Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 041902 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 202 PM EST WED MAR 4 2015 .SYNOPSIS... A WARM FRONT LINGERS OVER THE NORTHERN MID ATLANTIC THIS MORNING...WITH A COLD FRONT SLOWLY CROSSING THE REGION LATER THIS AFTERNOON THROUGH TONIGHT. THE FRONT WILL STALL OVER NORTH CAROLINA ON THURSDAY...WITH A WAVE OF LOW PRESSURE MOVING ALONG THE FRONT INTO THURSDAY NIGHT. THIS WILL BRING ANOTHER ROUND OF WINTRY WEATHER TO THE AREA...FOLLOWED BY COLD AND DRY CONDITIONS BY FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... QUICK UPDATE TO REFLECT ISSUANCE OF WINTER STORM WATCH OVER WICOMICO/DORCHESTER COUNTIES IN MARYLAND. INCOMING 12Z GUIDANCE BOLSTERING FORECAST CONFIDENCE OF THE GOING FORECAST...OUTLINED IN THE SHORT TERM SECTION BELOW. FORECAST CONFIDENCE FOR WINTER STORM HEADLINES IS SUFFICIENT TO JUSTIFY WATCH OVER THESE AREAS. WILL MAKE ADVISORY/WARNING DECISIONS THIS AFTN AS 12Z DATA CONTINUES TO FILTER IN. PREVIOUS DISCUSSION SENT 706 AM EST... THE CURRENT SURFACE ANALYSIS SHOWS A QUASI-STATIONARY FRONTAL BOUNDARY LINGERING FROM THE TENNESSEE VALLEY THROUGH THE NRN MID- ATLANTIC WITH A RESIDUAL WEDGE AIRMASS IN PLACE TO THE LEE OF THE MOUNTAINS. THE FRONTAL BOUNDARY IS SITUATED IN BETWEEN ARCTIC HIGH PRESSURE BUILDING OVER THE CENTRAL PLAINS AND HIGH PRESSURE OFF THE COAST...AND IS ALIGNED NEARLY PARALLEL TO THE UPPER LEVEL FLOW AND HENCE IT WILL MOVE VERY LITTLE TODAY. STRATUS WILL LINGER THROUGH AT LEAST MID- MORNING...WITH AREAS OF FOG EARLY...ESPECIALLY OVER SE VA/NE NC. HIGH TEMPERATURES WILL BE VERY CHALLENGING TODAY. THERE IS A POTENTIAL THAT FAR NRN PORTIONS STAY IN THE UPPER 40S...WITH LOW 70S ACROSS SRN PORTIONS. CENTRAL PORTIONS COULD EXPERIENCE A SPREAD OF AT LEAST 10-15F DEPENDING ON THE EVENTUAL POSITION OF THE FRONTAL BOUNDARY. THE HIGHEST POPS TODAY WILL BE ACROSS THE FAR NRN TIER COUNTIES IN CLOSER PROXIMITY TO THE BOUNDARY...WITH A SHARP GRADIENT ACROSS CENTRAL PORTIONS THAT TAPERS TO 10-20% ACROSS S/SE PORTIONS. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... A COLD FRONT PRESENTLY BACK OVER THE OHIO VALLEY DROPS INTO THE AREA THIS EVENING AND TRACKS NNW-SSE ACROSS THE AREA OVERNIGHT INTO THU MORNING. MEANWHILE...A WAVE OF LOW PRESSURE DEVELOPS ALONG THE FRONT AND TRACKS ACROSS THE CAROLINAS WEDNESDAY NIGHT INTO THURSDAY. MUCH COLDER AIR ARRIVES BEHIND THE FRONT WITH MOST OF THE AREA FALLING INTO THE UPPER 20S/LOW 30S BY THU AFTN. FORECAST SOUNDINGS SHOW DRY AIR LINGERING BETWEEN 