Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 030205 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1005 PM EDT WED SEP 2 2015 .SYNOPSIS...
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A DISTURBANCE WILL DIVE FROM CENTRAL VA TO EASTERN NC THROUGH EARLY THU. A LEE TROUGH WILL OTHERWISE LINGER OVER CENTRAL NC UNTIL A BACK DOOR COLD FRONT MOVES SOUTHWEST ACROSS THE AREA LATE FRI AND FRI NIGHT.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1000 PM WEDNESDAY... WATER VAPOR SATELLITE IMAGERY DEPICTS A WELL-DEFINED SHORTWAVE TROUGH OVER CENTRAL VA THIS EVENING. THIS FEATURE EARLIER FORCED SCATTERED TO NUMEROUS SHOWERS AND STORMS OVER VA...WHICH HAVE SUBSEQUENTLY PROPAGATED GENERALLY SOUTHEASTWARD INTO THE NORTHERN NC PIEDMONT AND COASTAL PLAIN. THE ASSOCIATED OUTFLOW BOUNDARY STRETCHED AT 0145Z FROM NEAR KBUY TO KRDU TO KASJ. WHILE SHOWERS HAVE PERCOLATED ALONG THE LENGTH OF THE BOUNDARY...THE ORIENTATION OF SHEAR VECTORS (FROM THE NW) RELATIVE TO THE BOUNDARY HAVE FOCUSED STRONG AND SUSTAINED CONVECTIVE MAINTENANCE ALONG THE SE-FACING OUTFLOW FLANK...AND THIS PROCESS WILL CONTINUE AND FAVOR FAR EASTERN HALIFAX AND EDGECOMBE COUNTIES FOR THE STRONGEST CONVECTION DURING THE NEXT HOUR. OTHERWISE...SCATTERED OR WIDELY SO SHOWERS AND ISOLATED THUNDER WILL OCCASIONALLY PERCOLATE...ALONG OUTFLOW...SOUTHEASTWARD WITH THE PASSAGE OF THE AFOREMENTIONED SHORTWAVE TROUGH AND ASSOCIATED FORCING FOR ASCENT AS IT CONTINUES SOUTHEASTWARD TOWARD THE PAMLICO SOUND BY 12Z - TIMING WHICH SHOULD RESULT IN RAIN CHANCES MOVING SOUTHEAST OF THE RAH CWFA BY AROUND 09Z. PERSISTENCE LOWS IN THE UPPER 60S TO LOWER 70S.
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 333 PM WEDNESDAY... THE MID LEVEL VORTICITY MAX SHOULD BE SHIFTING OFF THE NRN NC COAST THU MORNING... ALBEIT WITH A WEAK TRAILING SHEAR AXIS EXTENDING BACK ACROSS THE NRN CWA. THIS TRAILING VORTICITY WILL SINK SLOWLY SOUTHWARD THROUGH THE DAY BUT REMAIN EXTENDED ACROSS THE SRN CWA LATE THU THROUGH THU NIGHT. PW VALUES WILL HAVE FALLEN WITH A SLIGHTLY MORE STABLE AND SUBSIDING COLUMN BEHIND THE CORE OF THE EXITING WAVE... SO EXPECT ANY SHOWER/STORM COVERAGE TO BE FAIRLY SMALL GIVEN THE WEAK WIND FIELD... LACK OF STRONG FORCING FOR ASCENT... AND LIMITED CAPE. WILL RETAIN AN ISOLATED POP JUST ACROSS THE SOUTH AND SE NEAR THE SHEAR AXIS AND WHERE LOW LEVEL DEWPOINTS WILL LIKELY BE HIGHER. ANOTHER MUCH WEAKER WAVE WILL PUSH INTO THE REGION FROM THE SW LATE THU INTO THU NIGHT... BUT THIS APPEAR TO CONTRIBUTE VERY LITTLE DYNAMIC FORCING... AND WITH LACK OF HEATING AFTER SUNSET... COVERAGE SHOULD BE ISOLATED AT BEST WITH THIS SECOND WAVE. WILL KEEP A MENTION OF ISOLATED STORMS IN THE NE CWA THROUGH THE EVENING... THEN TREND POPS DOWN BELOW 15% OVERNIGHT. THIS PATTERN CORRELATES WITH THE LOCATION OF THE SREF`S HIGHER CHANCES OF MEASURABLE PRECIP. WITH GOOD MIXING AND CONTINUED ABOVE NORMAL THICKNESSES... EXPECT STEAMY HIGHS OF 90-95. LOWS 67-72 UNDER PARTLY CLOUDY SKIES. -GIH && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 