Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 251830 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 230 PM EDT TUE AUG 25 2015 .SYNOPSIS... HIGH PRESSURE OVER THE CENTRAL UNITED STATES WILL SLOWLY MOVE EAST OVER THE NEXT SEVERAL DAYS. IT WILL BECOME CENTERED OVER THE REGION BY FRIDAY AND GENERALLY REMAIN OVER THE REGION INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH WEDNESDAY/... MUCH DRIER AIR MASS CURRENTLY IN PLACE BEHIND THE FRONT WHICH PASSED LATE LAST NIGHT. TEMPERATURES ALSO SEVERAL DEGREES COOLER BUT NOT TOO FAR BELOW NORMAL FOR LATE AUGUST. COLD FRONT CURRENTLY LOCATED ALONG THE EAST COAST WILL CONTINUE SLIDING EASTWARD TONIGHT AND WEDNESDAY AS HIGH PRESSURE GRADUALLY BUILDS IN FROM THE WEST. ALOFT...WE REMAIN UNDER THE INFLUENCE OF THE CLOSED LOW IN SOUTHEASTERN CANADA AND IT WILL REMAIN IN THE SAME GENERAL AREA THROUGH WEDNESDAY. THERE IS A VERY WEAK DISTURBANCE PASSING AROUND THE LOW AND ACROSS OUR REGION OVERNIGHT...AND SOME MESOSCALE MODELS INDICATE A SHOWER OR TWO FORMING AS IT DOES SO. HOWEVER...BELIEVE THAT THE DRY AIR MASS WITH PW`S BELOW AN INCH AND STRONG INVERSION NOW IN PLACE ALOFT WILL LIKELY KEEP ANY SHOWERS FROM FORMING. LOWS WILL BE COOLER THAN LAST NIGHT WITH 50S IN MANY AREAS AND 60S IN THE URBAN CENTERS. PATCHY FOG MAY ALSO DEVELOP...MOST LIKELY ACROSS INLAND PORTIONS OF VIRGINIA. HIGHS ON WEDNESDAY WILL REBOUND TO SIMILAR...PERHAPS SLIGHTLY COOLER...READINGS ON WEDNESDAY AND HUMIDITY WILL REMAIN LOW UNDER A GOOD DEAL OF SUNSHINE. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... HIGH PRESSURE WILL REMAIN IN CONTROL THROUGH THE SHORT TERM...ALLOWING FOR DRY WEATHER AND TEMPERATURES A FEW DEGREES BELOW NORMAL. THURSDAY WILL BE THE COOLER OF THE TWO DAYS...AS COOLER AND DRIER AIR CONTINUES TO ADVECT IN FROM THE NORTH AND WEST. WEAK RETURN FLOW BEGINS FRIDAY...WITH A WEAK WARM FRONT LIFTING NORTH THROUGH THE AREA. THIS WILL HELP TO INCREASE TEMPERATURES A FEW DEGREES...THOUGH THEY WILL STILL BE BELOW NORMAL. QUALITY MOISTURE WILL BE LOCATED WELL SOUTH AND EAST...SO DEWPOINTS EXPECTED TO REMAIN AOB 60 EVEN WITH SOUTHERLY FLOW. LACK OF LOW-LEVEL MOISTURE AND/OR LIFTING MECHANISM WILL PRECLUDE SHOWER/THUNDERSTORM DEVELOPMENT DURING THE SHORT TERM. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... HIGH PRESSURE WEAKENS ITS GRIP SLIGHTLY OVER THE WEEKEND...AS WEAK WARM FRONT CONTINUES TO LIFT NORTH THROUGH THE MID-ATLANTIC. SOUTHERLY FLOW CONTINUES...BUT QUALITY LOW-LEVEL MOISTURE WILL STILL REMAIN SOUTH AND EAST OF OUR AREA...WHICH WILL KEEP SFC DEWPOINTS AOB 65. HOWEVER...ENOUGH MOISTURE WILL BE PRESENT OVER THE WEEKEND TO ALLOW FOR A FEW SPOTTY SHOWERS AND ISOLATED STORMS OVER THE HIGHER TERRAIN...WITH SOME SPILLAGE TO THE EAST SUNDAY. LACK OF DECENT LIFT AND MARGINAL INSTABILITY SHOULD KEEP MOST AREAS DRY MOST OF THE TIME. HIGH PRESSURE THEN BEGINS TO REASSERT ITS CONTROL MONDAY INTO TUESDAY. CONTINUED SOUTHERLY FLOW WILL USHER IN SLIGHTLY WARMER TEMPERATURES OVER THE WEEKEND AND INTO EARLY NEXT WEEK...WITH TEMPERATURES A FEW DEGREES ABOVE NORMAL. HOWEVER...HUMIDITY SHOULD REMAIN LOW ENOUGH TO HAVE LITTLE-TO-NO ADDED IMPACT ON HEAT. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR THROUGH THE PERIOD. LIGHT WEST TO NORTHWEST WINDS TONIGHT AND WEDNESDAY GENERALLY 10 KNOTS OR LESS. PATCHY FOG EXPECTED IN THE AREA LATE TONIGHT AND WEDNESDAY NIGHT BUT AT THIS TIME WE ARE NOT EXPECTING ANY FOG TO IMPACT THE TERMINALS. && .MARINE... HIGH PRESSURE WILL PROBABLY KEEP THE WINDS BELOW SCA LEVELS TONIGHT THROUGH WEDNESDAY NIGHT. PRESSURE GRADIENT DOES TIGHTEN UP TONIGHT AND AGAIN WEDNESDAY NIGHT...SO THERE IS A SMALL CHANCE WINDS COULD BE HIGHER THAN EXPECTED...BUT MIXED LAYER WINDS ARE GENERALLY BELOW 18 KNOTS SO HAVE NOT ISSUED ANYTHING YET. FEW MARINE CONCERNS THROUGH THE EXTENDED UNDER HIGH PRESSURE WITH DRY WEATHER AND LIGHT WINDS. AN ISOLATED SHOWER OR THUNDERSTORM IS POSSIBLE BY LATE SUNDAY...BUT MOST OF THE DAY SHOULD REMAIN DRY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...MSE LONG TERM...MSE AVIATION...MSE/RCM MARINE...MSE/RCM

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