Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 010231 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
931 PM EST SAT FEB 28 2015

.SYNOPSIS...
HIGH PRESSURE WILL OVER THE AREA TONIGHT WILL MOVE OFFSHORE 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 AM SUNDAY MORNING/...
AHEAD OF ANOTHER WAVE OF LOW PRESSURE FAST-APPROACHING FROM BEING
CARRIED BY A POTENT AND ZONAL UPPER JET. AT THIS LATE NIGHT
HR...THE EDGE OF THE INCOMING PRECIP WAVE HAS BARELY CROSSED OVER
INTO ERN OHIO. A STEADY TRACK OF THIS ACTIVITY WILL TAKE IT TO THE
APLCNS DURING THE MIDDLE OF THE OVERNIGHT PERIOD AND ON OUR
DOORSTEP BY THE PREDAWN HRS SUN MRNG.

LAPS SFC ANALYSES PLACES THE CENTER OF A +1040MB HIGH ON THE ERN
SHORE OF MD DRIFTING TO THE EAST. WINDS NEAR AND ON THE PERIPHERY
OF THE HIGH HAVE DROPPED WINDS TO CALM...AS WELL AS TEMPS W/ STILL
FAIRLY LOW DEWPOINTS IN PLACE. AFTER FALLING SHORT OF REACHING THE
FREEZING MARK EARLIER THIS AFTN...TEMPS HAVE DROPPED A SOLID 5-10F
IN THE PAST FEW HRS AND IS ON THE WAY TO MID-UPPER TEENS IN THE
COMING HRS - JUST AHEAD OF THE INCOMING PRECIP. CLOUDS WILL
INCREASE OVERNIGHT...AND PRECIPITATION WILL MOVE TOWARD OUR
WESTERN AND SOUTHERN AREAS BY SUNDAY MORNING. THERMAL PROFILES
WILL BE COLD ENOUGH FOR ALL SNOW DURING THIS TIME...BUT
PRECIPITATION AMOUNTS WILL BE LIGHT THROUGH TONIGHT.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
LOW PRESSURE WILL TRACK INTO NEW ENGLAND SUNDAY THROUGH SUNDAY
NIGHT WHILE THE COLD FRONT ASSOCIATED WITH THIS SYSTEM APPROACHES
THE AREA SUNDAY...AND PASSES THROUGH SUNDAY NIGHT. A SOUTHERLY
FLOW AHEAD OF THE COLD FRONT WILL ALLOW FOR WARM AND MOIST AIR TO
OVERRUN THE SURFACE COLD AIR IN PLACE...CAUSING MORE PRECIPITATION
TO OVERSPREAD THE AREA QUICKLY ON SUNDAY MORNING. THERMAL PROFILES
SUPPORT ALL SNOW FOR THE CWA THROUGH MID-MORNING...BUT WARMER AIR
WILL WORK ITS WAY INTO THE AREA...CAUSING SNOW TO CHANGE TO A
WINTRY MIX LATE SUNDAY MORNING THROUGH SUNDAY AFTERNOON. THE
HIGHEST SNOW AND SLEET TOTALS WILL BE CLOSER TO THE MASON-DIXON
LINE WHERE SNOW WILL LAST THE LONGEST. HOWEVER...SURFACE TEMPS
WILL STAY NEAR OR BELOW FREEZING FOR MUCH OF THE DAY ACROSS MOST
LOCATIONS...ALLOWING FOR ICE ACCUMULATION FROM FREEZING RAIN. ICE
ACCUMULATIONS AROUND ONE-TENTH OF AN INCH ARE EXPECTED. A WINTER
WEATHER ADVISORY IS IN EFFECT FOR THE ENTIRE CWA.

