Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250214 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1014 PM EDT FRI APR 24 2015 .SYNOPSIS... HIGH PRESSURE REMAINS OVERHEAD TONIGHT BEFORE MOVING OFF THE COAST SATURDAY. LOW PRESSURE WILL PASS BY TO OUR SOUTH SATURDAY NIGHT INTO SUNDAY AND AN UPPER-LEVEL TROUGH WILL REMAIN OVERHEAD FOR MONDAY. HIGH PRESSURE WILL RETURN TUESDAY...BUT LOW PRESSURE MAY IMPACT THE REGION DURING THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/...
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...UPDATE TO CANCEL SMALL CRAFT ADVISORY. PREVIOUS DISCUSSION FOLLOWS... SURFACE HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT. WINDS HAVE ALREADY DIMINISHED AND ARE EXPECTED TO BECOME LIGHT AND VARIABLE OVERNIGHT. LIGHT WINDS AND DRY AIR WILL ALLOW FOR RADIATIONAL COOLING TO SETUP. THEREFORE...MIN TEMPS WILL BE WELL BELOW NORMAL WITH FROST AND FREEZE CONDITIONS EXPECTED ACROSS MANY AREAS. A FREEZE WARNING IS IN EFFECT FOR NORTHERN MARYLAND...PORTIONS OF EASTERN WEST VIRGINIA AND PORTIONS OF NORTHERN VIRGINIA. A FROST ADVISORY IS IN EFFECT FOR THE BALTIMORE METROPOLITAN AREA...THE NORTHERN AND WESTERN SUBURBS OF WASHINGTON DC...AND PORTIONS OF THE VIRGINIA FOOTHILLS INTO THE CENTRAL SHENANDOAH VALLEY. LOW PRESSURE WILL TRACK THROUGH THE CENTRAL PLAINS TONIGHT AND HIGH/MID-LEVEL CLOUDS WELL AHEAD OF THIS SYSTEM WILL MOVE INTO OUR AREA WITH THE WESTERLY FLOW ALOFT. THE CLOUD LAYER SHOULD REMAIN THIN FOR MOST OF THE NIGHT...WHICH IS WHY THE FROST AND FREEZE HEADLINES ARE IN EFFECT...BUT THE CLOUD LAYER MAY THICKEN TOWARD MORNING. GIVEN THIS UNCERTAINTY...THE HEADLINE WAS NOT EXTENDED FARTHER SOUTH AND EAST...DESPITE THE LIGHT WINDS AND DRY CONDITIONS. LOW PRESSURE WILL TRACK INTO THE MIDWEST SATURDAY WHILE HIGH PRESSURE MOVES OFF THE COAST. WARM AND MOIST AIR WILL OVERRUN THE SURFACE COOLER AIR IN PLACE...RESULTING IN LOWERING/THICKENING CLOUDS AND PRECIPITATION THAT OVERSPREAD THE SOUTHWESTERN PORTIONS OF OUR CWA IN THE MORNING...THEN TOWARD THE WASHINGTON METROPOLITAN AREA...CENTRAL AND WESTERN MARYLAND...AND THE EASTERN WEST VIRGINIA PANHANDLE DURING THE MID TO LATE AFTERNOON HOURS. DRY CONDITIONS MAY PERSIST ACROSS NORTHEASTERN MARYLAND FOR SATURDAY...CLOSER TO THE DEPARTING HIGH. HIGH TEMPERATURES WILL REMAIN WELL BELOW NORMAL WITH READINGS ONLY REACHING THE UPPER 40S OVER THE HIGHER TERRAIN AND MID TO UPPER 50S ELSEWHERE.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... RAIN OVERSPREADING THE ENTIRE REGION BY SAT EVENING CENTER OF SFC LOW REACHES THE OH RIVER VALLEY...WITH A SFC TROUGH EXTENDING ACROSS THE MID ATLANTIC. HIGH CONFIDENCE PCPN WILL BE OVER SOUTHWESTERN HALF OF THE CWA FOR THIS TIME...QUESTION REMAINS ON HOW QUICKLY IT REACHES NORTHEASTERN MD...WITH THE THINKING IT SHOULD REACH SOMETIME BEFORE MIDNIGHT. STILL SOME UNCERTAINTY WHERE THE AXIS OF HEAVIEST PCPN ALIGNS...BUT WITH THE CONSENSUS GENERALLY SHOWING SHORTWAVE MOVING WV INTO SOUTHERN VA...EXPECTING THE HEAVIEST PCPN WILL BE CENTRAL VA AND SOUTH. AS THE LOW PUSHES EAST SUNDAY...PCPN PUSHES