Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 212100 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 400 PM EST SUN DEC 21 2014 .SYNOPSIS... HIGH PRESSURE MOVES OFF THE COAST TONIGHT. LOW PRESSURE MOVES NORTHEAST OUT OF THE GULF OF MEXICO AND UP ALONG THE CAROLINA COAST MONDAY INTO TUESDAY. A STRONG COLD FRONT WILL CROSS THE AREA WEDNESDAY NIGHT. HIGH PRESSURE RETURNS BY CHRISTMAS DAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST ANALYSIS DEPICTS ~1030 MB SFC HIGH PRESSURE CENTERED OVER ERN CANADA...RIDGING DOWN INTO THE MID ATLC REGION. A TROUGH OF LOW PRESSURE IS IN PLACE OFF THE COAST OF GA/SC...AND IS PROGGED TO SHIFT SLOWLY N/E OVERNIGHT. SKIES HAVE CLEARED OUT OVER THE LOCAL AREA WITH TEMPERATURES INTO THE 40S TO LOWER 50S. FOR TONIGHT...MAIN CONCERN WILL BE POTENTIAL FOR WINTRY MIX (PRIMARILY ZR) OVER FAR WRN PORTIONS OF THE CWA. HAVE ISSUED A FREEZING RAIN ADVISORY FOR THE 4 CLIMO FAVORED COUNTIES ACRS THE FAR WRN PORTION OF THE CWA (LOUISA/FLUVANNA/CUMBERLAND/PRINCE EDWARD). OVERALL PATTERN IS NOT FAVORABLE FOR MUCH IMPACT ANYWHERE ELSE IN THE CWA (SFC HIGH TOO WEAK/PUSHING TOO FAR EAST). THIS WILL BE A "MINIMAL IMPACT" ADVISORY FOR THE MOST PART...AS BUFKIT SOUNDINGS (ESPECIALLY THE GFS) SHOW LIMTED SATURATION THROUGH THE DENDRITIC GROWTH LAYER THROUGH THE DURATION OF THE EVENT (HEAVIER PRECIP STAYING EAST WHERE IT WILL BE ALL RAIN). STILL ENOUGH SUPPORT FOR ZR AS MAIN PTYPE (RATHER THAN SLEET) AND IF THE NAM/EC SCENARIO VERIFIES...THINK THERE IS A GOOD CHC FOR AT LEAST A FEW HUNDREDTHS OF AN INCH OF ICE ACCUMULATION. DESPITE SOME TIMING DIFFERENCES LTST MODELS IN GNRL AGREEMENT THAT PCPN OVERSPREADS THE AREA S-N BTWN 06Z-12Z. LL THICKNESSES WARM ENUF FOR LIQUID PCPN E OF I95 BUT REMAIN MARGINAL W OF I95. BUFKIT SNDGS CONT TO SHOW A NARROW LAYER OF BLO FREEZING SFC TMPS THRU 15Z OR SO ACROSS THE PIEDMONT. THNK P-TYPE WILL START OFF AS A FEW HRS OF SLEET W OF I95 AND N OF RT 460 LATE TONIGHT DUE TO EVAP COOLING WITH TMPS NEAR FREEZING. QPF LOOKS MINIMAL LOWS U20S-M30S. WEDGE BEGINS TO WEAKEN LATE MON MORNING AS HIGH PRES MOVES INTO ERN CANADA. THE NORMALLY COLDER CNTYS WILL LIKELY STAY NEAR 32 DEGREES THRU 15Z OR SO AS THE PCPN OVERSPREADS THE ENTIRE FA. EXPECT A QUICK TRANSITION OVER TO ALL RAIN MOST AREAS JUST AFTR 12Z EXCEPT FOR AREAS IN THE ADVISORY WHERE A PERIOD OF ZR SHUD CONT THRU AT LEAST 15Z BEFORE TMPS INCH ABV 32 F. AREAS FROM CAROLINE/NRN HALF OF NRN NECK CNTYS ON EAST TO DORCHESTER/WICOMICO MD MAY START OFF AS A RAIN/SLEET MIX AT THEN QUICKLY GO OVR TO RAIN. RAIN THEN BECOMES WIDESPREAD MON AFTRN AS THE BULK OF LIFT/MSTR TRACKS ACROSS THE FA. A RATHER COLD RAIN AS TMPS STRUGGLE TO GET OUT OF THE 30S PIEDMONT AND CENTRAL VA...40-45 EAST TOWARD THE ERN SHORE & SERN CHES BAY... M40S-L50S NE NC. