Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 300235 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1035 PM EDT FRI AUG 29 2014 .SYNOPSIS...A FRONT WILL REMAIN QUASI-STATIONARY OVER SOUTHEASTERN NC TONIGHT...THEN RETREAT NORTHEASTWARD ACROSS CENTRAL AND EASTERN NC AND VA ON SATURDAY. && .NEAR TERM /TONIGHT/... AS OF 1030 PM FRIDAY... TWO PRIMARY FORECAST CONCERNS FOR TONIGHT INVOLVE THE DEVELOPMENT OF LOW STRATUS AND FOG...AND SHOWERS. THE FORMER HAS A HIGHER PROBABILITY OF OCCURRENCE OWING TO A REGIME OF ABUNDANT LOW LEVEL MOISTURE - CHARACTERIZED BY SFC DEWPOINTS IN THE UPPER 60S TO MIDDLE 70S - THAT HAS POOLED INVOF THE FRONT STALLED OVER SE NC...AND WHICH HAS SINCE BECOME TRAPPED IN THE VERTICAL BY A SHALLOW INVERSION. LIGHT TO CALM SFC WIND AND ASSOCIATED COOLING OF THE BOUNDARY LAYER...IN BETWEEN PERCOLATING PATCHES OF 2-6 THOUSAND FT CLOUDINESS...SHOULD THEN SUPPORT THE DEVELOPMENT AND EXPANSION OF LOW CLOUDS AND FOG. THE HRRR SUGGESTS SOME FOG MAY BECOME DENSE IN PATCHES OVER THE SOUTHERN AND WESTERN PIEDMONT...WHERE SFC WINDS HAVE BEEN...AND WILL CONTINUE TO BE...RELATIVELY LIGHTER. THE PROBABILITY OF SHOWERS IS LESS CERTAIN. THERE IS A QPF SIGNAL FOR SHOWER DEVELOPMENT OVER THE NORTHERN PIEDMONT PER NEAR TERM GUIDANCE FROM BOTH THE HRRR AND RUC...BUT FORCING FOR ASCENT AND INSTABILITY TO DRIVE SUCH DEVELOPMENT...ARE EXPECTED TO BE VERY WEAK. THE FORCING FOR ASCENT WILL COME COURTESY OF WEAK AND SHALLOW ISENTROPIC UPGLIDE ATOP THE AFOREMENTIONED STALLED SFC FRONT TONIGHT...AND RECENT REGIONAL VWP WINDS CORROBORATE THIS IDEA WITH THEIR DEPICTION OF WEAK BUT VEERING WINDS IN THE LOWEST SEVERAL THOUSAND FT. WILL INTRODUCE JUST A SLIGHT CHANCE OF A SHOWER GENERALLY NORTH OF HIGHWAY 64 TO ACCOUNT FOR THIS POSSIBILITY. LOWS GENERALLY 69 TO 75. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 250 PM FRIDAY... CENTRAL NC WILL REMAIN UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE ON SATURDAY. THE LINGERING BACKDOOR FRONT IS EXPECTED TO WASH OUT DURING THE DAY AS THE SURFACE HIGH SHIFTS OFFSHORE AND A LIGHT SOUTHERLY RETURN FLOW DEVELOPS ACROSS THE REGION. ALL OF THIS WILL RESULT IN A TYPICAL SUMMERTIME PATTERN...WITH HIGHS RISING INTO THE LOWER 90S. WITH MARGINAL INSTABILITY EXPECTED TO DEVELOP (HIGHEST ACROSS THE SOUTHEAST)...ISOLATED DIURNAL CONVECTION WILL BE POSSIBLE...ALTHOUGH MANY AREA LIKELY REMAINING DRY. OVERNIGHT LOWS ARE EXPECTED TO BE IN THE UPPER 60S TO LOWER 70S. && .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 250 PM FRIDAY... SHORTWAVE ENERGY ORIGINATING FROM THE WESTERN GULF OF MEXICO AND ASSOCIATED TROPICAL MOISTURE PLUME WILL TRACK NORTHWARD INTO THE TN AND OHIO VALLEY ON SUNDAY AND THEN NORTHEASTWARD INTO THE MID- ATLANTIC STATES ON MONDAY. SUBTROPICAL RIDGE CENTERED OVER THE SOUTHEAST COAST SHOULD INITIALLY DEFLECT THE BETTER RAIN CHANCES WEST OF THE AREA THROUGH SUNDAY(VIA RING OF FIRE MOISTURE RETURN CONVECTION PATTERN ACROSS THE NC MTNS AND FOOTHILLS). HOWEVER BY MONDAY...UPPER RIDGE AXIS BEGINS TO DEAMPLIFY IN RESPONSE TO THE AFOREMENTIONED SHORTWAVE MOVING THROUGH THE MID-ATLANTIC REGION WITH MID/UPPER LEVEL SHEAR AXIS AND LEE SIDE THERMAL TROUGH PROVIDING SUFFICIENT FORCING TO SUPPORT ISOLATED TO SCATTERED CONVECTION MONDAY AFTERNOON AND EVENING. EXPECT A TYPICAL SUMMERTIME PATTERN THROUGH MID TO LATE WEEK AS SUBTROPICAL RIDGE AXIS SHIFTS WESTWARD INTO THE MID SOUTH-LOWER MS VALLEY...ALLOWING FOR ISOLATED TO WIDELY SCATTERED STORMS TO FIRE ALONG LEE SIDE THERMAL TROUGH EACH AFTERNOON. HIGHS IN THE UPPER 80S TO LOWER 90S WITH LOWS IN THE UPPER 60S T0 LOWER 70S. MODELS CONTINUE TO DELAY THE ARRIVAL OF A BACK-DOOR COLD FRONT INTO THE AREA...WITH LATEST TIMING NOW SUGGESTING THURSDAY NIGHT AND INTO FRIDAY. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AS OF 819 PM FRIDAY... CONDITIONS HAVE IMPROVED TO VFR AT ALL TERMINALS THIS EVENING. IFR CONDITIONS WILL RETURN TO THE AREA OVERNIGHT... AS A FRONTAL BOUNDARY REMAINS ACROSS THE AREA... WITH HIGH LOW LEVEL MOISTURE AND LIGHT WIND. CONDITIONS WILL IMPROVE AFTER SUNRISE... AND RETURN TO VFR DURING THE DAY SATURDAY AS THE BOUNDARY DISSIPATES. OUTLOOK...A SUMMERTIME PATTERN WILL PERSIST THROUGH EARLY/MID NEXT WEEK...WITH ISOLATED TO SCATTERED AFTERNOON/EVENING CONVECTION AND A POTENTIAL FOR EARLY MORNING FOG/STRATUS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...KRD LONG TERM...CBL AVIATION...SEC/KRD

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