Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 071840 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 240 PM EDT MON JUL 7 2014 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TUESDAY/... 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 HAS LEAD TO AN UNSTABLE ATMOSPHERE...BUT INSTABILITY IS SOMEWHAT LIMITED WITH DEWPOINTS IN THE LOWER AND MIDDLE 60S...INSTEAD OF THE 70S LIKE IT WAS LAST WEEK. LATEST MESOANALYSIS SHOWS 500 TO 1000 J/KG OF MLCAPE THIS AFTERNOON. 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 LATE 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...AN ISOLATED SHOWER OR THUNDERSTORM CANNOT BE RULED OUT NEAR THE POTOMAC HIGHLANDS...CLOSER TO AN APPROACHING UPPER-LEVEL TROUGH. AN UPPER-LEVEL TROUGH WILL CONTINUE TO DIG SOUTH AND EAST TOWARD OUR AREA TUESDAY WHILE THE COLD FRONT ASSOCIATED WITH THIS SYSTEM MOVES THROUGH THE GREAT LAKES. A SOUTHERLY FLOW AHEAD OF THE COLD FRONT AND BEHIND HIGH PRESSURE OVER THE ATLANTIC WILL CONTINUE TO USHER IN HOT AND HUMID CONDITIONS ACROSS OUR AREA. THE HOT AND HUMID CONDITIONS WILL LEAD TO AN UNSTABLE ATMOSPHERE ONCE AGAIN. SHOWERS AND THUNDERSTORMS ARE POSSIBLE...ESPECIALLY DURING THE AFTERNOON. DO THINK THUNDERSTORM COVERAGE WILL BE MORE THAN TODAY DUE TO LOWERING HEIGHTS AND MORE INSTABILITY. ALSO...SHEAR PROFILES WILL BE STRONGER AS WELL. THEREFORE...THERE IS A THREAT FOR SEVERE THUNDERSTORMS WITH LOCALLY DAMAGING WINDS AND LARGE HAIL. THE BEST THREAT FOR SEVERE THUNDERSTORMS WILL BE ACROSS NORTHERN MARYLAND AND FOR LOCATIONS NEAR AND WEST OF THE BLUE RIDGE TUESDAY AFTERNOON. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE REGION TUESDAY NIGHT WHILE THE UPPER-LEVEL TROUGH CONTINUES TO DIG TOWARD OUR AREA. THIS MAY ASSIST SHOWERS AND THUNDERSTORMS IN PROPAGATING FARTHER EAST INTO THE METROPOLITAN AREAS AND SOUTHERN MARYLAND. SOME THUNDERSTORMS TUESDAY EVENING WILL BE CAPABLE OF PRODUCING LOCALLY DAMAGING WIND GUSTS AND LARGE HAIL. DO THINK THE TREND IN CONVECTION WILL GO DOWN OVERNIGHT TUESDAY DUE TO THE LOSS OF DAYTIME HEATING. THE UPPER-LEVEL TROUGH AND ITS ASSOCIATED COLD FRONT WILL MOVE INTO THE REGION WEDNESDAY. HOT AND HUMID CONDITIONS WILL CONTINUE...BUT IT MAY NOT BE QUITE AS HOT AS MONDAY AND TUESDAY DUE TO THE FRONTAL PASSAGE. MORE SHOWERS AND THUNDERSTORMS ARE POSSIBLE...AND WITH RELATIVELY STRONG SHEAR PROFILES...SEVERE THUNDERSTORMS ARE POSSIBLE AS WELL DURING THE AFTERNOON AND EVENING. THE UPPER-LEVEL TROUGH WILL REMAIN OVERHEAD FOR WEDNESDAY NIGHT AND THURSDAY WHILE THE COLD FRONT STALLS OUT OVER CENTRAL VIRGINIA. HIGH PRESSURE WILL BUILD TO OUR NORTH AND A NORTHERLY FLOW AHEAD OF THE HIGH WILL ALLOW FOR COOLER AND LESS HUMID CONDITIONS ACROSS MOST AREAS. HOWEVER...A FEW SHOWERS AND THUNDERSTORMS CANNOT BE RULED OUT WITH THE TROUGH OVERHEAD. THE BEST CHANCE FOR CONVECTION WILL BE NEAR THE BOUNDARY ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... POSITIVELY TILTED GREAT LAKES UPPER TROUGH DIVES SOUTHEAST INTO THE NORTHEAST THURSDAY NIGHT THROUGH FRIDAY WHILE ASSOCIATED SURFACE COLD FRONT STALLS ACROSS THE MID-ATLANTIC. 