Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 141939 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 339 PM EDT MON APR 14 2014 .SYNOPSIS...
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A STRONG COLD FRONT APPROACHES FROM THE WEST TONIGHT AND CROSSES THE REGION TUESDAY. CANADIAN HIGH PRESSURE BUILDS IN FROM THE NORTHWEST TUESDAY NIGHT AND SETTLES OVER THE MID ATLANTIC AND NORTHEAST WEDNESDAY.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... MADE ONLY MINOR CHANGES TO SKY AND TEMP GRIDS. LEFT POPS INTACT WHICH HAS SLGT TO LOW CHC POPS BEGINNING AT 22Z OVER ALL BUT FAR ERN PORTIONS. THIS MAY BE MODIFIED/TRIMMED A LITTLE THIS AFTERNOON. REFLECTIVITY FROM SOME HIGH RES MODELS ARE CONSISTENT WITH THE CURRENT FORECAST. NOT EXPECTING MUCH PCPN DURING THIS PERIOD. THERE MAY BE A LULL IN THE ACTIVITY DURING THE LATE EVENING BEFORE THE MAIN AREA OF PCPN MOVES IN DURING THE EARLY MORNING HOURS. PREVIOUS DISCUSSION... THE CURRENT UPPER AIR ANALYSIS PER GOES WV IMAGERY INDICATES AN AMPLIFIED LONGWAVE PATTERN FEATURING A STRONG UPPER RIDGE OVER THE WESTERN ATLANTIC...WITH A DEEP POTENT TROUGH DIGGING ACROSS THE CENTRAL PLAINS. AT THE SURFACE...HIGH PRESSURE REMAINS ANCHORED OFF THE COAST...WITH A 995MB LOW OVER NRN IL AND A COLD FRONT TRAILING BACK THROUGH THE MID-MISSISSIPPI VALLEY. THE HIGH OFF THE COAST REMAINS THE DOMINANT FEATURE TODAY...WITH INCREASING UPPER LEVEL MOISTURE IN DEEP LAYER SSW FLOW PRODUCING INCREASING/THICKENING HIGH CLOUDS. SCT AFTERNOON CU SHOULD DEVELOP AS WELL...SO THE SKY CONDITION SHOULD LARGELY PROGRESS FROM PARTLY SUNNY TO MOSTLY CLOUDY. TEMPERATURES WILL REMAIN WARM...WITH HIGHS RANGING FROM THE UPPER 70S TO AROUND 80 (LOCALLY COOLER ALONG THE ATLANTIC COAST OF THE EASTERN SHORE). A S WIND OF 15-20 MPH...WITH GUSTS TO 25-30 MPH SHOULD PREVAIL FROM LATE MORNING THROUGH THE AFTERNOON. FORCING ASSOCIATED WITH THE GREAT LAKES LOW SHOULD REMAIN WELL NW OF THE LOCAL AREA...SO ANY SHRA WILL LIKELY HOLD OFF UNTIL TONIGHT. THE PLAINS TROUGH ADVANCES EASTWARD INTO THE MID-MISSISSIPPI VALLEY TONIGHT. GENERAL MODEL CONSENSUS INDICATES A WEAK SHORTWAVE TROUGH LIFTING NNE AHEAD OF THE MAIN TROUGH. THIS SHOULD COMBINE WITH INCREASING WARM/MOIST ADVECTION AND RESULT IN AN INCREASING CHC OF SHRA ESPECIALLY AFTER MIDNIGHT. OVERNIGHT LOWS WILL BE VERY MILD AND GENERALLY IN THE LOW/MID 60S. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... THE SITUATION BECOMES QUITE INTERESTING BY TUESDAY AFTERNOON. THE PRIMARY TROUGH LIFTS THROUGH THE TENNESSEE AND OHIO VALLEYS TUESDAY MORNING AND BEGINS TO TAKE ON A NEGATIVE TILT AS IT APPROACHES THE MID-ATLANTIC TUESDAY AFTERNOON. MEANWHILE...THE SURFACE COLD FRONT APPROACHES THE REGION FROM THE NW DURING THE DAY...WITH INCREASING LOW-LEVEL FRONTOGENESIS. 