TO THE SOUTH AND EAST. AREAS ALONG THE MASON-DIXON COULD DRY AS EARLY AS SUN MORNING...WITH MOST OF THE REMAINING AREA LOOKING TO BE DRY BY SUNSET SUN EVENING. THE ONE AREA THAT COULD SEE PCPN SUN NIGHT- MONDAY IS THE UPSLOPE REGIONS OF THE ALLEGHENIES AS A POTENT SHORTWAVE ROUNDS THE SOUTHWESTERN PERIPHERY OF AN UPPER LVL LOW. WAA OVERNIGHT THE WEEKEND WILL WARM UP BOTH HIGH AND LOW TEMPS. HOWEVER...DEPENDING ON THE TEMPS...CANNOT RULE OUT A SNOWFLAKE MIXING IN FOR A PERIOD LATE SUN NIGHT FOR THIS AREA AS WELL. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... ECMWF 500MB RIDGE BUILDING OVER MID ATLANTIC REGION BY MIDWEEK. LOW ON SOUTHERN TRACK MOVING TO WESTERN KENTUCKY/TENNESSEE BEFORE STALLING AND WEAKENING WEDNESDAY. SHORTWAVE ON NORTHERN TRACK WILL MOVE SOUTHWARD TO REINFORCE THE SOUTHERN LOW. THE LOW WILL MOVE SOUTH OF CWA AND OFFSHORE THURSDAY. SURFACE HIGH OVER THE EASTERN US THROUGH MIDWEEK. LOW CENTER OVER LOUISIANA COAST WILL MOVE NORTHEAST TO AFFECT THE CWA LATE WEDNESDAY AND THURSDAY. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS WILL PERSIST INTO SATURDAY MORNING FOLLOWED BY RAIN OVERSPREADING THE TERMINALS SATURDAY AFTERNOON AND EVENING. SUB-VFR CONDITIONS EXPECTED SAT NIGHT INTO SUN WITH RAIN IMPACTING ALL TERMINALS. IMPROVING CONDITIONS BY SUN AFTN...WITH VFR THEN SUN NIGHT THRU MON. && .MARINE...
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WINDS WILL DIMINISH TONIGHT AS HIGH PRESSURE BUILDS OVERHEAD. THE SMALL CRAFT ADVISORY HAS BEEN CANCELLED...BUT GUSTS AROUND 15 KNOTS ARE EXPECTED OVERNIGHT ALONG THE MIDDLE PORTION OF THE BAY AND LOWER TIDAL POTOMAC RIVER. SUB-SCA CONDITIONS EXPECTED SAT AND SAT NIGHT. MARGINAL SCA GUSTS ARE PSBL OVER THE CENTRAL CHESAPEAKE BAY WATERS SUN AFTN...WITH SUB- SCA CONDITIONS EVERYWHERE SUN NIGHT. INCRSG WINDS ON MON SHOULD BRING GUSTS UP TO 20 KTS ON ALL WATERS MON-MON NIGHT. PSBL LINGERING SCA GUSTS INTO TUES...WITH SUB-SCA CONDITIONS RETURNING BY TUES NIGHT.
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&& .FIRE WEATHER... WINDS HAVE DIMINISHED AND THE RELATIVE HUMIDITY HAS INCREASED. A SOAKING RAIN WILL OVERSPREAD THE AREA FROM SOUTHWEST TO NORTHEAST SATURDAY. THE SOAKING RAIN WILL CONTINUE FOR MOST AREAS SATURDAY NIGHT INTO SUNDAY. THE ONE EXPCEPTION MAY BE ACROSS NORTHEASTERN MARYLAND WHERE DRIER AIR MAY HOLD ON...CAUSING LIGHTER RAINFALL AMOUNTS. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...FROST ADVISORY FROM 2 AM TO 10 AM EDT SATURDAY FOR MDZ011- 503>506. FREEZE WARNING FROM 2 AM TO 10 AM EDT SATURDAY FOR MDZ003>006- 507-508. VA...FROST ADVISORY FROM 2 AM TO 10 AM EDT SATURDAY FOR VAZ025>027- 029-030-038>040-051>053-501-502-506>508. FREEZE WARNING FROM 2 AM TO 10 AM EDT SATURDAY FOR VAZ028-031- 505. WV...FREEZE WARNING FROM 2 AM TO 10 AM EDT SATURDAY FOR WVZ051>053. MARINE...NONE.
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&& $$ SYNOPSIS...KRW NEAR TERM...BJL/KRW SHORT TERM...SEARS LONG TERM...CEM AVIATION...BJL/SEARS/KRW MARINE...BJL/SEARS FIRE WEATHER...

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