Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 150846 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 446 AM EDT TUE APR 15 2014 .SYNOPSIS... A STRONG COLD FRONT WILL CROSS THE AREA TODAY...THEN MOVE OFF THE COAST THIS EVENING. CANADIAN HIGH PRESSURE BUILDS IN FROM THE NORTHWEST TUESDAY NIGHT AND SETTLES OVER THE MID ATLANTIC AND NORTHEAST WEDNESDAY AND THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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LITTLE CHANGE COMPARED TO PREVIOUS FORECASTS AS A STRONG COLD FRONT IS SET TO IMPACT THE REGION THIS AFTERNOON. REST OF THIS MORNING... LATEST WATER VAPOR IMAGERY AND UPPER AIR RAOB PLOTS DEPICT ANOMALOUS LONGWAVE TROUGH OVER THE CENTRAL CONUS...SLOWLY PROGRESSING EWD. ASSOCIATED COLD FRONT IS STRETCHING FROM THE OH VALLEY SWD INTO THE LOWER MS VALLEY/NRN GULF. ALSO VISIBLE ON WATER VAPOR IS A PLUME OF MOISTURE FROM THE NRN GULF NEWD INTO NEW ENGLAND...THANKS TO DEEP LAYER SWLY FLOW. PER BLENDED TOTAL PRECIP WATERS...PRECIP WATER VALUES HAVE REACHED 200+ PCT OVER THE LOCAL AREA. UPSLOPE FLOW AND ANOMALOUS MOISTURE HAS RESULTED IN WIDESPREAD PRECIP OVER THE CNTRL APPALACHIANS...WITH MOST OF THE PRECIP STAYING TO THE WEST OF OUR ERN VA PIEDMONT COUNTIES. ANOTHER AREA OF UPGLIDE ALONG THE COAST HAS PRODUCED SCT SHOWERS FROM ELIZABETH CITY NWD TO SALISBURY. ANOTHER AREA OF SHOWERS OVER S CNTRL NC WILL LIKELY LIFT OVER THE PIEDMONT INTO CNTRL VA EARLY THIS MORNING...AIDED STRONG UPPER LEVEL SUPPORT. FOR TODAY... STRONG SPEED MAX EMERGING FROM THE BASE OF THE UPPER TROUGH WILL EJECT THE TROUGH NEWD TODAY. THIS WILL RESULT IN THE TROUGH BECOMING NEGATIVELY TILTED AS IT LIFTS OVER THE MID-ATLANTIC REGION. COLD FRONT PROGGED TO REACH THE LOCAL AREA LATE MORNING- EARLY AFTERNOON. MODELS HAVE A GOOD HANDLE ON THE TIMING OF THE FRONT...PUSHING IT THRU THE LOCAL AREA THIS AFTERNOON AND OFFSHORE THIS EVENING. STRONG HEIGHT FALLS AND A SHARP TEMPERATURE CONTRAST WILL RESULT IN STRONG FRONTOGENETIC FORCING ALONG THE FRONT. RRQ OF 160+KT UPPER JET AND VORTICITY ADVECTION WILL PROVIDE STRONG UPPER LEVEL FORCING FOR ASCENT ALONG THE FRONT. INCREASING WINDS ALOFT WILL ALSO RESULT IN A STRONG LLJ...WITH 850 WINDS 50-60 KT (+3 TO +4 STD DEV). THE RESULT IS A FAVORABLE SYNOPTIC SETUP. INSTABILITY WILL BE RATHER LIMITED...BUT THETA-E ADVECTION AND TEMPS IN THE MID-UPPER 70S WILL PRODUCE A MARGINALLY UNSTABLE AIRMASS (MLCAPE 500-750 J/KG) DESPITE CLOUD COVER. THE EXCEPTION WILL LIKELY BE OVER THE PIEDMONT WHERE RAINFALL WILL FURTHER LIMIT INSTABILITY. 