Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 232321 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 721 PM EDT WED APR 23 2014 .SYNOPSIS... COOL CANADIAN HIGH PRESSURE SLOWLY BUILDS IN FROM THE NORTHWEST OVERNIGHT. HIGH PRESSURE THEN SLIDES OVER THE REGION INTO THURSDAY MORNING...LOCATING OFF THE SOUTHEAST COAST THURSDAY AFTERNOON. A SERIES OF WEAK FRONTS WILL CROSS THE AREA FRIDAY INTO THE WEEKEND. A PERIOD OF UNSETTLED WEATHER IS EXPECTED OVER THE AREA EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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UPPER TROUGH AXIS HAS SHIFTED OFFSHORE PER LATEST WATER VAPOR IMAGERY...AS SFC HIGH PRESSURE BUILDS SWD FROM THE GREAT LAKES REGION. THE RESULT WILL BE CLEAR SKIES OVERNIGHT AND DECREASING NW WINDS. WITH THE HIGH PRESSURE TO THE WEST OF THE AREA...ANOTHER ROUND OF CAA OVERNIGHT WILL PUSH TEMPS INTO THE MID-UPPER 30S INLAND AND INTO THE LOW 40S NEAR THE COAST. WINDS WILL NOT COMPLETELY DE-COUPLE TONIGHT...RANGING FROM 5-10 MPH INLAND TO 10 TO 15 NEAR THE COAST. COMBINE LIGHT MIXING WITH RATHER DRY GROUND CONDITIONS AND LOW DEWPOINTS...DO NOT ANTICIPATE WIDESPREAD FROST AND WILL LEAVE OUT OF GRIDS. HOWEVER...PATCHY FROST IS POSSIBLE IN SHELTERED LOCALES.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... SFC HIGH PRESSURE CENTERS OFF THE SE COAST THURS AS AN UPPER RIDGE BUILDS OVER THE ERN CONUS. UPPER TROUGH OVER THE INTERMOUNTAIN WEST WILL DE-AMPLIFY AND EJECT NEWD INTO THE PLAINS THURS...PUSHING AN ASSOCIATED COLD FRONT INTO THE MS VALLEY. FLOW RETURNS TO THE SOUTH LATE THURS-THURS NIGHT AS A WARM FRONT LIFTS OVER THE REGION. MID-LEVEL WLY FLOW OVER THE GULF STATES INTO THE MID-ATLANTIC WILL PREVENT MUCH OF A MOISTURE RETURN INTO THE REGION....SO DRY CONDITIONS WILL PREVAIL. NWLY WINDS WILL NOT BE AS STRONG THURS AFTERNOON...BUT MIN RH VALUES IN THE UPPER TEENS- LOW 20S AND DRY FUELS WILL AGAIN RESULT IN POTENTIAL FIRE WX CONCERNS. PLEASE REFER TO FIRE WEATHER SECTION BELOW FOR MORE INFORMATION. RIDGE AXIS PUSHES OFFSHORE FRI MORNING AS THE UPPER WAVE REACHES THE OH VALLEY. QUESTIONS STILL EXIST ON STRENGTH OF THE UPPER WAVE AS IT CROSSES THE MID-ATLANTIC REGION FRI AFTERNOON...WITH THE LATEST GFS TRENDING SHARPER THAN ITS PREVIOUS RUNS AND COMING MORE IN LINE WITH ITS NAM/ECMWF COUNTERPARTS. COLD FRONT WILL PUSH ACROSS THE REGION FRI AFTERNOON-EVENING. SHORT LIVED LOW-LEVEL SW FLOW WILL BE ABLE TO ADVECT MODEST PRECIP WATER VALUES OF 1-1.25 INCHES INTO THE REGION...BUT DEWPOINTS ONLY PROGGED TO WARM INTO THE UPPER 40S TO NEAR 50 FRI. WITH THE LOCAL AREA IN THE WARM SECTOR FRI...TEMPS WILL WARM INTO THE UPPER 70S TO NEAR 80 (DEPENDING ON FRONTAL TIMING). COMBINATION OF WARM TEMPS AND THETA-E ADVECTION WILL RESULT IN A MARGINALLY