Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 101050 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 650 AM EDT THU JUL 10 2014 .SYNOPSIS... A FRONTAL BOUNDARY STALLS OVER THE REGION TODAY THROUGH FRIDAY. A WEAK AREA OF LOW PRESSURE MOVES NORTHEAST ALONG THIS BOUNDARY TONIGHT THEN PUSHES OFFSHORE FRIDAY. HIGH PRESSURE BUILDS SOUTH ACROSS THE MID ATLANTIC REGION THIS WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST MSAS SHOWING FRONTAL BNDRY NOW STALLED ACROSS THE FA WITH A WEAK SFC TROF ALONG THE COAST. LATEST RADAR SHOWING SHWRS/TSTRMS CONTG TO DVLP ALONG THE COAST WITH SCNDRY BATCH OF LIGHTER PCPN APPRCHG WRN CNTYS FROM THE WEST. ADJUSTED MORNING GRIDS A BIT MORE TOWARD THESE CURRENT CNDTNS. PVS DSCN: MODELS AGREE THE FRONT STALLS ACROSS SERN PORTIONS OF FA LATER TODAY DUE TO A FLATTENING WSW FLOW ALOFT BCMG PARALLEL TO THE BOUNDARY. WHERE THE MODELS DIFFER IS WHAT THIS BOUNDARY DOES ONCE A WEAK S/W APPROACHES FROM THE SW BY THIS EVENING. NAM MOST AGGRESSIVE IN RETROGRADING THE BOUNDARY TO NEAR THE I95 CORRIDOR FOCUSING THE CONVECTION THERE. GFS/SREF HAVE IT MEANDERING AROUND THE COASTAL PLAIN AREAS...FOCUSING CONVECTION ACROSS SERN AREAS. TOSSED AROUND THE IDEA OF A FF WATCH FOR SERN VA/NE NC LATER TODAY AND TONIGHT GIVEN DUAL POLE ESTIMATES OF 2 TO 3.5 IN (WHICH HAS VERIFIED BY GROUND REPORTS) AND AN ADDITIONAL 1.5 TO 2.5 IN OF QPF. HOWEVER...MY CONFIDENCE LOWERED AFTER SEEING THE 00Z GUIDANCE WHERE THE NAM PUSHES AXIS OF HEAVIEST RAINFALL WEST OF WHERE ANY WATCH WOULD BE GIVEN THE RECENT RAINFALL AND WHERE IT HAS BEEN RATHER DRY OF LATE (I95 CORRIDOR) WHILE THE GFS ACTUALLY HAS THE HEAVIEST RAINFALL AFTER 00Z TONIGHT. DECIDED TO HOLD OFF AN ANY FF WATCH ATTM (FF GUID FOR THOSE AREAS AOA 2 IN PER HR)...BUT MENTIONED THE LCLLY HEAVY RAINFALL THREAT IN HWO. LEANED TOWARD A SREF TIMING SOLN WITH THIS PACKAGE WHICH SEEMS TO BE A COMPROMISE BTWN THE MODELS. GIVEN THE ABOVE SCENARIO...HAVE EXPANDED THE LIKELY POPS A BIT FURTHER NORTH THIS AFTRN BUT KEPT CHC POPS ACROSS NORTHERN HALF OF FA. ALSO KEPT THE CHC POPS ACROSS WRN HALF OF FA THIS MORNING GIVEN BATCH OF PCPN MOVG NE FROM WRN NC. HIGHS M-U80S. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... S/W ENERGY TRACKS NE ALONG THE BNDRY TONIGHT. THIS WILL NOT ONLY ENHANCE CONVECTION CHCS THIS EVENING BUT SHOULD KEEP THE THREAT OF PCPN GOING THROUGH THE NIGHT. HIGHEST POPS ACROSS SERN AREAS GIVEN A SREF SOLN. POPS WOULD LIKELY HAVE TO BE RAISED FURTHER WEST IF NAM VERIFIES. LOWS M60S-L70S. SYSTEM LINGERS ALONG COASTAL AREAS FRIDAY MORNING BEFORE SLOWLY EXITING OFF THE COAST DURING THE AFTRN. DATA SHOWS PLNTY OF MSTR ARND ALONG WITH SOME INSTABILITY TO INCLUDE CHC POPS THROUGH THE