Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 211851 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 251 PM EDT MON JUL 21 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN ALONG THE EASTERN SEABOARD THROUGH TUESDAY. TEMPERATURES WILL SLOWLY RISE THROUGH WEDNESDAY AHEAD OF A COLD FRONT EXPECTED TO MOVE INTO THE AREA THURSDAY. HIGH PRESSURE IS EXPECTED TO RETURN TO THE MID ATLANTIC STATES TO END THE WORKWEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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HIGH PRESSURE CONTINUES TO BE LOCATED FROM THE NEW ENGLAND COAST DOWN THROUGH THE MID-ATLANTIC...KEEPING A SOUTHEAST LOW LEVEL FLOW ACROSS THE CWA. SOME SHOWERS HAVE BEEN NOTED ACROSS THE POTOMAC HIGHLANDS AND ACROSS THE VIRGINIA FOOTHILLS. EXPECT MORE DEVELOPMENT THROUGH THE REST OF THE AFTERNOON...PARTICULARLY FROM THE FOOTHILLS AND NEAR THE BLUE RIDGE ON WEST. CAN/T RULE OUT ISOLATED THUNDER EITHER BUT WITH SO MUCH CLOUD COVER INSTABILITY IS WEAK AND THESE WILL BE FEW AND FAR BETWEEN. SHOWERS SHOULD FAVOR A DIURNAL TREND...THUS EXPECT DIMINISHING/LITTLE ACTIVITY AFTER DARK. CLOUDS WILL STICK AROUND...POSSIBLY MORPHING INTO A STRATUS DECK LATE TONIGHT. FAVORED BLEND OF BIAS CORRECTED SREFS/ADJMAV FOR MINIMA.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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FLAT RIDGE BUILDS IN FOR TUESDAY. DAY LIKELY STARTS OUT WITH PLENTY OF CLOUDS BUT SOME PEEKS OF SUNSHINE SHOULD OCCUR IN THE AFTERNOON. RIDGE MAY HELP LIMIT CONVECTION...BUT WITH BETTER MOISTURE/INSTABILITY THAN RECENT DAYS CAN/T RULE OUT A FEW SHOWERS/THUNDERSTORMS DURING THE AFTERNOON/EVENING MAINLY NEAR THE HIGHER TERRAIN. HEIGHTS START TO DECREASE FOR WEDNESDAY. DESPITE THIS...A SHIFT TO A SOUTHWEST WIND AND SOME SUNSHINE SHOULD SUPPORT WARMER TEMPERATURES LIKELY AOA 90 DEG EAST OF THE BLUE RIDGE. MODELS ALSO HINT AT THE PRESENCE OF A PRE-FRONTAL TROUGH...THUS EXPECT A CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE CWA BY AFTERNOON.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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HEAVY SHOWERS AND STRONG TO POSSIBLY SEVERE THUNDERSTORMS MAY DEVELOP DURING THE DAY THURSDAY DUE TO A COMBINATION OF UPPER ENERGY...A COLD FRONT AND DAYTIME HEATING. THE STRONGEST THUNDERSTORMS COULD PRODUCE DAMAGING WINDS AND LOCALLY HEAVY RAIN. HIGH CAPE AND LOW TO MODERATE SHEAR COULD LEAD TO THE DAMAGING WINDS...WHILE PRECIPITABLE WATER VALUES OF AROUND 2 INCHES COULD INDICATE HEAVY RAIN WOULD BE A THREAT FROM THE STORMS. AS OF NOW...TIMING OF THE HEAVIEST ACTIVITY APPEARS TO BE THURSDAY AFTERNOON AND EVENING. A SURFACE COLD FRONT WILL PUSH THROUGH OUR REGION THURSDAY NIGHT TO ALLOW FOR A RIDGE OF HIGH PRESSURE TO BUILD IN FROM THE NORTHWEST. THIS FRONT HAS THE POTENTIAL TO STALL NEAR THE VIRGINIA AND NORTH CAROLINA BORDER THURSDAY NIGHT INTO FRIDAY...THUS MAYBE KEEPING A SLIGHT CHANCE OF RAIN SHOWERS ACROSS THE SOUTHERN TWO-THIRDS OF THE CWA WITH A SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE VIRGINIA PIEDMONT AND MAIN STEM CHESAPEAKE BAY. HIGH PRESSURE SHOULD GRADUALLY PUSH THE FRONT FARTHER SOUTH TO ALLOW COOLER AND DRIER AIR TO MOVE IN ACROSS THE CWA FRIDAY AFTERNOON THROUGH MIDDAY SATURDAY. THE HIGH IS EXPECTED TO MOVE