THE COLD FRONT WILL PASS THROUGH SUNDAY NIGHT. THE DRY SLOT SHOULD
MOVE IN AHEAD OF THIS SYSTEM...CAUSING PRECIPITATION TO END ACROSS
MOST LOCATIONS SUNDAY EVENING. HOWEVER...LOW-LEVEL MOISTURE WILL
REMAIN TRAPPED UNDERNEATH THE SUBSIDENCE INVERSION AND POCKETS OF
DRIZZLE/FREEZING DRIZZLE MAY PERSIST. THEREFORE...THE WINTER
WEATHER ADVISORY CONTINUES INTO LATE SUNDAY NIGHT FOR NORTHERN AND
EASTERN AREAS WHERE PRECIPITATION MAY HOLD ON A BIT LONGER.
SURFACE TEMPS WILL HOVER NEAR FREEZING DURING THIS TIME. UPSLOPE
SNOW WILL INCREASE BEHIND THE COLD FRONT OVERNIGHT FOR LOCATIONS
ALONG AND WEST OF THE ALLEGHENY FRONT.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
COLD FRONT IS EXPECTED TO BE EAST OF THE FORECAST AREA BY MONDAY
MORNING. HIGH PRESSURE WILL BUILD OVER THE OHIO VALLEY. THE
COMBINATION OF A STRONG PRESSURE GRADIENT AND COLD ADVECTION WILL
LEAD TO GUSTY WINDS UP TO AROUND 20KTS. UPSLOPE SNOW OVER THE
POTOMAC HIGHLANDS WILL TAPER OFF DURING THE DAY...WITH MINIMAL
ADDITIONAL ACCUMULATION EXPECTED. FOR TEMPERATURES...SOME UPSLOPE
COMPONENT IS LIKELY WITH W-NW WINDS...ALLOWING HIGH TEMPS TO REACH
THE LOW 40S OVER MOST OF THE FORECAST AREA...WITH MID 40S POSSIBLE
OVER PORTIONS OF THE CENTRAL FOOTHILLS...VA PIEDMONT AND SRN MD.

HIGH PRESSURE BUILDS OVERHEAD MONDAY NIGHT...WITH THE RIDGE AXIS
REACHING THE I-95 CORRIDOR BY EARLY TUESDAY MORNING. WE SHOULD SEE
AT LEAST A PERIOD OF GOOD RADIATIONAL COOLING CONDITIONS WITH LIGHT
WINDS AND CLEAR SKIES...ALTHOUGH HIGHER CLOUDS WILL BE MOVING IN
AHEAD OF THE NEXT SYSTEM. LOW TEMPS WILL BE IN THE 20S OVER MOST OF
THE AREA...WITH TEENS LIKELY AT HIGHER ELEVATIONS.

HIGH PRESSURE RESIDES OVER THE AREA TUESDAY MORNING WITH MORNING LOW
TEMPERATURES BELOW NORMAL. BIG CHANGES BEGIN MID/LATE AFTERNOON
TUESDAY WITH STRONG LOW-LEVEL WAA AHEAD OF THE NEXT SYSTEM. LATEST
GUIDANCE CONSISTENT WITH OVERALL SYNOPTIC PATTERN FOR THIS
SYSTEM...BUT DIFFERENCES STILL REMAIN WITH REGARDS TO THE TIMING OF
SFC FEATURES AND ASSOCIATED QPF. INITIAL P-TYPE WITH THIS SYSTEM
WILL LARGELY DEPEND ON THE TIMING OF INITIAL PRECIPITATION AND HOW
QUICKLY THE RESIDUAL COLD AIR IS DISPLACED. NOT OUT OF THE QUESTION
FOR SOME WINTRY MIXED PRECIPITATION LATE TUESDAY/EARLY WEDNESDAY
MORNING...ESPECIALLY IN OUR NORTHERN ZONES...BEFORE THERMAL PROFILE
WARMS ENOUGH FOR ALL RAIN.

WEDNESDAY WILL BE THE WARMEST DAY OF THE WORKWEEK...WITH H85
TEMPERATURES NEAR 10C...EXPECT SFC TEMPERATURES TO BE AOA 50F OVER A
LARGE PART OF THE CWA. WEDNESDAY/WEDNESDAY NIGHT COULD BE RATHER WET
WITH RAIN SHOWERS THROUGHOUT THE DAY/NIGHT. DEWPOINTS WILL ALSO
INCREASE SUBSTANTIALLY ON WEDNESDAY...WHICH WILL BE NOTICEABLE
CONSIDERING WE HAVE BEEN ENTRENCHED IN ARCTIC AIRMASSES FOR THE PAST
FEW WEEKS. STRONG COLD FRONT MOVES THROUGH WEDNESDAY/EARLY THURSDAY
WITH VERY STRONG CAA. AS WITH THE BEGINNING OF THE STORM...WINTRY P-
TYPE NOT OUT OF THE QUESTION BY THURSDAY AS THE THERMAL COLUMN
COOLS.