12Z GFS DEFINITELY STRONGER WITH THIS SHORT WAVE...WHICH RESULTS IN FARTHER SOUTHWARD PROGRESSION OF THE SURFACE COLD FRONT. WILL MAINTAIN POPS ACROSS THE SOUTHERN HALF OF FORECAST AREAS THROUGH FRIDAY AS ECMWF SHOWS FRONT STALLED JUST OFF TO THE SOUTH ACROSS CENTRAL/SOUTHEAST VIRGINIA. TEMPS AND HUMIDITY SHOULD BE MORE COMFORTABLE NORTH OF THIS FRONT FOR FRIDAY WITH HIGHS IN THE 80S. SOUTHWEST THERMAL RIDGE BEGINS TO ADVECT TOWARD THE MID-ATLANTIC FOR THE WEEKEND WITH TERRAIN INDUCED MOUNTAIN THUNDERSTORMS MOST LIKELY DURING THIS TIME PERIOD. THERE IS THE POSSIBILITY OF COLD POOL STORM PROGRESSION FARTHER EAST DESPITE A WEAK MEAN WIND. NORTHERN EDGE OF THERMAL RIDGE ALONG WITH INCREASING FLOW ALOFT LOOK TO BRING BETTER CHANCE OF CONVECTION EVERYWHERE ON MONDAY. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT. SOUTHWEST WINDS GUSTING AROUND 20 KNOTS WILL DIMINISH AROUND SUNSET. AN ISOLATED SHOWER OR THUNDERSTORM CANNOT BE RULED OUT...BUT MOST OF THE TIME WILL BE DRY. SOUTHWEST WINDS WILL INCREASE TUESDAY WITH GUSTS AROUND 20 KNOTS DURING THE LATE MORNING THROUGH THE AFTERNOON. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE...ESPECIALLY ACROSS THE WESTERN TERMINALS DURING THE AFTERNOON...AND ACROSS THE EASTERN TERMINALS DURING THE EVENING. THUNDERSTORM COVERAGE WILL BE GREATER THAN TODAY AND SOME THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS AND HAIL. A COLD FRONT WILL MOVE INTO THE TERMINALS WEDNESDAY...BRINGING THE CHANCE FOR MORE SHOWERS AND THUNDERSTORMS. SOME THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS AND HAIL. THE BOUNDARY WILL STALL OUT ACROSS CENTRAL VIRGINIA THURSDAY. MOST OF THE TERMINALS WILL BE DRY...BUT A SHOWER OR THUNDERSTORM WILL REMAIN POSSIBLE ACROSS KDCA AND KCHO. HIGH PRESSURE WILL BUILD INTO THE REGION FOR FRIDAY...HOWEVER WARMER AND MORE HUMID CONDITIONS WILL RETURN WITH THE THREAT OF THUNDERSTORMS FOR THE WEEKEND. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC AND A SOUTHERLY FLOW WILL CONTINUE OVER THE WATERS THROUGH TUESDAY. A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL OF THE WATERS THIS AFTERNOON AND EARLY EVENING. SMALL CRAFT ADVISORIES REMAIN IN EFFECT TONIGHT AND TUESDAY MORNING FOR PORTIONS OF THE WATERS. A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL OF THE WATERS TUESDAY AFTERNOON AND EARLY EVENING...AND IT CONTINUES THROUGH TUESDAY NIGHT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. SOUTHWEST WINDS ARE EXPECTED AHEAD OF A COLD FRONT WEDNESDAY...BUT THE GRADIENT WILL NOT BE AS STRONG...SO SPEEDS HAVE BEEN CAPPED AROUND 15 KNOTS. A COLD FRONT WILL PASS THROUGH THE WATERS WEDNESDAY NIGHT INTO THURSDAY...WINDS MAY TURN AROUND TO THE NORTH-NORTHEAST BEHIND THE FRONT. SHOWERS AND THUNDERSTORMS ARE POSSIBLE DURING THE MIDDLE PORTION OF THE WEEK...ESPECIALLY TUESDAY AFTERNOON AND EVENING AS WELL AS WEDNESDAY AFTERNOON AND EVENING. THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS AND HAIL. HIGH PRESSURE WILL BUILD ACROSS THE NORTHERN PORTION OF THE BAY FOR FRIDAY...WHILE A STALLED FRONT WILL BRING A CONTINUED CHANCE OF STORMS TO THE SOUTHERN MARYLAND PORTION OF THE BAY. WARMER AND MORE HUMID CONDITIONS WILL RETURN ALONG WITH THE THREAT OF STORMS FOR THE WEEKEND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ531-537- 539>541. SMALL CRAFT ADVISORY FROM 1 PM TUESDAY TO 6 AM EDT WEDNESDAY FOR ANZ530-531-537-539>541. SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR ANZ530- 535-536-538-542. SMALL CRAFT ADVISORY FROM 1 PM TO 9 PM EDT TUESDAY FOR ANZ535- 536-538-542. SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ532>534- 543. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...AEB AVIATION...BJL/AEB MARINE...BJL/AEB

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