Area Forecast Discussion
Issued by NWS Sterling, VA

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215 FXUS61 KLWX 131458 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 958 AM EST SAT FEB 13 2016 .SYNOPSIS... ARCTIC HIGH PRESSURE WILL BUILD THROUGH EARLY SUNDAY THEN MOVE OFFSHORE SUNDAY NIGHT. LOW PRESSURE WILL MOVE ACROSS THE AREA TUESDAY. HIGH PRESSURE RETURNS FOR MIDDLE TO LATTER PART OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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THE ARCTIC COLD FRONT HAS MOVED WELL OFF TO THE EAST AND ARCTIC HIGH PRESSURE WILL CONTINUE TO BUILD TO OUR WEST OVER THE OHIO VALLEY AND MIDWEST TODAY. STRONG COLD ADVECTION AHEAD OF THE HIGH AND BEHIND THE COLD FRONT WILL CAUSE BITTERLY COLD CONDITIONS TODAY ALONG WITH GUSTY WINDS. THE WIND CHILL HEADLINES REMAIN IN EFFECT FOR THE BLUE RIDGE MOUNTAINS AND POTOMAC HIGHLANDS. WILL CONTINUE WITH THE WIND ADVISORY FOR NORTHERN AND CENTRAL PORTIONS OF THE AREA...BUT IT WILL BE MARGINAL. LATEST GUIDANCE SHOWS WINDS AROUND 35 TO 40 KNOTS AT THE TOP OF THE MIXING LAYER. THIS SUGGESTS THAT ISOLATED GUSTS UP TO 50 MPH ARE POSSIBLE TODAY...BUT A MAJORITY OF THE GUSTS WILL BE IN THE 30 TO 40 MPH RANGE. THE STRONG COLD ADVECTION HAS LED TO SNOW SQUALLS THIS MORNING. DRIER AIR HAS WORKED ITS WAY INTO THE AREA CAUSING THE HEAVIER BURSTS OF SNOW TO DIMINISH. HOWEVER...MORE INSTABILITY IS EXPECTED THIS AFTERNOON DUE TO PARTIAL SUNSHINE AND MORE COLD ADVECTION. A FEW SNOW SHOWERS ARE POSSIBLE AND AN ISOLATED SNOW SQUALL CANNOT BE RULED OUT. ANY SNOW SQUALLS WILL BE EXTREMELY LOCALIZED SO MOST AREAS WILL NOT SEE ADDITIONAL SNOWFALL ACCUMULATION...BUT FOR ANY AREAS THAT DO RECEIVE A SNOW SQUALL THERE CAN BE ACCUMULATIONS AROUND A HALF INCH. HARD TO PINPOINT EXACTLY WHERE HAS THE BEST CHANCE...BUT THE CURRENT FORECAST HAS THE HIGHEST POPS ACROSS NORTHEASTERN MARYLAND THIS AFTERNOON. LOWER HEIGHTS AND PVA ALONG WITH LESS OF A DOWNSLOPE COMPONENT DUE TO RELATIVELY LOWER TERRAIN UPSTREAM ARE THE REASONS WHY. WINDS WILL SLOWLY TAPER OFF INTO THE EVENING. HOWEVER... TEMPERATURES ARE EXPECTED TO DROP INTO THE SINGLE DIGITS AND LOW TEENS...BELOW ZERO ACROSS THE HIGHER ELEVATIONS. WIND CHILL VALUES WILL DROP AS WELL REACHING VERY COLD CONDITIONS EARLY SUNDAY MORNING.
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&& .SHORT TERM /SUNDAY/... HIGH PRESSURE MOVES OVERHEAD BY SUNDAY AFTERNOON AND WINDS WILL RELAX. TEMPS WILL BE AT OR SLIGHTLY WARMER THAN TODAY. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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ARCTIC HIGH OFF THE EAST COAST SUN NIGHT WILL BE RETREATING QUICKLY AS MOISTURE SPREADS QUICKLY FROM THE SOUTHWEST. SNOW BEGINS LATE SUN NIGHT AND CONTINUES THROUGH MON MORNING DUE TO OVERRUNNING BUT WARMER AIR ALOFT MOVES IN QUICKLY MON AFTERNOON WITH SNOW TRANSITIONING TO FZRA/PL AND RAIN. GUIDANCE IS CONSIDERABLY WARMER BOTH ALOFT AND AT THE SURFACE AND QUICKER TO BRING PRECIP THAN 24 HRS AGO AS MOST GFS AND ECMWF ENSEMBLE MEMBERS NOW SHOW SFC LOW PRES TRACKING WEST OF THE APPALACHIANS. POTENTIAL FOR SIX INCHES OF SNOW WILL BE CONFINED ONLY TO THE POTOMAC HIGHLANDS WITH 1-3 INCHES OF SNOW ELSEWHERE EXCEPT LESS IN FAR SOUTHERN MD. A BAND OF FZRA WITH ICE ACCUMULATIONS OF BETWEEN ONE AND TWO TENTHS OF AN INCH CAN ALSO BE EXPECTED FROM THE POTOMAC HIGHLANDS TO THE ROUTE 15 CORRIDOR. PRECIP SHOULD HAVE TRANSITIONED TO ALL RAIN BY 12Z TUE IN MOST AREAS EXCEPT PERHAPS HIGHER ELEVS. THIS TRANSITION IS ALSO FASTER THAN 24 HRS AGO. FLOODING IS NOW A MUCH BIGGER CONCERN AS SNOWMELT AND HEAVY RAINS ALL BECOME RUNOFF DUE TO FROZEN AND SNOW COVERED GROUND. WPC NOW HAS MOST OF THE AREA HIGHLIGHTED FOR EXCESSIVE RAINS DAY 3 VALID 12Z MON - 12Z TUE. ADDITIONAL FLOODING PROBLEMS ARE LIKELY TO OCCUR AS ICE IS BEGINNING TO AFFECT MOST RIVERS. MOST OF THE PRECIP CLEARS THE AREA BY TUE NIGHT BUT UPSLOPE PRECIP MAY CONTINUE THROUGH THURSDAY. DRY WX FOR THE END OF THE WEEK AS HIGH PRES BUILDS.
