Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 180805 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 405 AM EDT MON AUG 18 2014 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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LATEST GOES WV SAT DATA INDICATES A WEAKENING MID LEVEL SHORTWAVE TROUGH PUSHING ACROSS THE MID-SOUTH/TN VLY THIS MORNING. THIS SYSTEM WILL PUSH EAST ACROSS THE LOCAL AREA THROUGH THIS EVENING, IN THE PRESENCE OF AN INCREASINGLY MOIST ATMOSPHERE. PW VALUES GENERALLY BETWEEN 1.5 AND 1.75" ATTM...AND WILL CLIMB TO ~2" BY THIS EVENING. HAVE GONE WITH SCT SHRAS THIS MORNING ACROSS THE WESTERN HALF OF THE AREA, REACHING THE EASTERN HALF OF THE AREA BY MIDDAY/AFTN. DUE TO TIMING OF THE ONSET OF PCPN, MODELED INSTABILITY IS RATHER WEAK, BUT WILL HOLD ONTO THUNDER MENTION FOR NOW. HOWEVER, HEAVY RAIN IS BY FAR THE MAIN THREAT OVER THE LOCAL AREA TODAY INTO TONIGHT. HIGH TEMPERATURES WILL BE VERY TRICKY GIVEN TIMING OF SHOWERS DURING TYPICAL PEAK HEATING. HAVE STAYED ON THE LOW END OF GUIDANCE ENVELOPE ONCE AGAIN, AND EVEN UNDERCUT ACROSS THE WEST, KEEPING HIGHS IN THE LOWER AND MIDDLE 80S. SLIGHTLY WARMER WITH SLOWER ONSET OF POP ACROSS THE SE, WITH HIGHS IN THE U80S. LULL IN PCPN TONIGHT IN THE WAKE OF THE PASSING SHORTWAVE. CONTINUED A CHC POP FOR SOME LINGERING SCT SHRAS. OTHERWISE, MILD AND MUGGY WITH LOWS TO RANGE IN THE U60S TO L70S.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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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.
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&& .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 /08Z MONDAY THROUGH FRIDAY/... VFR CONDITIONS WILL PREVAIL THE REST OF TONIGHT WITH PATCHY FOG REDUCING VISIBILITIES FROM 3 TO 5SM...INCLUDING TAF SITES KSBY AND KECG. A COLD FRONT APPROACHES THE REGION FROM THE NORTH AND STALLS ACROSS THE AREA MONDAY AFTN. THE FRONT COUPLED WITH A WEAK SURFACE TROUGH WILL INCREASE THUNDERSTORM CHANCES ACROSS THE AREA MON/MON NIGHT. SE-S WINDS AOB 10 KT MON WILL VEER TO SW-W MON NIGHT. FOR TUESDAY AND WEDNESDAY...THE FRONT REMAINS STATIONARY ACROSS THE REGION AND CONTINUES A CHANCE FOR WIDESPREAD SHOWERS/STORMS. THE LACK OF UPSTREAM FEATURES AND GENERALLY LIGHT STEERING FLOW ALOFT (LESS THAN 25 KT) COULD LEAD TO MODERATE TO HEAVY RAINFALL IN SLOW-MOVING STORMS...THUS REDUCING VIS/CIGS UNDER THE STRONGEST STORM CORES. FOG WILL CONTINUE TO BE A POSSIBILITY OVERNIGHT AND SHOULD GENERALLY FORM IN AREAS THAT RECEIVE RAINFALL DURING THE AFTN/EVENING HOURS. DEVELOPING NW FLOW ALOFT WILL KEEP UNSETTLED CONDITIONS ACROSS THE AREA THURSDAY AND FRIDAY. && .MARINE...
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...MAM/TMG LONG TERM...SAM AVIATION...BMD MARINE...BMD

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