Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271056 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 656 AM EDT MON JUL 27 2015 .SYNOPSIS... WEAK FRONT OVER PENNSYLVANIA WILL STALL AND WEAKEN TO OUR NORTH TODAY AS HIGH PRESSURE REGAINS CONTROL TUESDAY INTO WEDNESDAY. COLD FRONT MOVES THROUGH THE AREA THURSDAY WITH UNSETTLED WEATHER POSSIBLE. HIGH PRESSURE THEN BUILDS IN FOR FRIDAY INTO THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AT PRESENT...SURFACE HIGH PRESSURES ARE CENTERED OVER THE TENNESSEE VALLEY...THE WESTERN ATLANTIC EAST OF THE DELMARVA...AND THE GREAT LAKES. IN BETWEEN THE HIGH OVER THE GREAT LAKES AND THE OTHER TWO...A SLOWING DOWN COLD FRONT IS POSITIONED OVER THE OHIO VALLEY AND PENNSYLVANIA. THIS FRONT WILL COME TO A HALT JUST TO OUR NORTH TODAY...THEN DISSIPATE THROUGH THE COURSE OF TONIGHT AND TOMORROW. A SHORTWAVE PASSING THROUGH THE REGION ALOFT HAS KEPT CONVECTION GOING THROUGH THE NIGHT...AND THIS WILL LIKELY CONTINUE FOR A FEW MORE HOURS. THERE MAY BE A BREAK MID-LATE MORNING BEFORE CONVECTION STARTS TO REFIRE BY THIS AFTERNOON AS ANOTHER PIECE OF ENERGY MOVES SOUTHEAST ACROSS THE REGION ALOFT. BOTTOM LINE IS THAT TODAY WILL BE A BIT COOLER THAN YESTERDAY...BUT MORE HUMID...WITH BETTER RISK OF SHOWERS AND THUNDERSTORMS. ISOLATED FLASH FLOODING IS A CONCERN WITH PW`S ABOVE 1.5" AND SOME POTENTIAL FOR TRAINING/BACK-BUILDING...BUT THINK IT WILL BE ISOLATED ENOUGH TO NOT NECESSITATE A WATCH. FRONT CONTINUES WEAKENING TONIGHT AND HEIGHTS WILL BE BUILDING AS A RIDGE PUSHES IN FROM THE WEST SO THE TREND SHOULD BE DOWNWARD FOR CONVECTION. PATCHY FOG WILL BE A CONCERN AGAIN INLAND. OTHERWISE...PARTLY CLOUDY AND MUGGY OVERNIGHT. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... RIDGE CONTINUES TO BUILD IN ON TUESDAY. WHATEVER IS LEFT OF THE FRONTAL BOUNDARY MAY ACTUALLY SLIDE SOUTH OF US BY TUESDAY...NOT REALLY ENOUGH TO CALL A FRONT EVEN...BUT COULD STILL ACT AS A TRIGGER FOR THUNDERSTORMS MAINLY IN CENTRAL VIRGINIA. FURTHER NORTH...MOSTLY DRY THOUGH HINTS THAT SOME SORT OF SEA BREEZE FRONT COULD ALSO TRIGGER ISOLATED CONVECTION. EITHER WAY...OVERALL A SUNNIER DAY WITH PLENTY OF HUMIDITY AND SLIGHTLY WARMER TEMPERATURES. H5 HEIGHT RISES CONTINUE INTO WEDNESDAY AS RIDGING OVER THE CENTRAL CONUS NUDGES TOWARD OUR AREA. CONTINUED SOUTHERLY FLOW WILL ALLOW TEMPERATURES TO RISE INTO THE L/M 90S ACROSS THE ENTIRE AREA...THOUGH DEWPOINTS AOB 70F SHOULD KEEP HEAT INDICES LESS THAN 100F. WITH LACK OF LIFT AND HEIGHT RISES...PRECIP CHANCES ARE RATHER LOW...BUT NON-ZERO. WITH THE BEST CHANCES IN THE HIGHER TERRAIN IN THE WEST. AFTER SUNSET EXPECT ANY ACTIVITY TO WEAKEN. && .LONG TERM /THURSDAY THROUGH SUNDAY/... BY THURSDAY MORNING COLD FRONT PROGGED TO BE TO OUR NORTH AND WEST. APPEARS MODEL CONSENSUS IS GROWING THAT A BROKEN LINE OF SHOWERS/STORMS ALONG THE FRONT WILL IMPACT THE AREA DURING THE DAY THURSDAY...SO INCREASED