Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 131506 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1106 AM EDT SUN JUL 13 2014 .SYNOPSIS...
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HIGH PRESSURE REMAINS WELL OFF THE COAST TODAY. LOW PRESSURE MOVES ACROSS THE GREAT LAKES REGION WITH A TRAILING COLD FRONT APPROACHING FROM THE NORTHWEST MONDAY INTO TUESDAY. THE FRONT IS EXPECTED TO SLOWLY PUSH THROUGH THE LOCAL AREA LATE TUESDAY INTO WEDNESDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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LATEST ANALYSIS SHOWING SFC HIGH PRESSURE WELL OFF THE COAST...WITH A DEEPENING LOW PRESSURE SYSTEM OVER ONTARIO CANADA. SOME WEAK SFC TROUGHINESS NOW NOTED OVER THE LOCAL AREA...AND LATEST RADAR IMAGERY REVEALS A FEW SHOWERS OVER SOUTH CENTRAL VA OVER PITTSYLVANIA AND CAMPBELL COUNTIES. RAP/NAM12 SHOW A FAIRLY STEEP 925 MB DEW PT BOUNDARY IN THE VICINITY OF THESE SHOWERS AND THEY PUSH THIS INCREASING MOISTURE ENE THROUGH THE NEXT FEW HRS. STILL ONLY LIMITED INSTABILITY ASSOCIATED WITH THIS SO IT MAY JUST REMAIN AS SHOWERS W/OUT ANY LIGHTNING FOR ANOTHER FEW HRS. DID ADD SOME LOW CHC POPS TO SW ZONES OVER THE NEXT FEW HRS...AND HAVE EXPANDED THE AREA OF 20% POPS FOR AFTN TSTMS FARTHER SOUTH TO INCLUDE ALL OF CENTRAL VA AND INTO PORTIONS OF SE VA LATER THIS AFTN (ALTHOUGH KEPT FORECAST DRY OVER FAR SE VA/NE NC INCLUDING HAMPTON ROADS). LITTLE SHEAR PRESENT TODAY (<20KT OF 0-6KM BULK SHEAR)...WITH HIGHEST INSTABILITY PROGGED TO BE OVER THE UPPER CHES BAY AND INTERIOR MD ERN SHORE BY 21Z. WILL CARRY CHC POPS/30% IN THESE AREAS. LITTLE ADJUSTMENT TO AFTN HIGHS DESPITE THIS EARLIER ONSET OF ISOLATED PRECIP AS SKIES ARE STILL LIKELY TO BE VARIABLY CLOUDY THROUGH THE AFTN. HIGHS WILL GENLY BE IN THE LOWER TO MID 90S...LOCALLY COOLER AT THE IMMEDIATE COAST BUT STILL WARM DUE TO A SW FLOW (MAINLY UPPER 80S TO LOWER 90S). ANY SHOWER/TSTM THAT DOES MAKE IT INTO THE AREA THIS EVENING WILL DISSIPATE BEFORE THE OVERNIGHT HOURS...SO WILL MAINTAIN A DRY FORECAST AFTER MIDNIGHT. PARTLY CLOUDY AND WARM/HUMID TONIGHT WITH LOWS 70-75 F.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY/...
