Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 230140 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 940 PM EDT TUE APR 22 2014 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE REGION OVERNIGHT. COOL CANADIAN HIGH PRESSURE BUILDS BACK OVER THE REGION WEDNESDAY AND THURSDAY. A SERIES OF WEAK FRONTS WILL CROSS THE AREA FRIDAY INTO THE WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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AS OF 930 PM...SFC COLD FRONT IS CURRENTLY CROSSING THE MOUNTAINS AND WILL CONTINUE TO ADVANCE EASTWARD LATE THIS EVENING...THEN OFF THE COAST AROUND 06Z. LATEST RADAR IMAGERY CONTINUES TO DEPICT ONLY ISOLATED -SHRA ACROSS NORTHERN/EASTERN PORTIONS OF THE FA. BASED ON THIS...HAVE REMOVED POPS ACROSS SOUTHERN AREAS WHILE KEEPING LOW END POPS (20-30%) ACROSS NORTHERN/EASTERN LOCALS THRU MIDNIGHT. A QUICKLY CLEARING SKY IS EXPECTED AFTER MIDNIGHT...AS COOL CANADIAN HIGH PRESSURE BUILDS IN FROM THE NW. ENOUGH MIXING WILL OCCUR OVERNIGHT TO KEEP TEMPS FROM ONLY FALLING INTO THE UPR 40S INLAND AND OVER THE EASTERN SHORE...TO LOW 50S SE COAST.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... MODIFYING CANADIAN HIGH PRESSURE BUILDS IN FROM THE NW ON WED...WITH A BREEZY TO WINDY AND VERY DRY DAY EXPECTED. BUFKIT SOUNDINGS SUGGEST FREQUENT GUSTS TO 35-40 MPH ON THE ERN SHORE AND 25-35 MPH ELSEWHERE (SEE FIRE WX SECTION BELOW). SKIES WILL BE MAINLY CLEAR ALTHOUGH A FEW SCATTERED CU WILL PERSIST ACRS THE ERN SHORE DUE TO COLD POOL ALOFT ON THE BACK SIDE OF THE UPPER TROUGH (LOCATED JUST OFFSHORE). LOCAL THICKNESS TOOLS INDICATE HIGHS ONLY IN THE LOWER TO MIDDLE 60S OVER THE LOCAL AREA. HOWEVER, WITH DEWPOINTS WILL MIX INTO THE UPR 20S/LOW 30S (YIELDING MINIMUM RH VALUES IN THE MID 20S INLAND) AND WITH DOWNSLOPE FLOW COMPONENT, BUMPED TEMPS INTO THE MID TO UPPER 60S INLAND ALL ZONES (NOT MUCH DIFFERENCE AT THE COAST DUE TO STRONG NW FLOW). HIGH PRESSURE BEGINS TO BUILD IN FROM NW WED NIGHT UNDER CLEAR SKIES. EARLY MORNING LOWS THU MORNING IN THE MID-UPPER 30S ALONG/W OF I-95 TO THE UPPER 30S TO LOWER 40S ELSEWHERE (DO NOT EXPECT A FREEZE AND PROBABLY TOO DRY FOR MUCH IN THE WAY OF FROST). DRY AGAIN ON THU AS HIGH PRESSURE SLIDES OVER THE REGION, BEFORE SLIDING OFF OFF THE CAROLINA COAST LATE THU/ERY FRIDAY. HIGHS THURS GENERALLY IN THE UPPER 60S (A LITTLE COOLER NEAR THE COAST). ONCE AGAIN, MIN RH VALUES FALL INTO THE 20S THU AFTN BUT WINDS WILL BE LIGHTER. NEXT FAST MOVING WAVE OF MOISTURE MOVES IN FROM THE W ON FRI. HAVE BLENDED THE FASTER GFS AND SLOWER NAM/ECMWF FOR NOW...WITH CHC POPS ALL ZONES AT SOME POINT...MAINLY FROM LATE MORNING THROUGH LATE AFTN. WARMER SSW FLOW SHOULD PUSH HIGHS WELL INTO THE 70S. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... PROGRESSIVE FLOW WILL BEGIN TO EVOLVE INTO A HIGHLY AMPLIFIED/BLOCKY PATTERN OVER THE CONUS DURING THE EXTENDED...LIKELY RESULTING IN A COOL/WET PERIOD BY EARLY NEXT WEEK. MEDIUM RANGE GUIDANCE TENDS TO STRUGGLE WITH BLOCKY FLOW...AND THIS IS NO EXCEPTION. TRENDED TOWARD ENSEMBLE AND WPC GUIDANCE TO SMOOTH OUT DIFFERENCES IN THE MODELS. OVERALL...UPPER PATTERN WILL BE CHARACTERIZED BY AN ANOMALOUS UPPER TROUGH OVER THE WRN CONUS...HIGH PRESSURE RIDGING FROM THE GULF STATES INTO THE NORTHWEST TERRITORIES AND ANOTHER UPPER TROUGH OVER SE CANADA AND NEW ENGLAND. WHILE MEANINGFUL DIFFERENCES EXIST IN THE MODELS...A SECOND (DRY) COLD FRONT IS PROGGED TO CROSS THE LOCAL AREA ON SAT. THIS FRONT WILL BRING COOLER/DRIER AIR TO THE REGION ON SUN. A STATIONARY BOUNDARY WILL THEN SET UP OVER THE MID-ATLANTIC REGION (DEPENDING ON THE MODEL IT COULD BE FROM THE CAROLINAS NWD TO THE MASON DIXON LINE). THIS BOUNDARY WILL BE THE FOCUS OF PRECIP EARLY NEXT WEEK. MEANWHILE...A BROAD AREA OF LOW PRESSURE OVER THE PLAINS WILL PROGRESS EWD SUN-TUES...TAPPING INTO GULF MOISTURE. WILL MAINTAIN SLIGHT CHANCE POPS SUN NIGHT-TUES BASED ON UNCERTAINTY...BUT INCREASE TO LOW-END CHANCE POPS TUES NIGHT AS THE UPPER/SFC LOW GETS CLOSER. HAVE TRENDED TO THE COOLER SIDE OF GUIDANCE WITH HIGHS GENERALLY IN THE MID-UPPER 60S SUN-TUES. OVERNIGHT LOWS GENERALLY IN THE UPPER 40S-LOW 50S. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... AS OF 23Z...PRE-FRONTAL SHOWERS HAVE PRACTICALLY DISSIPATED AND DID NOT INCLUDE ANY PCPN IN THE TAFS. A STRONG COLD FRONT WAS MOVING THROUGH THE MOUNTAINS AND IS FORECAST TO REACH RIC/SBY SHORTLY AFTER MIDNIGHT AND ECG AROUND 09Z/5AM EDT. BKN MID LEVEL CLOUDS SHOULD QUICKLY CLEAR BEHIND THE FRONT. GUSTY NW OR N WINDS WILL IMMEDIATELY FOLLOW THE FRONT. WINDS DIMINISH SOME (EXCEPT AT ORF) A COUPLE OF HOURS FOLLOWING THE FRONTAL PASSAGE AND THEN INCREASE ONCE AGAIN LATE WEDNESDAY MORNING. GUSTS MAY REACH OVER 30 KNOTS AT SBY AND AROUND 25 KNOTS AT THE OTHER TAF SITES. OUTLOOK...VFR CONDITIONS WILL CONTINUE THROUGH THURSDAY NIGHT. THE NEXT COLD FRONT CROSSES THE AREA FRIDAY WITH SCT SHWRS/TSTMS IN THE AFTERNOON. ANOTHER FRONT CROSSES THE AREA SATURDAY BUT THE WEEKEND IS FORECAST TO BE DRY. && .MARINE... PRE-FRONTAL TROUGH HAS ALIGNED ALONG THE WATERS LATE THIS AFTERNOON AS A COLD FRONT LOCATES OVER THE CNTRL APPALACHIANS. S-SW WINDS CURRENTLY OVER THE WATERS AVERAGING 10-15 KT WITH WAVES 1-2 FT AND SEAS 3-4 FT. COLD FRONT WILL CROSS THE WATERS THIS EVENING AS A STRONG NW SURGE COMMENCES. PRESSURE GRADIENT STRENGTHENS BTWN BUILDING CANADIAN HIGH PRESSURE OVER THE GREAT LAKES AND THE DEPARTING COLD FRONT. 