FOR AT LEAST 1-2
MORE HOURS BEFORE TRIMMING. THERE HAVE BEEN A FEW REPORTS OF
NEAR TWO TENTHS OF AN INCH OF ICE ON SOME OF THE HIGHER RIDGES
IN WEST-CENTRAL VA INTO EASTERN WV AS EXPECTED, BUT ANY 0.25+
INCH TOTALS SHOULD BE VERY LOCALIZED. THAT, PLUS THE FACT PRECIP
WILL END WITHIN THE NEXT FEW HOURS, PRECLUDES THE NEED FOR AN
UPGRADE TO A WINTER/ICE STORM WARNING AT THIS TIME.
PREVIOUS DISCUSSION...
THE RIDGES OF THE BLUE RIDGE AND CATOCTIN MOUNTAINS, AND THE
ALLEGHENY AND POTOMAC HIGHLANDS, AS WELL AS THE SHENANDOAH
VALLEY INTO THE CENTRAL VIRGINIA PIEDMONT WEST OF I-95 ARE
EXPECTED TO HOLD ON TO SURFACE TEMPS BELOW FREEZING IN AN IN-
SITU CAD SETUP. THIS WILL SUPPORT A PERIOD OF FREEZING RAIN/ICE
FROM AROUND DAYBREAK THROUGH MID TO LATE MORNING AS AIR ALOFT
WARMS. TO THE NORTH OVER NORTHERN MARYLAND (NORTH OF I-70), COLD
AIR MAY BE DEEP ENOUGH TO SUPPORT AT LEAST SEVERAL HOURS OF
STEADY SNOW BEFORE A TRANSITION TO PELLETS OR ICE OCCURS. THE
END RESULT WILL BE A MESSY MIX OF PRECIPITATION WEST OF I-95 AND
ESPECIALLY WEST OF US-15 AND NORTH OF I-70 THROUGH THE FIRST
HALF OF TODAY, LIKELY AFFECTING THE MORNING COMMUTE. A BRIEF
RAIN/SLEET MIX IS EXPECTED ALONG THE IMMEDIATE I-95 CORRIDOR.
THE PROGRESSIVE NATURE OF THE SYSTEM SHOULD KEEP PRECIP AMOUNTS
ON THE MODEST SIDE, WITH GENERALLY 0.10-0.25" OF ICE IN THE
ABOVE MENTIONED FAVORED AREAS, AND 1-3" OF SNOW/SLEET ACROSS
NORTHERN MARYLAND. ONE CHANGE MADE TO THE FORECAST WAS TO
INCREASE THE SNOWFALL BY ABOUT AN INCH OR TWO ACROSS WESTERN
MARYLAND. MODEL GUIDANCE HAS COME UP IN QPF IN THIS AREA AND
THEREFORE SNOWFALL WHICH COULD RESULT IN LOCALIZED HIGHER SNOW
TOTALS OF 3 TO 5". THIS IS MAINLY DUE TO FORCING FROM THE MID-
LEVEL FGEN/COUPLED UPPER JET. NORTHERN MARYLAND IS ANOTHER AREA
TO KEEP AN EYE ON FOR "OVERPERFORMING" SNOWFALL WISE. FARTHER
TO THE SOUTH AND WEST, SOME ICE AMOUNTS NEAR ONE QUARTER OF AN
INCH ARE POSSIBLE OVER THE BLUE RIDGE MOUNTAINS AS WELL AS THE
RIDGES IN HIGHLAND, PENDLETON, AUGUSTA, AND ROCKINGHAM COUNTIES
(GW NAT'L FOREST, SHENANDOAH MOUNTAIN, ETC.). HOWEVER, HEAVY
PRECIP RATES AND A STRONGER WARM NOSE ALOFT COULD KEEP ICE
TOTALS IN CHECK (HEAVIER PRECIP TENDS TO RUN OFF BEFORE
FREEZING, ESPECIALLY IF TEMPS ARE MARGINAL).
ACROSS THE METROS, A PERIOD OF SLEET AND RAIN IS ANTICIPATED
WHICH SHOULD OVERLAP THE MORNING COMMUTE. TEMPS GENERALLY NEAR
OR ABOVE FREEZING AT THE SURFACE SHOULD KEEP ACCUMULATION VERY
LOCALIZED AND LIMITED TO ELEVATED SURFACES, IF AT ALL. STILL, BE
MINDFUL OF SLICK SPOTS DURING THE MORNING COMMUTE ALONG THE
I-95 CORRIDOR FROM BALTIMORE MD TO FREDERICKSBURG VA.
