Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 251850
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
250 PM EDT WED MAR 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE COAST THROUGH TONIGHT.
A WARM FRONT WILL PASS THROUGH THE AREA THURSDAY MORNING FOLLOWED
BY A POTENT COLD FRONT THAT WILL MOVE THROUGH LATE THURSDAY INTO
THURSDAY NIGHT. AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE
AREA LATER FRIDAY THROUGH SATURDAY...AND HIGH PRESSURE WILL RETURN
FOR SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE COAST THROUGH TONIGHT.
LOW PRESSURE WILL TRACK THROUGH THE TENNESSEE VALLEY AND INTO THE
OHIO VALLEY TONIGHT. A SOUTHERLY FLOW WILL ALLOW FOR MILDER
CONDITIONS COMPARED TO RECENT NIGHTS. IN FACT...TEMPS MAY RISE A
BIT AS A WARM FRONT APPROACHES FROM THE SOUTH. PLENTY OF CLOUDS
WILL CONTINUE TO OVERSPREAD THE AREA DUE TO WARM AND MOIST AIR
OVERRUNNING THE SURFACE COOLER AIR IN PLACE.

LIGHT RAIN OR SPRINKLES CANNOT BE RULED OUT THROUGH THIS
EVENING...BUT MOST OF THE TIME WILL BE DRY DUE TO LITTLE IN THE
WAY OF A LIFTING MECHANISM. A PLUME OF MOISTURE WILL OVERSPREAD
SOUTHERN PORTIONS OF THE AREA LATE TONIGHT...AND THIS MAY CAUSE
SHOWERS TO BE MORE WIDESPREAD ACROSS THE VIRGINIA PIEDMONT INTO
SOUTHERN MARYLAND. ELSEWHERE...ANY PRECIPITATION WILL BE LIGHT AND
MUCH OF THE TIME WILL TURN OUT DRY.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
THE WARM FRONT WILL PASS THROUGH OUR AREA THURSDAY MORNING. A FEW
SHOWERS ARE POSSIBLE WITH THE FRONTAL PASSAGE...ESPECIALLY ACROSS
SOUTHERN MARYLAND AND THE VIRGINIA PIEDMONT WHERE ATLANTIC
MOISTURE WILL GET DRAWN INTO THE AREA.

THERE MAY BE A SIGNIFICANT BREAK IN PRECIPITATION BEHIND THE WARM
FRONT THURSDAY. GUSTY SOUTHERLY WINDS ARE EXPECTED TO DEVELOP AND
THIS WILL USHER IN UNUSUALLY WARM CONDITIONS FOR THIS TIME OF
YEAR. IN FACT...MAX TEMPS ARE EXPECTED TO BE IN THE 70S ACROSS
MOST LOCATIONS. THERE MAY EVEN BE A FEW LOCATIONS IN THE VIRGINIA
PIEDMONT THAT APPROACH 80 DEGREES. A POTENT COLD FRONT WILL MOVE
INTO THE POTOMAC HIGHLANDS LATE IN THE AFTERNOON BEFORE PASSING
THROUGH THE BALTIMORE AND WASHINGTON METROPOLITAN AREAS EARLY IN
THE EVENING...THEN EVENTUALLY PAST SOUTHERN MARYLAND OVERNIGHT. A
LINE OF GUSTY SHOWERS AND POSSIBLY EVEN A COUPLE THUNDERSTORMS
WILL ACCOMPANY THE FRONT. GUSTY WINDS ARE EXPECTED...BUT AS OF NOW
THE THREAT FOR SEVERE WEATHER IS LOW DUE TO A CAPPING INVERSION IN
THE LOW-LEVELS LIMITING INSTABILITY. WILL HAVE TO CONTINUE TO
MONITOR...BECAUSE THERE ARE PLENTY OF STRONG WINDS ALOFT THAT WILL
BE ABLE TO MIX DOWN TO THE SURFACE IF THE ATMOSPHERE IS UNSTABLE
ENOUGH AHEAD OF THE BOUNDARY.

