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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