Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 311859 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 259 PM EDT THU JUL 31 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH FRIDAY...BUT A SERIES OF UPPER-LEVEL DISTURBANCES WILL PASS THROUGH DURING THIS TIME. A COASTAL FRONT WILL DEVELOP FRIDAY NIGHT...LASTING THROUGH THIS WEEKEND INTO EARLY NEXT WEEK. UPPER-LEVEL DISTURBANCES WILL CONTINUE TO MOVE OVER THE AREA DURING THIS TIME.
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&& .NEAR TERM /THROUGH FRIDAY/...
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AN UPPER-LEVEL DISTURBANCE IS TRACKING INTO UPSTATE NEW YORK AND NEW ENGLAND THIS AFTERNOON WHILE ANOTHER TRACKS THROUGH THE CAROLINAS INTO SOUTHERN VIRGINIA. HIGH PRESSURE WILL REMAIN ALONG THE EASTERN SEABOARD...AND A SOUTHERLY FLOW IS EXPECTED AROUND THIS HIGH. THIS HAS CAUSED SOMEWHAT WARMER AND MORE HUMID CONDITIONS COMPARED TO RECENT DAYS...BUT STILL COMFORTABLE FOR THIS TIME OF YEAR. MAX TEMPS WILL RANGE FROM THE 70S IN THE MOUNTAINS TO THE MIDDLE 80S ACROSS MOST OTHER LOCATIONS. A STRAY SHOWER CANNOT BE COMPLETELY RULED OUT THIS AFTERNOON...BUT THE FORECAST REMAINS DRY. THIS IS DUE TO WEAK INSTABILITY ALONG WITH LITTLE TO NO FORCING SINCE SHORTWAVE ENERGY IS BOTH TO OUR NORTH AND SOUTH. THERE WILL BE A SCT/BKN CU DECK DEVELOPING THIS AFTERNOON. THE UPPER-LEVEL DISTURBANCE TO OUR SOUTH WILL MOVE NORTHEAST INTO OUR AREA TONIGHT. THIS WILL BRING MORE MOISTURE WITH IT. THE WARM AND MOIST AIR WILL OVERRUN THE RELATIVELY COOLER AIR IN PLACE...RESULTING IN INCREASING CLOUDS ALONG WITH A BETTER CHANCE FOR SHOWERS. PRECIPITATION AMOUNTS WILL STILL BE LIGHT DUE TO A LACK OF INSTABILITY. PRECIPITATION AMOUNTS WILL RANGE BETWEEN A FEW HUNDREDTHS UP TO A QUARTER INCH. THE BEST CHANCE FOR PRECIPITATION WILL BE LATE TONIGHT ACROSS CENTRAL VIRGINIA. SURFACE HIGH PRESSURE WILL REMAIN ALONG THE NEW ENGLAND AND MID- ATLANTIC COASTS. A SOUTHEAST FLOW WILL CONTINUE TO USHER IN MOISTURE OFF THE ATLANTIC OCEAN...WHILE MORE WARM AND MOIST AIR STREAM IN ALOFT IN THE SOUTHWEST FLOW. A SERIES OF UPPER-LEVEL DISTURBANCES WILL PASS THROUGH DURING THIS TIME. SHOWERS ARE LIKELY...ESPECIALLY NEAR AND WEST OF THE BLUE RIDGE WHERE FORCING WILL BE STRONGER AND HEIGHTS WILL BE LOWER. MAX TEMPS WILL RANGE FROM THE 60S AND LOWER 70S IN THE MOUNTAINS TO THE LOWER AND MIDDLE 80S NEAR WASHINGTON AND BALTIMORE.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
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A COASTAL FRONT WILL DEVELOP ALONG THE MID-ATLANTIC COAST FRIDAY NIGHT AND IT WILL REMAIN NEARBY THROUGH SUNDAY. THE FORECAST REMAINS UNCERTAIN AT THIS TIME DUE TO THE UNCERTAINTY WITH THE EXACT LOCATION OF THE FRONT ALONG WITH TIMING OF UPPER-LEVEL DISTURBANCES THAT WILL PASS THROUGH IN THE SOUTHWEST FLOW ALOFT. A POTENT UPPER-LEVEL DISTURBANCE WILL LIKELY PASS THROUGH FRIDAY NIGHT...BRINGING A GOOD CHANCE FOR SHOWERS AND PERHAPS A COUPLE THUNDERSTORMS. SHOWERS WILL REMAIN POSSIBLE FOR SATURDAY...BUT THE COVERAGE OF THE SHOWERS WILL BE DEPENDENT ON THE LOCATION OF THE COASTAL FRONT. IF THE FRONT IS