PRECIPITATION IS EXPECTED TO COME TO AN END AS THE TROUGH AND
LOW SWING TO THE EAST BY EARLY TO MID AFTERNOON, THOUGH SOME
LINGERING UPSLOPE SNOW SHOWERS ARE LIKELY ALONG AND WEST OF THE
ALLEGHENY FRONT. AN ADDITIONAL COATING TO LOCALLY TWO INCHES OF
SNOW IS POSSIBLE THIS AFTERNOON/EARLY TONIGHT ALONG FAVORED
UPSLOPE LOCALES OF ALLEGHENY MOUNTAINS. SOME GUIDANCE DOES HAVE
FREEZING DRIZZLE MIXING IN ACROSS THE HIGHEST PEAKS, BUT LOW
CONFIDENCE AT THIS TIME. BEFORE WINDS INCREASE, THERE IS A
SEVERAL HOUR WINDOW WHERE FOG COULD FORM, AND SOME GUIDANCE HAS
THIS BECOMING DENSE AROUND MIDDAY INTO EARLY/MID AFTERNOON.
WINDS WILL INCREASE AND FOG/CLOUDS WILL QUICKLY CLEAR EAST OF
THE APPALACHIANS BY DARK. BREEZY NORTHWEST WINDS WILL USHER IN
DRIER AIR AND CLEARING SKIES THROUGH TONIGHT EAST OF THE
APPALACHIANS, THOUGH SOME STRATOCU ARE POSSIBLE AT TIMES. ANY
AREAS THAT DO SEE ACCUMULATING SNOW AND SOME MELTING COULD SEE A
REFREEZE TONIGHT WITH TEMPS FALLING INTO THE LOW TO MID 20S
AREAWIDE.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
DRY CONDITIONS AND BELOW NORMAL TEMPERATURES ARE EXPECTED
WEDNESDAY WITH NORTHWEST WINDS AS HIGH PRESSURE BRIEFLY BUILDS
ACROSS THE AREA. MID/HIGH CLOUDS WILL LIKELY INCREASE WEDNESDAY
NIGHT AHEAD OF A REINFORCING COLD FRONT THURSDAY. THIS FRONT MAY
HAVE ENOUGH MOISTURE TO BRING SOME SNOW SHOWERS TO THE
ALLEGHENIES, THOUGH MOST GUIDANCE KEEPS ACCUMULATIONS LESS THAN
ONE INCH.
LONG TERM /FRIDAY THROUGH MONDAY/
VERY COLD FRI MORNING WITH HIGH PRESSURE OVERHEAD. HIGH
PRESSURE QUICKLY MOVES OFFSHORE FRI AFTERNOON WITH LOW PRESSURE
SYSTEM EXPECTED TO PASS WELL SOUTH OF THE AREA SATURDAY
AFTERNOON BEFORE LIFTING OUT TO SEA SUNDAY. THIS SYSTEM MAY
SPREAD SOME VERY LIGHT PRECIP (RAIN OR SNOW) ON ITS NORTHERN
SIDE FRIDAY NIGHT BEFORE PUSHING OFFSHORE SATURDAY. IT LOOKS
LIKE THERE WILL BE LESS COLD AIR AVAILABLE THIS TIME AROUND WHEN
COMPARED TO TODAY.
MUCH COLDER AIR WILL FOLLOW TO START NEXT WEEK AS TROUGH PATTERN
ANCHORED ON A SUB-500 DM HUDSON BAY LOW AMPLIFIES. IN THIS
PATTERN, FAST MOVING ALBERTA CLIPPERS WILL RIDE ALONG THE FAST
JET STREAK AND MAY BRING SOME VERY LIGHT SNOWS ACROSS PORTIONS
OF THE MID-ATLANTIC FROM TIME TO TIME NEXT WEEK.
AVIATION /12Z TUESDAY THROUGH SATURDAY/
CONDITIONS HAVE DETERIORATED RAPIDLY THIS MORNING, WITH IFR OR
LOWER CONDITIONS EXPECTED THROUGH EARLY AFTERNOON. FZRA SHOULD
TRANSITION TO RA AT KCHO WITHIN THE HOUR, WITH MORE OF AN ICY
MIX FAVORED NEAR KMRB UNTIL LATE MORNING/MIDDAY. FOR THE
METROS, PLAIN RAIN IS ANTICIPATED FROM HERE ON OUT. A PERIOD OF
FOG IS POSSIBLE ONCE STEADIER PRECIP ENDS FROM ROUGHLY 16Z-20Z.
