Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280733 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 332 AM EDT SUN SEP 28 2014 .SYNOPSIS...HIGH PRESSURE WILL EXTEND ACROSS THE MIDDLE ATLANTIC STATES THROUGH TONIGHT. A WEAK AREA OF LOW PRESSURE WILL DEVELOP AND TRACK ACROSS THE GULF COAST STATES MONDAY...THEN MOVE OFF THE SOUTHEAST COAST MONDAY NIGHT AND TUESDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 330 AM SUNDAY... LOW-MID LEVEL RIDGE ALONG THE EAST COAST THIS MORNING...INCLUDING A 1023 MB SFC HIGH CENTERED OVER THE MIDDLE ATLANTIC STATES...WILL DRIFT OFFSHORE TODAY. MEANWHILE...A MID-UPPER TROUGH OVER THE CENTRAL CONUS...ONE COMPRISED OF A COUPLE OF WELL-DEFINED CIRCULATIONS OVER IA AND EASTERN TX...WILL MOVE INITIALLY SLOWLY EAST THIS MORNING THEN ACCELERATE EASTWARD LATER TODAY AND TONIGHT...OWING TO THE APPROACH OF A KICKER TROUGH FROM SW CANADA. THE NORTHERN EDGE OF AN AREA OF HIGH BASED STRATOCUMULUS (6-8 THOUSAND FT) ARCING FROM SE NC TO THE NC FOOTHILLS (JUST WEST OF THE YADKIN) WILL PIVOT NORTHWESTWARD AND SPREAD - IN A THINNING/ SCATTERING STATE INTO THE SOUTHERN AND WESTERN PIEDMONT TODAY PER THE 00Z GFS AND RECENT RAP RUNS...WHEREAS THE 00Z NAM APPEARED TOO AGGRESSIVE/PESSIMISTIC WITH THESE SKY CONDITIONS PER COMPARISON TO RECENT OBSERVATIONAL DATA. AS SUCH...THE NAM/S DEPICTION OF BKN TO OVC 6-8 THOUSAND FT SKY COVERAGE OVER THE SOUTHERN AND WESTERN PIEDMONT BY 18Z IS CONSIDERED AN OUTLIER AND WILL BE DISCOUNTED IN FAVOR OF GENERALLY SCT COVERAGE AND ASSOCIATED PARTLY CLOUDY CONDITIONS THROUGH THE BETTER PART OF THE AFTERNOON. THE REMAINDER OF CENTRAL NC SHOULD REMAIN MOSTLY SUNNY...BENEATH PASSING CIRRUS THAT WILL GRADUALLY THICKEN FROM THE WEST LATE IN THE DAY. PROJECTED LOW LEVEL THICKNESS VALUES ABOUT 10 METERS HIGHER THAN THOSE OF SATURDAY SUPPORT HIGHS IN THE UPPER 70S TO LOWER 80S...OR ABOUT 3 DEGREES HIGHER THAN SATURDAY. TONIGHT: NWP GUIDANCE IS RELATIVELY GOOD AGREEMENT REGARDING THE APPROACH OF THE MID-UPPER TROUGH FROM THE WEST...WITH A CONSENSUS POSITION OF THE PARENT UPPER LOW OVER THE LOWER OH VALLEY/NORTHERN TN VALLEY BY 12Z MON. ASSOCIATED HEIGHT FALLS ALOFT...ON THE ORDER 30-50 METERS AT H5 OVERNIGHT...SHOULD SUPPORT THE NORTHEASTWARD EXPANSION/DEVELOPMENT OF MID AND HIGH LEVEL/MIXED PHASE-GENERATED RAIN. WITH CLOUD BASES EXPECTED TO HOLD AOA 10 THOUSAND FT...IT IS LIKELY THAT ONLY VIRGA WILL FALL FROM THESE MID LEVEL CEILINGS...OR AT PERHAPS A FEW SPRINKLES INVOF THE YADKIN RIVER AROUND DAYBREAK. OTHERWISE...INITIALLY PARTLY TO MOSTLY CLEAR SKIES THIS EVENING OVER THE NE PIEDMONT AND NORTHERN COASTAL PLAIN...AND DELAYED ARRIVAL OF THE THICKER CLOUD COVER...GOOD RADIATIONAL COOLING CONDITIONS. LOWS THERE ARE LIKELY TO DIP INTO THE MID-UPPER 50S...RANGING TO LOWER- MIDDLE 60S OVER THE SOUTHERN PIEDMONT.