315 PM WEDNESDAY... THE MAIN PLAYER IN THE WEATHER PATTERN FOR THE LONG TERM WILL BE A 1026 MB SURFACE HIGH PRESSURE SYSTEM OVER NEW ENGLAND THAT WILL PUSH A BACKDOOR COLD FRONT THROUGH THE AREA ON FRIDAY NIGHT AND SET UP A WEDGE FRONT THAT IN PATTERN WILL BE REMINISCENT OF A COLD AIR DAMMING SCENARIO BUT WITHOUT THE ISENTROPIC LIFT THAT WE USUALLY SEE CONTRIBUTING TO MORE STRATIFORM RAIN ACROSS THE TRIAD. THE FEATURE THROUGH WILL CAUSE LOW CLOUDS TO SPREAD ACROSS MUCH OF THE AREA ON SATURDAY AND BRING IN MUCH COOLER HIGH TEMPERATURES (LOW TO MID 80S). AS THE WEEKEND CONTINUES...A VERY WEAK LOW OFF OF THE FLORIDA COAST WILL ATTEMPT TO HELP FORM AN INVERTED TROUGH ALONG THE CAROLINA COAST BUT THE STRENGTH OF THIS FEATURE REMAINS UNCERTAIN AT THIS TIME. CURRENT MODEL RUNS SUGGEST THAT THIS FEATURE MAY REMAIN FAIRLY WEAK BUT IT WILL CERTAINLY CAUSE AN UPTICK IN POPS ACROSS EASTERN PORTIONS OF THE CWA...PARTICULARLY SUNDAY AND MONDAY AFTERNOONS DURING PEAK HEATING WITH PSEUDO WEDGE FRONT BOUNDARY HELPING TO INITIATE CONVECTION. THE EXACT LOCATION OF THIS BOUNDARY IS TO BE DETERMINED AND THUS THE AFTERNOON FORECAST REMAINS FAIRLY LOW CONFIDENCE BUT GENERAL TRENDS SUGGEST THAT RAIN WILL BE MORE LIKELY FURTHER EAST. ON TUESDAY THE SURFACE HIGH BREAKS DOWN AND TEMPERATURES WILL START A SLOW WARMING TREND INTO THE MID TO UPPER 80S BY MID WEEK. THE MAIN THREAT FOR PRECIPITATION WILL BE WITH A FEW SHORTWAVES ALONG THE SOUTH CAROLINA COAST WHICH MAY PROVIDE SOME FORCING FOR DIURNAL SHOWERS OR STORMS BOTH DAYS. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 145 PM WEDNESDAY... HIGH CONFIDENCE IN VFR CONDITIONS HOLDING THROUGH MID AFTERNOON THU... ALTHOUGH THERE WILL BE ONE BRIEF PERIOD OF EXCEPTION. THE PASSAGE OF AN UPPER LEVEL DISTURBANCE FROM NW TO SE THROUGH THE REGION LATE TODAY THROUGH THIS EVENING WILL BRING SCATTERED STORMS... MOST LIKELY TO AFFECT RWI AND PERHAPS RDU... WITH INT/GSO SEEING A SLIGHTLY LOWER CHANCE OF STORMS AND FAY SEEING THE LEAST CHANCE. THE PRIMARY WINDOW OF STORM POTENTIAL WILL BE 21Z-01Z AT INT/GSO/RDU/RWI. A SHORT PERIOD OF GUSTY WINDS AND MVFR TO IFR CONDITIONS CAN BE EXPECTED IN AND NEAR ANY STORMS... ALTHOUGH COVERAGE WILL BE SMALL AND DURATION LESS THAN AN HOUR AT ANY GIVEN LOCATION. OTHERWISE... ANY CIGS ARE LIKELY TO BE ABOVE 6K FT AGL. LIGHT AND VARIABLE SURFACE WINDS WILL BECOME PREDOMINANTLY FROM THE NE OR NORTH TONIGHT BUT REMAIN LIGHT THROUGH THU. LOOKING BEYOND 18Z THU... VFR CONDITIONS LIKELY TO HOLD. THE CHANCE OF SHOWERS AND STORMS INCREASES LATE FRI INTO FRI NIGHT IN ASSOCIATION WITH A COLD FRONT PASSAGE... FOLLOWED BY A LOWER CHANCE SAT AFTERNOON. SUB-VFR LOW CLOUDS AND FOG POSSIBLE LATE FRI NIGHT / EARLY SAT MORNING... AND AGAIN LATE SAT NIGHT / EARLY SUN MORNING WITH A LOW LEVEL FLOW FROM THE EAST OR NE BEHIND THE FRONT DRAWING ATLANTIC MOISTURE INTO THE AREA. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...26 SHORT TERM...HARTFIELD LONG TERM...ELLIS AVIATION...HARTFIELD

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