Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 021748 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 145 PM EDT WED SEP 2 2015 .SYNOPSIS...A DISTURBANCE WILL DROP SOUTHEAST THROUGH THE AREA TONIGHT THROUGH EARLY THURSDAY...BUT OTHERWISE DEEP HIGH PRESSURE WILL HOLD OVER THE REGION THROUGH FRIDAY. A COLD FRONT WILL MOVE SOUTHWARD THROUGH THE AREA LATE FRIDAY INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1015 AM WEDNESDAY... PLENTY OF SUNSHINE THIS MORNING ALTHOUGH IT`S BEING FILTERED SOMEWHAT BY AREAS OF THIN MID-HIGH CLOUDS BLOWN OFF OF CONVECTION OVER AND SOUTH OF THE LOWER MISS VALLEY. THE POTENT MID LEVEL WAVE WE`VE BEEN WATCHING FOR THE LAST FEW DAYS OVER CENTRAL INDIANA IS NOTED THIS MORNING OVER SE OHIO IS ON TRACK TO DROP SE INTO AND THROUGH THE AREA LATER TODAY THROUGH TONIGHT. THE TIMING INDICATED BY THE SPC SSEO / NSSL WRF / 3KM NAM CONUS NEST / NCAR ENSEMBLE NEIGHBORHOOD PROBABILITIES ARE FAIRLY CLOSE TO THE EXISTING FORECAST... BRINGING GOOD COVERAGE INTO THE EXTREME NORTHERN CWA AFTER 19Z OR 20Z... THEN DROPPING TO THE SSE PEAKING IN COVERAGE AROUND 00Z... THEN MOVING INTO THE SRN/SE CWA WHILE CONTINUING TO WEAKEN BEFORE DISSIPATING AROUND OR SOON AFTER 06Z. HAVE MADE MINOR TIMING DIFFERENCES AND HAVE INCREASED INITIAL COVERAGE IN THE 21Z- 03Z TIME FRAME ACROSS THE NORTH. HAVE ALSO ADDED IN LOW CHANCE POPS IN THE YADKIN VALLEY LATE THIS AFTERNOON AS THE HRRR AND NSSL WRF DEPICT MOUNTAIN CONVECTION DRIFTING INTO THE SW AND EXTREME WRN CWA LATE. MODELS CONTINUE TO VARY ON INSTABILITY POTENTIAL WITH THE NAM (AND IT`S SLIGHTLY HIGHER SURFACE DEWPOINTS) SHOWING MUCAPE VALUES NEARLY A MAGNITUDE GREATER THAN THE GFS. DEEP LAYER SHEAR REMAINS MARGINAL AT JUST 20-25 KTS... SO EITHER WAY DON`T EXPECT A GREAT SEVERE THREAT... ALTHOUGH A FEW STORMS COULD GET STRONG GIVEN THE DYNAMIC CONTRIBUTION FROM DPVA. THICKNESSES AND HRRR/GRIDDED LAMP/ LOCAL WRF GUIDANCE SUPPORT HIGHS OF 90-94. -GIH ISOLATED-SCATTERED CONVECTION WILL SLOWLY WANE TONIGHT AS THE LOW LEVEL AIR MASS UNDERGOES ITS NORMAL NOCTURNAL STABILIZATION. BULK OF CONVECTION WILL DISSIPATE PRIOR TO 06Z THOUGH POTENTIAL FOR A FEW SHOWERS TO PERSIST IN THE COASTAL PLAIN UP TO SUNRISE. MIN TEMPS 67- 73. -WSS && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 258 AM WEDNESDAY... WEAK SUBSIDENCE BEHIND THE DEPARTING DISTURBANCE SHOULD INHIBIT CONVECTIVE REDEVELOPMENT THURSDAY MORNING. HEATING OF THE AIR MASS OVER CENTRAL NC SHOULD TRIGGER ISOLATED CONVECTION ABOUT ANYWHERE IN THE MID-LATE AFTERNOON HOURS. ANOTHER UPPER DISTURBANCE...THOUGH WEAKER THAN THE SYSTEM EXPECTED TONIGHT...WILL APPROACH FROM THE NW LATE IN THE DAY AND CROSS CENTRAL NC THURSDAY NIGHT. THIS SYSTEM MAY PROVIDE ENOUGH LIFT TO INITIATE/SUSTAIN A SHOWER OR TWO BUT FEEL THAT MOST PLACES WILL REMAIN DRY THURSDAY NIGHT. MAX TEMPS THURSDAY SHOULD BE COMPARABLE TO DAY...90-95 DEGREES...WITH MIN TEMPS THU NIGHT 67-72. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 305 AM WEDNESDAY... FRIDAY THROUGH SATURDAY NIGHT: A BACKDOOR COLD FRONT WILL SINK SOUTHWARD THROUGH THE AREA ON FRIDAY INTO FRIDAY EVENING AS ANOTHER WEAK IMPULSE IN THE NORTH-NORTHWEST TO NORTHWESTERLY MID LEVEL FLOW MOVES ACROSS THE AREA. THIS WILL TRIGGER AT LEAST ISOLATED TO SCATTERED SHOWERS AND SOME STORMS FRIDAY AFTERNOON INTO THE EVENING. OVERALL DEEP FLOW CONTINUES TO BE QUITE WEAK. GIVEN THIS AND RATHER WEAK TO MODEST INSTABILITY EXPECT LITTLE IN THE WAY OF A SEVERE THREAT... WITH THE ONLY LIMITED THREAT FROM LOCALIZED.... MAINLY URBAN... FLOODING AS PW/S ARE EXPECTED TO BE AROUND 1.75" OR SO ON FRIDAY. HIGH TEMPS FRIDAY IN ADVANCE OF THE FRONT ARE EXPECTED TO REACH INTO THE UPPER 80S TO LOWER 90S. SURFACE HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH/NORTHEAST ON FRIDAY NIGHT INTO SATURDAY. HOWEVER... WE WILL LIKELY SEE SOME LINGERING PRECIP CHANCES AS A WEAK MID LEVEL LOW DEVELOPS JUST TO THE SOUTH OF THE AREA. THUS... EXPECT LOW POPS (SLIGHT CHANCE) IN THE NORTHEAST... WITH THE HIGHEST POPS (CHANCE) IN THE SOUTHWEST. GIVEN NORTHEAST TO EASTERLY LOW LEVEL FLOW... WE WILL LIKELY START THE DAY WITH A GOOD BIT OF CLOUD COVER/LOW STRATUS. GIVEN THE COOLER AIR MASS FROM THE NORTH AND EXPECTED CLOUD COVER... WILL GO WITH HIGHS ON SATURDAY IN THE LOWER TO MID 80S (AND THIS MAY STILL BE TOO WARM IN SPOTS). LOWS SATURDAY MORNING ARE EXPECTED TO BE IN THE UPPER 60S AND IN THE MID TO UPPER 60S SUNDAY MORNING. SUNDAY THROUGH TUESDAY: THE WEAK MID LEVEL LOW WILL CONTINUE TO LINGER ACROSS THE SOUTHEAST U.S. DURING THIS TIMEFRAME WHILE SLOWLY SINKING SOUTHWESTWARD... YET STILL EXTENDING INTO OUR AREA... ALONG WITH AN INVERTED SURFACE TROUGH NEAR THE COAST TO EASTERN PORTIONS OF OUR AREA. THIS WILL GENERALLY RESULT IN THE BEST CHANCES FOR PRECIP TO THE SOUTH OF OUR AREA... BUT WE COULD SEE SOME ISOLATED TO SCATTERED SHOWERS AND STORMS EACH DAY (MAINLY DIURNAL IN NATURE) AND GENERALLY ACROSS EASTERN AND SOUTHEASTERN PORTIONS OF CENTRAL NC. HIGHS WILL REMAIN IN THE 80S... COOLEST ON SUNDAY... WITH LOWS IN THE 60S. && .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...HARTFIELD NEAR TERM...HARTFIELD/WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...HARTFIELD

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