THE COLD FRONT WILL PUSH OFF TO THE EAST OVERNIGHT THURSDAY...BUT
THE UPPER-LEVEL TROUGH WILL REMAIN WELL BEHIND OVER THE GREAT
LAKES INTO THE OHIO VALLEY. AN UPPER-LEVEL DISTURBANCE AHEAD OF
THE TROUGH WILL SWING THROUGH OUR AREA...CAUSING MORE RAIN BEHIND
THE FRONT. NORTHWEST WINDS WILL CAUSE MUCH COLDER CONDITIONS AS
WELL. IN FACT...RAIN WILL CHANGE TO SNOW ACROSS THE ALLEGHENY AND
POTOMAC HIGHLANDS. SNOWFALL ACCUMULATIONS WILL BE CONFINED MAINLY
TO AREAS ABOVE 2KFT ALONG AND WEST OF THE ALLEGHENY FRONT.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
FOR FRIDAY THROUGH SATURDAY...PERIOD IS DOMINATED BY H5 HEIGHT FALLS
AS SHORT WAVE OVER GREAT LAKES PRODUCES CUTOFF LOW ON SATURDAY OVER
THE MASON-DIXON LINE AS INDICATED BY THE 12Z GFS. SFC TEMPS DURING
THIS TIME WILL BE 10-15F BELOW NORMAL.

ON FRIDAY...THE SURFACE FRONT IS PROGGED BY BOTH THE 12Z GFS AND 12Z
ECMWF TO BE EAST OF DELMARVA.  THIS WILL PUT DECREASING POPS FROM
WEST TO EAST ACROSS THE CWA IN THE MORNING...WITH THE EXCEPTION OF
AN UPSLOPE COMPONENT IN THE HIGHLANDS WHERE SNOW SHOWERS WILL BE
LIKELY.  FRIDAY NIGHT THE CWA WILL BE PRECIP FREE XCPT FOR UPSLOPE
AGAIN IN H85 CAA AND DOWNSLOPING.

BY 12Z SATURDAY...H85 TEMPS ARE PROGGED TO BE A0B -9C ACROSS THE
ENTIRE CWA...WHICH WILL MAKE FOR A VERY CHILLY AND BLUSTERY DAY ON
SATURDAY WITH CHC OF SNOW SHOWERS ACROSS THE ENTIRE REGION DUE TO
LOW LEVEL INSTABLITY AND APPROACHING CUT UPPER LOW...WITH HIGHER
POPS IN UPSLOPE AREAS AGAIN.

AN UPPER-LEVEL TROUGH WILL BE MOVING AWAY SATURDAY NIGHT INTO
SUNDAY WHILE HIGH PRESSURE BUILDS OVER THE REGION. THE HIGH WILL
MOVE OFF THE COAST ON SUNDAY. HIGH TEMPS WILL BE IN LOW 50S.

A COLD FRONT APPROCHES THE REGION AND WILL MOVE ACROSS THE AREA
EARLY ON MONDAY... BRINGING A CHANCE FOR SHOWERS. HIGH PRESSURE
RETURNS ON TUESDAY AND A WARM FRONT APPROACHES ON WEDNESDAY.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
CIGS WILL LOWER TO MVFR LEVELS LATE THIS AFTERNOON AND EVENING
AHEAD OF A WARM FRONT. A PERIOD OF IFR LEVELS ARE POSSIBLE LATE
TONIGHT INTO THURSDAY MORNING AS THE WARM FRONT SWINGS THROUGH.
WILL CONTINUE WITH A LOW-LEVEL WIND SHEAR GROUP IN THE TAFS
TONIGHT THROUGH EARLY THURSDAY MORNING DUE TO A POTENT LOW-LEVEL
JET AND A LACK OF MIXING CAUSING LIGHT WINDS NEAR THE SURFACE.

