Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 192032 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 432 PM EDT TUE AUG 19 2014 .SYNOPSIS... LOW PRESSURE OFF THE VIRGINIA COAST WILL PULL AWAY FROM THE COAST TONIGHT...WHILE A WEAK FRONT SLOWLY SINKS SOUTH ACROSS SOUTHERN VA. THE FRONT RETURNS AS A WARM FRONT ON WEDNESDAY...AND REMAINS STALLED ACROSS THE AREA THROUGH THE COMING WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/... THE SLOW MOVING LOW PRESSURE SYSTEM OFF THE VA CAPES CONTINUES TO SLOWLY PULL AWAY FROM THE COAST THIS AFTERNOON. STILL SEEING SOME BANDS OF SHOWERS OVER THE LOWER DELMARVA. THE MODELS SHOW THAT THIS AREA OF RAIN SHOULD GRADUALLY DIMINISH OVER THE NEXT COUPLE OF HOURS AS THE LOW MOVES AWAY AND CONVERGENCE ZONE WEAKENS. MEANWHILE...THE NEXT SHORTWAVE MOVING ACROSS UPSTATE SC CONTINUES TO LIFT ENE AND MAY PROVIDE ENOUGH FORCING TO GENERATE SOME CONVECTION ACROSS NERN NC LATE THIS AFTERNOON AND THIS EVENING. BUT LOOKING A CURRENT RADAR AND WATER VAPOR...THIS WAVE MAY REMAIN JUST SOUTH OF THE AREA. SO FOR NOW HAVE GONE WITH A LOW CHANCE POP THROUGH 3Z. BY 3Z...SHOULD SEE THE WEAK FRONT OVER SRN VA CONTINUE TO GET DRUG SOUTHWARD AND INTO NRN NC WITH WEAK HIGH PRESSURE CENTERED OVER THE NERN US PUSHING SOUTHWARD. THIS WILL PROVIDE A PERIOD OF DRY WEATHER AND SOME CLEARING. THIS SHOULD ALLOW TEMPERATURES TO DROP A FEW MORE DEGREES THAN LAST NIGHT WITH READINGS IN THE MID TO UPPER 60S IN NRN PORTIONS OF THE CWA AND LOW 70S SOUTH. ON WEDNESDAY...THE UPPER LOW OVER THE GREAT LAKES BEGINS TO DIG INTO THE MID ATLANTIC STATES WITH A COLD FRONT PUSHING INTO THE OHIO VALLEY. THIS WILL FORCE THE FRONT SOUTH OF THE AREA TO LIFT BACK NORTH AS A WARM FRONT. WITH SOME DAYTIME HEATING AND THE RESIDUAL LOW LEVEL MOISTURE STILL AROUND...SHOULD SEE SOME AFTERNOON TO EVENING CONVECTION FORM IN THE PIEDMONT AND THEN HEAD EASTWARD WITH THE WARM FRONT. THE 12Z NAM IS MORE EXCITED AND MUCH MORE LIFT THAN THE GFS OR ECMWF. THE MODELS TEND TO AGREE ON AREAS ACROSS NORTHERN VA FOR RAIN BUT NOT AS MUCH FURTHER SOUTH SO HAVE TAPERED POPS A BIT LOWER IN THE SOUTH. FOR TEMPERATURES HAVE LEANED TOWARD THE MET NUMBERS AS THE MAV HAVE BEEN TOO WARM...BUT SHOULD SEE MID TO UPPER 80S WITH MORE SUNSHINE. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... THE OVERALL PATTERN IS AGREED UPON IN THE MID RANGE PART OF THE FORECAST AS THE UPPER LOW OVER THE GREAT LAKES SLIDES INTO THE EAST AND THE UPPER RIDGE OVER THE MS VALLEY BUILDS NORTHWARD...SETTING UP NW OVER OF THE MID ATLANTIC REGION. HOWEVER...BEYOND THE THAT...THE TIMING OF INDIVIDUAL WAVES AND THE POTENTIAL FOR CONVECTIVE COMPLEXES MAKES THE TIMING OF PRECIPITATION VERY UNCERTAIN FOR THURSDAY AND FRIDAY. AT THE SURFACE...THE FRONTAL BOUNDARY THAT WILL BE IN THE VICINITY SHOULD BE SOME STATIONARY AND PARALLEL TO THE FLOW ALOFT AND COULD ALSO BE A FOCUS FOR CONVECTION. AT THIS POINT...WITH THE UNCERTAINTY...LEANED MORE TOWARD CLIMATOLOGY WITH BEST CHANCES IN THE PIEDMONT EARLY IN THE AFTERNOON AND THEN AREA WIDE IN LATE AFTERNOON THROUGH ABOUT MIDNIGHT. SUCCEEDING MODEL RUNS WILL HOPEFULLY IMPROVE THE CONFIDENCE IN THE TIMING OF THE INDIVIDUAL WAVES AND COMPLEXES. FOR TEMPERATURES...CONTINUED A SLOW WARMING TREND FOR THURSDAY AND FRIDAY...BUT DID NOT GO AS WARM AS THE MAV NUMBERS...LEANING TOWARD THE MET NUMBERS WHICH LEANED TOWARD THE UPPER 80S TO LOW 90S ON THURSDAY AND SLIGHTLY COOLER ON FRIDAY WITH MORE CLOUDS POSSIBLE. FOR LOWS HAVE LEANED WARM THAN GUIDANCE THINKING MORE CLOUDS AROUND AND A MORE HUMID AIR MASS LIMITING THE COOLING. