Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 311957 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 357 PM EDT SUN MAY 31 2015 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN ANCHORED OFF THE MID ATLANTIC COAST TONIGHT INTO MONDAY AS A SLOW MOVING COLD FRONT APPROACHES FROM THE NORTHWEST. THIS COLD FRONT WILL DROP INTO THE REGION MONDAY NIGHT...AND STALL OVER THE AREA TUESDAY INTO WEDNESDAY.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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GOES WV IMAGERY SHOWS A STRONG UPPER RIDGE ANCHORED OVER THE WRN ATLANTIC...WITH A TROUGH OVER THE CENTRAL US. A SHORTWAVE TROUGH IS EMBEDDED WITHIN THE SW FLOW REGIME BETWEEN THE LONGWAVE TROUGH/RIDGE COUPLET AND IS LIFTING TOWARD THE ERN GREAT LAKES. AT THE SURFACE...WEAK LOW PRESSURE IS DEPICTED OVER ERN OH...WITH A WARM FRONT EXTENDING W-E ACROSS PA...AND A COLD FRONT TRAILING BACK THROUGH THE TENNESSEE VALLEY. MORE WIDESPREAD CONVECTION HAS DEVELOP IN VICINITY OF THE WARM FRONT OVER PA...WITH ISO-SCT CONVECTION EXTENDING DOWN THROUGH THE APPALACHIANS AND PIEDMONT. LOCALLY...WE HAVE BEEN ON THE ERN FRINGE OF THIS ACTIVITY DURING THE AFTERNOON...WITH ISO SHOWERS/TSTMS OCCURRING FROM THE RIC METRO TO THE ERN VA PIEDMONT. MLCAPE VALUES ARE ON THE ORDER OF 1000-1500 J/KG...AND DEEP LAYER SHEAR IS MINIMAL...SO THE CONVECTION LOCALLY HAS BEEN SINGLE CELL IN NATURE. SKY COVER IS PARTLY TO MOSTLY SUNNY THIS AFTERNOON (OUTSIDE OF SHOWERS/TSTMS) WITH TEMPERATURES RANGING FROM 85-90F...WITH LOCALLY MILDER VALUES ALONG THE IMMEDIATE COAST. INITIAL SHOWERS/TSTMS SHOULD DISSIPATE QUICKLY THIS EVENING. THE MID-LEVEL FLOW SHIFTS ENOUGH OVERNIGHT IN RESPONSE TO THE TROUGH TRACKING N OF THE REGION...WHICH COULD ALLOW FOR SOME CONVECTION OVER THE HIGHER TERRAIN TO MOVE E. THIS HOWEVER IS A RATHER LOW PROBABILITY...WITH ONLY A 20-30% POP N OF ROUGHLY A FVX-RIC-WAL LINE. OTHERWISE...PARTLY CLOUDY TO MOSTLY CLEAR TONIGHT. LOWS SHOULD RANGE FROM THE MID TO UPPER 60S.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
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12Z/31 NUMERICAL MODELS CONTINUE THE TREND OF SLOWING DOWN THE PROGRESSION OF THE LONGWAVE PATTERN EARLY THIS WEEK...WHICH IS NOT THAT MUCH OF A SURPRISE GIVEN THE BLOCKY NATURE OF THE PATTERN OVER THE PAST SEVERAL WEEKS. THE TROUGH PRESENTLY OVER THE CENTRAL US IS EXPECTED TO GRADUALLY SHIFT E MONDAY-WEDNESDAY AND CLOSE OFF IN VICINITY OF THE TENNESSEE VALLEY. THE GREAT LAKES TROUGH IS EXPECTED TO TRACK ENE THROUGH THE SAINT LAWRENCE VALLEY...WITH WILL EVENTUALLY ALLOW