Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271415 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1015 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/...
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MID-LEVEL DRY AIR IS ENTERING THE AREA FROM THE NW PER WATER VAPOR IMAGERY BUT BLENDED TPW PRODUCT STILL SHOWS PLENTY OF LOW-LEVEL MOISTURE WITH 1.8 INCHES OF PWAT. THERE ARE ALSO WEAK HEIGHT RISES PROGGED FOR TODAY AND COUPLED WITH MID-LEVEL DRY AIR THINKING CONVECTIVE CVRG WILL BE LESS TODAY THAN LAST NIGHT SO CUT DOWN IN CVRG FOR THIS AFTERNOON. SO REDUCED POPS SLIGHTLY AND ADJUSTED THEM MORE TOWARD THE EAST AND CNTRL SHENANDOAH VALLEY. WRN MD AND ERN WV PANHANDLE WILL HAVE THE LEAST RISK OF SEEING A T-STORM.
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&& .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 /14Z MONDAY THROUGH FRIDAY/...
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SCT T-STORMS EXPECTED POINTS EAST AND SOUTH. LEAST CHANCE AT KMRB. 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.
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&& .MARINE...
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WILL LET SCA EXPIRE AT 15Z TODAY. 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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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ531>534-537- 538-542-543.
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&& $$ SYNOPSIS...MSE NEAR TERM...LFR SHORT TERM...MSE/RCM LONG TERM...MSE AVIATION...MSE/LFR MARINE...MSE/LFR

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