925MB WINDS INCREASE TO 35-40 KT AS LOW LEVEL LAPSE RATES SHARPEN. THE RESULT WILL BE SOLID SCA CONDITIONS OVER THE WATERS...INCLUDING THE RIVERS AND SOUND. DECIDED TO NOT GO LOW-END GALE BASED ON THE LIMITED STRENGTH OF THE SFC PRESSURE GRADIENT AND COOL WATERS. HOWEVER...AN OCCASIONAL GUST TO 35 KT IS POSSIBLE...ESPECIALLY OVER THE NRN BAY AND NRN COASTAL WATERS. TOP OF THE MIXED LAYER AT KSBY YIELDS GUST TO ONLY 30-33 KT. WILL MONITOR FUTURE OBS/MODEL TRENDS TO SEE IF GALE HEADLINES ARE NEEDED. REGARDLESS...CONDITIONS WILL DETERIORATE RAPIDLY AROUND MIDNIGHT. WAVES WILL BUILD TO 3-5 FT IN THE BAY...2-3 FT IN THE RIVERS AND 2 FT IN THE SOUND. SEAS WILL BUILD TO 5-8 FT...HIGHEST IN THE NRN COASTAL WATERS. HIGH PRESSURE WILL CONTINUE TO BUILD SWD OVER THE OH VALLEY WEDS AS SCA CONDITIONS PERSIST THRU THE DAY. THE HIGH WILL NUDGE OVER THE WATERS WED NIGHT...ALLOWING THE PRESSURE GRADIENT TO RELAX AND WINDS TO DIMINISH. SCA HIGH PRESSURE WILL SLIDE OVER THE REGION THURS...LOCATING OFFSHORE LATE THURS. FLOW WILL RETURN TO THE SOUTH...WITH SEAS SUBSIDING BELOW 5 FT LATE THURS. SCA HEADLINES FOR THE RIVERS AND SOUND DROP OFF LATE WEDS...LOWER JAMES AND BAY THURS MORNING. A WEAKER COLD FRONT CROSSES THE WATERS FRI AFTERNOON WITH A SECOND COLDER FRONT CROSSING THE WATERS SATURDAY. SCA CONDITIONS MAY BE POSSIBLE SAT NIGHT. && .FIRE WEATHER...
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GIVEN THE EXPECTED DRY AND BREEZY CONDITIONS WEDNESDAY...AND AFTER COORDINATION WITH STATE FIRE OFFICIALS/NEIGHBORING OFFICES...A FIRE WX WATCH IS IN EFFECT FOR WEDNESDAY AFTERNOON/EVENING FOR PORTIONS OF CENTRAL AND EASTERN VA AND THE LOWER MD EASTER SHORE. WINDS ARE EXPECTED TO BE THE STRONGEST (20-25 MPH WITH GUSTS TO 35-40 MPH) ALONG AND NORTH OF A LINE FROM FVX-PTB- LFI...AND THIS IS WHERE THE WATCH IS IN EFFECT. FARTHER SOUTH...WINDS WILL NOT BE AS STRONG (10-20 MPH WITH GUSTS TO 30 MPH)...SO HAVE OPTED TO LEAN TOWARD AN SPS FOR INCREASED FIRE DANGER INSTEAD. WILL LIKELY UPGRADE THE FIRE WX WATCH TO A RED FLAG WARNING OVERNIGHT. MIN RH VALUES WED AFTN WILL DROP TO BETWEEN 20-30% FOR MOST LOCATIONS. DRY CONDITIONS (MIN RH VALUES 20-25%) WILL OCCUR AGAIN ON THURSDAY. HOWEVER...WINDS ARE NOT EXPECTED TO BE AS STRONG. THIS WILL LIKELY PRECLUDE THE NEED FOR ANY FIRE WX STATEMENTS...EXCEPT FOR THE LOWER MD EASTERN SHORE WHERE WINDS MAY REMAIN ELEVATED.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR MDZ021>025. NC...INCREASED FIRE DANGER FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR NCZ012>017-030>032. VA...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR VAZ048-049-061>064-068>078-081>086-089>091- 094-099-100. INCREASED FIRE DANGER FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR VAZ060-065>067-079-080-087-088-092- 093-095>098. MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THURSDAY FOR ANZ650-652- 654-656-658. SMALL CRAFT ADVISORY UNTIL 7 PM EDT WEDNESDAY FOR ANZ633- 635>637. SMALL CRAFT ADVISORY UNTIL 10 AM EDT THURSDAY FOR ANZ630>632- 634. SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ638.
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&& $$ SYNOPSIS...LKB NEAR TERM...JDM SHORT TERM...LKB LONG TERM...SAM AVIATION...LSA MARINE...SAM FIRE WEATHER...JDM

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