600-400MB TONIGHT...SO ANY PCPN (IN THE FORM OF -RA) WILL BE LIGHT. A STRONG ANTI-CYCLONIC JET IS PRESENTLY LOCATED FROM THE MID-MISSISSIPPI VALLEY THROUGH ATLANTIC CANADA. THIS JET STRUCTURE WILL TRANSLATE EWD THROUGH THU AS A STRONG TROUGH DIGS ACROSS THE UPPER MIDWEST AND GREAT LAKES BY LATER THU MORNING INTO THU AFTERNOON. IT IS AT THIS TIME THAT DEEPER MOISTURE WILL ARRIVE AND RRQ FORCING WILL BE IDEALIZED AND TRIGGER THE ONSET OF WINTRY PCPN FROM NW-SE ACROSS THE AREA. IT IS NOT UNTIL 21Z THU TO 00Z FRI THAT SUB 1540M 850-700MB THICKNESS VALUES ARRIVE INTO NW PORTIONS OF THE AREA. HOWEVER...BY THIS TIME THE STRONGEST UVM WILL BE EXITING THE COAST. OVERALL IT APPEARS THAT SLR VALUES WILL BE LOW (PERHAPS 5:1-8:1) GIVEN THAT THERE WILL BE A PERIOD OF SLEET...AND THAT MID-LEVEL THICKNESSES WILL BE `WARM` DURING THE STRONGEST FORCING. THE CURRENT FORECAST HAS A NARROW BAND OF 3-4" FROM LOUISA COUNTY TO DORCHESTER COUNTY BORDERED BY A BAND OF 2-3" FOR OTHER PORTIONS OF THE NW PIEDMONT...NRN NECK...AND LOWER MD EASTERN SHORE. CURRENTLY 1-2" IS FORECAST FROM THE RIC METRO DOWN THROUGH HAMPTON ROADS...WITH 1" OR LESS FARTHER S. A BRIEF PERIOD OF FZRA IS POSSIBLE DURING THE TRANSITION FROM RA TO SN/IP WITH ANY ICE ACCUM ONLY TRACE TO A FEW HUNDREDTHS OF AN INCH. CONFIDENCE IS NOT HIGH ENOUGH FOR A WATCH ACROSS THE FAR N AT THIS TIME GIVEN THAT THIS IS A LATER THIRD PERIOD EVENT...SO THIS WILL CONTINUED TO BE HIGHLIGHTED IN THE HWO. WINTRY PCPN SHOULD TAPER OFF THU EVENING...WITH DRIER AIR ARRIVING FROM THE NW DURING THE LATE EVENING. TEMPERATURES WILL CONTINUE TO PLUMMET WITH LOWS FRI MORNING RANGING FROM THE LOW TEENS NW...TO LOW 20S SE. HIGHS FRI WILL STRUGGLE TO REACH 30-35 FRI UNDER A MOSTLY SUNNY SKY. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... EXTENDED PERIOD WILL BE HIGHLIGHTED BY GENERALLY DRY CONDITIONS AND A RETURN TO NEAR SEASONABLE NORMAL TEMPS. MEDIUM RANGE GUIDANCE IN GENERAL CONSENSUS WITH THE UPPER FLOW THRU THE EXTENDED...CHARACTERIZED BY RIDGING/BLOCKING OVER THE WRN CONUS/ERN PACIFIC AND BROAD TROUGHING OVER THE CNTRL AND ERN CONUS. TO BEGIN THE PERIOD...COLD/DRY 1030+MB ARCTIC HIGH PRESSURE CENTERS OVER THE MID-ATLANTIC REGION. THURSDAYS COLD FRONT LOCATES OFF THE COAST...EXTENDING SWWD INTO THE NRN GULF. H85 TEMPS DROP TO AROUND -8C FRI (~-1 STD DEV)...SLIGHTLY WARMER THAN DEPICTED 24 HRS AGO. HIGHS FRI GENERALLY IN THE LOW-MID 30S INLAND AND UPPER 20S-LOW 30S COASTAL AREAS. AIRMASS MODIFIES FRI NIGHT-SAT AS THE COLD/DRY AIR RETREATS NWD. HIGH PRESSURE