DAY WITH THE HIGHEST POPS SERN AREAS. HIGHS GNRLY IN THE M80S. SCT EVENING POPS FRI NIGHT...OTW BCMG PT CLDY. LOWS 65-70. MODELS INDICATING THE FRONT WASHES OUT / DISSIPATES ACROSS THE AREA SAT. KEPT A 20-30% POP OVER THE FAR NW AND IN SE VA/NE NC. PARTLY SUNNY WITH HIGHS IN THE M-U80S. QPF NXT 72 HRS AVGG 2/3RDS TO 1 IN ACROSS NWRN AREAS...1 TO 1.5 IN ACROSS CNTRL AREAS...1.5 TO 2.5 ACROSS SERN VA/NE NC. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AMPLIFIED UPPER FLOW OVER THE HIGHER LATITUDES WILL PUSH ANOTHER ANOMALOUS TROUGH INTO THE NERN CONUS EARLY NEXT WEEK. THE RESULT WILL BE BELOW NORMAL TEMPS AND WET CONDITIONS FROM THE UPPER MIDWEST TO THE OH VALLEY. HOWEVER...THE LOCAL AREA REMAINS SEASONABLY WARM AS MUCH OF THE COOLER AIR WILL BE LOCKED WEST OF THE CNTRL APPALACHIANS. FOR THE LATTER HALF OF THE WEEKEND...ONGOING RETURN FLOW ON THE BACKSIDE OF HIGH PRESSURE ANCHORED OVER THE WRN ATLANTIC WILL RESULT IN SLIGHTLY WARMER TEMPS AND DEWPOINTS SUN COMPARED TO SAT. THICKNESSES YIELD TEMPS RIGHT AROUND 90 DEGS. A COLD FRONT WILL PUSH INTO THE GREAT LAKES REGION SUN WITH SFC TROUGHING DEVELOPING OVER THE LOCAL AREA. THETA-E ADVECTION AND A MOIST BL WILL RESULT IN MLCAPE VALUES ~1500 J/KG. MODEL DERIVED PRECIP WATERS RANGE FROM 1.75 TO 2 INCHES. WHILE MOISTURE/INSTABILITY LOOK FAVORABLE...BEST DYNAMICS/FORCING REMAINS WELL WEST OF THE AREA WITH THE BETTER HEIGHT FALLS AND STRONGER WINDS ALOFT. SHEAR IS ALSO UNIMPRESSIVE AND SOUNDINGS DEPICT SUBSIDENCE/WARM AIR ALOFT. WILL CARRY CHANCE POPS IN THE NW...TAPERING OFF TO SILENT IN THE SE. BETTER COVERAGE EXPECTED MON AS HEIGHT FALLS AND INCREASING WINDS ALOFT PROVIDE BETTER FORCING FOR ASCENT AND COOLER MID-LEVEL TEMPS. COLD FRONT IS EXPECTED TO REACH THE CNTRL APPALACHIANS LATE MON...SHARPENING THE THERMAL TROUGH OVER THE LOCAL AREA. WARMER TEMPS AND DEWPOINTS WILL PUSH MLCAPE VALUES HIGHER...BUT SHEAR REMAINS MARGINAL (AOB 20 KT). THE RESULT WILL BE SCT AFTERNOON SHOWERS/THUNDERSTORMS ACROSS MUCH OF THE REGION. COLD FRONT DROPS INTO THE REGION TUES-TUES NIGHT. EXACT TIMING OF THE FRONT WILL IMPACT SENSIBLE WEATHER OVER THE LOCAL AREA. WILL TREND TOWARD A BLEND BTWN THE MEDIUM RANGE GUIDANCE...KEEPING THE BEST POPS ALONG THE COAST TUES. BASED ON THE AIRMASS...WILL ALSO CARRY SLIGHT CHANCE POPS MON NIGHT-TUES MORNING AS THE FRONT CROSS THE REGION. UPPER LOW BEGINS TO EJECT FROM THE GREAT LAKES REGION TUES INTO SE CANADA...SLOWING THE FRONT AS IT PUSHES OFFSHORE TUES NIGHT-WEDS MORNING. CONFIDENCE IS NOT HIGH ATTM...BUT WILL HANG ON TO SLIGHT CHANCE POPS ALONG THE COAST WEDS BASED ON THE FRONT LIKELY STALLING OFFSHORE. TEMPS WILL REMAIN AROUND SEASONABLE NORMS...WARMING INTO THE UPPER 80S-LOW 90S THRU THE PERIOD. ANTICIPATE TUES TO BE THE WARMEST IN ADVANCE OF THE FRONT...WITH HIGHS GENERALLY IN THE LOW 90S. OVERNIGHT LOWS WILL GENERALLY BE IN THE UPPER 60S-LOW 70S...WITH MID 70S NEAR THE COAST. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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TSTMS CONTINUE TO DEVELOP ALONG THE ALBEMARLE SOUND. THIS IS ALONG THE OUTFLOW FROM THE EARLIER CONVECTION. LOOKING AT THE HRRR THINK THESE WILL FINALLY END BY AROUND 14Z. WILL HAVE A TEMPO GROUP AT KECG AS THESE TSTMS COULD MOVE ACROSS THERE AT TIMES. UPPER TROF CONTINUES ACROSS THE AREA TODAY. THERE WILL BE SEVERAL BOUNDARIES ACROSS THE AREA WHICH COULD FOCUS CONVECTION THIS AFTERNOON INTO TONIGHT. ALL MODELS AGREE ON CONVECTION DEVELOPING JUST NOT SURE WHETHER TO THE WEST MOSTLY RECEIVES IT OR BACK ACROSS THE SOUTHEAST. MOST HI RES MODELS ARE LEANING TOWARD SE VA AND NE NC SO WILL PUT A TEMPO GROUP IN THAT AREA THIS AFTERNOON. HOWEVER THINK MOST AREAS WILL GO TO MVFR OR EVEN IFR IN TSTMS SOMETIME THIS AFTERNOON OR TONIGHT. WITH DIMINISHING FLOW BY TONIGHT ANY THUNDERSTORMS THAT DO FORM WILL BE SLOW TO MOVE. OUTSIDE OF THE PRECIPITATION EXPECT VFR CONDITIONS WITH SOME CLOUDS AROUND 10 THOUSAND FEET. FRONT CROSSES AREA BY FRIDAY...LEAVING FRI NGT/SAT DRY ATTM. NEXT FRONT COULD BRING THE POTENTIAL FOR MORE SHWRS/TSTMS TO THE REGION LATE SUNDAY OR MONDAY.
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&& .MARINE... SUB-SCA CONDITIONS ARE EXPECTED OVER THE WATERS THROUGH THE WEEK. A WEAK TROF IS TO THE WEST OF THE WATERS KEEPING MAINLY A LIGHT SOUTHERLY WIND OVER THE WATERS. A WEAK LOW PRESSURE SYSTEM WILL MOVE ALONG THIS BOUNDARY TONIGHT AND FRIDAY. THIS WILL ALLOW THE WINDS TO BE MORE SOUTHEAST AT TIMES. AFTER THE LOW MOVES PAST FRIDAY NIGHT THE TROF WILL MOVE OFF THE COAST SATURDAY. WILL HAVE LIKELY THUNDERSTORMS THIS AFTERNOON AND TONIGHT OVER THE SOUTHERN WATERS WITH A CHANCE ACROSS THE NORTHERN WATERS.SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS THE WATERS FRIDAY INTO FRIDAY NIGHT. WINDS WILL BECOME MORE WEST TO NORTH OVER THE WEEKEND. FLOW VEERS TO THE SOUTH SUN...REMAINING SUB SCA AT 10-15 KT. SEAS REMAIN 2-3 FT. LOW PRESSURE LIFTS INTO THE GREAT LAKES REGION MON AS A COLD FRONT PUSHES INTO THE OH VALLEY. GRADIENT WILL STRENGTHEN SLIGHTLY OVER THE WATERS SUN NIGHT-MON...BUT REMAINS SUB-SCA. PERSISTENT SLY FLOW WILL PUSH SEAS TO 4 FT IN THE NRN WATERS...BUT ANTICIPATE SEAS TO REMAIN UNDER 5 FT. COLD FRONT CROSSES THE WATERS TUES NIGHT-WED MORNING. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...MPR NEAR TERM...MPR SHORT TERM...MPR LONG TERM...SAM AVIATION...JAB MARINE...JAB

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