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... LOW PRESSURE PROGGED TO LIFT NE ALONG THE CAROLINA COAST MONDAY NIGHT WITH STDYST PCPN ENDING SW-NE BY 06Z. SNDGS INDCTG ENUF MSTR FOR LGT RAIN / DRIZZLE THRU THE OVRNITE HRS. TMPS STDY IN THE M30S NW TO M40S SE. QPF 1/4 TO 1/2 IN. MID-LEVEL RIDGING BRIEFLY BUILDS INTO THE REGION TUESDAY. HOWEVER... MOIST EASTERLY FLOW WILL PREVAIL. KEPT LOW CHC (30%) POPS THRU THE DAY ALTHOUGH SOME DRIZZLE MAY LINGER THROUGH THE MORNING HRS. BIG TMP DIFFERENCES SEEN IN MOS DATA WHERE NAM IS SOME 5-10 DEGREES COLDER THAN THE GFS. GIVEN MODELS MAINTAIN AN ERLY SFC FLOW...WILL SPLIT THE DIFFERENCE FOR NOW AND GO WITH HIGHS FROM THE M-U40S OVR THE PIEDMONT TO M-U50S CSTL AREAS. && .LONG TERM /THURSDAY THROUGH SUNDAY/... A COASTAL LOW JUST OFF THE MID ATLANTIC COAST CONTINUE TO WASH OUT TUE NIGHT AS A WARM FRONT STARTS TO LIFT NORTH THROUGH THE REGION. MEANWHILE...A VERY STRONG AND VIGOROUS SFC LOW DEEPENS OVER THE OH/TN VALLEYS AND PUSHES A STRONG COLD FRONT TWD THE AREA. INITIAL PUSH OF STRATIFORM PRECIPITATION ASSOCIATED WITH THE WARM FRONT TUE NIGHT WILL LIKELY GIVE WAY TO MORE SHOWERY PRECIPITATION AS THE MID ATLANTIC REGION BECOMES WARM-SECTORED AHEAD OF THE APPROACHING COLD FRONT. THE SFC PRESSURE GRADIENT TIGHTENS SIGNIFICANTLY ON WED AS THE PARENT LOW DEEPENS OVER THE GREAT LAKES AND A STRONG JET STREAK (90-150 KT) NOSES INTO THE REGION FROM THE SSW. HIGHS SHOULD RANGE FROM 60-65 NW AND MD/VA LOWER EASTERN SHORE TO 65-69 FROM ROUGHLY RICHMOND TO SE VA/NE NC. IN ADDITION TO DEWPOINTS APPROACHING 60 DEGREES ACROSS THE SERN HALF OF THE CWA...A THETA-E RIDGE IS EXPECTED TO SURGE NWD ALONG THE SE WED MORNING INTO THE SRN MID ATLANTIC COAST BY WED AFTN/EVENING. THE COMBINATION OF THESE FEATURES/CONVECTIVE PARAMETERS MEANS THAT A SLIGHT CHANCE FOR THUNDERSTORMS HAS BEEN ADDED TO THE FORECAST ACROSS SE VA AND NE NC DURING THE AFTN/EARLY EVENING HOURS. THE FRONT EXITS THE REGION LATE WED NIGHT AND PRECIP WILL TAPER OFF FROM WEST TO EAST...COMING TO AN END EARLY THU MORNING. THE UPPER TROUGH ASSOCIATED WITH THE GREAT LAKES SFC LOW SWINGS THROUGH THE REGION LATE WED NIGHT THROUGH THU AFTN. UPPER LEVEL INSTABILITY AND ABUNDANT SFC MOISTURE FROM RECENT PRECIPITATION SHOULD KEEP SCT-BKN CUMULUS OVER THE AREA THROUGH THE DAY ON THU. CAA OCCURRING BEHIND THE COLD FRONT AND A CONTINUED TIGHT SFC PRESSURE GRADIENT WILL RESULT IN GUSTY WSW WINDS OF 20-25MPH WITH GUSTS AROUND 35MPH...AND SHOULD BE FAIRLY UNIFORM ACROSS THE REGION. THE GUSTY WINDS SHOULD DECOUPLE BY THU EVENING. OVERALL CONDITIONS FRI THROUGH THE WEEKEND SHOULD BE DRY. A LEE TROUGH FORMS ACROSS THE AREA ON FRI AND A WEAK CAD WEDGE DEVELOPS. THE PRESSURE GRADIENT RELAXES BRIEFLY FRI/FRI NIGHT AS HIGH PRESSURE BUILDING OVER THE SE STATES EXTENDS UP INTO THE MID ATLANTIC REGION. MEANWHILE...A BROAD UPPER TROUGH PUSHES A DRY COLD FRONT ACROSS THE REGION ON SAT WHICH WILL USHER MUCH COLDER 850MB TEMPS OVER THE AREA (-5 TO -15C). CAA AND A RE-TIGHTENING OF THE SFC PRESSURE GRADIENT WILL BRING A RETURN TO BREEZY SW WINDS ON SAT AND BREEZY NW WINDS ON SUN BEHIND THE NEXT COLD FRONTAL PASSAGE. