Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 281429
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
929 AM EST SAT FEB 28 2015

.SYNOPSIS...
HIGH PRESSURE WILL RESIDE OVER THE CENTRAL MID- ATLANTIC THROUGH
TONIGHT BEFORE MOVING OFF THE COAST SUNDAY. A COLD FRONT WILL
PASS THROUGH THE AREA SUNDAY NIGHT. HIGH PRESSURE BRIEFLY BUILDS
MONDAY NIGHT...THEN A WARM FRONT THEN COLD FRONT WILL CROSS THE
AREA TUESDAY AND WEDNESDAY. THE COLD FRONT LOOKS TO STALL ALONG
THE CAROLINA COAST THROUGH THURSDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE WILL CONTINUE TO BRING DRY AND COLD CONDITIONS TO
THE REGION TODAY. AN UPPER-LEVEL DISTURBANCE IN THE SOUTHWEST FLOW
ALOFT WILL CAUSE A BKN DECK OF HIGH AND MID-LEVEL CLOUDS. MAX
TEMPS WILL RANGE FROM THE LOWER 20S IN THE MOUNTAINS TO THE MID
AND UPPER 20S ACROSS MOST OTHER LOCATIONS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
FLOW BECOMES WESTERLY ALOFT THIS EVENING AS WARM AIR ADVECTION
INCREASES ACROSS THE TN VALLEY AND SE US. HIGH PRESSURE WILL STAY
WEDGED ACROSS THE REGION AND TEMPS ARE EXPECTED TO REACH THE UPPER TEENS
AND LOW 20S BY LATE TONIGHT. TEMPS WILL BEGIN TO RISE LATE TONIGHT
AND INTO SUNDAY MORNING. A FEW UPPER LEVEL WAVES IN THE WESTERLY
FLOW ALOFT WILL CROSS THE NRN OHIO VALLEY INTO SUNDAY MORNING.
WARM AIR ADVECTION COUPLED WITH FORCING TO THE NORTH WILL RESULT
IN SNOW ACROSS THE NRN POTOMAC HIGHLANDS SUNDAY MORNING. SNOW
WILL MOVE N-NE SUNDAY MORNING AND AROUND AN INCH TO LESS THAN AN
INCH OF SNOW IS EXPECTED ACROSS THE NRN POTOMAC HIGHLANDS.

A 30KT SOUTHERLY JET OFF THE SE US COAST WILL ALSO PUMP MOISTURE
INTO THE REGION. OVERRUNNING WILL RESULT IN PRECIPITATION TO
APPROACH THE CENTRAL FOOTHILLS AND PIEDMONT SUNDAY MORNING . A
HOLE IN BETWEEN MAY RESULT ACROSS THE BLUE RIDGE AND SHENANDOAH
VALLEY BUT EVENTUALLY FILL IN. PRECIPITATION IS EXPECTED TO START
AS SNOW AS THE ENTIRE COLUMN WILL BE BELOW ZERO. SNOW WILL MOVE
NORTH AND EAST ACROSS THE ENTIRE MID-ATLANTIC BY SUNDAY AFTERNOON.
WARMER AIR ALOFT WILL RESULT IN SNOW CHANGING TO IP/ZR SUNDAY
AFTERNOON EAST OF THE ALLEGHENY FRONT. THE WEDGE OF HIGH PRESSURE
WILL SLOWLY MOVE OFF THE COAST AND TEMPS WILL SLOWLY CLIMB ABOVE
FREEZING FROM W-SW TO E-NE RESULTING IN A CHANGEOVER TO RAIN.
AREAS WEST OF THE BLUE RIDGE WILL LIKELY RISE ABOVE FREEZING
FASTER THAN THOSE EAST. TEMPS WILL LIKELY STAY BELOW FREEZING
ACROSS NORTHEAST MARYLAND AND ZR AS THE PROMINENT PTYPE IS
EXPECTED BY SUNDAY AFTERNOON IN THESE PARTS. THERE ARE DIFFERENCES
IN HOW MUCH LIQUID WILL FALL SUNDAY. GENERALLY EXPECTING LESS THAN
A QUARTER INCH WITH THE HIGHER AMTS ACROSS THE NRN POTOMAC
HIGHLANDS AND MUCH OF MARYLAND. AT THIS TIME...A FEW HUNDREDTHS OF
ICE ACCUMULATION ARE POSSIBLE ACROSS MUCH OF MARYLAND WITH AMTS
NEAR A TENTH OF AN INCH IN FAR NORTHEAST MARYLAND.