0-3KM BULK SHEAR OF 50-60 KT WILL LIKELY RESULT IN ANY DEVELOPING CONVECTION TO ORGANIZE INTO LINE SEGMENTS...WITH SOME BOWING SEGMENTS POSSIBLE. THIS WILL LEAD TO AN ENHANCED THREAT FOR DAMAGING WINDS IN EXCESS OF 50 KT THANKS TO STRONG LLJ. LATEST NAM/SREF/ECMWF GUIDANCE INDICATE A WAVE DEVELOPING ALONG THE FRONT OVER CNTRL NC EARLY THIS AFTERNOON...LIFTING INTO NE NC/POSSIBLE SE VA. IF THIS OCCURS...THIS WOULD INCREASE LOW LEVEL HELICITY...WITH ISOLATED WEAK TORNADOES POSSIBLE IN BROKEN LINE SEGMENTS. MUCH OF THE LOCAL AREA REMAINS UNDER A SLIGHT RISK FOR SEVERE WEATHER. BEST CHANCES FOR SEVERE WEATHER WILL BE MID-LATE AFTERNOON ALONG THE IMMEDIATE FRONT AS IT REACHES INTERSTATE 95 AND POINTS EWD. THE EXCEPTION WILL BE THE MD/VA ERN SHORE WHERE A MARINE ENVIRONMENT WILL LIMIT SEVERE POTENTIAL. ANOMALOUS MOISTURE AND STRONG DYNAMICS WILL ALSO RESULT IN PERIODS OF HEAVY RAINFALL. COLD FRONT MAY SLOW SLIGHTLY AS IT REACHES THE COAST...BUT WILL PUSH OFFSHORE EARLY THIS EVENING...WITH PRECIP ENDING SHORTLY THEREAFTER. TOTAL QPF AMOUNTS WILL RANGE FROM 1-1.5 INCHES. THE IMPACT THEN BECOMES INCREASING NW WINDS AND THE ASSOCIATED COLD AIR SURGING INTO THE REGION. SKIES WILL ALSO BEGIN TO CLEAR QUICKLY W-E AS THE BEST MOISTURE QUICKLY PUSHES OFFSHORE AND THE TROUGH LIFTS NE OF THE REGION.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
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ANOMALOUS HIGH PRESSURE BUILDS OVER THE OH VALLEY TONIGHT BEHIND THE FRONT. STRONG CAA (1000-850MB LOW LEVEL THICKNESSES AT RIC DROP ~100MB IN 18 HRS!) WILL RESULT IN RAPIDLY DROPPING TEMPS BEHIND THE FRONT AS SKIES QUICKLY CLEAR. LOWS FORECAST TO BE IN THE UPPER 20S-LOW 30S ACROSS MUCH OF THE REGION. THE EXCEPTION WILL BE SE VA/NE NC WHERE TEMPS WILL DROP INTO THE MID-UPPER 30S. AS A RESULT...FREEZE WARNINGS/WATCHES HAVE BEEN ISSUED. PLEASE REFER TO HEADLINE FOR MORE INFORMATION. IN ADDITION...BREEZY NWLY WINDS WITH GUSTS OF 25-30 (NEAR 40 MPH NEAR THE COAST) ARE EXPECTED THIS EVENING. WINDS WILL DIMINISH OVERNIGHT...BUT REMAINING 10-15 MPH. AS A RESULT...FROST IS NOT ANTICIPATED. COLD WEDNESDAY UNDER SUNNY SKIES. LIKELY WILL BE SOME STREAMERS OVER THE BAY INTO SE VA/NE NC WEDS MORNING. H85 TEMPS WILL FALL TO ~-5C (-2 STD DEV)...TRANSLATING TO DAYTIME TEMPS GENERALLY IN THE LOW 50S...EVEN UNDER THE STRONG APRIL SUN. TEMPS AGAIN MAY FALL TO AROUND FREEZING OVER INLAND COUNTIES WED NIGHT-THURS MORNING. THERE IS A POSSIBILITY FOR LIGHT RAIN NEAR THE NC COAST BY THURS.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... 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). && .AVIATION /09Z TUESDAY THROUGH SATURDAY/...
