Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 181837 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 237 PM EDT MON AUG 18 2014 .SYNOPSIS... A WEAK COLD FRONT WILL DROP SOUTH ACROSS THE REGION TODAY. A SERIES OF WEAK SYSTEMS WILL MOVE ACROSS THE BOUNDARY THROUGH MIDWEEK...MAINTAINING UNSETTLED WEATHER ACROSS THE REGION. && .NEAR TERM /THROUGH TONIGHT/... SHORTWAVE ENERGY CONTINUES TO PUSH EAST ACROSS THE OHIO VALLEY THIS MORNING AND SHOWERS ARE DEVELOPING ACROSS WRN VA IN ADVANCE OF IT. MEANWHILE...A FRONTAL BOUNDARY HAS STALLED OVER SRN VA AND EXPECT THAT THIS FRONT AND THE SHORTWAVE ENERGY WILL COMBINE TO PRODUCE SHOWERS AND SOME EMBEDDED THUNDERSTORMS THIS AFTERNOON AND EVENING. SO HAVE INCREASED THE POPS NORTH OF THE FRONT UP TO 80 PERCENT. TONIGHT...THE MODELS CONTINUE TO SHOW LOW PRESSURE DEEPENING OVER EASTERN PORTIONS OF THE AREA AS THIS SHORTWAVE AND THE SFC FRONT INTERACT. THIS WILL KEEP THE CHANCES FOR RAIN CONTINUING WITH THE HEAVIEST RAIN NORTHEAST OF THE SFC LOW...WHICH SHOULD IMPACT THE NRN NECK AND PORTIONS OF THE DELMARVA. SO HAVE HELD ONTO THE HIGH POPS IN THIS REGION. FOR TEMPERATURES...THE HIGHS TODAY ARE STILL TRICKY AS THE CLOUD COVER AND SHOWERS WILL IMPACT HOW WARM IT GETS. WITH THE CURRENT READINGS GENERALLY WITH IN 5 TO 9 DEGREES OF THE FORECAST HIGHS...DID NOT WANT TO LOWER VALUES ANY...BUT IT IS QUITE POSSIBLE THAT TEMPERATURES WILL REMAIN NEARLY STEADY THROUGH MUCH OF THE DAY WITH THE CLOUDS IN PLACE...ESPECIALLY IN THE PIEDMONT COUNTIES WHERE THE RAIN IS EXPECTED TO BEGIN FIRST. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... WILL SEE A FEW SCT SHRAS IN THE MORNING TUESDAY. OTHERWISE, WL NEED TO WATCH SECONDARY SHORTWAVE ACROSS THE PLAINS THIS MORNING. THIS SHORTWAVE ENERGY WILL PUSH ACROSS THE CAROLINAS IN WEAK UPR AIR TROUGHINESS, AND WILL RESULT IN SLIGHT (20%) TO LOW END CHC (30%) POPS ACRS THE AREA TUESDAY AND WED AFTNS...HIGHEST CHCS ACROSS THE SE CWA. MAX TEMPS WILL MAINLY RANGE FM THE MID 80S TO NEAR 90 BOTH DAYS...WITH MIN TEMPS RANGING FM THE MID 60S TO LWR 70S. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... BLOCKY PATTERN OVER ERN CANADA AND THE NRN ATLANTIC WILL RESULT IN AN UNSETTLED WEATHER PATTERN THROUGH THE PERIOD. TEMPS WILL BE NEAR SEASONABLE...LATE SUMMER NORMS. SPLIT/BLOCKY FLOW IS TYPICALLY PROBLEMATIC FOR MEDIUM RANGE GUIDANCE...AND THIS TIME IS NO EXCEPTION. CONTINUE TO TREND FORECAST TOWARD THE ECMWF AND ENSEMBLE MEANS BASED ON RUN TO RUN CONSISTENCY AND WPC GUIDANCE...BUT CONFIDENCE IS NOT HIGH ATTM. THIS GUIDANCE REMAINS BTWN THE MORE AMPLIFIED 17/12Z GFS AND THE NEARLY ZONAL 17/12Z CANADIAN. WITH THAT SAID...FLOW AMPLIFIES OVER THE ERN CONUS AS MID LEVEL HIGH PRESSURE BUILDS OVER THE GULF STATES. MEANWHILE...ANOMALOUS HIGH PRESSURE BUILDS OVER ERN CANADA. SRN STREAM ENERGY OVER THE GREAT LAKES/NE STATES WILL PUSH A SHORTWAVE INTO THE NE STATES WITH TROUGHING EXTENDING SWD ALONG THE ERN SEABOARD. QUASI-STATIONARY BOUNDARY WILL SETTLE ACROSS THE MID-ATLANTIC REGION (ABOUT 100 MILES FARTHER SOUTH THAN 24 HOURS AGO) DURING THE PERIOD AS FLOW ALOFT REMAINS GENERALLY WLY. THE FRONT WILL BE THE FOCUS FOR SHOWERS/THUNDERSTORMS THRU THE PERIOD AS WEAK PERTURBATIONS IN THE FLOW PRODUCE WAVES OF LOW PRESSURE ALONG THE BOUNDARY. WARM/HUMID AIRMASS WILL BE IN PLACE WITH DEWPOINTS IN THE UPPER 60S TO LOW 70S AND TYPICAL LATE SUMMER PWATS BTWN 1.5 AND 2 INCHES. HOWEVER...LACK OF CONFIDENCE FACTORS INTO RELATIVELY LOW CHANCE POPS. CLIMO THIS TIME OF YEAR IS AROUND 20 PCT...BUT WILL GO HIGHER DURING THE AFTERNOON (30-40%) AND NEAR CLIMO OVERNIGHT DUE TO MOIST AND MARGINALLY UNSTABLE AIRMASS. IF THE TROUGH PUSHES OFFSHORE FRI NIGHT-SAT...PERTURBATIONS IN THE NW FLOW COULD BRING ADDITIONAL CHANCES OF PRECIP TO THE REGION THRU THE WEEKEND...ESPECIALLY IN THE NE. WARM THURS AND FRI WITH HIGHS IN THE UPPER 80S TO AROUND 90...COOLING OFF DUE TO CLOUDS/PRECIP THIS WEEKEND. LOW LEVEL THICKNESSES YIELD TEMPS GENERALLY IN THE MID 80S SAT AND SUN. OVERNIGHT LOWS GENERALLY IN THE UPPER 60S TO LOWER 70S THRU THE PERIOD. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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MID LVL TROF AND ASSOCIATED SFC LO PRES WILL CROSS THE REGION THIS AFTN INTO MIDDAY TUE. EXPECT SHOWERS AND POSSIBLY A TSTM AT THE TAF SITES INTO THIS EVENG...WITH JUST RAIN OR RAIN SHOWERS AT THE TAF SITES FM THIS EVENG INTO MIDDAY TUE. SHOULD HAVE MAINLY VFR OR MVFR CONDITIONS DURING THIS TIME PERIOD...BUT ISLTD IFR CONDITIONS COULD OCCUR IN ANY HEAVIER SHOWERS OR TSTMS. MAINLY VFR CONDITIONS EXPECTED LATE TUE THRU THU...BUT ISLTD OR SCTD PCPN (ESPLY WED AND THU AFTN/EVENG) COULD PRODUCE LWR CIGS AND VSBYS.
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