UNSTABLE AIRMASS (MLCAPE <500 J/KG)...MOSTLY OVER ERN VA/NERN NC. ALSO...LITTLE INSTABILITY/LIFT PROGGED IN THE MIXED PHASE LAYER SO ANTICIPATE ONLY ISOLATED/SLIGHT CHANCE THUNDER IN CONVECTION. JUST LIKE YESTERDAYS FRONT...BIGGEST LIMITATIONS ARE WSW FLOW AND LOW DEWPOINTS. SHEAR IS ALSO MARGINAL (~30-35 KT) SO DO NOT ANTICIPATE ORGANIZED CONVECTION ALONG THE WEAKLY FORCED FRONT. WITH THAT SAID...WILL MAINTAIN CHANCE POPS OVER THE REGION FRI AFTERNOON ALONG/BEHIND THE FRONT. QPF AMOUNTS WILL GENERALLY BE LESS THAN ONE TO TWO TENTHS. FRONT PUSHES OFFSHORE FRI NIGHT AS A SECONDARY DRY COLD FRONT ASSOCIATED WITH AN UPPER LOW OVER THE GREAT LAKES APPROACHES FROM THE NW. BREEZY WLY/DOWNSLOPE FLOW SAT AND INCREASING LOW LEVEL THICKNESS VALUES WILL RESULT IN DAYTIME TEMPS AROUND 80 DEGS MOST LOCALES...EVEN BEHIND FRIDAYS FRONT. NARROW BAND OF MOISTURE AND MEASURABLE PRECIP FORECAST TO REMAIN NORTH OF THE LOCAL AREA LATE SAT-SAT EVENING. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... MODELS CONTINUE TO POINT TO A HIGHLY AMPLIFIED/BLOCKY PATTERN OVER THE CONUS NEXT WEEK...RESULTING IN AN INCREASINGLY WET PERIOD. MODELS CONTINUE TO STRUGGLE WITH THIS BLOCKY FLOW...MAINLY IN LOCATION OF FRONTAL BOUNDARY PROGGED TO BE DRAPPED ACROSS THE RGN ALONG WITH TIMING OF SEVERAL BATCHES OF MSTR PROGGED TO ROTATE NE FROM THE DEEP SOUTH. WHAT TODAYS MODELS SHOW DIFFERENT FROM YSTRDYS IS A SLOWER START TO THE PCPN MON...SOMEWHAT HIGHER CONFIDENCE FOR AN EXTNDD PRD OF WETNESS FROM MON NITE THRU WED ALONG WITH A FRONTAL BOUNDARY THAT WILL LIKELY PLAY HAVOC WITH TEMPS. KEPT SUN DRY / SEASONABLE AS H5 RIDGE BUILDS ACROSS THE AREA. WARM FRONT APPRCHS THE RGN FROM THE SW SUN NIGHT...BUT GUID SUGGESTS ANY MOISTURE STAYS W OF FA THRU 12Z MON. LOWS SAT / SUN NIGHTS IN THE M40S-L50S. HIGHS SUN 70-75 WEST OF THE BAY...M-U60S ALONG THE COAST. FORECAST RATHER PROBLEMATIC NEXT WEEK AS THE MODELS DIFFER ON WHERE THIS FRONTAL BNDRY SETS UP. THIS WILL LIKELY DETERMINE TMPS AND PCPN TYPES (CONVECTIVE VS STRATIFORMED RAIN). UPR LVL LOW PROGGED TO SLOWLY EJECT EAST FROM THE NATIONS MID SECTION MON NIGHT ONLY TO THE OHIO VLLY BY WED. A MOIST E-SE FLOW WILL LIKELY ADD TO THE MOISTURE CONTENT RESULTING IN PERIODIC CHCS FOR PCPN THRU THE PRD. FRNTL BNDRY MAY ALSO TRY TO MAKE A RUN FARTHER NORTH BY WED AS SFC LOW BEGINS TO CROSS THE MTS. TRAILING COLD FRONT WILL EVENTUALLY PUSH ALL THIS OUT TO SEA...BUT THAT MIGHT NOT BE UNTIL THURSDAY. UPSHOT WILL CARRY HIGH CHC POPS (SHWRS) MON THROUGH WED. TMPS COOLEST (L-M60S) ALONG THE COAST DUE TO AN ONSHORE FLOW. HIGHS U60S-L70S WEST OF THE BAY. LOWS IN THE 50S. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... AS THE FRONT CONTINUES TO PUSH FARTHER OFF SHORE...THE PRESSURE GRADIENT WILL TIGHTEN UP NEAR THE IMMEDIATE COAST WHERE WNW-NW WINDS SHOULD AVERAGE CLOSE TO 20G30KT BEFORE TAPERING OFF DURING THE EVENING AND OVERNIGHT HOURS. NW WIND SPEEDS BRIEFLY INCREASE THU MORNING AND THEN DROP OFF THROUGH THE AFTN AS HIGH PRESSURE SLIDES ACROSS THE AREA AND BECOMES LOCATED OFF THE SOUTHEAST COAST BY THU EVENING. THE NEXT COLD FRONT APPROACHES THE REGION THU NIGHT...CAUSING NW WINDS TO BACK AROUND TO THE S-SE. THE FRONT IS EXPECTED TO CROSS THE MID ATLANTIC REGION FRI EVENING...BRINGING SHOWERS AND A SLIGHT CHANCE FOR THUNDERSTORMS TO AREA TAF SITES. BEHIND THIS FRONT...WINDS WILL GENERALLY BE NLY AROUND 15 KT OR LESS THROUGH THE REST OF THE WEEKEND. && .MARINE... MIXING STILL PRODUCING GUSTY WINDS LATE THIS AFTRN ACROSS THE WATERS. EXPECT WINDS OVER THE RIVERS AND CURRITUCK SOUND TO SLOWLY DMNSH NXT FEW HRS...SO SCA WILL CONTINUE THRU 7 PM THERE....10 PM FOR LWR JAMES IVOF ORF. SECONDARY SURGE NOTED IN MODELS KEEPS SCA HEADLINES FOR CHES BAY / CSTL WTRS INTO WED MORNING. 25-30 KT GUSTS PSBL AS WELL. HIGH PRS BUILDS INTO THE AREA WED AFTRN THEN SHIFTS OFFSHORE WED NITE AND THURSDAY. THIS RESULTS IN DMNSH WINDS AND IMPROVING SEAS. THUS...SCA`S WILL GRADUALLY END WED...LATEST OVR COASTAL WATERS WHERE IT MAY TAKE SEAS A FEW HRS LONGER TO DROP BLO 5 FT. SE FLOW BECOMES S THEN SW AS BY FRI AS RETURN FLOW ESTABLISHES ITSELF ON BACK SODE OF RETREATING HIGH. NEXT FRNT PROGGED ACROSS THE RGN FRI NIGHT WITH A SECONDARY TROF CROSSING THE WATERS SAT. EXPECT CONDITIONS TO REMAIN BLO SCA LEVELS THROUGH SAT...ALTHOUGH ANOTHER WEAKER NW SURGE IS PSBL SAT AFTRN. && .FIRE WEATHER...
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DRY CONDITIONS (MIN RH VALUES 15-25%) WILL OCCUR AGAIN ON THURSDAY. HOWEVER...WINDS WILL BE LIGHTER THAN TODAY. THIS WILL PRECLUDE THE NEED FOR ANY RED FLAG WARNINGS OVER THE LOCAL AREA. NW WINDS DO INCREASE TO AROUND 15 MPH WITH GUSTS 20-25 MPH DURING THE LATE MORNING/EARLY AFTN HOURS ON THE LOWER MD EASTERN SHORE. GIVEN HOW LOW RH VALUES WILL BE THURS AFTN COUPLED WITH LOW FUEL MOISTURE CONDITIONS...HAVE OPTED FOR AN INCREASED FIRE DANGER STATEMENT FOR OUR MD COUNTIES...AFTER COORDINATION WITH MD FIRE OFFICIALS.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...INCREASED FIRE DANGER FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR MDZ021>025. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT THURSDAY FOR ANZ630>632- 634. SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ638. SMALL CRAFT ADVISORY UNTIL 4 PM EDT THURSDAY FOR ANZ650-652- 654-656-658.
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&& $$ SYNOPSIS...SAM NEAR TERM...JDM/SAM SHORT TERM...SAM LONG TERM...MPR AVIATION...DAP MARINE...MPR FIRE WEATHER...JDM

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