Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180133 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 933 PM EDT THU JUL 17 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVER THE AREA TONIGHT...THEN MOVE OFF THE COAST FRIDAY. HIGH PRESSURE WILL REMAIN ALONG THE NORTHEAST AND MID-ATLANTIC COASTS THIS WEEKEND INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/...
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HARDLY AN ECHO ON REGIONAL RADARS FOR HUNDREDS OF MILES W/ MUCH OF THE EAST COAST STILL UNDER AREA OF SFC HIGH PRESSURE TO CLOSE OUT THE WORK WEEK. AN UPPER TROUGH - THE LAST ONE ASSOCIATED W/ THE ANOMALOUSLY COLD GREAT LAKES UPPER LOW FROM THE PAST FEW DAYS - NOW PASSING BY TO OUR NORTH. THIS FEATURE BROUGHT ONLY A SCATTERED CUMULUS FIELD EARLIER TODAY...WHICH HAS LARGELY DISSIPATED OUTSIDE THE BLUE RIDGE. MID-AFTN DEWPOINTS IN THE M-U50S INDICATE SIMILAR LEVELS FOR OVERNIGHT LOWS TONIGHT...W/ TEMPS DROPPING WELL INTO THE 60S IN THE COMING HRS AND BOTTOM-OUT IN THE M-U50S BY THE PREDAWN HRS. LIGHT WINDS OUT OF THE NW WILL GRADUALLY DROP OFF TO NEAR CALM CONDITIONS OVERNIGHT. A KIND OF AIRMASS OR REGIME CHANGE IS ON THE WAY FOR THE COMING DAYS...AND EVEN THOUGH WE`LL STILL HAVE THE INFLUENCE OF HIGH PRESSURE - SOME CHANGE ARE FORTHCOMING. THE SFC HIGH THAT HAS BEEN PUSHING DRY NW FLOW ACROSS THE REGION FOR THE PAST COUPLE OF DAYS...WILL BEGIN TO SHIFT OFF THE COAST INTO EARLY FRI. WINDS WILL SHIFT TOWARD NELY TMRW...WHICH IS STILL A RELATIVELY DRY AND COOL FLOW BUT MORE ONSHORE. THIS FLOW WILL ALLOW FOR A STEADY BANKING OF LOW LEVEL MOISTURE INTO THE LEEWARD SIDE OF THE BLUE RIDGE. MID AND UPPER CLOUD DECKS WILL INCREASE THROUGHOUT THE DAY...W/ PATCHES OF SUNSHINE AGAIN BRINGING TEMPS BACK INTO THE L80S BY MID AFTN. USED A BLEND OF BIAS CORRECTED MAV/MET FOR TEMPERATURES THROUGH FRIDAY.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... INFLUENCE OF A SHORTWAVE OVER THE OHIO VALLEY WILL KEEP A CHANCE OF SHOWERS AND A FEW THUNDERSTORMS OVER THE POTOMAC HIGHLANDS/HIGHER ELEVATIONS FRIDAY NIGHT INTO SATURDAY UNTIL IT LIFTS TO THE NORTHEAST. FURTHER EAST SHOULD REMAIN DRY BUT EXPECT MORE CLOUDS /ENOUGH SO FOR MOSTLY CLOUDY/ GIVEN UPSTREAM SHORTWAVE AND ALSO EASTERLY FLOW IN THE LOW LEVELS WITH HIGH PRESSURE ALONG THE NEW ENGLAND COAST. CONVECTION LOOKS MAINLY FOCUSED OVER THE HIGHER TERRAIN AGAIN ON SUNDAY. IT/S POSSIBLE THAT A WAVE OF LOW PRESSURE RIDING ALONG A NEARLY STATIONARY BAROCLINIC ZONE OFF THE SOUTHEAST COAST BRINGS A FEW SHOWERS INTO LOWER SOUTHERN MARYLAND SATURDAY NIGHT INTO SUNDAY BUT A TIGHT PRECIPITATION GRADIENT IS EXPECTED AND MUCH OF RAIN LOOKS OFFSHORE. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... STAGNANT PATTERN INTO MID WEEK FEATURING SURFACE HIGH NEAR THE COAST...BAND OF MOISTURE EXTENDING FROM CAROLINA OFFSHORE TO CANADIAN MARITIMES AND WEAK WEST TO SOUTHWESTERLY FLOW PRESENT ALOFT. PATTERN WILL SHIFT SOMEWHAT BY WEDNESDAY WHEN AN AIRMASS FROM CENTRAL CANADA PUSHING A COLD FRONT INTO THE CWA. BEST CHANCE FOR PCPN SEEMS TO BE WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/...
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AS HIGH PRESSURE BUILDS IN NW WINDS WILL ALSO BECOME LIGHT/VRB OVERNIGHT. DRY AIR SHOULD PREVENT FOG FORMATION...AND VFR IS EXPECTED TO PREVAIL THROUGH THE VALID TAF PERIOD. VFR LIKELY TO CONTINUE INTO THE WEEKEND INTO EARLY NEXT WEEK AS HIGH PRESSURE WILL BE LOCATED ALONG THE NEW ENGLAND/MID-ATLANTIC COAST. THERE WILL BE MORE CLOUDS...BUT AT THIS TIME THEY LOOK TO MAINLY BE OF THE VFR VARIETY. TSRA CHANCE LOOKS MAINLY RELEGATED TO THE HIGHER TERRAIN.
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&& .MARINE...
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HIGH PRESSURE BUILDS IN TONIGHT...SO EXPECT WEAKER GRADIENT. HIGH PRESSURE MOVING OFF THE COAST WILL ALLOW WINDS TO BECOME EAST LATER FRIDAY...LIKELY LASTING INTO THE WEEKEND AND INCREASING TO 10 TO 15 KT.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ UPDATE...GMS PREV DISCUSSION...BPP/CEM

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