Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250713 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 315 AM EDT MON AUG 25 2014 .SYNOPSIS...SURFACE HIGH PRESSURE CENTERED OVER THE MID-ATLANTIC WILL EXTEND SOUTHWARD INTO THE CAROLINAS THROUGH MID-WEEK. && .NEAR TERM /THROUGH TUESDAY/... AS OF 225 AM MONDAY... TODAY AND TONIGHT: SURFACE HIGH PRESSURE CONTINUES TO EXTEND INTO CENTRAL NC THIS MORNING FROM THE MID-ATLANTIC REGION... WHILE MID LEVEL RIDGING BUILDS EAST FROM THE OZARKS INTO THE OHIO VALLEY AND NORTHEAST U.S. MID LEVEL HEIGHTS ARE FORECAST TO INCREASE ACROSS CENTRAL NC AS THE RIDGE AXIS SLOWLY SINKS SOUTHWARD TODAY. THIS WILL RESULT IN AN ABUNDANCES OF MID LEVEL DRY AIR ACROSS CENTRAL NC FOR THE NEXT SEVERAL DAYS. HOWEVER... WITH A GENERAL NORTHEAST TO EAST- NORTHEASTERLY LOW LEVEL FLOW PERIODS OF MOISTURE ARE EXPECTED TO ADVECT INTO THE REGION FROM TIME TO TIME. OUTSIDE OF SOME HIGH CIRRUS THIS MORNING... SKIES ARE LARGELY CLEAR/MOSTLY CLEAR AS A POCKET OF DRIER LOW LEVEL AIR HAS FILTER INTO THE AREA... HELPING TO SCOUR OUT THE LINGERING LOW LEVEL CLOUDS ACROSS THE AREA. HOWEVER... LOW LEVEL MOISTURE AT AROUND 850 MB IS EXPECTED TO INCREASE AGAIN LATE THIS MORNING INTO THE AFTERNOON... YIELDING AT LEAST SOME PARTLY SUNNY TO MOSTLY CLOUDY CONDITIONS ACROSS THE COASTAL PLAIN AND SANDHILLS... PERHAPS A FAR WEST AS THE TRIANGLE. GIVEN THE STOUT SUBSIDENCE INVERSION LOCATED AT AROUND 850-775 MB EXPECT THE CLOUD COVER WILL SPREAD OUT BENEATH THE INVERSION... POSSIBLY RESULTING IN A PERIOD OF MOSTLY CLOUDY SKIES. THUS... WILL GO WITH HIGHS ONLY RANGING FROM 81 TO 84 ACROSS THE AREA... BELOW NORMAL (ALSO... AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO RUN ABOUT 20 METERS BELOW NORMAL). WE MAY SEE SOME LINGERING MOISTURE TRAPPED BELOW THE SUBSIDENCES INVERSION ACROSS PORTIONS OF THE AREA THIS EVENING. HOWEVER... LOW LEVEL FLOW IS FORECAST TO BACK TO MORE OF A NORTH-NORTHEASTERLY DIRECTION AND ALLOW FOR SOME DRIER AIR TO AGAIN BEGIN WORKING INTO THE AREA LATE TONIGHT. THUS... WILL SHOW SKIES BECOMING MOSTLY CLEAR EVERYWHERE BY EARLY TUESDAY MORNING. LOWS TUESDAY MORNING ARE EXPECTED TO GENERALLY BE IN THE UPPER 50S TO LOWER 60S AGAIN. TUESDAY: MOSTLY SUNNY SKIES ARE EXPECTED FOR TUESDAY WITH LOW LEVEL FLOW CONTINUING TO BE MORE NORTH-NORTHEASTERLY. THIS SHOULD YIELD A BIT WARMER TEMPS. AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO REBOUND BY SOME 5 TO 10 METERS. THIS COMBINED WITH MORE SUN SHOULD ALLOW FOR AFTERNOON HIGH TEMPS IN THE MID TO UPPER 80S (83- 87). && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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AS OF 315 AM MONDAY... TRANQUIL WEATHER PATTERN THIS PERIOD AS CENTRAL NC WEATHER WILL BE INFLUENCED BY AN AREA OF HIGH PRESSURE AT THE SURFACE AND ALOFT. THE PRESENCE OF WEATHER SYSTEM WILL MAINTAIN A RELATIVELY DRY AIR MASS OVER OUR REGION...LEADING TO ABUNDANT SUNSHINE DURING THE DAY AND CLEAR SKIES AT NIGHT. THE AIR MASS WILL MODIFY WITH TIME. LOW LEVEL THICKNESSES AVERAGE ABOUT 10M ABOVE NORMAL WEDNESDAY AND 15-20M ABOVE NORMAL BY THURSDAY. THIS YIELDS MAX TEMPS WELL INTO THE 80S TO AROUND 90 WEDNESDAY AND UPPER 80S TO LOWER 90S THURSDAY. A BACKDOOR COLD FRONT ASSOCIATED WITH A S/W CROSSING NEW ENGLAND WILL MAKE A RUN FOR OUR NORTHERN COUNTIES LATE THURSDAY. LIFT ALONG THIS BOUNDARY IS WEAK AND UPPER LEVEL SUPPORT IS SIMILARLY WEAK. AT THIS TIME PLAN TO LIMIT POPS TO SLIGHT CHANCE AND CONFINED TO THE FAR NORTHERN COUNTIES.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