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 315 AM SUNDAY... SHORTWAVE EXTENDING FROM THE OHIO VALLEY TO THE MISSISSIPPI VALLEY MONDAY MORNING... WITH A WEAK SURFACE LOW DEVELOPING OVER GA/FL. THIS IS FURTHER SOUTH THAN PREVIOUS MODEL RUNS. TAIL END OF THE UPPER JET EXTENDING SOUTHWARD FROM NEW ENGLAND WILL PROVIDE UPPER LEVEL SUPPORT FOR WIDESPREAD LIFT... HOWEVER GIVEN THE POSITION OF THE LOW FURTHER SOUTH... MOISTURE TRANSPORT LOOKS LIMITED. HAVE SCALED BACK QPF TO UNDER A HALF INCH ACROSS THE AREA... LOWER AMOUNTS CLOSER TO THE VA BORDER. SHORTWAVE WILL BE APPROACHING THE COAST TUESDAY MORNING... AS THE SURFACE LOW MOVES NORTHEAST ALONG THE COAST. PRECIP WILL DIMINISH AS SUBSIDENCE AND MIDLEVEL DRYING FOLLOWS... HOWEVER LINGERING LOW LEVEL MOISTURE MAY BE SUFFICIENT TO PRODUCE SOME PATCHY LIGHT RAIN/DRIZZLE IN TO WEDNESDAY. WEAK COLD AIR DAMMING WILL ALSO PROLONG LOW LEVEL CLOUD COVER IN TO EARLY WEDNESDAY. PARENT HIGH REMAINS FAR TO THE NORTH OVER QUEBEC... UNFAVORABLY POSITIONED FOR A PROLONGED DAMMING EVENT... AND ANY REMAINING WEDGE WILL ERODE DURING THE DAY. HIGH TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THIS TIME. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 318 AM SUNDAY... HIGH PRESSURE WILL EXTEND ACROSS THE REGION THROUGH THURSDAY... AS A STRONG TROUGH APPROACHES FROM THE WEST. HIGH TEMPERATURES WILL TREND TOWARD NORMAL THURSDAY AND FRIDAY AHEAD OF THIS SYSTEM. MODEL AGREEMENT CONTINUES TO BE GOOD... WITH THE PARENT LOW MOVING NORTH THROUGH THE GREAT LAKES AND THE ASSOCIATED COLD FRONT CROSSING THE AREA FRIDAY NIGHT/EARLY SATURDAY. HIGH TEMPERATURES SATURDAY WILL LIKELY BE DEPENDENT ON THE PASSAGE OF THIS FRONT. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 210 AM SUNDAY... UNDER THE CONTINUED INFLUENCE OF MODIFIED CANADIAN HIGH PRESSURE OVER THE MIDDLE ATLANTIC STATES...MAINLY VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. THE EXCEPTION TO VFR WILL BE SHALLOW FOG AND ASSOCIATED LIFR-MVFR VISIBILITY RESTRICTIONS AT KRWI/KRDU/KFAY... LOWEST AND LONGEST AT KRWI. A BRIEF PERIOD OF MAINLY SCATTERED MVFR RANGE CLOUD BASES MAY FOLLOW AS THE MOIST LAYER RISES AND DISPERSES THROUGH 16Z AT KRWI AND KFAY. OTHERWISE...BENEATH PERIODS OF PASSING CIRRUS...AN AREA OF 6-8 THOUSAND FT STRATOCUMULUS NEAR THE SC BORDER THIS MORNING WILL SPREAD NORTH INTO CENTRAL NC TODAY...MOST NOTABLY AT WESTERN TERMINALS WHERE ASSOCIATED CEILINGS COULD RESULT BY LATE THIS AFTERNOON OR EVENING. OUTLOOK: THE APPROACH OF AN UPPER LEVEL TROUGH FROM THE WEST WILL CAUSE MID-HIGH CLOUDS TO THICKEN AND LOWER FROM WEST TO EAST LATE TONIGHT...WITH PERHAPS A FEW SPRINKLES FROM MID LEVEL CLOUD BASES AT TRIAD TERMINALS AROUND DAYBREAK MONDAY. A PERIOD OF MEASURABLE RAIN AND CEILINGS LOWERING INTO MVFR RANGE WILL THEN BE POSSIBLE MON INTO EARLY TUE...ESPECIALLY AT KFAY...AS SURFACE LOW PRESSURE SYSTEM DEVELOPS AND TRACKS ACROSS THE GULF COAST (WELL SOUTH OF CENTRAL NC). A SURGE IN NE LOW LEVEL FLOW IN THE WAKE OF THE LOW PRESSURE SYSTEM MAY PRODUCE ANOTHER BRIEF PERIOD OF MVFR CEILINGS AT KRWI AND KFAY ON WED. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...SEC LONG TERM...SEC AVIATION...MWS

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