OFFSHORE SATURDAY AFTERNOON AND SATURDAY NIGHT. AN ONSHORE FLOW DEVELOP DURING THE PERIOD...AIDING IN AN INCREASE IN LOW LEVEL MOISTURE. GIVEN THE UNCERTAINTY OF THE POSITION OF THE HIGH...NEAR LONG ISLAND OR THE TIDEWATER OF VIRGINIA...WE LEFT A CHANCE OF RAIN SHOWERS SATURDAY AND A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM SATURDAY NIGHT. DESPITE THE HIGH BEING THE FAVORITE...BOTH THE EURO AND GFS INDICATE A FEW RIPPLES IN THE UPPER LEVEL FLOW THAT MAY INDICATE A WEAK DISTURBANCE OR TWO MAY FIND ITS WAY ACROSS OUR CWA...HENCE THE CHANCE OF A SHOWER OR STORM. SUNDAY AND MONDAY WILL BE A PRECURSOR OF AN ACTIVE MIDWEEK OF SHOWERS AND THUNDERSTORMS AS A STRONGER UPPER LEVEL STORM SYSTEM PIVOTS ACROSS THE GREAT LAKES.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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VFR PREVAILS AT THE TERMINALS THIS AFTERNOON...HOWEVER PERIODIC MVFR CIGS STILL POSSIBLE AT MRB/CHO THROUGH AFTERNOON AND COULD EVEN LINGER INTO THE EVENING. GIVEN SOUTHEAST FLOW...ALSO EXPECT STRATUS TO DEVELOP TOWARD THE HUBS TONIGHT...AND HAVE INCLUDED MVFR TO IFR CIGS IN TAFS LATE TONIGHT INTO EARLY TUESDAY MORNING. FOLLOWED TRENDS OF SREFS/LAMP/MAV IN A RETURN TO VFR BY TUESDAY AFTERNOON ALTHOUGH THERE WILL BE SCATTERED SHOWERS. AFTERNOON/EVENING THUNDERSTORMS ARE POSSIBLE ON WEDNESDAY. IFR OR LIFR CONDITIONS ARE POSSIBLE AT ANY OF THE TERMINALS THURSDAY AS LOCALLY HEAVY RAINFALL AND GUSTY WINDS ACCOMPANY THE SHOWERS AND THUNDERSTORMS.
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&& .MARINE...
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HIGH PRESSURE ALONG THE COAST KEEPS A SOUTHEAST FLOW IN PLACE THIS AFTERNOON...ALTHOUGH WEAK GRADIENT SHOULD KEEP SPEEDS 10 KT OR LESS. WINDS TURN MORE TO THE SOUTH TONIGHT INTO TUESDAY...CHANNELLING LIKELY TO PROMOTE WINDS INCREASING CLOSER TO 15 KT UP THE MAIN CHANNEL OF THE BAY. CHANNELLING COULD RESULT IN MARGINAL SCA CONDITIONS UP THE BAY BY WEDNESDAY EVENING. NO MARINE HAZARDS EXPECTED THURSDAY THROUGH FRIDAY...EXCEPT FOR POSSIBLE GUSTY WINDS IN THUNDERSTORMS THURSDAY.
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&& .TIDES/COASTAL FLOODING...
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ANOMALIES CONTINUE TO BE AROUND 1 FT ABOVE NORMAL ON THE WESTERN SHORE OF THE CHESAPEAKE BAY THIS AFTERNOON. THESE MAY EVEN MOVE UPWARD A LITTLE THROUGH TONIGHT GIVEN SOUTHEAST FLOW. GIVEN CURRENT ANOMALIES...THIS WILL PUT WATER LEVELS ABOVE MINOR FLOOD AT ANNAPOLIS AND RIGHT NEAR MINOR FLOOD AT BALTIMORE. CBOFS HAS BOTH LOCATIONS ABOVE MINOR FLOOD DURING HIGH TIDE AS WELL AND WITH DECENT CONFIDENCE WILL BE ISSUING A COASTAL FLOOD ADVISORY FOR ANNE ARUNDEL AND SOUTHERN BALTIMORE COUNTIES FOR TONIGHT/S HIGH TIDE. WILL HAVE TO WATCH OTHER COUNTIES ON THE WESTERN SHORE OF THE BAY IF ANOMALIES INCREASE FURTHER. RISK OF MINOR TIDAL FLOODING MAY OCCUR AGAIN DURING HIGH TIDE TUESDAY NIGHT WITH SOUTHERLY FLOW IN PLACE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY FROM 1 AM TO 6 AM EDT TUESDAY FOR MDZ011-014. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...BPP NEAR TERM...BPP SHORT TERM...BPP LONG TERM...KLW AVIATION...BPP/KLW MARINE...BPP/KLW TIDES/COASTAL FLOODING...BPP

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