14/00Z NAM/GFS EACH INDICATE STRONG VERTICAL ASCENT IN THE RRQ OF A STRENGTHENING UPPER JET OVER ERN CANADA AND THE NERN US. THE PROBABILISTIC APPROACH FROM THE 14/03Z SREF MEAN SHOWS A 50+ KT LLJ ACROSS THE REGION TUESDAY (+3-4 ST DEV) AND THE DETERMINISTIC NAM/GFS (DESPITE SOME SPATIAL DIFFERENCES) EACH INDICATE THE POTENTIAL FOR THIS TO REACH 60-65KT. 0-3KM BULK SHEAR IS PROGGED TO REACH 50KT BY TUESDAY AFTERNOON ACROSS PORTIONS OF THE LOCAL AREA...WITH FORECAST HODOGRAPHS DEMONSTRATING CLOCKWISE CURVATURE FROM 0-3KM. THE NET RESULT IS A FAVORABLE SYNOPTIC/KINEMATIC ENVIRONMENT FOR STRONG TO SEVERE LINEAR CONVECTION. INSTABILITY IS PROGGED TO BE MINIMAL (DUE TO DEEP MOISTURE)...BUT WILL LIKELY BE THE DETERMINING FACTOR FOR STORM ORGANIZATION. IF THE ENVIRONMENT BECOMES MORE UNSTABLE THE LIKELIHOOD FOR EMBEDDED INTENSE CELLS AND BOWING SEGMENTS WILL INCREASE. OVERALL THE GREATEST THREAT FOR SEVERE STORMS APPEARS TO BE ACROSS SOUTHERN PORTIONS OF THE AREA...WITH THE MARINE ENVIRONMENT LIMITING SEVERE POTENTIAL OVER THE EASTERN SHORE. MODERATE TO HEAVY RAIN WILL ACCOMPANY THE CONVECTION WITH STORM TOTAL QPF AMOUNTS AVERAGING 1.0-1.5IN. TUESDAY SHOULD BE BREEZY AND MILD OUTSIDE OF SHOWERS/STORMS. HIGHS SHOULD RANGE FROM THE UPPER 60S TO NEAR 70 W...TO THE MID 70S E...ALONG WITH A SOUTH WIND OF 15-20 MPH...WITH GUSTS TO 30 MPH. THE COLD FRONT SWEEPS ACROSS THE REGION TUESDAY EVENING...USHERING IN A VERY COOL DRY AIRMASS. STRONG PRESSURE RISES FOLLOW THE FRONT AVERAGING +6-8MB/3HR ACROSS THE LOCAL AREA. THIS WILL DRIVE A STRONG NNW WIND IN THE WAKE OF THE FRONTAL PASSAGE. THE WIND WILL BE STRONGEST ACROSS THE EASTERN THIRD OF THE AREA (ESPECIALLY ALONG THE COAST)...WHERE SPEEDS SHOULD AVERAGE 20-30 MPH...WITH GUSTS TO AROUND 45 MPH. LOWS WEDNESDAY MORNING WILL LIKELY RANGE FROM THE UPPER 20S/LOW 30S OVER THE PIEDMONT TO THE UPPER 30S/LOW 40S ALONG THE COAST. HIGHS WEDNESDAY WILL BE CHILLY RANGING FROM 50-55 UNDER A MOSTLY SUNNY SKY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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STRONG SFC HIGH PRESSURE REMAINS ANCHORED OVER NEW ENGLAND TO BEGIN THE MEDIUM RANGE FORECAST PERIOD, RESULTING IN CONTINUED NE FLOW OVER THE MID ATLANTIC FRIDAY. TEMPERATURES WILL BE COOL TO BEGIN THE PERIOD FRIDAY...ABOUT ONE STANDARD DEVIATION BELOW NORMAL...WITH TEMPS MODERATING A BIT SATURDAY. ALOFT, NORTHERN STREAM SHORTWAVE TROUGH, AND ATTENDANT SFC LOW IS EXPECTED TO PUSH ACROSS THE MID MS VLY TOWARDS THE EASTERN GREAT LAKES FRI-SAT, EVENTUALLY PUSHING A MAINLY DRY COLD FRONT THROUGH SAT NGT AND EARLY SUNDAY. BOTH MODELS DO TAKE A PIECE OF SHORTWAVE ENERGY ACROSS THE MID-SOUTH TOWARDS THE CAROLINA COAST FRIDAY-SATURDAY, WITH RESULTANT WEAK INVERTED TROUGHING THAT DEVELOPS PROMPTING SOME LOW POPS LATER FRIDAY AND SATURDAY. THE 12Z/14 EURO SOLUTION REMAINS A BIT WETTER THAN THE PROGRESSIVE GFS SOLUTION. HAVE SPLIT THE DIFFERENCE BETWEEN THE GFS/UKMET FOR THIS PACKAGE. RIGHT NOW, IT APPEARS THAT THE BEST RAIN CHC WOULD BE OVER EASTERN SECTIONS ALONG THE COASTAL TROUGH FRIDAY NIGHT THROUGH MIDDAY SATURDAY. UPPER TROUGH EJECTS NORTHEAST LATER SATURDAY, WITH SHORTWAVE RIDGING ARRIVING FROM THE WEST SHUNTING SYSTEM OFFSHORE. QUICK CLEARING EXPECTED THEREAFTER TOWARDS THE TAIL END OF THE PERIOD (EASTER SUNDAY AND MONDAY).