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AS OF 315 AM MONDAY... BACKDOOR COLD FRONT PROJECTED TO DRIFT INTO CENTRAL NC THURSDAY NIGHT AND STALL. UPPER LEVEL HEIGHTS SLOWLY BUILD IN THE WAKE OF THE DEPARTING S/W OFF THE NEW ENGLAND COAST AND AS T.C. CRISTOBAL MOVES NORTH-NE BETWEEN THE NC COAST AND BERMUDA. THE MODEST SUBSIDENCE INVERSION IN THE MID LEVELS MAY BE ENOUGH TO CAP OFF THE ATMOSPHERE FOR MOST OF OUR FORECAST AREA. HOWEVER...STRONG HEATING COUPLED WITH AVAILABLE (THOUGH MARGINAL) MOISTURE TO TRIGGER ISOLATED CONVECTION FRIDAY AFTERNOON AND AGAIN SATURDAY AFTERNOON. MODEL GUIDANCE HINTS THAT THE BETTER PROBABILITY OF THIS OCCURRING WILL BE OVER THE NE PIEDMONT-NORTHERN COASTAL PLAIN ALONG AND BEHIND THE STALLED SFC BOUNDARY. LOW LEVEL THICKNESSES WILL CONTINUE TO AVERAGE 10-12M ABOVE NORMAL...SUPPORTIVE OF MAX TEMPS 2-3 DEGREES ABOVE NORMAL FOR LATE AUGUST. MAX TEMPS FRIDAY-SATURDAY SHOULD REMAIN WELL INTO THE 80S TO THE LOWER 90S. SFC DEWPOINTS WILL INCREASE AS SFC BOUNDARY WILL AID TO POOL LOW LEVEL MOISTURE. THUS IT WILL FEEL MORE HUMID AS WE GET TO THE END OF THE WEEK. APPEARS THAT BY SUNDAY...CENTRAL NC WILL BEGIN TO BE INFLUENCED BY AN APPROACHING MID LEVEL TROUGH AND ACCOMPANYING SFC BOUNDARY. WHILE MOISTURE ADVECTION WEAK-MODEST...ENOUGH INSTABILITY WILL EXIST COUPLED WITH AFTERNOON HEATING TO INCREASE CONVECTIVE COVERAGE TO SCATTERED...MAINLY IN THE PIEDMONT. IF THE MID-UPPER LEVEL RIDGE HOLDS ON...THE BETTER CONVECTIVE CHANCES MAY BE DELAYED UNTIL MONDAY/LABOR DAY.
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&& .AVIATION /06Z MONDAY THROUGH THURSDAY/... AS OF 140 AM MONDAY... 24-HR TAF PERIOD: VFR CONDITIONS AND A STEADY NORTHEAST BREEZE SHOULD PREVAIL THROUGH THE TAF PERIOD AS DRY SURFACE HIGH PRESSURE OVER THE MID-ATLANTIC EXTENDS SOUTHWARD INTO THE CAROLINAS. HOWEVER... THE GENERAL NORTHEASTERLY LOW LEVEL FLOW WILL ALLOW FOR PERIODS OF MOISTURE TO FILTER INTO THE AREA AT TIMES. THIS COUPLED WITH DAYTIME HEATING WILL ALLOW FOR THE DEVELOPMENT OF SOME CIGS LATE MORNING INTO THE EARLY AFTERNOON... PRIMARILY ACROSS THE EASTERN HALF OF CENTRAL NC... KFAY AND KRWI... POSSIBLY KRDU. EXPECT ANY CIGS THAT DEVELOP TO BE IN THE VFR RANGE THOUGH... 3500 FT TO AROUND 4500 FT. SOME OF THIS CLOUD COVER COULD LINGER AFTER SUNSET AS THE MOISTURE WILL BE TRAPPED UNDER THE SUBSIDENCE INVERSION. REGARDLESS... EXPECT VFR CONDITIONS THROUGHOUT THE TAF PERIOD.... WITH A NORTHEASTERLY BREEZE... STRONGEST DURING THE DAYTIME... 10 TO 15 MPH SUSTAINED... WITH AGAIN EVEN A FEW GUSTS TO AROUND 20 MPH FROM TIME TO TIME (BEST CHANCE OF GUSTS AT KRWI AND KFAY). OUTLOOK: VFR CONDITIONS SHOULD PREVAIL THROUGH MID-WEEK AS SURFACE HIGH PRESSURE OVER THE MID-ATLANTIC CONTINUES TO EXTEND SOUTHWARD INTO THE CAROLINAS AND TROPICAL CYCLONE CRISTOBAL MAINTAINS A HEALTHY DISTANCE OFFSHORE THE SOUTHEAST COAST AS IT TRACKS NORTH OF THE BAHAMAS. SOME POTENTIAL (ALBEIT LOW) FOR CONVECTION WILL BE POSSIBLE BY THE END OF THE WEEK (THU/FRI) IN ASSOC/W NW FLOW ALOFT DOWNSTREAM OF AN APPROACHING UPPER LEVEL RIDGE. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PWB NEAR TERM...BSD SHORT TERM...WSS LONG TERM...WSS AVIATION...BSD/VINCENT

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