Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 210537 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 137 AM EDT TUE APR 21 2015 .SYNOPSIS... RAIN SHOWERS WILL TAPER OFF OVERNIGHT AS A COLD FRONT CROSSES THE AREA AND OFFSHORE BY TUESDAY MORNING. HIGH PRESSURE BUILDS BACK IN FROM THE SOUTHWEST ON TUESDAY. ANOTHER COLD FRONT CROSSES THE AREA LATE WEDNESDAY INTO WEDNESDAY NIGHT. HIGH PRESSURE RETURNS THURSDAY AND FRIDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A LINE SEGMENT OF TSTMS HAS DEVELOPED FROM N-CENTRAL NC INTO FAR SRN VA OVERNIGHT IN VICINITY OF A PRE-FRONTAL SURFACE TROUGH. THE ENVIRONMENT REMAINS STRONGLY SHEARED WITH EFFECTIVE SHEAR VALUES AROUND 40-45KT ACROSS THE COASTAL PLAIN. ADDITIONALLY...MUCAPE VALUES ARE ~1000 J/KG. AN ISOLATED SEVERE THREAT WILL CONTINUE OVERNIGHT ACROSS THE WATCH AREA...BEFORE CONVECTION WEAKENS LATER TONIGHT. MEANWHILE...THE SFC COLD FRONT CURRENTLY SITS FROM NCNTRL VA DOWN INTO SW/SCNTRL VA AND WILL MOVE OFF THE COAST BY SUNRISE TUESDAY MORNING. TEMPERATURES ARE MILD RANGING FROM THE UPPER 60S TO LOW 70S. EVENTUALLY...LOWS SHOULD BE IN THE MID/UPPER 50S WEST OF I-95 AND IN THE UPPER 50S/LOW 60S EWD TO THE COAST. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/... STACKED UPPER LOW ANCHORS OVER THE GREAT LAKES REGION AND SRN CANADA THRU THE SHORT TERM PERIOD THANKS TO BLOCKY FLOW OVER THE HIGH LATITUDES. IN WAKE OF TONIGHTS (MON NIGHTS) COLD FRONT...HIGH PRESSURE FORECAST TO BUILD ACROSS THE SE STATES TUES...EXTENDING NEWD OVER THE LOCAL AREA. THE RESULT WILL BE DRY CONDITIONS AND A WLY WIND. HIGHS FORECAST IN THE UPPER 60S E TO LOW 70S W UNDER A MOSTLY SUNNY SKY. SERIES OF UPPER LEVEL DISTURBANCES WILL ROUND THE BASE OF THE UPPER LOW...WITH THE FIRST ROUNDING THE BASE TUES NIGHT- WEDS. ASSOCIATED FAST MOVING COLD FRONT DROPS INTO THE OH VALLEY WEDS. HIGH PRESSURE PUSHES OFF THE SE COAST WEDS...WITH INCREASING SWLY LOW LEVEL FLOW OVER THE LOCAL AREA. WEAK FRONT REACHES THE CNTRL APPALACHIANS WEDS AFTERNOON. WILL MAINTAIN SLIGHT CHANCE- CHANCE POPS ACROSS THE NRN LOCAL AREA WEDS AFTERNOON...CLOSEST TO BEST MOISTURE/DYNAMICS. HIGHS WEDS GENERALLY IN THE LOW-MID 70S. FRONT DROPS ACROSS THE LOCAL AREA WEDS NIGHT. WILL MAINTAIN SLIGHT CHANCE-CHANCE POPS ALONG THE COAST WEDS NIGHT. FRONTAL BOUNDARY STALLS JUST SOUTH OF THE LOCAL AREA EARLY THURS MORNING. WAVE OF LOW PRESSURE PROGGED TO DEVELOP ALONG THE STALLED BOUNDARY THURS MORNING AS SRN STREAM ENERGY TRAVERSES THE GULF STATES. GFS/ECMWF SOLUTIONS KEEP MEASURABLE PRECIP SOUTH OF THE LOCAL AREA THURS...BUT NAM/SREF SOLUTIONS SPREAD PRECIP INTO S AND SE VA/NE NC. WILL CARRY SLIGHT CHANCE POPS THURS ACROSS THOSE AREAS BASED ON UNCERTAINTY. COOLER THURS WITH WNW FLOW BEHIND THE FRONT. HIGHS GENERALLY IN THE LOW-MID 60S. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... COLD FRONT MOVES SOUTH OF THE AREA THURS NIGHT FOLLOWED BY COOL HIGH PRESSURE BUILDING IN FROM THE NW. DRY WITH LOWS BOTH THURS AND FRI NIGHTS 40-50 XCPT A FEW U30S NWRN MOST CNTYS. HIGHS FRI M-U60S. NXT SYSTM PROGGED TO TRACK ACROSS THE CAROLINAS SAT. ECMWF SOMEWHAT FRTHR SOUTH WITH ITS MOISTURE FIELDS THAN GFS. BEST SPRT FOR PCPN WILL BE ACROSS SRN HALF OF FA WHERE CHC POPS WILL BE MAINTAINED. SLGHT CHC ACROSS THE NRTH. COOL SAT WITH HIGHS 60-65. PCPN ENDS SAT EVE AS SYSTM EXITS OFF THE COAST. LOWS IN THE 40S. CANADIAN HIGH PRESSURE DOMINATES ERLY NEXT WEEK WITH ANY PCPN STAYING SOUTH OF FA. DRY WITH A SLOW MODERATING TREND. HIGHS SUN IN THE L-M60S. LOWS SUN NIGHT IN THE 40S. HIGHS MON M-U60S. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 06Z...A COLD FRONT WAS SITUATED OVER CENTRAL VIRGINIA AND IS EXPECTED TO CROSS THE TAF SITES BETWEEN 10 AND 14Z. CONVECTION HAS BEEN RATHER ISOLATED SO FAR AND WITH DAYTIME HEATING CUT OFF... WIDESPREAD TSTMS ARE UNLIKELY. CANNOT RULE OUT A TSTM OVERNIGHT AT ORF/PHF/ECG BUT NOT INCLUDED IN THE TAF DUE TO LO PROBABILITY. S WINDS GRADUALLY VEER BECOMING W/NW FOLLOWING THE FRONTAL PASSAGE. WINDS ARE FORECAST TO GUST TO AROUND 20 KNOTS AND BACK TO THE WEST THIS AFTN. OUTLOOK...THE SURFACE HIGH MOVES OFFSHORE WEDNESDAY. A COLD FRONT CROSSES THE AREA WEDNESDAY NIGHT WITH A CHC OF SHOWERS MAINLY AT RIC AND SBY. DRY WEATHER RETURNS FOR THE REST OF THE WEEK.
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&& .MARINE... 10 PM UPDATE...SCA HOISTED FOR THE BAY AND LOWER JAMES FOR S WINDS 15 TO 20 KNOTS AND 4 TO 5 FT WAVES AT THE MOUTH OF THE BAY. CONDITIONS ARE EXPECTED TO SUBSIDE DURING THE EARLY MORNING HOURS WITH THE SCA CURRENTLY SCHEDULED TO EXPIRE AT 4 AM. SEAS REMAIN AT OR ABOVE 5 FT...SO WILL CONT THE SCA HEADLINES WITH AN EMPHASIS ON SUBSIDING CONDITIONS THROUGH TUES. A COLD FRONT CROSSES THE AREA LATE TONIGHT. SW WINDS AHEAD OF THIS BOUNDARY WILL SHIFT TO THE WEST BUT REMAIN BLO 20 KTS...SO NO HEADLINES (WIND WISE) XPCTD BEHIND THE FRNT. NEXT TROF / FRONT PROGGED ACROSS THE WATERS WED NIGHT / ERLY THURSDAY SWITCHING THE WNDS TO A NW THEN N DIRECTION. ONCE AGAIN...SURGE BEHIND THIS BOUNDARY NOT STRONG ENUF TO GENERATE HEADLINES. NW FLOW SETS UP BEHIND THIS BOUNDARY INTO THE WEEKEND WITH CONDITIONS REMAINING BLO SCA LEVELS. && .HYDROLOGY... OVERNIGHT RAINFALL OF ONE TO ONE HALF INCH RESULTED IN RISES OVER AREA RIVERS DURING THE DAY. MINOR FLOODING ON THE RIVANNA RIVER AT PALMYRA SHOULD END BEFORE MIDNIGHT. RISES ARE EXPECTED OVERNIGHT TONIGHT FOR THE JAMES RIVER...WITH THE RICHMOND WESTHAM GAUGE APPROACHING MINOR FLOODING TUESDAY NIGHT AND WEDNESDAY. && .TIDES/COASTAL FLOODING... SOUTHERLY FLOW INTO THIS EVENING WILL HELP MAINTAIN ~1.0 FT ANOMALIES IN THE MIDDLE BAY THROUGH TONIGHT. BISHOPS HEAD WILL APPROACH THE MINOR THRESHOLD LATE TONIGHT. A COASTAL FLOOD STATEMENT HAS BEEN ISSUED TO ACCOUNT FOR THIS. OTHER LOCATIONS IN THE MIDDLE BAY SHOULD STAY BELOW MINOR THRESHOLDS. TIDAL ANOMALIES WILL BEGIN TO SUBSIDE TUESDAY AS THE FLOW BECOMES OFFSHORE. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT EARLY THIS MORNING FOR ANZ630>632-634-638. SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR ANZ654- 656-658. SMALL CRAFT ADVISORY UNTIL 1 PM EDT THIS AFTERNOON FOR ANZ650- 652. && $$ SYNOPSIS...JDM/SAM NEAR TERM...AJZ/BMD/SAM SHORT TERM...SAM LONG TERM...MPR AVIATION...MAS/LSA MARINE...AJZ/MPR/LSA HYDROLOGY... TIDES/COASTAL FLOODING...

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