POPS ACCORDINGLY. OVERALL FLOW ALOFT IS EXTREMELY WEAK WITH H5 WINDS AOB 15KTS...SO SVR THREAT SHOULD REMAIN MARGINAL. HOWEVER MODERATE INSTABILITY COULD ALLOW SOME PULSE SVR. BEFORE COLD FRONT ARRIVES...IT WILL BE HOT...BUT ATTM THINK HEAT INDICES SHOULD REMAIN AOB 100. COLD FRONT PUSHES THROUGH MOST OF THE AREA BY FRIDAY MORNING...WHICH WILL KNOCK THE TEMPS AND DEWPOINTS DOWN A TOUCH. HIGH TEMPS THROUGH THE WEEKEND WILL REMAIN NEAR 90F...BUT HUMIDITY SHOULD REMAIN REASONABLE...SO NOT TOO OPPRESSIVE. PRECIP CHANCES MAINLY CONFINED ALONG OUR SOUTHERN ZONES THROUGH THE WEEKEND. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... MAIN CONCERN TODAY IS PATCHY INLAND FOG EARLY THIS MORNING...AND THEN CONTINUED SCATTERED CONVECTION WITH MVFR CIGS/VIS POSSIBLE IN STORMS THROUGH TODAY. CONDITIONS WILL IMPROVE TONIGHT AND TUESDAY BUT PATCHY FOG AGAIN POSSIBLE TONIGHT MAINLY INLAND SITES (CHO/MRB). MAINLY VFR EXPECTED WEDNESDAY UNDER HIGH PRESSURE...THOUGH THERE IS A SMALL CHANCE OF A THUNDERSTORM IN THE WEST. SUB-VFR CONDITIONS POSSIBLE THURSDAY AFTERNOON WITH SHOWERS AND STORMS ALONG COLD FRONT. && .MARINE...
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GRADIENT REMAINS JUST A BIT TIGHT THIS MORNING SO RE-ISSUED SCA THROUGH NOON. SHOULD RELAX THIS AFTERNOON. OTHER THAN THAT..MAIN ISSUE NEXT 36 HOURS IS THUNDERSTORMS...PRIMARILY THIS AFTERNOON. SOUTHERLY CHANNELING COULD LEAD TO SMALL CRAFT GUSTS WEDNESDAY. BETTER CHANCE OF SCA WEDNESDAY NIGHT INTO THURSDAY AS COLD FRONT APPROACHES THE WATER. MARINERS SHOULD ALSO MONITOR FOR THUNDERSTORMS ON THURSDAY.
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&& .TIDES/COASTAL FLOODING... THE HIGHER OF THE TWO HIGH TIDE CYCLES EARLY THIS MORNING HAS RESULTED IN MINOR INUNDATION AT VULNERABLE SITES /PARTICULARLY ANNAPOLIS...BUT POSSIBLY UP INTO BALTIMORE HARBOR AS WELL/. ESTOFS IS STILL RUNNING A LITTLE HIGH BUT NOT QUITE AS MUCH HIGHER COMPARED TO OTHER GUIDANCE AS IN PREVIOUS DAYS...SO HAVE CONSIDERED ITS OUTPUT WITH THIS ASSESSMENT. COASTAL FLOOD ADVISORY WAS BEEN ISSUED FOR THE OVERNIGHT HIGH TIDE CYCLE NEAR ANNAPOLIS AND BALTIMORE. THE WATER LEVELS WILL BE CLOSE TO MINOR FLOODING THRESHOLDS ELSEWHERE...BUT CURRENT FEELING IS THAT THEY WILL REMAIN JUST BELOW. THIS IS ALSO CONSISTENT WITH THE LATEST CBOFS AND ESTOFS GUIDANCE AS WELL. THE SOUTHERLY FLOW WILL CONTINUE THROUGH TODAY...AND MORE MINOR TIDAL FLOODING IS POSSIBLE TONIGHT INTO TUESDAY MORNING NEAR HIGH TIDE. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MDZ011- 014. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ531>534-537- 538-542-543. COASTAL FLOOD ADVISORY UNTIL 8 AM EDT THIS MORNING FOR ANZ538.
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&& $$ SYNOPSIS...MSE NEAR TERM...RCM SHORT TERM...MSE/RCM LONG TERM...MSE AVIATION...MSE/RCM MARINE...MSE/RCM TIDES/COASTAL FLOODING...

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