THE SURFACE COLD FRONT TO DROP INTO THE REGION. BASED ON THE LATEST MODEL TRENDS...THE SURFACE COLD FRONT WILL DROP INTO THE REGION MONDAY NIGHT...BEFORE STALLING OVER THE AREA TUESDAY-WEDNESDAY. THE RIDGE OFF THE COAST SHOULD REMAIN THE DOMINANT FEATURE LOCALLY MONDAY...AT LEAST UNTIL LATE AFTERNOON/EVENING. HIGHS ARE EXPECTED TO BE AROUND +1 ST DEV...WITH READINGS RANGING FROM 85-90F...AND LOCALLY MILDER VALUES ALONG THE IMMEDIATE ATLANTIC COAST. THE DAY BEGINS PARTLY TO MOSTLY SUNNY...BEFORE CLOUDS INCREASE OVER NW PORTIONS LATER IN THE DAY DUE TO THE DEVELOPMENT OF SHOWERS/TSTMS OVER THE NRN MID ATLANTIC. BY LATER AFTERNOON AND EVENING...POPS RANGE FROM 40-60% ACROSS NW PORTIONS...WHILE REMAINING BELOW 15% ACROSS FAR SE PORTIONS. CHC POPS WILL CONTINUE OVERNIGHT MONDAY NIGHT ACROSS THE NW HALF OF THE AREA. OTHERWISE...WARM AND HUMID WITH LOWS IN THE MID/UPPER 60S. A BETTER CHC FOR SHOWERS/TSTMS AND BENEFICIAL RAIN ARRIVES FOR MOST OF THE AREA BY TUESDAY AFTERNOON. NRN STREAM ENERGY PUSHES OFFSHORE AS THE CLOSED UPPER LOW REMAINS OVER THE GULF STATES. LARGE SCALE CONFLUENCE WILL REMAIN OVER SE CANADA...KEEPING SFC HIGH PRESSURE NORTH OF THE REGION. LIKELY POPS ARE FORECAST FOR MOST OF THE AREA...WITH THE SURFACE BOUNDARY OVER THE REGION...AND ACTUALLY SOME UPPER SUPPORT IN THE RRQ OF A ~100KT JET OVER SE CANADA. LOCALLY HEAVY RAINFALL IS POSSIBLE AS ANOMALOUS PWATS COMBINE WITH WEAK STEERING FLOW. CLOUD COVER/PRECIP WILL LIMIT INSTABILITY...WITH ONLY 15-20 KT EFFECTIVE SHEAR EXPECTED...LIMITING THE POTENTIAL FOR SEVERE WEATHER. COOLER TUE WITH HIGHS IN THE LOW-MID 80S (COOLER ALONG THE COAST AND OVER THE NW PIEDMONT). THE FRONT LINGERS OVER THE REGION INTO WEDNESDAY. THE UPPER SUPPORT IS WEAKER...WHICH SHOULD SOMEWHAT REDUCE COVERAGE...BUT STILL 30-50% POPS ARE FORECAST. MOSTLY CLOUDY AND COOLER WITH HIGHS AVERAGING FROM 75-80F. MORNING LOWS SHOULD BE IN THE 60S. GEFS/SREF PROBABILITIES INDICATE A WIDESPREAD BENEFICIAL ONE HALF INCH TO ONE INCH IS EXPECTED ACROSS MUCH OF THE LOCAL AREA. THE EXCEPTION WILL BE THE SE COUNTIES AND THE IMMEDIATE COAST...WITH ABOVE GENERALLY AOB ONE QUARTER OF AN INCH. DUE TO THE CONVECTIVE NATURE OF THE EVENT...THERE WILL BE SOME WIDE VARIATIONS IN QPF.