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ANOMALOUSLY DEEP UPPER LOW OVER SOUTHERN CANADA LOOKS TO PUSH A STRONG SHORTWAVE SE THROUGH THE GREAT LAKES/UPPER MIDWEST ON MON. THIS ALLOWS LOW LEVEL FLOW FROM THE SW TO INCREASE FURTHER. SPC NOW HAS MUCH OF THE CWA OUTLINED IN A SLIGHT RISK FOR SEVERE TSTMS ALTHOUGH SOME UNCERTAINTY REMAINS. A STRONG SW FLOW IN THE BOUNDARY LAYER OFTEN DRIES THE AKQ CWA OUT (ESPECIALLY SE VA/NE NC). FOR NOW...WILL MAINTAIN HIGH CHC POPS DEVELOPING BY MON AFTN OVER THE NW COUNTIES TAPERED TO ONLY 20% POPS IN SE VA/NE NC. HIGHS 90-95 AGAIN. POPS ACTUALLY SHOULD INCREASE SOMEWHAT MON EVENING ALL THE WAY TO THE COAST AS LOW-LEVEL JET ENERGY INCREASES (AND A BETTER CHANCE OF STRONG TO SVR STORMS MAY MATERIALIZE)...SO WILL HAVE AT LEAST 35% POPS ALL ZONES. WARM/HUMID MON NIGHT W/ LOWS MAINLY 70-75. BY TUE...THE SFC COLD FRONT MOVES INTO THE REGION AND UPPER LEVEL SUPPORT INCLUDING RRQ FORCING FROM THE UPPER JET ARRIVES. WILL CARRY LIKELY POPS BY AFTN ALL ZONES...SOME SEVERE POTENTIAL WILL TEND TO TRANSITION TO MAINLY A HEAVY RAIN THREAT TUE NIGHT AS THE COLD FRONT SLOWLY MOVES EAST. BEST CHANCE OF SEVERE TSTMS ON TUESDAY (SLIGHT RISK BY SPC) WILL BE ACROSS SE VA AND NE NC WHERE BEST BUOYANCY/INSTABILITY WILL BE LOCATED ALONG AND SOUTH OF THE COLD FRONT. LOCALIZED FLOODING MAY ALSO BE AN ISSUE GIVEN SLOW MOVEMENT OF THE FRONT...STRONG FORCING FOR ASCENT...AND PW`S IN EXCESS OF 2 INCHES. WILL CONTINUE TO HIGHLIGHT THESE THREATS IN THE HWO. HIGHS TUESDAY WILL BE TEMPERED BY CLOUDS/PCPN AND SHOULD GENERALLY REMAIN IN THE MID/UPR 80S.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... AS AN ANOMALOUS TROUGH DEVELOPS OVER THE ERN CONUS...HEIGHT FALLS AND INCREASING WINDS ALOFT WILL RESULT IN BETTER FORCING FOR ASCENT OVER THE LOCAL AREA. STRONG SPEED MAX ROUNDS THE DEEP CLOSED LOW OVER THE GREAT LAKES TUES...EJECTING THE LOW NEWD INTO SE CANADA. THE COLD FRONT DROPS INTO THE REGION TUES NIGHT. STRONGEST DYNAMICS LIFT WELL NORTH OF THE REGION WITH THE CLOSED LOW...BUT HEIGHT FALLS AND PERTURBATIONS IN THE WSW FLOW WILL RESULT IN SCT-NUMEROUS SHOWERS/THUNDERSTORMS. STRONG TO SEVERE THUNDERSTORMS ALSO POSSIBLE AS MODELS DEPICT MARGINAL SHEAR AND MLCAPE > 2000 J/KG. ANOMALOUS TROUGH WILL PUSH THE SRN PORTION OF THE FRONT INTO THE DEEP SOUTH...BUT THE ERN PORTION LIKELY STALLING OVER/OFF THE MID-ATLANTIC COAST AS AN ANOMALOUS UPPER RIDGE REMAINS PARKED OVER THE WRN ATLANTIC. WILL MAINTAIN ELEVATED POPS WEDS ACROSS THE SE AS THE FRONT WILL LIKELY LINGER OVER THE REGION. HIGHS EXPECTED IN THE LOW TO MID 80S FOR THE WEEK AFTER FRONTAL PASSAGE. SFC