Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 270756 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 356 AM EDT FRI MAR 27 2015 .SYNOPSIS...
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AN UPPER-LEVEL TROUGH WILL SLOWLY MOVE ACROSS THE EASTERN UNITED STATES TODAY AND SATURDAY. HIGH PRESSURE WILL BUILD OVERHEAD SUNDAY. SEVERAL WEAK FRONTS WILL CROSS THE AREA NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AT 4 AM...THE SFC COLD FRONT IS PUSHING INTO SE VA. HOWEVER MID LEVEL FGEN FORCING REMAINS BEHIND THE SFC FRONT AS A STRONG UPPER JET STREAK PARALLELS THE APPALACHIANS. WAVES OF PRECIP CONTINUE TO STREAM ALONG THIS ZONE. SOME OF IT IS MODERATE AT TIMES...BUT SHOULD NOT BE PROLONGED ENOUGH AT ANY ONE LOCATION TO CAUSE ISSUES. CAA HAS BEGUN ON NW WINDS...WITH TEMPS FALLING THROUGH THE 40S. IT MAY BE COLD ENOUGH FOR A MIX AND AT SOME POINT ALL SNOW IN THE HIGHEST ELEVATIONS...BUT LITTLE ACCUMULATION IS EXPECTED. AS A DEEP UPPER LEVEL TROUGH PROGRESSES EAST TODAY AND A SFC LOW DEVELOPS OFF THE CAROLINA COAST...THE FRONTAL ZONE WILL CONTINUE TO SHIFT TO THE SE. MAY HAVE TO EXTEND POPS A LITTLE IN TIME...BUT OTHERWISE THERE SHOULD BE A NW TO SE DRYING TREND THROUGH TODAY. CANNOT TOTALLY RULE OUT SOME ISOLATED SHOWERS BEHIND THE MAIN PRECIP BAND AS THE UPPER LEVEL TROUGH MOVES OVERHEAD AND LOW LEVEL LAPSE RATES STEEPEN UNDER CAA. THERE IS A TREND IN GUIDANCE TO SUGGEST THIS CHANCE MAY BE A BIT HIGHER TOWARD CENTRAL VA. DOWNSLOPE FLOW WILL BE THE ONLY THING TO ADD TO TEMPS TODAY...AS CLOUDS WILL BE SLOW TO THIN. HIGHS IN THE 40S TO PERHAPS SOME LOWER 50S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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STRONG SHORTWAVE TROUGH WILL ROTATE OUT OF THE GREAT LAKES TONIGHT...WITH AN ATTENDANT ARCTIC AIRMASS SEEN IN THETA-E FIELDS. A SECOND UPPER JET STREAK WILL ALSO BE LIFTING THROUGH THE MEAN TROUGH. SEEING AN INCREASE IN MEAN RH AND MODEST LIFT MAY BE ABLE TO PRODUCE A FEW RAIN AND SNOW SHOWERS DEPENDING ON TIMING. TEMPS WILL BE QUITE CHILLY...WITH TEENS IN THE HIGHER ELEVATIONS AND 20S FOR THE REST EXCEPT EAST OF I-95. FOR SATURDAY...THE UPPER TROUGH AXIS WILL BE OVERHEAD AND CAA WILL CONTINUE. AN ALMOST WINTRY-LIKE PATTERN WILL BE IN PLACE WITH STEEP LOW LEVEL LAPSE RATES AND THE CLOUD LAYER INTERSECTING THE SNOW GROWTH ZONE. 850 MB TEMPERATURES WILL LIKELY BE BELOW -10C...LEADING TO TEMPS STRUGGLING TO RISE...EVEN IF THE SUN IS OUT. HIGHS WILL ONLY BE IN THE 30S TO LOWER 40S...WITH SOME 20S IN THE MOUNTAINS. THE BEST CHANCE FOR PRECIP WILL BE ACROSS THE NORTHERN THIRD OF THE AREA. EVEN IF SFC TEMPS ARE ABOVE FREEZING...THAT LAYER WILL BE VERY SHALLOW AND THE PREDOMINANT P-TYPE IN ANY SHOWER WOULD LIKELY BE SNOW ACROSS MUCH OF THE AREA.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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AS THE MAIN UPPER LEVEL TROUGH AXIS SWINGS EAST TO THE EASTERN SEABOARD SATURDAY NIGHT...A BRIEF RIDGE OF HIGH PRESSURE WILL BUILD FROM THE MIDWEST U.S. TO THE MID ATLANTIC REGION SATURDAY NIGHT INTO SUNDAY. GUSTY NORTHWEST WINDS WILL DIMINISH SATURDAY NIGHT ONLY TO BECOME SOUTHWEST THEN SOUTHERLY THROUGH THE DAY ON SUNDAY. WHILE DRY CONDITIONS ARE EXPECTED SATURDAY NIGHT THROUGH SUNDAY...HIGH CLOUDS WILL BE ACCOMPANIED BY MID LEVEL CLOUDS SUNDAY AFTERNOON THROUGH SUNDAY NIGHT. A SLIGHT CHANCE OF RAIN SHOWERS IN THE POTOMAC HIGHLANDS SUNDAY NIGHT WITH THE NEXT TROUGH OF LOW PRESSURE EXPECTED TO SWING EAST FROM THE GREAT