FARTHER WEST INTO OUR AREA...THEN MORE INSTABILITY WILL RESULT IN MORE SHOWERS. HOWEVER...IF THE FRONT IS CLOSER TO THE COAST...THEN IT WILL BE MORE STABLE WITH WITH SHOWERS BEING WIDELY SCATTERED. MODELS DO CONVERGE ON BRINGING THE COASTAL FRONT FARTHER WEST SUNDAY...WHICH SHOULD RESULT IN A BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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SERIES OF WEAK 500MB TROUGHS AND PVA WILL AFFECT CWA THROUGH THE PERIOD. UPWARD VERTICAL MOTION AND MOISTURE GREATEST OVER VA TIDEWATER...SOUTHERN MD AND CHESAPEAKE BAY SUNDAY NIGHT THROUGH MONDAY NIGHT. DRY AIRMASS WILL REPLACE SURFACE LOW PRESSURE TROUGH AND ASSOCIATED MOISTURE BY TUESDAY. COLD FRONT WILL ENTER CWA EARLY WEDNESDAY. ASSOCIATED MOISTURE...UPWARD VERTICAL MOTION AND PVA WILL MOVE OVER CWA WEDNESDAY MORNING/AFTERNOON. GREATEST CHANCE OF PRECIPITATION SUNDAY NIGHT INTO MONDAY EVENING AND AGAIN WEDNESDAY.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING. SOUTHERLY WINDS THIS AFTERNOON WILL BECOME LIGHT AND VARIABLE. A SERIES OF UPPER- LEVEL DISTURBANCES WILL BRING MORE CLOUDS TONIGHT THROUGH FRIDAY ALONG WITH A BETTER CHANCE FOR SHOWERS. SUBVFR CONDITIONS ARE POSSIBLE IN SHOWERS...ESPECIALLY ACROSS KCHO. MOISTURE WILL CONTINUE TO STREAM IN FROM THE GULF OF MEXICO AND ATLANTIC OCEAN FRIDAY NIGHT THROUGH SUNDAY...BRINGING A GOOD CHANCE FOR SHOWERS AND EVEN SOME THUNDERSTORMS. DETAILS ARE STILL UNCERTAIN THIS FAR OUT. HIGH PRESSURE MAY BRIEFLY BUILD OVERHEAD EARLY NEXT WEEK.
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&& .MARINE...
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HIGH PRESSURE WILL REMAIN ALONG THE MID-ATLANTIC COAST THROUGH TONIGHT. SOUTHERLY WINDS WILL CHANNEL UP THE CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. A SMALL CRAFT ADVISORY IS IN EFFECT TONIGHT FOR THE MARYLAND CHESAPEAKE BAY FROM SANDY POINT TO SMITH POINT AND THE LOWER TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT. A COASTAL FRONT WILL DEVELOP ALONG THE MID-ATLANTIC COAST FRIDAY THROUGH EARLY NEXT WEEK. A SOUTHERLY FLOW IS EXPECTED MOST OF THE TIME...BUT THE GRADIENT SHOULD BE RELATIVELY WEAK...SO MOST OF THE TIME WINDS SHOULD REMAIN BELOW SCA CRITERIA.
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&& .TIDES/COASTAL FLOODING...
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A SOUTHERLY FLOW WILL CONTINUE THROUGH FRIDAY. THE FLOW WILL STRENGTHEN LATE TONIGHT INTO FRIDAY MORNING AND THIS WILL CAUSE TIDAL ANOMALIES TO INCREASE. THE HIGH TIDE WILL BE THE HIGHER OF THE TWO FRIDAY MORNING...SO WATER LEVELS WILL BE CLOSE TO MINOR FLOODING THRESHOLDS. HOWEVER...CURRENT FEELING AT THIS TIME IS THAT WATER LEVELS WILL REMAIN JUST BELOW MINOR FLOODING THRESHOLDS SINCE THE ASTRONOMICAL NORMS ARE A BIT LOWER SINCE WE ARE HEADED TOWARD THE FIRST QUARTER PHASE OF THE MOON.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT FRIDAY FOR ANZ532>534-537-540-541-543.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...CEM AVIATION...BJL/CEM MARINE...BJL/CEM TIDES/COASTAL FLOODING...BJL

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