HIGH PRESSURE WILL BE SLOW TO BUILD INTO THE REGION IN WAKE OF THE FRONT AS UPPER TROUGH REMAINS OVER THE ERN CONUS. MODEL GUIDANCE DEPICTING THE HIGH RIDGING SOUTH ACROSS THE MID-ATLANTIC CREATING NE/ENE WINDS. THIS SETUP CAN CAUSE DAYTIME TEMPS TO BE BELOW CLIMO WITH CLOUDY CONDITIONS. THE STALLED FRONTAL BOUNDARY REMAINS ACROSS THE SE THROUGH THE WEEKEND AND WITH A PASSING SHORTWAVE TROUGH...SHOWERS AND THUNDERSTORMS MAY BE POSSIBLE SAT NIGHT INTO SUN. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... SURFACE HIGH PRESSURE MOVES OFFSHORE TODAY AS LOW PRESSURE TRACKS WELL N OF THE REGION. ANY LINGERING FOG AND STRATUS AT SBY SHOULD DISSIPATE BETWEEN 12-13Z. OTHERWISE...EXPECT PASSING MID AND HIGH CLOUDS WITH SCT AFTERNOON CU. A SSW WIND WILL INCREASE TO 10-12KT DURING THE LATE MORNING AND AFTERNOON AND WILL BECOME LOCALLY GUSTY TO 15-20KT AT RIC AND SBY. THERE WILL BE A SLIGHT CHC OF AFTERNOON/EVENING SHRA/TSRA MAINLY ALONG AND NW OF A LINE FROM RIC TO SBY. A WEAK SHORTWAVE TROUGH MOVES ACROSS THE AREA MONDAY AFTERNOON/EVENING AND THIS WILL BRING A HIGHER CHC OF SHRA/TSRA...SOME OF WHICH COULD PRODUCE STRONG WIND GUSTS. A COLD FRONT WILL CONTINUE TO BRING THE POTENTIAL FOR SHRA/TSRA TUESDAY INTO WEDNESDAY. && .MARINE... A SOUTHERLY WIND WILL AVERAGE 10-15KT TODAY AS HIGH PRESSURE MOVES OFF THE MID ATLANTIC COAST AND LOW PRESSURE LIFTS NE OF THE GREAT LAKES. HIGH PRESSURE BECOMES ANCHORED OFF THE SOUTHEAST COAST TONIGHT INTO MONDAY AS A LEE-SIDE TROUGH DEVELOPS OVER THE PIEDMONT. THIS SHOULD HELP BOOST WIND SPEEDS OVER THE OCEAN TO 15-20KT...WITH A SOLID 15KT IN THE BAY...AND 10-15KT ELSEWHERE. A COLD FRONT SLOWLY APPROACHES FROM THE WEST MONDAY NIGHT INTO TUESDAY...AND SLOWLY CROSSES THE MID ATLANTIC COAST TUESDAY NIGHT INTO WEDNESDAY. THE WIND SHOULD REMAIN SSW THROUGH TUESDAY WITH SPEEDS OVER THE OCEAN CONTINUING TO AVERAGE 15-20KT...WITH 10-15KT ELSEWHERE. A WIND SHIFT TO NE IS EXPECTED BEHIND THE FRONT. AT THIS TIME THERE IS NOT MUCH OF A COOL AIR SURGE EXPECTED BEHIND THE FRONT...SO POST-FRONTAL WIND SPEEDS ARE FORECAST TO REMAIN AOB 10KT. LIGHT ONSHORE FLOW IS EXPECTED TO CONTINUE LATER IN THE WEEK AS HIGH PRESSURE BUILDS N OF THE REGION AND WEAK LOW PRESSURE LINGERS OVER THE SOUTHEAST. SEAS OUT NEAR 20NM N OF PARRAMORE ISLAND WILL BUILD TO 3-4FT TONIGHT INTO MONDAY DUE TO PERSISTENT SOUTHERLY FLOW...AND COULD REACH ~5FT LATE MONDAY AFTERNOON INTO MONDAY NIGHT. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...LKB NEAR TERM...LKB SHORT TERM...JDM/LKB LONG TERM...DAP AVIATION...AJZ MARINE...AJZ

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