LAKES TO THE NORTHEAST U.S. TEMPERATURES SATURDAY NIGHT WILL BE WELL BELOW NORMAL...REACHING THE LOWER 20S TO UPPER TEENS. ALTHOUGH TEMPERATURES ARE EXPECTED TO REMAIN BELOW NORMAL SUNDAY WITH HIGHS IN THE UPPER 40S TO NEAR 50 IN NORTHERN VIRGINIA AND CENTRAL PARTS OF MARYLAND...SUNDAY NIGHT LOW TEMPERATURES SHOULD REBOUND NICELY FROM THE LOWER 20S SATURDAY NIGHT TO THE MIDDLE 30S SUNDAY NIGHT. A FEW LINGERING RAIN SHOWERS WITH A TROUGH OF LOW PRESSURE MONDAY WILL GIVE WAY TO PARTIAL CLEARING AS AN UPPER LEVEL TROUGH SWINGS EASTWARD. HIGH PRESSURE WILL BUILD IN BRIEFLY MONDAY NIGHT...ONLY TO GIVE IN TO A CHANCE OF RAIN SHOWERS ALONG THE MASON DIXON AREA TUESDAY AND TUESDAY NIGHT. TEMPERATURES WILL MODIFY TO NEAR NORMAL VALUES MONDAY NIGHT THROUGH TUESDAY NIGHT. THE NEXT DISTURBANCE WILL PASS BY TO THE NORTH WEDNESDAY INTO WEDNESDAY NIGHT...ONLY TO DRAG A COLD FRONT ACROSS NORTHERN PARTS OF THE AREA. THIS FRONT WILL SET THE STAGE FOR A LOW PRESSURE SYSTEM TO RIDGE ALONG IT THURSDAY INTO FRIDAY...BRINGING A CHANCE FOR RAIN SHOWERS ONCE AGAIN. TEMPERATURES SHOULD WARM TO A FEW DEGREES ABOVE NORMAL FROM MID TO LATE WEEK DESPITE THE SLIGHT RAIN CHANCES. A PERSISTENT SOUTHWEST TO WEST FLOW WITH ANY KIND OF AMPLE SUNSHINE SHOULD BE THE REASON FOR THIS TEMPERATURE MODIFICATION.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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RAIN IN A FRONTAL ZONE CONTINUES TO FALL...MODERATELY IN POCKETS... ACROSS THE AREA. IT IS PRIMARILY FALLING OUT OF A VFR BASE...ALTHOUGH MVFR CIGS AND VSBYS CAN BE EXPECTED THROUGH EARLY MORNING AT TIMES. EXPECT A GRADUAL IMPROVING TREND FROM NW TO SE THROUGH THE DAY AS THE PRECIP ENDS. NW WINDS WILL PREVAIL THROUGH THE TAF PERIOD...POSSIBLY GUSTING UP TO 20 KT THROUGH MIDDAY. FRIDAY NIGHT AND SATURDAY ARE EXPECTED TO BE PRIMARILY VFR. THERE IS A SMALL CHANCE OF SNOW SHOWERS AT TIMES...PERHAPS SLIGHTLY HIGHER AT THE NORTHERN TERMINALS. NW WINDS WILL CONTINUE TO BE GUSTY AT TIMES. VFR CONDITIONS SATURDAY NIGHT THROUGH SUNDAY NIGHT. MVFR CONDITIONS POSSIBLE MONDAY...THEN AGAIN TUESDAY AND TUESDAY NIGHT FOR ANY RAIN SHOWERS OR ANY RAIN OR SNOW SHOWERS MAINLY NEAR MRB...MTN OR BWI FOR TUESDAY AND TUESDAY NIGHT. VFR CONDITIONS WEDNESDAY WITH A CHANCE FOR MVFR OR IFR CONDITIONS WEDNESDAY NIGHT THROUGH THURSDAY NIGHT WITH THE CHANCE OF RAIN SHOWERS.
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&& .MARINE...
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A COLD FRONT HAS PASSED SE OF THE WATERS. RAIN WITH REDUCED VSBY WILL CONTINUE INTO TODAY...TAPERING OFF FROM N TO S BY THIS AFTERNOON. NW WINDS MAY REACH SCA LEVELS AT TIMES. THE SCA CONTINUES THROUGH THIS AFTERNOON...ALTHOUGH GUSTS MAY BECOME MORE MARGINAL WITH TIME. WINDS ARE EXPECTED TO INCREASE AGAIN TONIGHT INTO SATURDAY AS LOW PRESSURE DEVELOPS OFFSHORE AND A SURGE OF ARCTIC AIR PUSHES IN. A SCA WILL BE ISSUED FOR THE NW GUSTS. SMALL CRAFT CONDITIONS POSSIBLE SATURDAY NIGHT INTO EARLY SUNDAY...THEN AGAIN TUESDAY AND THURSDAY WITH THE PASSING STORM SYSTEMS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT SATURDAY FOR ANZ530>534- 537>541-543. SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ535- 536-542. SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT SATURDAY FOR ANZ535-536.
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&& $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...KLW AVIATION...ADS/KLW MARINE...ADS/KLW

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