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VARIABLE CONDITIONS ACRS THE REGION EARLY THIS MORNING...PATCHY IFR CIGS/VSBYS POSSIBLE THROUGH 12Z MAINLY AT KSBY...EVENTUALLY KRIC. MORE LIKELY TO REMAIN MVFR ELSEWHERE. BREEZY SOUTHERLY WINDS CONTINUE TODAY (GUSTS OF 25-30 KT) AS THE FRONT APPROACHES FROM THE WEST. COLD FRONT CROSSES THE REGION BETWEEN 21Z AND 00Z THIS EVENING...ACCOMPANIED BY WIDESPREAD RAINFALL WITH PERIODIC IFR VSBYS RESTRICTIONS IN HEAVY RAIN. THERE IS ALSO THE POTENTIAL FOR A STRONG LINE OF CONVECTION ON THE LEADING EDGE OF THE FRONT DURING THIS TIMEFRAME. WIND GUSTS UP TO 30-40 KT ARE LIKELY AS WITH THE FRONTAL PASSAGE (A FEW HIGHER GUSTS WILL BE POSSIBLE IN TSTMS). OUTLOOK...BEHIND THE FRONT, LOOK FOR WINDS TO BACK TO THE NNW AND REMAIN GUSTY THROUGH WED MORNING...WITH FREQUENT GUSTS TO 30-35 KT THROUGH 06Z INLAND AND THROUGH 15Z AT KORF/KPHF/KECG. IMPROVING CONDITIONS WED THRU FRIDAY AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTH.
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&& .MARINE...
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RAISED GALE WARNINGS FOR ALL MARINE ZONES...REMOVED RAMP-UP SCA`S AS WE ARE WITHIN ~ 12 HRS OF THE ONSET OF GALE CONDITIONS. SOUTHERLY FLOW TODAY WILL INCREASE TO AROUND 20-25 KT WITH GUSTS TO 30 KT...AS PRESSURE FALLS MOVE INTO THE AREA AHEAD OF THE APPROACHING COLD FRONT. HOWEVER...STRONGER WINDS ARE ANTICIPATED BETWEEN ABOUT 20Z AND 00Z AS WINDS SHIFT IN ASSOCIATION WITH THE FRONT (AND MAY BE ENHANCED BY SCATTERED CONVECTION). THIS EVENING...IMPRESSIVE PRESSURE RISES ON THE ORDER OF 12 TO 15 MB IN A 6 HR PERIOD SHOULD BRING GUSTS OF 35-40 KT FOR ALL ZONES. THIS WILL ALSO USHER IN MUCH COLDER AIR THAT WILL ENHANCE MIXING OVER THE WATERS. WAVES WILL BLD TO 4 TO 6 FT OVR THE CHES BAY...AND SEAS WILL BLD TO 5 TO 9 FT ON THE COASTAL WATERS. HI PRES WILL THEN BLD JUST TO THE N BY WED AFTN...WHICH WILL ALLOW THE GRADIENT TO WEAKEN SIGNIFICANTLY. HAVE THE GALES ENDING AT 12Z FOR THE BAY/RIVERS...BUT HOLDING INTO EARLY AFTN FOR THE COAST AND CURRITUCK SOUND. HIGH PRESSURE SLIDES NE ACRS NEW ENGLAND AND INTO THE CANADIAN MARITIMES WED NGT THRU FRI...AS A WEAK COASTAL TROUGH DEVELOPS OFF THE SE COAST. THIS WILL RESULT IN NE WINDS AND ELEVATED SEAS THRU THE END OF THE WEEK.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR MDZ021>024. NC...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR NCZ012. VA...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR VAZ078-084>090-092-093. FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR VAZ048-049- 060>077-079>083. MARINE...GALE WARNING UNTIL 1 PM EDT WEDNESDAY FOR ANZ650-652-654-656- 658. GALE WARNING FROM 8 AM THIS MORNING TO 7 AM EDT WEDNESDAY FOR ANZ635>638. GALE WARNING UNTIL 7 AM EDT WEDNESDAY FOR ANZ630>632-634. GALE WARNING FROM 8 AM THIS MORNING TO 1 PM EDT WEDNESDAY FOR ANZ633. && $$ SYNOPSIS...LSA NEAR TERM...SAM SHORT TERM...SAM LONG TERM...MAM/JEF AVIATION...LKB MARINE...LKB

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