REMAINS OVER THE REGION SAT...WITH LIGHT RETURN FLOW HELPING TO MODERATE LOW LEVEL THICKNESSES. TEMPS WARM INTO THE UPPER 40S-LOW 50S INLAND AND LOW- MID 40S COASTAL AREAS. SKY AVG MOSTLY SUNNY-PARTLY CLOUDY. HIGH PRESSURE REMAINS OVER THE REGION SUN...RESULTING IN CONTINUED DRY AND WARMING CONDITIONS. HIGHS IN THE LOW-MID 50S INLAND AND LOW 40S TO UPPER 40S COASTAL AREAS. ATTENTION THEN TURNS OUT WEST...WHERE MODELS CONTINUE TO STRUGGLE HANDLING SPLIT/BLOCKY FLOW AND SRN STREAM ENERGY OVER THE DESERT SW/BAJA. GOOD NEWS IS THAT NOW THE DETERMINISTIC ECMWF HAS TRENDED DRY SUN NIGHT-EARLY NEXT WEEK...MATCHING THE GFS AND ENSEMBLES. HOWEVER...SPLIT FLOW CONTINUES RESULTING IN LOW CONFIDENCE EARLY NEXT WEEK. FRONT OVER THE GULF WILL ATTEMPT TO AMPLIFY AND LIFT NWD AS SRN STREAM ENERGY APPROACHES...BUT WILL KEEP POPS SILENT. HIGHS EARLY NEXT WEEK (MON AND TUES) CONTINUE TO WARM INTO THE MID 50S INLAND AND LOW-UPPER 40S COASTAL AREAS THANKS TO COLD WATER. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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MORNING LIFR-IFR CONDITIONS HAVE IMPROVED TO MVFR OR EVEN VFR SRN VA TO NE NC IN WAKE OF THIS MORNINGS WARM FRONT. HOWEVER...MVFR- VFR CONDITIONS WILL BE SHORT LIVED AS A COLD FRONT DROPS ACROSS THE REGION LATE TODAY INTO EARLY TONIGHT. BKN-OVC CIGS WITH DECKS AROUND 1500 FT AGL OBSERVED ACROSS CNTRL AND ERN VA...AS WELL AS SE VA. IFR CONDITIONS PREVAIL OVER THE ERN SHORE THANKS TO LOW STRATUS AND FOG. VSBYS HAVE IMPROVED...BUT REMAIN GENERALLY 2-4 MILES. ONLY LIGHT DRIZZLE OBSERVED OVER THE MD ERN SHORE. WINDS GENERALLY S-SW AOB 10 KT NORTH AND 10-15 KT NE NC. FOR THE REST OF THE AFTERNOON...EXPECT TO SEE A FEW BREAKS IN THE CLOUDS ALL AREAS EXCEPT THE ERN SHORE...WHERE IFR CONDITIONS WILL LIKELY PERSIST. HOWEVER...AS THE FRONT DROPS INTO THE REGION...EXPECT CIGS AND VSBYS TO LOWER BACK TO LATE TODAY AND THEN BACK TO IFR THIS EVENING. POST FRONTAL/OVERRUNNING RAIN EXPECTED TO IMPACT SE VA/NE NC BTWN 06 AND 09Z. PRECIP WILL BE IN THE FORM OF RAIN TONIGHT...BUT BY EARLY THURS MORNING A WINTRY MIX OF PRECIP IS EXPECTED. THERE MAY BE A BRIEF PERIOD OF FREEZING RAIN BEFORE THE CAA CHANGES THE RAIN OVER TO SLEET THURS MORNING AND SNOW BY THURS AFTERNOON. SNOWFALL ACCUMULATIONS WILL RANGE FROM 3-5 INCHES IN THE FAR NORTH TO AROUND 1 INCH IN THE SOUTH. NORTH WINDS BEHIND THE FRONT INCREASE TO 10-15 KT LATE TONIGHT THRU THURS...WITH A FEW GUSTS OF 25 KT NEAR THE COAST. HIGH PRESSURE THEN BUILDS IN WITH DRY WEATHER FRIDAY THROUGH SUNDAY.