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... UNSETTLED WEATHER PATTERN CONTINUES INTO THE EXTENDED PERIOD IN NWLY FLOW ALOFT...BUT DRIER CONDITIONS EXPECTED BY EARLY NEXT WEEK. TEMPS WILL BE SLIGHTLY BELOW SEASONABLE...LATE SUMMER NORMS TO BEGIN THE EXTENDED BEFORE RETURNING TO NEAR NORMAL EARLY NEXT WEEK. UPPER LEVEL FLOW DURING THE EXTENDED IS HIGHLIGHTED BY SPLIT/BLOCKY FLOW OFF THE ERN CANADA AND NERN US COAST AND AMPLIFYING HIGH PRESSURE OVER THE SRN CONUS. THIS PLACES THE MID-ATLANTIC REGION IN NWLY FLOW ALOFT. ASSOCIATED BACK DOOR FRONT WILL PUSH SOUTH OF THE LOCAL AREA SATURDAY MORNING. SFC HIGH PRESSURE PROGGED OVER THE NE WILL RIDGE SWWD ALONG THE COAST AND INTO CNTRL VA. NLY LOW-LEVEL FLOW INDICATED IN MEDIUM RANGE GUIDANCE WILL DRIVE DEWPOINTS DOWNWARD INTO THE MID 60S. HOWEVER...MODEL DERIVED PWATS REMAIN AROUND 1.8 TO 2.0 INCHES. COMBINED WITH PERTURBATIONS IN THE NWLY FLOW...WILL MAINTAIN CHANCE POPS FOR DIURNALLY DRIVEN SHOWERS/THUNDERSTORMS. WILL ALSO NEED TO WATCH FOR POSSIBLE MCS DEVELOPMENT UPSTREAM...ROUNDING THE RIDGE AND DROPPING INTO THE REGION OVERNIGHT THRU THE WEEKEND. BY EARLY NEXT WEEK THE RIDGE AXIS WILL BEGIN TO BUILD INTO THE REGION AS SFC HIGH PRESSURE IS PROGGED TO LOCATE OFF THE COAST. BLOCK WILL REMAIN OFF THE NE COAST...BUT MOISTURE FEED WILL BE CUT OFF. DECREASING MOISTURE AND INCREASING SUBSIDENCE WILL LIKELY RESULT IN DRY CONDITIONS. HOWEVER...CONFIDENCE IS NOT HIGH ATTM...SO WILL LEAVE POPS SILENT. NORTH OF THE BOUNDARY...THICKNESSES AND GUIDANCE YIELD TEMPS IN THE LOW TO MID 80S THRU MONDAY (AROUND -1 STD DEV). OVERNIGHT LOWS GENERALLY IN THE UPPER 60S TO LOW 70S NEAR THE WATER. WARMING BACK UP TO NEAR SEASONABLE NORMS TOWARD THE MIDDLE OF NEXT WEEK. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... WEAK LO PRES WILL SLOWLY MOVE ENE AWAY FM THE VA/NC CST LATER THIS AFTN THRU WED. EXPECTING MAINLY VFR/MVFR CONDITIONS THRU THE TAF PERIOD...WITH SCTD -RA INTO THIS EVENG POSSIBLE AT PHF/ORF/ECG/RIC. ISLTD IFR CONDITIONS AT PHF/ORF DUE TO THE -RA. POTENTIAL REDEVELOPMENT OF IFR CONDITIONS LATE TNGT OR EARLY WED MORNG...AS WINDS REMAIN ONSHORE. SLO IMPROVEMENT WED MORNG...WITH MAINLY VFR CONDITIONS FM LATE MORNG/MIDDAY THRU THE AFTN HRS WITH ONLY ISLTD CONVECTION...ESPLY AWAY FM THE CST. ISLTD TO SCTD CONVECTION POSSIBLE MAINLY THU AND FRI AFTN/EVENGS...AS MORE WEAK FRONTS OR SHRTWV ENERGY AFFECTS THE REGION. && .MARINE... SUB-SCA CONDITIONS PREVAIL THRU THE FORECAST PERIOD. LOW PRESSURE HAS JUST LOCATED OFF THE VA CAPES THIS AFTERNOON WITH A FRONTAL BOUNDARY EXTENDING WWD OVER SRN VA. GENERALLY ONSHORE FLOW 10-15 KT OVER THE WATERS...NORTH OF THE LOW. SEAS HAVE ALSO BUILT TO 3-4 FT IN THE NRN WATERS. WAVES GENERALLY 1-2 FT. LOW PRESSURE PUSHES SLOWLY OFFSHORE TONIGHT AS WEAK HIGH PRESSURE RIDGES OVER THE NRN WATERS. LOW PRESSURE REMAINS JUST OFFSHORE THRU THE END OF THE WEEK AS A WEAK BOUNDARY REMAINS OVER THE WATERS. HIGH PRESSURE BUILDS OVER NEW ENGLAND...RIDGING SWD OVER THE LOCAL AREA. THE RESULT WILL BE PERSISTENT ONSHORE FLOW...AVG AROUND 10 KT. SEAS REMAIN 2-3 FT. BY THE WEEKEND...THE GRADIENT TIGHTENS WITH NELY WINDS INCREASING TO 10-15 KT. WILL PUSH SEAS IN THE NRN WATERS TO 3-4 FT...WITH 5 FT POSSIBLE 20NM OUT. FRONT PUSHES SOUTH OF THE WATERS SAT AS HIGH PRESSURE BUILDS BACK OVER THE WATERS. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...MODERATE RIP CURRENT RISK UNTIL 8 PM EDT THIS EVENING FOR MDZ025. NC...NONE. VA...MODERATE RIP CURRENT RISK UNTIL 8 PM EDT THIS EVENING FOR VAZ099-100. MARINE...NONE. && $$ SYNOPSIS...ESS NEAR TERM...ESS SHORT TERM...ESS LONG TERM...SAM AVIATION...TMG MARINE...SAM

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