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... LOW PRESSURE AND ITS ASSOCIATED COLD FRONT SLOWLY SAG SOUTH OF THE REGION TUE NIGHT. THE FRONT STALLS ALONG THE SE COAST WED THROUGH THE REMAINDER OF THE WEEK. MEANWHILE...SFC HIGH PRESSURE MOVES INTO NEW ENGLAND ON WED AND SLOWLY SHIFTS EWD THROUGH FRI. TO THE WEST OF THE STALLED FRONT AND SFC HIGH TO THE NORTH...AN UPPER TROUGH GETS STUCK OVER THE GULF COAST STATES. THE LOCATIONS OF ALL THE AFOREMENTIONED FEATURES WILL CAUSE MOISTURE AND SHORTWAVE ENERGY SPINNING AROUND THE TROUGH TO BE SQUEEZED UP THE COASTAL PLAIN OF THE CAROLINAS AND VIRGINIA...KEEPING UNSETTLED CONDITIONS ACROSS THE MID ATLANTIC REGION DURING THE MID TO END OF THE WEEK TIMEFRAME. 12Z MODEL TRENDS SHOW THE TROUGH SLOWLY SHIFTING OVER THE SE STATES DURING THE WEEKEND WITH A SFC LOW TRAVELLING UP THE SE/CAROLINA COASTS ALONG THE STALLED FRONTAL BOUNDARY. OVERALL...PERIODS OF SHOWERS AND THUNDERSTORMS SHOULD BE ANTICIPATED. GIVEN THE LIGHT STEERING FLOW ALOFT OF 5-15/20KT THROUGHOUT THE LONG TERM FORECAST PERIOD...IT IS TOO DIFFICULT TO NAIL DOWN THE EXACT TIMING AND PLACEMENT OF PRECIPITATION AND WILL THUS LEAN THE FORECAST TWD A 10-30 PERCENT CHANCE POP AT ANY GIVEN TIME. WITH THE PERIODIC SHOWERS/STORMS WILL COME PERIODS OF CLOUDS AND SUN. LOWS WILL GENERALLY BE IN THE 60S. HIGHS WILL GENERALLY BE IN THE UPPER 70S WED WITH A WARMING TREND THROUGH THE REST OF THE WEEK. HIGHS IN THE LOW-MID 80S THU/FRI...MID-UPPER 80S SAT (AROUND 5 DEGREES COOLER AT THE IMMEDIATE COAST). && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... VFR CONDS EXPECTED THRU THE TAF PERIOD. SOME ISOLD CONVECTION PSBL THIS AFTN/EVENING BUT MOSTLY WEST OF RIC. SOME ISOLD CONVECTION ALSO PSBL ALONG SEA BREEZE BNDRYS THAT DEVELOP ESPECIALLY OVER NE NC. OUTLOOK...NXT CHC FOR SHOWERS/TSTMS COMES LATE MON THRU TUE AS A COLD FRONT CROSSES THE REGION. ONSHORE FLOW LATE TUE INTO WED COULD RESULT IN MARGINAL CIGS/VSBYS ESPECIALLY SRN PORTIONS. && .MARINE... UPDATE...LITTLE CHANGE TO THE ONGOING WEATHER PATTERN AND OVERALL AIRMASS WILL RESULT IN ANOTHER DAY WITH LIGHT AND VARIABLE WINDS AOB 10KT THROUGH EARLY AFTN...BECOMING SSE AND INCREASING TO AOB 15 KT LATE THIS AFTN INTO THE EARLY EVENING HOURS. A FEW WIND GUSTS COULD REACH 20 KT IN SRN CHES BAY AND NRN COASTAL WATERS... BUT SCA FLAGS ARE NOT ANTICIPATED. WAVES BUILDING TO 2-3FT DURING THE AFTN/EVENING...SEAS 2-3FT WITH UP TO 4FT OUT NEAR 20NM. PREVIOUS DISCUSSION...LOW PRS TRACKS NE ACROSS NRN VA TUESDAY. THE TRAILING COLD FRNT PROGGED TO CROSS THE AREA TUE AFTN AND NIGHT. SOME UNCERTAINTY AS TO HOW FAR S AND E THIS BNDRY ACTUALLY GETS (MAY STALL OVR THE RGN THRU THE MID WEEK PERIOD). DESPITE WNDS SHFTG TO AN ELY DRCTN...SPEEDS XPCTD TO REMAIN BLO SCA LVLS. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ SHORT TERM...AJZ/SAM LONG TERM...BMD AVIATION...MPR/JEF MARINE...BMD/MPR

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