Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 021033 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 633 AM EDT WED SEP 2 2015 .SYNOPSIS... A WEAK TROUGH OF LOW PRESSURE WILL PERSIST OVER THE MID ATLANTIC THROUGH THURSDAY WITH WEAK HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. STRONGER HIGH PRESSURE THEN SLOWLY DROPS DOWN FROM THE NORTHEAST STATES FRIDAY INTO THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST GOES WATER VAPOR IMAGERY CENTERS SUBTROPICAL HIGH PRESSURE OFF THE SOUTHEAST COAST...WITH THE RIDGE AXIS EXTENDING NWD ALONG THE ERN SEABOARD. AT THE SFC...HIGH PRESSURE REMAINS CENTERED OVER THE OH VALLEY. DEWPOINTS HAVE CLIMBED BACK INTO THE LOW 70S...RESULTING IN MILD TEMPS IN THE UPPER 60S TO LOW 70S EARLY THIS MORNING. PATCHY GROUND FOG LIMITED TO MAINLY SE VA/NE NC AND THE MD ERN SHORE...AND WILL QUICKLY BURN OFF AFTER SUNRISE. FOR TODAY...A COMPACT UPPER LOW OVER THE OH VALLEY WILL OPEN AND DROP SEWD TOWARD THE MID-ATLANTIC REGION. SHORTWAVE ENERGY AND UPSLOPE FLOW WILL PRODUCE SHOWERS/THUNDERSTORMS OVER THE CENTRAL APPALACHIANS THIS AFTERNOON. LOWER RES MODELS PUSH THIS CONVECTION EWD INTO THE PIEDMONT AND CENTRAL VA LATE THIS AFTERNOON AND EARLY EVENING...BUT HI RES GUIDANCE LIMITS ANY PRECIP TO THE PIEDMONT. A WARM/MOIST AND MARGINALLY UNSTABLE AIR MASS WILL BE IN PLACE OVER THE LOCAL AREA...BUT DOWNSLOPE WINDS...LIMITED MOISTURE AND WEAK FLOW/SHEAR WILL LIMIT CONVECTION POTENTIAL. HAVE CAPPED AT LOW END CHANCE POPS. SLIGHT INCREASE IN LOW LEVEL THICKNESSES AND H85 TEMPS +16 TO 18 (+1 STD DEV) WILL RESULT IN A DEG OR TWO OF WARMING TODAY COMPARED TO 24 HOURS AGO. HIGHS FORECAST IN THE LOW 90S...EXCEPT UPPER 80S ALONG THE COAST. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... ANOMALOUS UPPER RIDGE BUILDS EWD DURING THE SHORT TERM PERIOD...RESULTING IN GENERALLY WEAK NWLY FLOW ALOFT. AN UPPER TROUGH DROPS OVER THE CANADIAN MARITIMES THURS...PUSHING AN ASSOCIATED SFC LOW OFF THE ERN CANADIAN COST. A WEAK SFC TROUGH WILL EXTEND SWD OVER ERN VA. SHORTWAVE ENERGY CONTINUES TO DROP OVER THE SRN LOCAL AREA THURS AFTERNOON...RESULTING IN SUBTLE FORCING FOR ASCENT ALONG THE SFC TROUGH. WARM/MOIST AIR MASS REMAINS IN PLACE. WEAK FLOW UNDER THE RIDGE PRODUCES LITTLE SHEAR...SO ORGANIZED/WIDESPREAD CONVECTION IS NOT EXPECTED. WILL RETAIN SLIGHT CHANCE TO LOW END CHANCE POPS...FOCUSED ALONG THE SFC TROUGH IN THE SE. H85 TEMPS OF +16 TO 18C (+1 STD DEV) WILL AGAIN RESULT IN TEMPS IN THE LOW 90S. MILD THURS MORNING WITH LOWS IN THE UPPER 60S TO LOW 70S. LARGE SCALE CONFLUENCE ACROSS SERN CANADA IN WAKE OF THE DEPARTING UPPER TROUGH WILL ALLOW STRONG SFC HIGH PRESSURE TO BUILD SEWD INTO NEW ENGLAND FRIDAY. THIS WILL PUSH A BACKDOOR FRONT INTO THE REGION. WEAK PERTURBATIONS IN NWLY FLOW MAY BE ENOUGH TO PROVIDE SUBTLE FORCING...BUT MOISTURE REMAINS LIMITED WITH NEAR NORMAL PWATS AND 60- 70 PCT 1000-500MB MEAN RH. WILL MAINTAIN LOW END CHANCE POPS. HIGH PRESSURE RIDGING INTO THE REGION WILL RESULT IN NELY/ONSHORE FLOW AND COOLER TEMPS COMPARED TO THURS. HIGHS FORECAST IN THE MID TO UPPER 80S. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... GOING WITH A BLEND OF THE 12Z GFS/12Z ECMWF FOR THE EXTENDED PERIOD. INITIALLY...20-30% POP FOR A SHOWER AND MAYBE A TSTM FRI NGT THRU SAT AFTN...AS WEAK BACKDOOR FRONT DROPS THRU THE AREA...AS HI PRES BLDS FM ERN CANADA SWRD TO ALNG THE NEW ENGLAND CST. THEN...WILL HAVE DRY WX FM SAT NGT THRU TUE...AS THE CNTR OF HI PRES BLDS DOWN OVR THE MID ATLC REGION AND JUST OFFSHR. HIGHS WILL BE 80 TO 85 SAT AND SUN...GENERALLY IN THE MID 80S MON...AND IN THE MID TO UPR 80S TUE. LOWS WILL BE IN THE MID 60S TO LWR 70S SAT MORNG...IN THE 60S SUN AND MON MORNGS...AND IN THE MID 60S TO NEAR 70 TUE MORNG. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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ANY REMAINING FOG BURNS OFF NEXT HR OR SO WITH VFR CNDTNS AFTR THAT. XPCT ANTHR DAY OF SEA BREEZE DVLPMNT SO ADDED ANTHR LINE TO THE CSTL TAFS SITES FOR THIS AFTR 16Z. NEXT CONCERN IS FOR ISLTD CONVECTION DVLPNG ALONG THE SEA BREEZE BNDRY MUCH LIKE YSTRDY ALONG WITH SCT CONVECTION THAT DVLPS OVR THE MTS THEN DRIFTS EASTWRD INTO THE PIEDMONT DRNG THE LATE AFTRN/ERLY EVE. KEPT PCPN OUT OF FCST ATTM GIVEN LOW CONFIDENCE OF WHERE ANY CONVECTION DVLPS. OUTLOOK...DRY WEATHER IS EXPECTED THROUGH SUNDAY XCPT FOR SCT PSBL DIURNAL CONVECTION THU/FRI. ALSO LOOK FOR SOME STRATUS AND FOG AT SOME OF THE TAF SITES WITHIN A FEW HOURS OF SUNRISE.
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&& .MARINE... NO HEADLINES IN SHORT TERM. WNDS REMAIN AOB 10 KTS ALONG WITH SEAS AOB 2 FT THRU THU NIGHT AS HIGH PRS DOMINATES. XPCT ONSHORE SEA BREEZES BOTH THIS AFTRN AND THU AFTRN WITH WNDS BCMG MORE WSW AT NIGHT. DATA SUGGESTS HIGH PRS TO THE N WILL BE STRONG ENUF TO PUSH A BKDR CDFRNT S ACROSS THE WTRS FRI. THE HIGH WILL BE SLOW TO MOVE OFF THE NEW ENGLAND COAST THIS WKEND. THIS SCENARIO RESULTS IN A XTNDD PRD OF NE FLOW. DATA EVEN SUGGESTS SOLID SCA CNDTNS DVLPNG N-S FRI NIGHT AND CONTG SAT AS WNDS INCRS TO BTWN 15-25 KTS ALONG WITH BLDG SEAS TO BTWN 4-6 FT. IN ADDITION...THE ONSHORE FLOW WILL LIKELY RESULT IN NEARSHORE WAVES OF 3-4 FT WHICH WILL INCRG THE RIP CURRENT THREAT FOR THE UPCOMING HOLIDAY WKEND. DESPITE BEING OUT 3 DAYS...TIDAL GUID SUGGESTS TIDES BUILDING TO BTWN 1/2 TO 1 FOOT ABOVE NRML BY SAT...BUT REMAINING BLO MINOR FLOODING THRESHOLDS. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...MAS NEAR TERM...SAM SHORT TERM...SAM LONG TERM...AKQ AVIATION...MPR MARINE...MPR

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