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... VFR CONDITIONS WILL PREVAIL THROUGH EARLY MONDAY MORNING. LOW PRESSURE FORMING OFF THE SC COAST ALONG WITH HIGH PRESSURE WEDGING SOUTH WILL CREATE A SETUP FOR A COOL/RAINY PERIOD MON MORNING THROUGH MON NIGHT WITH MVFR/IFR VIS/CIGS EXPECTED. AS THE LOW MOVES NORTH...OVER-RUNNING PRECIP WILL TRACK S TO N MON MORNING... EVENTUALLY REACHING EVERY AKQ TAF SITE. EXPECT A BRIEF PERIOD OF 15-20 KT WIND GUSTS ALONG THE COAST AS THE LOW MOVES NORTH AND THE PRESSURE GRADIENT TIGHTENS. OUTLOOK...A SERIES OF LOW PRESSURE SYSTEMS AND COMPLEX FRONTAL BOUNDARIES WILL BRING CHANCES FOR RAIN AND PERIODS OF LOW CEILINGS AND VISIBILITIES MONDAY THROUGH WEDNESDAY. A COLD FRONT PASSES THROUGH WEDNESDAY NIGHT WITH VFR CONDS AND DRY WEATHER THURSDAY. && .MARINE... N-NE WINDS AOB 10 KT WILL PREVAIL TODAY WITH HIGH PRESSURE IN PLACE. WINDS TURN MORE EASTERLY TONIGHT AND INCREASE TO 10-15 KT MOST AREAS AS LOW PRESSURE ORGANIZING OFF THE SOUTHEAST COAST SLOWLY PUSHES NORTH. THE SFC LOW CONTINUES TO MOVE NORTHEAST OF THE NC COAST ON MONDAY...BUT WEAKENS BY LATE MONDAY/MONDAY NIGHT. WINDS WILL GENERALLY REMAIN E-NE AOB 15 KT ALL WATERS DURING THIS TIME...BUT TENDING TO BECOME MORE NORTHERLY AOB 10 KT BY EARLY TUES MORNING. LATEST GUIDANCE INDICATES POTENTIAL FOR SEAS TO BUILD TO AROUND 5 FT OUT 20 NM LATE MON/MON EVE ACROSS THE SOUTHERN COASTAL WATERS. CONFIDENCE NOT HIGH ENOUGH TO ISSUE A 3RD PERIOD SCA ATTM. LIGHT NW WINDS EXPECTED TUES AS HIGH PRESSURE REMAINS IN PLACE OVER THE MID-ATLANTIC...AND THE NEXT LOW PRESSURE SYSTEM ORGANIZES OVER THE DEEP SOUTH. WINDS TURN E-SE TUESDAY NIGHT AND GRADUALLY BEGIN TO INCREASE AS A WARM FRONT LIFTS NORTH THROUGH THE AREA. A STRONG COLD FRONT APPROACHES THE WATERS FROM THE WEST ON WEDNESDAY WITH WINDS BECOMING SOUTHERLY AND INCREASING TO SCA THRESHOLDS (SAVE THE RIVERS). THE FRONT QUICKLY SWEEPS THROUGH THE AREA WED NIGHT AND OFFSHORE EARLY THURSDAY. WINDS REMAIN ABOVE SCA LEVELS THRU LATE THURSDAY WHILE BECOMING SW THEN W. HIGH PRESSURE RETURNS THU NIGHT INTO THE START OF NEXT WEEKEND FOR IMPROVED CONDITIONS. SEAS WILL GENERALLY BUILD TO 5-7 FT ON WED BEFORE SUBSIDING AGAIN LATE THU. WAVES WILL REACH 4 FT ON THE CHES BAY. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...FREEZING RAIN ADVISORY FROM 5 AM TO NOON EST MONDAY FOR VAZ048- 049-060-061. MARINE...SMALL CRAFT ADVISORY FROM 7 AM TO 10 PM EST MONDAY FOR ANZ632- 634. SMALL CRAFT ADVISORY FROM 4 AM TO 4 PM EST MONDAY FOR ANZ633. && $$ SYNOPSIS...LKB NEAR TERM...LKB SHORT TERM...LKB/MPR LONG TERM...MAS AVIATION...DAP MARINE...MAS

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