Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 041807 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 207 PM EDT TUE AUG 4 2015 .SYNOPSIS... A COLD FRONT CROSSES THE AREA LATER TODAY..THEN STALLS OVER THE CAROLINAS TONIGHT INTO THURSDAY AS LOW PRESSURE MOVES NORTHEAST ALONG THE MID ATLANTIC COAST. THE ENTIRE SYSTEM MOVES OFF THE MID ATLANTIC COAST BY FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... WENT AHEAD AND BUMPED UP POPS ACROSS NC / SERN VA FOR CONVECTION DVLPNG ACROSS NC ASSCTD WITH CSTL LOW MOVG NORTH. OTW...CRNT FCST ON TRACK WITH ONLY MINOR CHANGES TO THE GRIDS THIS MORNING. ALSO BUMPED UP POPS SOME THIS EVENING AS IT APPEARS ANY CONVECTION WITH THE FROPA CONTS THRU MIDNIGHT OVER MOST OF THE FA...A BIT LATER ALONG THE COAST DUE TO THE CSTL LOW. PVS DSCN: SCT-BKN MID TO HIGH LEVEL CLOUDS WILL CROSS THE FA THROUGH MID MORNING. FOR THE REST OF TODAY AND TONIGHT...MID AND UPPER LEVEL TROUGHING RESIDES OVER THE NE CONUS FROM THE GREAT LAKES TO NEW ENGLAND... RESULTING IN WLY FLOW ALOFT OVER THE MID ATLANTIC REGION. MEANWHILE...A WEAK SFC TROUGH EXTENDS FROM THE DELMARVA INTO THE NC COASTAL PLAIN AND IS EXPECTED TO SHIFT TWD THE COAST THROUGHOUT THE DAY. MODEL CROSS SECTIONS AND SOUNDINGS INDICATE THAT MOISTURE IS RATHER SHALLOW/LIMITED AND OVERALL ATMOSPHERIC LIFT IS WEAK. HOWEVER...SHOWERS AND THUNDERSTORMS SHOULD DEVELOP ALONG AND EAST OF THE TROUGH AXIS AS A SFC COLD FRONT AND ITS ASSOCIATED SHORTWAVE ENERGY CROSS THIS BOUNDARY. IN ADDITION...THE FRINGE OF A JET STREAK IS EXPECTED TO CROSS THE DELMARVA REGION THIS AFTN/EVENING (60-80KT) THUS SUPPORTING BETTER CHANCES FOR THUNDERSTORM DEVELOPMENT ACROSS NRN COUNTIES (MAINLY NORTH OF A LOUISA-RICHMOND-MELFA LINE). WITH PWATS ON THE ORDER OF 1.00 TO 1.50 INCHES...QPF AMOUNTS WILL BE RATHER LIGHT WITH 0.25 INCHES OR LESS OF RAINFALL ANTICIPATED. TEMPERATURES WILL BE SLIGHTLY WARMER THAN MONDAY AS THE THERMAL TROUGH AXIS NUDGES FARTHER NWD INTO CNTRL VA TODAY AND BREEZY SSW WINDS PROMOTE AFTN MIXING. EXPECT HIGHS IN THE LOW-MID 90S INLAND AND UPPER 80S TO LOW 90S AT THE IMMEDIATE COAST. SHOWER ACTIVITY SHOULD TAPER OFF LATE THIS EVENING AND COME TO AND END ALONG THE COAST AROUND MIDNIGHT. HIGH PRESSURE STARTS TO BUILD IN FROM THE W-NW LATE TONIGHT AND WILL HELP TO COOL OVERNIGHT TEMPS INTO THE UPPER 60S FOR FAR NWRN COUNTIES. LOW-MID 70S INLAND...MID-UPPER 70S CLOSER TO THE COAST. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... HIGH PRESSURE CONTINUES TO BUILD INTO THE REGION FROM THE W-NW AS THE SFC TROUGH GETS COMPRESSED AND THE SFC COLD FRONT BECOMES MORE EAST TO WEST ORIENTED ACROSS NC. THERE IS EVEN LESS MOISTURE/LIFT AVAILABLE TO WORK WITH ON WEDNESDAY AND ANTICIPATE AN OVERALL DRY FORECAST...WITH THE EXCEPTION OF LOCATIONS ALONG AND SOUTH OF THE VA/NC WHERE A SLIGHT CHANCE OF SHOWER/STORMS WILL BE POSSIBLE LATE IN THE AFTN THROUGH THE EVENING. SLIGHTLY COOLER AND MORE COMFORTABLE WITH HIGHS IN THE LOWER 90S (MID-UPPER 80S AT THE BEACHES) AND DEWPOINTS IN THE LOW-MID 60S INLAND AND UPPER 60S TO LOWER 70S CLOSER TO THE COAST. LOWS WEDNESDAY NIGHT IN THE MID-UPPER 60S FAR NRN COUNTIES...LOWER 70S INLAND...MID 70S AT THE COAST. THE FRONT REMAINS STALLED ACROSS THE CAROLINAS AND POSSIBLY FAR SE VA INTO THURSDAY. WEAK LOW PRESSURE IS EXPECTED TO DEVELOP ALONG THIS BOUNDARY AND LIFT A WARM FRONT TWD THE FA ON THURSDAY NIGHT...BRINGING MORE WIDESPREAD SHOWERS AND THUNDERSTORMS TO THE AREA FROM THE AFTN THROUGH THE OVERNIGHT HOURS. THIS SCENARIO IS SUPPORTED BY PWATS INCREASING TWD 2.00 INCHES THURSDAY NIGHT AS WELL AS CROSS SECTIONS SHOWING AMPLE (AND DEEPER) ATMOSPHERIC LIFT AS THE THETA-E RIDGE AXIS BUILDS ALONG THE WARM FRONTAL FEATURE. QPF AMOUNTS COULD BE PRETTY HEFTY...ESPECIALLY UNDER STRONGER STORM CORES... WITH RAINFALL AMOUNTS OF 0.30 TO 1.00 INCHES POSSIBLE DURING THIS 24 HOUR PERIOD. COOL HIGH TEMPS CONTINUE ON THURSDAY WITH SLIGHTLY WARMER DEWPOINTS BRINGING AN UPTICK IN HUMIDITY LEVELS. EXPECT HIGHS IN THE MID-UPPER 80S NW OF RICHMOND TO THE LOWER 90S FOR METRO RICHMOND AND LOCATIONS TO THE SE. LOWS THURSDAY NIGHT COULD BE TRICKY DUE TO RAIN-COOLED AREAS. HOWEVER... TEMPS ARE CURRENTLY EXPECTED TO RANGE FROM THE UPPER 60S NW TO LOW-MID 70S SE. && .LONG TERM /FRIDAY THROUGH MONDAY/... UNSETTLED WX TO START OFF THE LONG TERM PERIOD WITH FREQUENT CHANCES OF RAIN DUE TO AN UPR-LEVEL TROF OVER THE FAR ERN CONUS AND TRANSIENT SHORTWAVE TROFS PASSING THRU THE MID ATLC REGION. 12Z GFS/ECMWF CONTINUE TO DIFFER ON EXACT TIMING OF PCPN...BUT FOR NOW THE FORECAST CALLS FOR A 30-40% CHANCE OF RAIN THU NIGHT THRU FRI NIGHT. DRYING TREND THEN COMMENCES INTO THIS WEEKEND AS THE UPR-LEVEL TROF AXIS PULLS OFFSHORE AND SFC HI PRES BLDS IN FM THE W. AS FOR TEMPS...HIGHS WILL RANGE THRU THE 80S EVERY DAY WITH LOWS AVGG IN THE MID 60S TO LWR 70S. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... LOW PRESSURE IS SITUATED NEAR MYRTLE BEACH SC EARLY THIS AFTERNOON WITH A WEAK SURFACE RIDGE OF HIGH PRESSURE N OF THE LOW ACROSS SRN VA/NRN NC. A BAND OF SHRA/TSRA LIFTED N FROM THE LOW AND BRIEFLY AFFECTED ECG...BEFORE DISSIPATING. FARTHER NW...A COLD FRONT EXTENDS FROM ERN PA BACK THROUGH THE CENTRAL APPALACHIANS. SHRA/TSRA ARE EXPECTED TO DEVELOP AHEAD OF THIS BOUNDARY LATER THIS AFTERNOON ACROSS THE HIGHER TERRAIN OF WV/WRN MD/NRN VA...BEFORE TRACKING EWD TOWARD THE DELMARVA THIS EVENING. SBY HAS THE BEST POTENTIAL FOR THUNDER THIS EVENING...SO A TEMPO GROUP FOR THUNDER HAS BEEN INCLUDED BEGINNING AT 23Z. FOG IS ALSO POSSIBLE LATER TONIGHT AT SBY...BUT WILL BE CONDITIONAL ON THE AMOUNT OF RAIN THAT FALLS. DRIER CONDITIONS ARRIVE LATER TONIGHT INTO WEDNESDAY AS THE FRONT PUSHES OFF THE COAST. MORE UNSETTLED CONDITIONS ARRIVE LATER THURSDAY INTO FRIDAY AS LOW PRESSURE AND ITS ASSOCIATED COLD FRONT AFFECT THE AREA. HIGH PRESSURE BUILDS IN FROM THE N SATURDAY AND SUNDAY. && .MARINE... 1PM UPDATE... SCA HAZARDS OVER THE BAY HAVE BEEN ALLOWED TO EXPIRE AS WINDS HAVE DROPPED TO AOB 15 KT. STILL A CHANCE OF ANOTHER ROUND OF SCA CONDS THIS EVENG BUT NOT CONFIDENT ENUF ATTM TO ISSUE SO WILL REASSESS WITH THE 4PM UPDATE. PREVIOUS DISCUSSION... S/SW WINDS HAVE DIMINISHED OVER THE LOWER JAMES SO HAVE ALLOWED SCA TO END THERE AS WELL AS COASTAL WATERS S OF PARRAMORE ISLAND WHERE SEAS ARE BELOW 5 FT. SEAS AVG 4-6 FT ACRS NRN COASTAL WATERS AND HAVE EXTENDED THE HEADLINES THERE THROUGH 10 PM TONIGHT. SEAS AVG 3-4 FT ELSEWHERE. WAVES IN THE BAY AVG 2-3 FT. SFC PRESSURE GRADIENT AND LOW LEVEL NOCTURNAL JET INFLUENCES LOOK TO WEAKEN BY LATER THIS MORNING SO SHOULD SEE WINDS TREND DOWN TO AVG 10-15 KT AND WILL PROBABLY BE ABLE TO END THE BAY HEADLINES. HOWEVER...EXPECT WINDS TO INCREASE AGAIN LATER THIS AFTN AND MAY NEED ANOTHER ROUND OF SCA`S FOR THE BAY (OR IF WINDS DO NOT DROP OFF LATER THIS MORNING DAYSHIFT MAY JUST EXTEND SCA`S THROUGH THE AFTN/EVENING). THE FRONT DROPS THRU THE AREA LATE TONIGHT...WITH RELATIVELY LIGHT N/NW FLOW WED FOLLOWING THE FROPA. SUB-SCA CONDS THEN EXPECTED INTO THU NIGHT...THOUGH PATTERN NOW SUGGESTS THE PRESENCE OF A WEAK WARM FRONT LIFTING THROUGH THE WATERS ON FRI AND CONDITIONS MAY APPROACH SCA THRESHOLDS FOR THE BAY. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ650- 652. && $$ SYNOPSIS...BMD NEAR TERM...BMD/MPR SHORT TERM...BMD LONG TERM...MAS AVIATION...AJZ MARINE...LKB/MAS

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