Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 071416 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1016 AM EDT MON JUL 7 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN THROUGH TUESDAY...CAUSING HOT AND HUMID CONDITIONS OVER THE AREA. A COLD FRONT WILL APPROACH THE REGION TUESDAY NIGHT...CROSS THE AREA WEDNESDAY...AND STALL OVER SOUTHERN VIRGINIA WEDNESDAY NIGHT INTO THURSDAY. HIGH PRESSURE THEN BUILDS OVER THE NORTHERN MID- ATLANTIC ON FRIDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC THROUGH TONIGHT. A SOUTHWEST FLOW AROUND THE HIGH WILL CAUSE HOT AND HUMID CONDITIONS TO RETURN OVER THE AREA THIS AFTERNOON. MAX TEMPS WILL RANGE FROM THE 80S IN THE MOUNTAINS TO THE LOWER AND MIDDLE 90S ACROSS MOST OTHER LOCATIONS. THE HEAT AND HUMIDITY WILL LEAD TO AN UNSTABLE ATMOSPHERE...BUT INSTABILITY MAY BE SOMEWHAT LIMITED WITH DEWPOINTS IN THE LOWER AND MIDDLE 60S...INSTEAD OF THE 70S LIKE IT WAS LAST WEEK. NAM/GFS BUFKIT AND THE MODIFIED 12Z KIAD RAOB INDICATE AROUND 500 TO 1000 J/KG OF MLCAPE THIS AFTERNOON. ANY INVERSION WILL BE WEAK...AND A SURFACE TROUGH SHOULD ACT AS A LIFTING MECHANISM TO TRIGGER A FEW SHOWERS AND THUNDERSTORMS...ESPECIALLY ACROSS NORTHERN AND CENTRAL VIRGINIA TOWARD CENTRAL MARYLAND AND THE WASHINGTON METROPOLITAN AREA THIS AFTERNOON AND EVENING. SHEAR PROFILES WILL BE RELATIVELY WEAK...AND WITH LIMITED INSTABILITY ANY SEVERE THREAT SHOULD BE LIMITED. WARM AND HUMID CONDITIONS WILL PERSIST TONIGHT...MOST AREAS SHOULD BE DRY AFTER ANY EVENING CONVECTION DISSIPATES. HOWEVER...A FEW SHOWERS AND THUNDERSTORMS CANNOT BE RULED OUT NEAR THE POTOMAC HIGHLANDS...CLOSER TO AN APPROACHING UPPER-LEVEL TROUGH.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... SYNOP SETUP TUE WL BE SIMLR TO TDA...XCPT THE FNT WL BE CLOSER AND HGT FALLS WL YIELD BETTER INSTBY/LAPSE RATES. DECENT SWLY FLOW WL PRODUCE A MARGINALLY SHEARED ENVIRONMENT. WITH THAT IN MIND...AM BGNG TO THINK THAT TUE HAS A BETTER TSRA POTL...AND MAYBE EVEN A SVR POTL. SPC CONCURS...W/ SLGT RISK IN THE W AND 5 PCT /SEE TEXT/ IN THE E. THREATS BOTH WND AND HAIL. POPS SLGTLY HIER THAN PRVS FCST... ALTHO HV CONFINED LKLY POPS FOR THE PTMC HIGHLANDS DURING THE EVNG. ACTIVITY SHUD WANE SOMEWHAT OVERNGT...ALTHO LINGERING INSTBY SUGGESTS CANNOT RULE OUT NOCTURNAL RUMBLERS. THE CDFNT WL REMAIN NW OF CWFA THRUT THE PD...BUT IT/LL BE GETTING CLOSE TO ALLEGANY FRONT BY DAWN. H8 TEMPS REMAIN CLS TO 20C...SO HV CONTD W/ MAXT LWR-MID 90S. HEAT INDEX VALUES AOB 100F...SO HEAT WONT BE MENTIONED IN HWO AS ITS UNDER ADVY CRITERIA. HV CARRIED OVER TUE NGT MIN-T FCST AS DEWPTS WUD BE AWFULLY NEAR 70F BASED ON ANTICIPATED TSRA. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A LEE TROUGH AND COLD FRONT WILL BE THE CONCERN ON WEDNESDAY. WARM AND HUMID AIR WILL BE PRESENT WEDNESDAY AND SHOWERS AND THUNDERSTORMS ARE LIKELY TO START EARLY WED WEST OF THE BLUE RIDGE AS A 100KT JET MOVES ACROSS THE OHIO VALLEY. DISTURBANCES WILL BE POSSIBLE IN THE SW FLOW ALOFT AND WILL ACT AS A SUPPORT FOR THUNDERSTORMS IN THE MORNING. THE COLD FRONT WILL MOVE THROUGH WED AFTERNOON AND NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED. SOME THUNDERSTORMS MAY BECOME SEVERE WITH LITTLE INHIBITION AND MARGINAL SHEAR. THE FRONT WILL MOVE TO THE SOUTHEAST BY WED EVENING AND DRY WESTERLY FLOW WILL MOVE IN BEHIND THE FRONT. THIS FRONT MAY STALL ACROSS CENTRAL VA AND LEAD TO SHOWERS AND ISOLATED THUNDERSTORMS WED NIGHT AND INTO THURSDAY. HIGH PRESSURE WILL MOVE ACROSS THE GREAT LAKES THURSDAY WHILE THE COLD FRONT MOVES INTO THE TIDEWATER REGION. A FEW LINGERING SHOWERS ARE POSSIBLE ACROSS CENTRAL VA AND SRN MD THURSDAY BUT OTHERWISE DRY. AN UPPER LEVEL TROUGH AXIS WILL CROSS THE MID ATLANTIC FRIDAY AS HIGH PRESSURE MOVES INTO THE REGION. DRY CONDITIONS ARE EXPECTED FRIDAY. A DISTURBANCE MAY CROSS THE REGION SATURDAY AND SHOWERS AND THUNDERSTORMS ARE POSSIBLE. A UPPER LEVEL TROUGH DIGS INTO THE GREAT LAKES SUNDAY AND LOW PRESSURE IS EXPECTED TO MOVE NORTH OF THE MID-ATLANTIC. A COLD FRONT MAY APPROACH THE REGION AND LEAD TO SHOWERS AND THUNDERSTORMS SUNDAY. FCST TEMPS WILL FALL BACK INTO THE 80S AFTER THE FROPA THURSDAY AND THROUGH THE END OF THE WEEKEND. && .AVIATION /14Z MONDAY THROUGH FRIDAY/...
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VFR TDA-TNGT. CU SHUD BE DVLPG TAFTN...BASES SCT-BKN050. SW FLOW WL PEAK AT 15-20 KT MID-LT AFTN...BUT WNDS WL DIMINISH IN THE EVNG. AN ISOLATED SHOWER/THUNDERSTORM CANNOT BE RULED OUT LATE THIS AFTERNOON AND EVENING. SCT TSRA WL DVLP DURING DAYTIME HEATING TUE...CONTG INTO THE EVNG. WHILE VFR WL PREVAIL OUTSIDE OF STORMS...BRIEF IFR FLGT RESTRICTIONS PSBL W/IN. TSRA ARE LIKELY WEDNESDAY AS A COLD FRONT MOVES THROUGH THE REGION. LOW CIGS AND VSBYS WILL BE POSSIBLE WITHIN ACTIVITY. VFR CONDITIONS EXPECTED FOR THE END OF THE WEEK.
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&& .MARINE...
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RELATIVELY STRONG SWLY FLOW WL CONT THRU TUE AHD OF A CDFNT. THE GRADIENT FLOW JUSTIFIES SCA FOR ALL WATERS BY MID AFTN. WL CUT THAT BACK A LTL FOR THE NIGHT TIME HRS /DROPPING N OF POOLES...UPRIVER OF COBB ISL...BALT HARBOR AND THE LWR TIDAL PATUXENT/...AND WL CONT THE MAIN CHANNEL OF THE MID-BAY AND TANGIER SOUND FOR THE MRNG HRS TUE. HV ALSO ADDED AN ADVY FOR ALL WATERS TUE AFTN. A COLD FRONT WILL CROSS THE WATERS WED EVENING/THURSDAY AND COULD STALL NEAR THE LOWER TIDAL POTOMAC AND MD CHESAPEAKE BAY LEADING TO A PROLONGED PERIOD OF SHOWERS AND THUNDERSTORMS REDUCING VSBYS AND CAUSING GUSTY WINDS. HIGH PRESSURE IS EXPECTED FOR THE END OF THE WEEK.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 AM EDT TUESDAY FOR ANZ531-537-539>541. SMALL CRAFT ADVISORY FROM 1 PM TO 7 PM EDT TUESDAY FOR ANZ530- 531-535>542. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 9 PM EDT THIS EVENING FOR ANZ530-535-536-538-542. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 7 PM EDT TUESDAY FOR ANZ532>534-543.
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&& $$ SYNOPSIS...HTS NEAR TERM...BJL SHORT TERM...HTS LONG TERM...HAS AVIATION...HAS/HTS MARINE...HAS/HTS

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