LIGHT N WINDS ARE EXPECTED THROUGH EARLY AFTERNOON, THEN
INCREASE OUT OF THE NW AS LOW PRESSURE PULLS AWAY BY LATE
AFTERNOON. SOME GUSTS OF AROUND 25 KTS ARE POSSIBLE LATE
THIS AFTERNOON INTO THE EVENING AS CONDITIONS RETURN TO VFR.
PASSING VFR CLOUDS AND MODEST NW BREEZES ARE EXPECTED TONIGHT
THROUGH WEDNESDAY NIGHT AS HIGH PRESSURE PIVOTS ACROSS. VFR
CONDITIONS ARE EXPECTED TO PERSIST THURSDAY INTO MUCH OF FRIDAY.
A DRY COLD FRONT RACES ACROSS THE REGION ON THURSDAY LEADING TO
AN UPTICK IN NORTHWESTERLY WINDS. GUSTS UP TO 15 TO 25 KNOTS
ARE POSSIBLE DURING THIS NORTHWESTERLY SURGE. HIGH PRESSURE
BUILDS IN FOR THURSDAY NIGHT THROUGH THE FIRST HALF OF FRIDAY
WITH LIGHTER WINDS EXPECTED.
AN AREA OF LOW PRESSURE MAY BRING SOME WINTRY PRECIPITATION TO THE
REGION FRIDAY NIGHT INTO SATURDAY MORNING. HOWEVER, THERE IS A GREAT
DEAL OF UNCERTAINTY WITH THIS SYSTEM AT THIS TIME. SOME GUIDANCE HAS
US COMPLETELY DRY AND JUST COLD, WHILE OTHERS BRING A LIGHT WINTRY
MIX. SO AT THIS POINT, JUST SOMETHING TO KEEP AN EYE ON AS WE GET
CLOSER TO THE EVENT.
MARINE
LIGHT SOUTHEAST WINDS EXPECTED TO CONTINUE THROUGH THE MORNING.
RAIN WILL CONTINUE INTO THE AFTERNOON. FOG IS POSSIBLE AS
PRECIP EXITS AND WINDS BECOME LIGHT OUT OF THE NORTH. AN
INCREASE IN NORTHWEST WINDS IS ANTICIPATED MID TO LATE AFTERNOON
AS LOW PRESSURE PULLS AWAY, WITH WINDS LIKELY REMAINING
ELEVATED WITH 25-35 KNOT GUSTS THROUGH TONIGHT. A GALE WARNING
REMAINS IN EFFECT ACROSS THE WIDER WATERS OF THE MIDDLE
CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER TO ACCOUNT FOR
THIS, WITH SMALL CRAFT ADVISORIES ELSEWHERE. LIGHTER WINDS ARE
THEN EXPECTED WEDNESDAY INTO WEDNESDAY NIGHT AS HIGH PRESSURE
BRIEFLY BUILDS OVERHEAD.
BEHIND A QUICK-MOVING COLD FRONT, NORTHWESTERLY WINDS INCREASE
IN EARNEST ON THURSDAY. SMALL CRAFT ADVISORIES WILL LIKELY BE
NEEDED LATE THURSDAY AFTERNOON INTO PORTIONS OF THE NIGHT. HIGH
PRESSURE BUILDS IN BEFORE EXITING OFFSHORE BY FRIDAY AFTERNOON
AS WINDS DROP BELOW ADVISORY LEVELS. SOME WINTRY PRECIPITATION
IS POSSIBLE FRIDAY NIGHT INTO EARLY SATURDAY MORNING WITH A
QUICK-MOVING LOW PRESSURE SYSTEM. HOWEVER, THERE IS A LOT OF
UNCERTAINTY AT THIS POINT, SO JUST KEEP CHECKING FOR UPDATES ON
THE FORECAST AS WE GET CLOSER TO THE EVENT.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
MDZ003>006-501-502-507-509-510.
WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
MDZ503-505.
VA...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR VAZ025>031-
036>040-050-051-501>505-507-508.
WV...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
WVZ051>053-501-503-504.
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR WVZ050-055-
502-505-506.
MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 4 AM EST
WEDNESDAY FOR ANZ530>532-535-536-538>540.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 4 AM EST WEDNESDAY
FOR ANZ533-534-537-541>543.
SYNOPSIS...DHOF/CPB
NEAR TERM...DHOF/CPB
SHORT TERM...DHOF/CPB
LONG TERM...LFR
AVIATION...LFR/DHOF/CPB
MARINE...LFR/DHOF/CPB
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