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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VFR CONDITIONS ACROSS AREA TERMINALS THIS AFTERNOON WITH GUSTS TO 20-25KT WHICH SHOULD BRIEFLY DIMINISH THIS EVENING.CIGS SLOWLY DETERIORATE TO MVFR TONIGHT...W/PERIODIC IFR CIGS POSSIBLE TOWARDS SUNRISE AS MOISTURE ADVECT IN ADVANCE OF THE FRONT. BREEZY SOUTHERLY WINDS CONTINUE TUESDAY (GUSTS OF 30-35 KT) AS THE FRONT APPROACHES FROM THE WEST. COLD FRONT CROSSES THE REGION TUESDAY, ACCOMPANIED BY WIDESPREAD RAINFALL TUES-TUES NIGHT WITH PERIODIC IFR VSBY RESTRICTIONS IN HEAVY RAIN. THERE IS ALSO THE POTENTIAL FOR A STRONG LINE OF CONVECTION ON THE LEADING EDGE OF THE FRONT TUES AFTERNOON MAINLY ACROSS SOUTHEASTERN TERMINALS (PHF-ORF-ECG)W/ HEAVY RAIN AND STRONG WIND GUSTS UP TO 50 KT POSSIBLE. OUTLOOK...BEHIND THE FRONT, LOOK FOR WINDS TO BACK TO THE NW AND REMAIN GUSTY. SOME GUSTS UP TO 40 KT POSSIBLE ALONG THE COAST. IMPROVING CONDITIONS WED THRU FRIDAY AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTH.
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&& .MARINE... HIGH PRESSURE REMAINS ANCHORED OVER THE WRN ATLANTIC AS A STRONG COLD FRONT SLOWLY APPROACHES FROM THE WEST. BREEZY...BUT SUB SCA...SLY WINDS CONTINUE OVER THE WATERS...AVERAGING 10-15 KT. WAVES AVERAGE 1-2 FT WITH SEAS 2-3 FT. NRN COASTAL WATERS HAVE BUILT TO NEAR 4 FT 20 NM OUT...BUT ARE EXPECTED TO REMAIN BELOW 5 FT THRU THIS AFTERNOON DUE TO SLY FLOW. CONDITIONS WILL REMAIN SUB-SCA TODAY AS THE FRONT SLOWLY APPROACHES FROM THE WEST...WITH THE STRONGEST HEIGHT FALLS OCCURRING TUESDAY. HOWEVER...A FEW GUSTS APPROACHING 20 KT CANNOT BE RULED OUT. AS THE FLOW OVER THE WATERS BECOMES MORE SELY...SEAS WILL LIKELY BUILD TO 3-5 FT IN THE NRN WATERS...NORTH OF CAPE CHARLES LIGHT...BY LATE TODAY. LOW LEVEL GRADIENT WILL ALSO STRENGTHEN LATE TODAY-TONIGHT AS THE FRONT REACHES THE OH VALLEY. WHILE A STEEP LOW LEVEL INVERSION STILL EXISTS OVER THE WATERS...EXPECT PRESSURE FALLS AND GRADIENT WINDS TO PROVIDE BETTER MIXING OVER THE WATER. WHILE STILL MARGINAL...HAVE OPTED TO HOIST SCA HEADLINES TONIGHT FOR THE BAY. STRONGEST PRESSURE FALLS ARRIVE EARLY TUES...WITH LOW-END SCA CONDITIONS OVER THE BAY/SOUND/ERN VA RIVERS. SEAS ALSO EXPECTED TO BUILD TO 3-5 FT IN THE SRN WATERS (HIGHEST 20 NM OUT) TUES MORNING. SEAS WILL BUILD TO 5-8 FT TUES AFTERNOON. IN ADDITION...A LINE OF CONVECTION IS POSSIBLE ALONG THE LEADING EDGE OF THE FRONT TUES AFTERNOON. WITH WINDS A FEW THOUSAND FT OFF THE WATER REACHING 45-50 KT...CONVECTION WILL LIKELY BE ABLE TO MIX THESE HIGHER VELOCITY WINDS DOWN. WILL HANDLE THIS WITH SHORT FUSED PRODUCTS. THE MAIN IMPACT WILL BE BEHIND THE FRONT TUESDAY NIGHT AS A MUCH COLDER/DRIER AIRMASS SURGES INTO THE REGION. GALE CONDITIONS ARE EXPECTED OVER ALL WATERS...WITH NW GUSTS REACHING 35-40 KT. HAVE HELD OFF ON A GALE WATCH ATTM AS IT WILL STILL BE DURING THE 4TH PERIOD FORECAST. HIGH PRESSURE QUICKLY BUILDS BACK OVER THE WATERS EARLY WEDS MORNING...RESULTING IN IMPROVING CONDITIONS OVER THE BAY. FLOW VEERS AROUND TO THE NE WEDS...RESULTING IN PERSISTENT ONSHORE FLOW THRU THE END OF THE WEEK. THIS WILL RESULT IN ELEVATED SEAS THRU THE END OF THE WEEK. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT TUESDAY FOR ANZ633- 635>638. SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ630>632-634- 650-652-654. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT TUESDAY FOR ANZ656-658.
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&& $$ SYNOPSIS...AJZ NEAR TERM...AJZ/LSA SHORT TERM...AJZ LONG TERM...MAM AVIATION...MAM MARINE...SAM

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