Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 230811 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 411 AM EDT TUE SEP 23 2014 .SYNOPSIS...
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HIGH PRESSURE BUILDS ACROSS THE NORTHERN MID ATLANTIC TODAY AS LOW PRESSURE DEVELOPS OFF THE SOUTHEAST COAST. THIS AREA OF LOW PRESSURE WILL SLOWLY MOVE UP THE COAST WEDNESDAY AND THURSDAY. MEANWHILE...HIGH PRESSURE WILL REMAIN ANCHORED ACROSS NEW ENGLAND.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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CURRENT GOES WV IMAGERY SHOWS A HIGHLY MERIDIONAL MID/UPPER PATTERN ACROSS ERN NORTH AMERICA...WITH A VIGOROUS TROUGH DIGGING ACROSS THE GULF COAST...AND DEEP SSW FLOW ALONG THE EAST COAST. AT THE SURFACE...1026MB HIGH PRESSURE IS CENTERED OVER THE OHIO VALLEY...AND THE COLD FRONT THAT CROSSED THE REGION YESTERDAY MORNING HAS STALLED IN VICINITY OF THE GULF STREAM. THIS GENERAL PATTERN WILL PERSIST THROUGH THE DAY. A CONSIDERABLE AMOUNT OF CIRRUS WILL CONTINUE TO STREAM NNE WITHIN THE SSW FLOW ALOFT...AND THIS WILL PRODUCE PARTLY TO MOSTLY CLOUDY CONDITIONS. LOW-LEVEL NE FLOW WILL RESULT IN A COOLER DAY...WITH HIGHS RANGING FROM THE UPPER 60S ALONG THE COAST...TO THE LOW 70S INLAND.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/...
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SURFACE HIGH PRESSURE SHIFTS TO NRN NEW ENGLAND TONIGHT AND BUILDS TO ~1035MB. MEANWHILE...AN INVERTED TROUGH WILL BEGIN TO SHARPEN OFF THE SOUTHEAST COAST IN RESPONSE TO THE SLOW NE ADVANCEMENT OF THE GULF COAST TROUGH. FORECAST SOUNDINGS INDICATE A SIGNIFICANT LAYER OF DRY AIR CENTERED AROUND 800MB...AND GIVEN THIS MOST OF THE REGION SHOULD REMAIN DRY OVERNIGHT...WITH THE EXCEPTION OF NE NC WHERE 20-30% POPS WILL BE FORECAST AFTER 06Z. THE PATTERN BECOMES HIGHLY BLOCKED WEDNESDAY INTO WEDNESDAY NIGHT AS A CLOSED 700MB HIGH BUILDS N OF A WEAK LOW OVER THE SOUTHEAST STATES. AT THE SURFACE...HIGH PRESSURE REMAINS ANCHORED OVER NEW ENGLAND AS A WEAK COASTAL LOW DRIFTS UP THE COAST. A SUBSTANTIAL PLUME OF MOISTURE WILL ADVECT NORTHWARD FROM THE GULF STREAM WEDNESDAY INTO WEDNESDAY NIGHT AND HIT A +2 ST DEV MID AND SURFACE HIGH N OF THE REGION. THIS WILL RESULT IN A STRONG EASTERLY LLJ AND BRING THE POTENTIAL FOR HEAVY RAINFALL. MODEL DERIVED QPF ON AVERAGE SUPPORTS 1.5-2.0IN STORM TOTAL E OF I-95...ALTHOUGH THERE IS THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS. SPATIAL AND TIMING DIFFERENCES STILL EXIST AMONGST NUMERICAL MODEL GUIDANCE. THIS FORECAST GENERALLY FOLLOWS THAT OF THE 23/00Z NAM/ECMWF...WHICH FOCUSES RAIN OVER SE PORTIONS WEDNESDAY AFTERNOON/EVENING...AND THEN UP THE COAST OVERNIGHT WEDNESDAY NIGHT...BUT CONFIDENCE DOES REMAIN RATHER LOW. THE PATTERN BEGINS TO RELAX THURSDAY...ALTHOUGH LINGERING CLOUD COVER IS EXPECTED ALONG WITH A CHC OF RAIN CONTINUING MAINLY OVER NE PORTIONS. A NE WIND WILL BECOME RATHER BREEZY WEDNESDAY AFTERNOON AND EVENING ALONG THE COAST...WITH SPEEDS AVERAGING ~20MPH...WITH GUSTS OF 25-30MPH. HIGHS WEDNESDAY AND THURSDAY SHOULD RANGE FROM THE UPPER 60S/AROUND 70 OVER THE PIEDMONT...TO THE LOW/MID 70S ALONG THE COAST...BUT WILL ULTIMATELY BE DEPENDENT ON CLOUD COVER AND RAIN. LOWS SHOULD GENERALLY RANGE THROUGH THE 60S...WITH UPPER 50S POSSIBLE OVER THE NW PIEDMONT COUNTIES.