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&& .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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PREVAILING VFR CONDITIONS EXPECTED THROUGH SUNDAY. AN ISOLATED SNOW SHOWER CANNOT BE RULED OUT THROUGH THIS AFTERNOON. NW WINDS WILL GUST AROUND 30 TO 35 KNOTS THIS AFTERNOON WITH ISOLATED GUSTS UP TO 40 KNOTS. WINDS WILL BE SLIGHTLY LOWER AT CHO THROUGH THE DAY. VFR CONDITIONS EXPECTED TONIGHT INTO SUNDAY. NW WINDS 10-15 G20KT EXPECTED SUNDAY MORNING. HEAVY PRECIP MON-TUE MORNING WITH IFR CONDITIONS EXPECTED. SNOW LATE SUN NIGHT AND MON MORNING TRANSITIONING TO RAIN AT KDCA...KBWI KMTN AND FZRA AT KCHO...KIAD AND KMRB. PRECIP SHOULD HAVE TRANSITIONED TO ALL RAIN AT ALL TAF SITES BY 12Z TUE WITH PRECIP ENDING BY TUE EVENING.
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&& .MARINE...
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GUSTY NORTHWEST WINDS EXPECTED THROUGH THIS AFTERNOON BEHIND A COLD FRONT. A GALE WARNING IS IN EFFECT FOR THE WATERS. THE GUSTY NORTHWEST WINDS WILL CONTINUE TONIGHT BEFORE DIMINISHING SUNDAY. THE GALE WARNING CONTINUES THROUGH TONIGHT AND A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE WATERS SUNDAY. A FREEZING SPRAY ADVISORY IS ALSO IN EFFECT THROUGH EARLY SUNDAY. A SMALL CRAFT ADVISORY MAY NEEDED SUNDAY AFTERNOON. HIGH PRESSURE WILL BUILD OVER THE WATERS LATER SUNDAY BEFORE MOVING OFF THE EAST EARLY NEXT WEEK. SMALL CRAFT CONDITIONS LIKELY MON NIGHT-TUE THEN WED-FRI.
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&& .TIDES/COASTAL FLOODING...
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GUSTY NORTHWEST WINDS THROUGH TONIGHT WILL CAUSE TIDAL ANOMALIES TO APPROACH 2 FEET BELOW THE ASTRONOMICAL NORMS. THE FLOW WILL WEAKEN SUNDAY AND WATER LEVELS WILL RETURN CLOSER TO NORMAL.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR DCZ001. WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 9 AM EST SUNDAY FOR DCZ001. MD...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR MDZ501. WIND CHILL WARNING UNTIL 9 AM EST SUNDAY FOR MDZ501. WIND CHILL ADVISORY UNTIL 9 AM EST SUNDAY FOR MDZ502. WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR MDZ003>006-011- 013-014-016>018-503>508. WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 9 AM EST SUNDAY FOR MDZ003>006-011-013-014-016>018-503>508. VA...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ503. WIND CHILL WARNING UNTIL 9 AM EST SUNDAY FOR VAZ503. WIND CHILL ADVISORY UNTIL 9 AM EST SUNDAY FOR VAZ504-507-508. WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ028-031- 052>054-505-506. WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 9 AM EST SUNDAY FOR VAZ025>031-036>040-050>057-501-502-505-506. WV...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ501- 503-505. WIND CHILL WARNING UNTIL 9 AM EST SUNDAY FOR WVZ501-503-505. WIND CHILL ADVISORY UNTIL 9 AM EST SUNDAY FOR WVZ050-055-502- 504-506. WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ051>053. WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 9 AM EST SUNDAY FOR WVZ051>053. MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 1 PM EST SUNDAY FOR ANZ530>543. FREEZING SPRAY ADVISORY UNTIL 1 PM EST SUNDAY FOR ANZ530>543. GALE WARNING UNTIL 6 AM EST SUNDAY FOR ANZ530>543. && $$ SYNOPSIS...LFR NEAR TERM...BJL/HAS SHORT TERM...HAS LONG TERM...LFR AVIATION...BJL/HAS/LFR MARINE...BJL/HAS TIDES/COASTAL FLOODING...BJL

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