TEMPERATURES WILL PLUMMET THURSDAY NIGHT AS HIGH PRESSURE SETTLES
INTO THE REGION...LEADING TO A VERY COLD MORNING FRIDAY. AIRMASS
MODIFICATION BEGINS FRIDAY...HOWEVER TEMPERATURES STILL EXPECTED TO
BE BELOW NORMAL THROUGH SATURDAY.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS THROUGH TONIGHT. SNOW AND SLEET WILL OVERSPREAD THE
TERMINALS SUNDAY MORNING. PRECIPITATION WILL CHANGE TO FREEZING
RAIN AND RAIN LATE SUNDAY MORNING INTO SUNDAY AFTERNOON FROM SOUTH
TO NORTH. IFR AND POSSIBLE SUBIFR CONDITIONS ARE EXPECTED DURING
THIS TIME. PRECIPITATION WILL TAPER OFF SUNDAY NIGHT...BUT LOW
CLOUDS AND PATCHY FOG MAY PERSIST.

VFR CONDITIONS MONDAY AND MONDAY NIGHT. W-NW WINDS MONDAY WITH GUSTS
TO AROUND 20KT...OCCASIONALLY HIGHER GUSTS PSBL. WINDS DIMINISH
MONDAY NIGHT.

VFR CONDITIONS EXPECTED EARLY TUESDAY...SUB-VFR POSSIBLE TUE NIGHT
THROUGH THURSDAY NIGHT. FRIDAY WILL LIKELY SEE A RETURN TO VFR
CONDITIONS.

&&

.MARINE...
LIGHT WINDS FROM HIGH PRESSURE WILL STAY PARKED OVER THE AREA INTO
EARLY SUNDAY. A SOUTHERLY FLOW WILL BRIEFLY CHANNEL UP THE MAIN
STEM OF THE DAY SUNDAY AFTN BUT LIKELY REMAIN BELOW SCA CRITERIA.
THE FLOW WILL TURN TOWARD THE NORTHWEST BEHIND THE FRONT BY
MONDAY.

DAYTIME SCA GUSTS LIKELY WITH NW WINDS OVER THE WATERS MONDAY AS A
COLD FRONT MOVES EAST OF THE WATERS. WINDS MAY DIMINISH BELOW SCA
CRITERIA BY LATE AFTERNOON AS HIGH PRESSURE BUILDS IN FROM THE WEST.
WINDS EXPECTED TO BE 10KT OR LESS MONDAY NIGHT.

WINDS WILL PICK UP PRIOR TO COLD FRONTAL PASSAGE WITH SCA POSSIBLE
BEGINNING LATE TUESDAY NIGHT AND CONTINUING THRU FRONTAL PASSAGE
ON WEDNESDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 3 AM EST MONDAY
     FOR DCZ001.
MD...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 6 AM EST MONDAY
     FOR MDZ501.
     WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 3 AM EST MONDAY
     FOR MDZ005-006-011-013-014-016>018-503>508.
     WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 3 AM EST MONDAY
     FOR MDZ003-004-502.
VA...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 6 AM EST MONDAY
     FOR VAZ503.
     WINTER WEATHER ADVISORY FROM 4 AM TO 7 PM EST SUNDAY FOR
     VAZ025>027-029-030-036>040-050-051-501-502-504-507-508.
     WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 3 AM EST MONDAY
     FOR VAZ052>054-506.
     WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 3 AM EST MONDAY
     FOR VAZ028-031-505.
     WINTER WEATHER ADVISORY FROM 7 AM TO 7 PM EST SUNDAY FOR
     VAZ055>057.
WV...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 6 AM EST MONDAY
     FOR WVZ501-503-505.
     WINTER WEATHER ADVISORY FROM 4 AM TO 7 PM EST SUNDAY FOR
     WVZ055-502-506.
     WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 3 AM EST MONDAY
     FOR WVZ050>053-504.
MARINE...NONE.

&&

$$
UPDATE...GMS
PREV DISCUSSION...BJL/KCS/ME/DFH



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