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... MODEL DIFFERENCES CONTINUE TO MAKE FOR A RATHER LOW CONFIDENCE XTNDD PERIOD. NOT QUITE BUYING THE XTNDD WET PERIOD (CUT-OFF LOW) ECMWF HAS PAINTED ACROSS THE AREA (GIVEN TIME OF YEAR AND PREVIOUS PERFORMANCES) SO HAVE GONE WITH THE DRYER GFS / CANADIAN SOLN. GIST IS THAT OCEANIC MOISTURE WILL BE BATTLING THE DRY AIR FROM THE HIGH PRS TO THE NORTH. LAST TIME THIS HAPPENED...THE HIGH WON OUT EXCEPT ALONG COASTAL SECTIONS. HAVE TRENDED THIS FORECAST IN THE SAME MANNER MEANING THE BEST CHCS FOR PCPN WILL BE ALONG COASTAL SCTNS WITH MAINLY DRY CONDITIONS WEST OF THE CHES BAY THRU THE WEEKEND. COOLEST DAY FRI. HIGHS IN THE L-M70S. 75-80 BOTH SAT & SUN. LOWS M50S-M60S. NEXT TROF OF LOW PRESSURE MOVES EAST ACROSS THE MTS MON. LOW CHC POPS WITH THIS FEATURE FOR NOW. HIGHS 75-80. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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VFR CONDITIONS PREVAIL EARLY THIS MORNING OVER THE TAF SITES AS HIGH PRESSURE BUILDS IN FROM THE WEST. PRESSURE GRADIENT OVER THE REGION HAS RESULTED IN GOOD MIXING TONIGHT AND WINDS GENERALLY 8-12 KT. NLY SURGE OVER THE BAY IS PRODUCING LOCALLY STRONGER WINDS AT KORF...WITH A FEW GUSTS UP TO 25 KT. OTHERWISE...BKN-OVC HIGH CLOUDS AOA 20K FT AGL SPREADING OVER THE REGION FROM THE SW. FOR TODAY...HIGH PRESSURE BUILDS JUST NORTH OF THE LOCAL AREA WITH A SFC RIDGE EXTENDING INTO THE SE COASTAL PLAINS. PRESSURE GRADIENT BTWN HIGH PRESSURE AND A FRONTAL BOUNDARY OFF THE SE COAST WILL RESULT IN NE WINDS 10-15 KT WITH A FEW GUSTS UP TO 20-25 KT DURING PEAK HEATING. OTHERWISE...VFR CIGS/VSBYS WITH A FEW MID LEVEL CLOUDS 4-6K FT AGL AND HIGH CLOUDS AOA 20K FT. MEASURABLE PRECIP REMAINS SOUTH OF THE REGION. LOW PRESSURE FORECAST TO DEVELOP ALONG THE COASTAL FRONT WEDS AND LIFT TOWARD THE REGION INTO WEDS NIGHT. THIS WILL BRING PERIODS OF RAIN...ESPECIALLY NEAR THE COAST...ALONG WITH REDUCED VSBY AND LOW CIGS. BREEZY NE WINDS ALSO EXPECTED ALONG THE COAST.
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&& .MARINE...
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&& .TIDES/COASTAL FLOODING... PERSIST NE FLOW IS EXPECTED TO DEVELOP TUESDAY NIGHT AND STRENGTHEN WEDNESDAY INTO THURSDAY AS HIGH PRESSURE REMAINS ANCHORED OVER NEW ENGLAND...AND LOW PRESSURE DEVELOPS OFF THE CAROLINA COAST. CURRENT GUIDANCE SUGGESTS TIDAL DEPARTURES RISE TO BTWN 1-1.5FT ABOVE NORMAL WEDNESDAY NIGHT INTO THURSDAY. THIS WOULD PUT SEVERAL LOCATIONS RIGHT AROUND THE MINOR FLOODING THRESHOLDS. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...MODERATE RIP CURRENT RISK THROUGH THIS EVENING FOR MDZ025. NC...MODERATE RIP CURRENT RISK THROUGH THIS EVENING FOR NCZ102. VA...MODERATE RIP CURRENT RISK THROUGH THIS EVENING FOR VAZ098>100. MARINE...SMALL CRAFT ADVISORY FROM 7 AM WEDNESDAY TO MIDNIGHT EDT WEDNESDAY NIGHT FOR ANZ635>638. SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR ANZ630>634-638. SMALL CRAFT ADVISORY FROM 7 AM WEDNESDAY TO 6 AM EDT THURSDAY FOR ANZ630>632-634-650-652-654. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO MIDNIGHT EDT WEDNESDAY NIGHT FOR ANZ633. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EDT THURSDAY FOR ANZ656-658.
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&& $$ SYNOPSIS...AJZ NEAR TERM...AJZ SHORT TERM...AJZ LONG TERM...MPR AVIATION...SAM MARINE...SAM TIDES/COASTAL FLOODING...AKQ

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