Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 261342 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 942 AM EDT SAT JUL 26 2014 .SYNOPSIS... HIGH PRESSURE IS MOVING OFFSHORE. LOW PRESSURE IS EXPECTED TO TRACK ACROSS PENNSYLVANIA SUNDAY NIGHT WITH AN ASSOCIATED COLD FRONT MOVING INTO THE MID ATLANTIC. A REINFORCING FRONT WILL CROSS THE REGION MONDAY. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING COOLER AND DRIER CONDITIONS DURING MIDWEEK. && .NEAR TERM /THROUGH TONIGHT/... A SHORTWAVE TROUGH WILL CONTINUE TO MOVE ACROSS THE MID ATLANTIC THIS MORNING. SCT SHOWERS WILL EXIT THE CHESAPEAKE BAY REGION THIS MORNING WHILE A SCT SPRINKLES DIMINISH ACROSS NOVA. RETURN FLOW WILL CONTINUE ACROSS THE REGION AND TEMPS WILL REACH THE MID TO UPPER 80S BY THIS AFTERNOON. AS WESTERLY FLOW INCREASES ALOFT...A SFC TROUGH WILL FORM ACROSS THE REGION WHICH WILL CAUSE AN AREA OF WEAK CONVERGENCE NEAR THE I-95 CORRIDOR BY THIS AFTERNOON. INSTABILITY WILL INCREASE BEHIND THE EXITING SHORTWAVE TROUGH TODAY AND ISO-SCT SHOWERS AND TSTORMS WILL BE POSSIBLE ACROSS THE WASH/BALT REGION...NRN PIEDMONT AND SOUTHERN MD. ACTIVITY IS EXPECTED TO BE NON- SEVERE AS FORCING...SHEAR AND INSTABILITY WILL BE WEAK. NOTE...SUNDAY IS A CRITICAL WEATHER DAY WITH SEVERE WEATHER EXPECTED FOR THE MID-ATLANTIC. && .SHORT TERM / SUNDAY THROUGH 6 AM SUNDAY/... A POTENT SHORTWAVE IN THE WESTERLY FLOW ALOFT WILL APPROACH THE AREA TONIGHT. MOST OF THE FORCING SHOULD REMAIN TO THE WEST...BUT THE SURFACE TROUGH WILL STRENGTHEN OVERHEAD AND EVEN RETROGRADE WESTWARD. THEREFORE...A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE TONIGHT...BUT COVERAGE ACROSS MOST AREAS SHOULD BE ISOLATED OR WIDELY SCATTERED SINCE MOST OF THE FORCING WILL REMAIN TO OUR WEST OVER THE OHIO VALLEY. MIN TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE MIDDLE 70S IN DOWNTOWN WASHINGTON AND BALTIMORE... AND IT WILL FEEL NOTICEABLY MORE HUMID. && .LONG TERM /SUNDAY THROUGH FRIDAY/... THE PRIMARY ACTION DURG THE XTND PD LOOKS TO BE COMING AT THE BEGINNING. SYNOPTICALLY THIS SUMMER CERTAINLY HAS BEEN OUT OF THE NORM (IE..AN ABSENCE OF THE SUB TROP HIGH) AND IT LOOKS LK THIS WL HOLD TRUE FOR THE END OF JUL AS WELL. IT APPEARS THAT AN UNUSUALLY STRONG AREA OF LOW PRES WL BE TRACKING ACROSS PA SUN EVE. THIS WL PLACE THE MID ATLC SUN IN AN UNSTABLE AIR MASS W/ CAPES OVR 1000. SPC HAS ENTIRE CWA IN A SLT RISK. ONE THING THAT WOULD MAKE THIS THREAT STRONGER IS IF AREA GETS BRKS IN CLDS DURG MIDDAY TO ALLOW FOR HTG/INSTABILITY. HIGHS SEASONABLE... GNRLY IN U80S...PSBLY 90 IN THE CIITES. CHC FOR RA/TSTMS XPCTD TO CONT SUN NGT AHD OF A CD FNT. HOW MUCH INSTABILITY WL RMN POST-SUNSET WL HELP TO DETERMINE IF THERE WL BE A CONT SVR THREAT. LOWS RANGING FM THE M60S TO L70S. CURRENTLY IF LOOKS LK THE ACTUAL CD FNT WON`T PUSH E OF THE RGN UNTIL LATE MON...HENCE MORE POPS/CHCS FOR CNVCTN. HIGHS IN LM80S. AFTR THAT THE NEXT SVRL DAYS - THE LAST PART OF JUL...THE CONTINENTAL U.S. SHOULD BE UNDER A WRN RDG/ERN TROF. THIS WL KEEP TEMPS IN THE MID ATLC BLO NRML. AS I`VE WRITTEN IN SVRL DSCNS RECENTLY WE ARE AT THE CLIMATOLOGICALLY WARMEST TIME OF THE YR - HIGHS SHOULD GNRLY BE IN THE U80S/LOWS IN THE MU60S. AS OF NOW IT LOOKS LK HIGHS TUE-FRI SHOULD BE IN THE L80S. LOW TEMPS OUTSIDE OF WARMER CITIES WL BE A60...PSBLY EVEN INTO THE U50S. IT LOOKS LK IT SHOULD BE DRY TUE-FRI. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... PATCHY BR IS POSSIBLE EARLY THIS MORNING ACROSS THE WESTERN TERMINALS. VFR CONDITIONS WILL PERSIST FOR THE REST OF TODAY. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THE EASTERN TERMINALS...ESPECIALLY THIS AFTERNOON. HOWEVER...COVERAGE WILL BE ISOLATED TO WIDELY SCATTERED. A FEW MORE SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THE TERMINALS TONIGHT...BUT AGAIN COVERAGE WILL BE ISOLATED TO WIDELY SCATTERED SINCE MOST OF THE FORCING WILL BE TO OUR WEST OVER THE OHIO VALLEY. PATCHY BR MAY REDUCE VSBYS LATE TONIGHT. IN THE XTND...TSTMS ARE PSBL SUN..SUN NGT...AND MON. IT IS LKLY THAT L.T. VFR CONDS WL OCCUR IF STORMS DVLP OVR AN AIRPORT ALONG W/ THE PSBLTY OF STRONG WINDS. CONDS XPCTD TO BE VFR TUE AND WED. && .MARINE... A SOUTHERLY FLOW HAS DEVELOPED AROUND DEPARTING HIGH PRESSURE AND THE SOUTHERLY FLOW WILL CONTINUE THROUGH TONIGHT. THE PRESSURE GRADIENT WILL STRENGTHEN A BIT THIS AFTERNOON AND TONIGHT...CAUSING SOUTHERLY WINDS TO CHANNEL UP THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY FROM SOUTH OF POOLES ISLAND TO SMITH POINT...AND THE LOWER TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT. WIND GUSTS MAY BE MARGINAL THIS AFTERNOON DUE TO THE RELATIVELY COOLER WATERS...BUT WILL CONTINUE WITH THE HEADLINE FOR NOW DUE TO THE STRENGTHENING GRADIENT. HIGHER CONFIDENCE WITH SCA WIND GUSTS IS FOR TONIGHT. TSTMS XPCTD ON THE WATERS...ESPECIALLY SUN AFTN/EVE. THESE MAY GENERATE STRONG GUSTY WINDS. AN SCA IS XPCTD MON AS A CD FNT MOVES THRU THE WATERS. THIS MAY CONT INTO MON NGT. TUE-THU LOOK MORE TRANQUIL. && .TIDES/COASTAL FLOODING... A LIGHT SOUTHERLY FLOW HAS CAUSED TIDAL ANOMALIES TO INCREASE TO AROUND ONE-HALF FOOT ABOVE NORMAL. THIS WILL CAUSE WATER LEVELS TO APPROACH MINOR FLOODING FOR SENSITIVE AREAS NEAR HIGH TIDE THIS MORNING FOR LOCATIONS ALONG THE WESTERN SHORE OF THE MARYLAND CHESAPEAKE BAY AND THE SHORE OF THE UPPER TIDAL POTOMAC RIVER. HOWEVER...WATER LEVELS SHOULD REMAIN JUST BELOW THESE THRESHOLDS SINCE THE FLOW WILL BE LIGHT. THE HIGH TIDE CYCLE THIS AFTERNOON AND EVENING WILL BE THE LOWER OF THE TWO...SO MINOR FLOODING IS NOT EXPECTED. HOWEVER...THE SOUTHERLY FLOW MAY STRENGTHEN A BIT TONIGHT AND THE HIGH TIDE CYCLE LATE TONIGHT INTO SUNDAY MORNING WILL BE THE HIGHER OF THE TWO. MINOR TIDAL FLOODING IS POSSIBLE FOR SENSITIVE AREAS NEAR HIGH TIDE LATE TONIGHT INTO SUNDAY MORNING. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EDT SUNDAY FOR ANZ531>534-537-539>543. && $$ UPDATE...HAS PREVIOUS...BJL/WOODY!

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