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&& .MARINE... HAVE EXTENDED DENSE FOG ADVISORIES NWD TO INCLUDE THE ENTIRE BAY...ERN VA RIVES AND COASTAL WATERS TO CHINCOTEAGUE AS WAA OVERSPREADS COLD WATERS. WAA WILL WANE THROUGH THE AFTERNOON...ALLOWING VISIBILITIES TO IMPROVE. MAY NEED TO EXTEND THE DENSE FOG HEADLINES WITH THE NEXT UPDATE. SW WINDS HAVE DIMINISHED THIS MORNING AS THE STRONGEST GRADIENT WINDS PUSH OFFSHORE. SEAS HAVE SUBSIDED BELOW 5 FT EXCEPT IN THE SRN COASTAL WATERS WHERE SE SWELL HAS HELPED MAINTAIN SCA CONDITIONS. HAVE OPTED TO ISSUE SCA HEADLINES SOUTH OF CAPE CHARLES LIGHT FOR TODAY...AS SEAS WILL REMAIN 4-5 FT. .PREV DISCUSSION... A COLD FRNT APPROACHES FM THE W TDA WITH S/SW FLOW CONTINUING OUT AHEAD OF THE FRNT. WINDS MAY COME CLOSE TO SCA THRESHOLDS THIS MORNG OVER THE LWR BAY DUE TO A STRONG LLJ...BUT WAA AND COLD WATERS WILL CAUSE A SHARP INVERSION THAT SHOULD KEEP SUSTAINED WINDS UP TO ~15 KT THERE. ISSUED A DENSE FOG ADVSRY FOR CSTL WTRS S OF CAPE CHARLES LIGHT DUE TO EXPECTED VSBYS AOB 1 MI THRU THE MIDDAY HRS IN ASSOCIATION WITH VERY MOIST LO LEVELS. THE FRNT SLOWLY DROPS THRU THE AREA LATE TDA INTO TNGT AS A WAVE OF LO PRES DEVELOPS ALONG THE FRNT. AS THE FRNT FINALLY PUSHES S OF THE AREA TNGT...SCA CONDS WILL COMMENCE OVR THE WTRS. THESE CONDS WILL CONTINUE INTO THU NGT AS WELL SO EXTENDED THE HEADLINES INTO THE 4TH PERIOD. WINDS MAY COME CLOSE TO GALE FORCE OVR SRN CSTL WTRS BUT CONFIDENCE IS NOT HI ENUF TO ISSUE A GALE WATCH/WARNG ATTM. ALSO KEPT ALL RIVER ZONES EXCEPT THE LWR JAMES OUT OF THE ADVSRY FOR NOW BUT WILL CONTINUE TO MONITOR. WAVES OVER THE BAY UP TO 4-5 FT WITH SEAS OVER CSTL WTRS UP TO 7-8 FT. SFC HI PRES THEN BLDS IN FOR FRI INTO THE WEEKEND LEADING TO IMPROVING MARINE CONDS. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...WINTER STORM WATCH FROM 1 AM EST THURSDAY THROUGH THURSDAY EVENING FOR MDZ021-022. NC...NONE. VA...NONE. MARINE...DENSE FOG ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR ANZ630>638-652-654-656-658. SMALL CRAFT ADVISORY FROM 4 AM THURSDAY TO 4 AM EST FRIDAY FOR ANZ630>632-634. SMALL CRAFT ADVISORY FROM 7 AM THURSDAY TO 4 AM EST FRIDAY FOR ANZ633-638. SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR ANZ650-652-654- 656-658.
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&& $$ SYNOPSIS...AJZ/LKB NEAR TERM...AJZ/MAM SHORT TERM...AJZ LONG TERM...SAM AVIATION...SAM MARINE...MAS/SAM

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