CIGS WILL IMPROVE BEHIND THE BOUNDARY LATER THURSDAY MORNING.
SOUTHERLY WINDS WILL BECOME GUSTY AHEAD OF AN APPROACHING COLD
FRONT THURSDAY AFTERNOON. GUSTS AROUND 25 TO 30 KNOTS ARE
EXPECTED. VFR CONDITIONS WITH GUSTY NORTHWEST ARE EXPECTED FRIDAY
THROUGH SATURDAY.

VFR CONDITIONS ARE EXPECTED FOR SUNDAY. COLD FRONT MOVING ACROSS
ON MONDAY WILL BRING A CHANCE FOR SHOWERS TO THE TERMINALS.

THE COLD FRONT WILL PASS THROUGH LATE THURSDAY AFTERNOON AND
EVENING. A LINE OF SHOWERS AND PERHAPS A COUPLE THUNDERSTORMS WILL
ACCOMPANY THE FRONTAL PASSAGE. GUSTY WINDS ARE POSSIBLE WITH THIS
LINE OF CONVECTION. WINDS WILL SHIFT TO THE NORTHWEST BEHIND THE
FRONT. MORE RAIN WILL HANG AROUND FOR OVERNIGHT THURSDAY WITH
POSSIBLE SUBVFR CONDITIONS.

&&

.MARINE...
SOUTHERLY WINDS WILL INCREASE A BIT THIS AFTERNOON. A SMALL CRAFT
ADVISORY REMAINS IN EFFECT FOR THE NORTHERN PORTION OF THE BAY FOR
GUSTS UP TO 20 KNOTS. ELSEWHERE...THE GRADIENT SHOULD BE WEAK
ENOUGH FOR GUSTS TO REMAIN JUST BELOW SCA CRITERIA.

WINDS WILL DIMINISH TONIGHT...BUT REMAIN SOUTH TO SOUTHEAST AHEAD
OF AN APPROACHING WARM FRONT. THE WARM FRONT WILL PASS THROUGH THE
WATERS THURSDAY MORNING AND GUSTY SOUTHERLY WINDS ARE EXPECTED
BEHIND THE BOUNDARY. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE
WATERS DURING THIS TIME. THE SMALL CRAFT ADVISORY CONTINUES
THROUGH THURSDAY NIGHT. SOUTHERLY WINDS WILL SHIFT TO THE
NORTHWEST BEHIND THE COLD FRONT. A LINE OF HEAVY SHOWERS AND
PERHAPS A COUPLE THUNDERSTORMS WILL ACCOMPANY THE FRONTAL PASSAGE.
LOCALLY GUSTY WINDS ARE POSSIBLE AS THIS SYSTEM PASSES THROUGH.

A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS
FRIDAY. NO MARINE HEADLINES ANTICIPATED FRIDAY NIGHT THROUGH
SUNDAY. SCA MAY BE NEEDED ON MONDAY AS COLD FRONT MOVES ACROSS
THE REGION.

&&

.TIDES/COASTAL FLOODING...
SOUTHERLY WINDS WILL DEVELOP THROUGH TONIGHT AND THE SOUTHERLY
FLOW WILL INCREASE AHEAD OF A COLD FRONT THURSDAY. THE INCREASED
SOUTHERLY FLOW WILL CAUSE WATER LEVELS TO ELEVATE...AND TIDAL
ANOMALIES MAY BE HIGH ENOUGH FOR MINOR FLOODING NEAR TIMES OF HIGH
TIDE THURSDAY INTO THURSDAY NIGHT.

THE COLD FRONT WILL PASS THROUGH LATER THURSDAY EVENING AND A
NORTHWEST FLOW WILL CAUSE WATER LEVELS TO DECREASE LATE THURSDAY
NIGHT INTO FRIDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR
     ANZ530>533-538>541.
     SMALL CRAFT ADVISORY FROM 10 AM THURSDAY TO 6 AM EDT FRIDAY
     FOR ANZ530>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...LEE/IR
AVIATION...BJL/LEE/IR
MARINE...BJL/LEE/IR
TIDES/COASTAL FLOODING...BJL



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