FRONTAL SYSTEM PIVOTS ACROSS THE AREA SUNDAY NIGHT...WITH
PRECIPITATION LIKELY ENDING FROM WEST TO EAST DURING THE OVERNIGHT
HOURS. EXPECT AREAS SUCH AS NORTHEASTERN MARYLAND TO REMAIN WEDGED
IN COLDER AIR FOR THE MAJORITY OF THE EVENT...SO HAVE HELD ONTO
RA/ZR MENTION IN THOSE AREAS. CONDFIDENCE NOT QUITE HIGH ENOUGH TO
GO WITH A WATCH YET THOUGH DUE TO UNCERTAINTIES IN QPF AMOUNTS.
WILL CONTINUE TO HIGHLIGHT IN HWO AND MONITOR LATEST MODEL TRENDS.

UPSLOPE RAIN/SNOW SHOWERS BECOME ALL SNOW BY EARLY MONDAY
MORNING...WITH A PERIOD OF ACCUMULATING SNOW POSSIBLE. MODELS DIFFER
ON HOW QUICKLY COLD AIR IS ABLE TO MOVE BACK IN BUT ADVISORY LEVEL
SNOWFALL CANNOT BE RULED OUT DURING THIS TIME SO WILL MENTION IN HWO.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ACTIVE LONG TERM PERIOD EXPECTED WITH MULTIPLE WAVES OF LOW
PRESSURE RIDING ALONG A STALLED FRONT EXPECTED TUESDAY-THURSDAY.
PRECIPITATION STARTS OUT OVERRUNNING COLD AIR AT THE SURFACE AND
ANOTHER PERIOD OF A WINTRY MIX IS POSSIBLE TUESDAY NIGHT INTO
WEDNESDAY. EXACTLY WHERE THE FRONT SETS UP WILL DETERMINE PTYPE
THEREAFTER BUT IT LOOKS LIKE A MOSTLY RAIN EVENT WEDNESDAY INTO
WEDNESDAY EVENING...BEFORE PRECIPITATION GRADUALLY ENDS WEST TO
EAST THROUGH THURSDAY /POSSIBLY A MIX BEFORE ENDING ESPECIALLY OUT
WEST/.

ANOTHER SHOT OF COLD AIR LOOKS TO FOLLOW THIS FRONTAL SYSTEM BY THE
END OF NEXT WEEK.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
HIGH PRESSURE WILL BRING LIGHT WINDS AND VFR CONDITIONS TODAY AND
TONIGHT. SNOW IS EXPECTED TO MOVE INTO THE REGION SUNDAY MORNING
BEFORE CHANGING TO IP/ZR BY SUNDAY AFTERNOON. MVFR/IFR
RESTRICTIONS WILL BE POSSIBLE SUNDAY. PRECIPITATION WILL CHANGE TO
RAIN FROM SW-W TO N-NE SUNDAY.

SUB-VFR EXPECTED SUN NIGHT INTO MON...MAINLY RA DCA SOUTH
AND WEST...WITH ZR LIKELY ESPECIALLY DURING THE EVENING INVOF
BWI/MTN. L/V WINDS.

REBOUND TO VFR LATER MON THROUGH EARLY TUE.. THEN SUB-VFR POSSIBLE
IN MIXED PRECIP TUE NIGHT-WED AM. WLY WINDS 10-20 KTS MON BECOME
LIGHT NE MON NIGHT-TUE PM.

&&

.MARINE...
HIGH PRESSURE WILL REMAIN OVER THE WATERS TODAY. WINDS WILL BE
LIGHT. A WINTRY MIX IS EXPECTED SUNDAY WITH SNOW CHANGING TO
IP/ZR BY AFTERNOON AND THEN CHANGING TO RA BY SUNDAY EVENING.
LIGHT WINDS EXPECTED SUNDAY.

GENERALLY LIGHT WINDS WITH WEDGING/WEAK GRADIENT SUN NIGHT.
WLY SURGE TO SCA LEVELS LIKELY MON INTO MON NIGHT...THEN LIGHTENING
UP AGAIN AS WEDGING RE-ESTABLISHES TUE-TUE NIGHT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...HAS
NEAR TERM...BJL/HAS
SHORT TERM...HAS/DFH
LONG TERM...DFH
AVIATION...BJL/HAS/DFH
MARINE...BJL/HAS/DFH


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