Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 050712 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 310 AM WED AUG 5 2015 .SYNOPSIS...A COLD FRONT WILL APPROACH FROM THE NORTHWEST AND SETTLE INTO NORTH CAROLINA TODAY. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 310 AM WEDNESDAY... A COLD FRONT CURRENTLY ORIENTED W-E ACROSS THE OHIO VALLEY AND NORTHERN MID ATLANTIC REGION WILL SLOWLY DRIFT SOUTH TO THE VA/NC BORDER BY THIS EVENING...THEN GRADUALLY MOVE SOUTHWARD ACROSS NC THROUGH THE NIGHT. LOOK FOR MOSTLY FAIR WEATHER IN ADVANCE OF THE FRONT DURING THE DAYTIME TODAY...ALTHOUGH AN ISOLATED SHOWER/TSTM CAN`T BE RULED OUT LATER IN THE DAY AS THE FRONT APPROACHES. THIS EVENING AND TONIGHT...A FEW SHOWERS WILL BE POSSIBLE MAINLY ALONG AND NORTH OF THE BOUNDARY (BEST CHANCE N OF HWY 64) AS SYNOP SCALE FORCING IMPROVES FROM THE WEST WITH THE APPROACH OF A MID LEVEL SHORT WAVE. FORECAST SOUNDINGS AND LATEST GUIDANCE CONTINUES TO SHOW HOT CONDITIONS AHEAD OF THE FRONT...HIGHS IN THE MID-UPPER 90S...AND LOWS AROUND 70. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 310 PM TUESDAY... THE COLD FRONT TO OUR NW IS EXPECTED TO DROP TO THE SSE THROUGH WED MORNING... LIKELY ENDING UP STRETCHED ROUGHLY ALONG OR JUST SOUTH OF THE NC/VA STATE LINE. THE LOW LEVEL FLOW FROM THE WNW SHOULD ALLOW DEWPOINTS TO DROP DOWN INTO THE 60S WITH DEEP MIXING ANTICIPATED BY EARLY TO MID AFTERNOON. SO WE SHOULD INITIALLY BE IN A RELATIVE PRECIP LULL OF BRIEF FLAT FLOW OR WEAK SHORTWAVE RIDGING... BEHIND THE DEPARTING LOW AND ITS ASSOCIATED SHORTWAVE TROUGH... AND AHEAD OF THE NEXT SHORTWAVE TROUGH NOW STRETCHING FROM NRN WY SE TO NE OK. AS THE LEADING EDGE OF THIS FEATURE APPROACHES LATE IN THE DAY AND INTO WED NIGHT... MID AND UPPER LEVELS WILL SLOWLY MOISTEN... AND THE INCREASING DYNAMIC FORCING FOR ASCENT ALONG WITH THE IMPROVING DEEP LAYER WIND FIELD SHOULD FACILITATE ISOLATED TO SCATTERED STORMS... DESPITE THE LATE DAY ARRIVAL. WILL TREND POPS UP TO CHANCE ESPECIALLY ACROSS THE NORTH AND WEST DURING THE MID TO LATE AFTERNOON... KEEPING A 20-30% CHANCE THROUGH THE NIGHT WITH CONTINUED RISING PW VALUES AND MID LEVEL HEIGHT FALLS. EXPECT RATHER HOT TEMPS DUE TO THE DEEP MIXING... ABOVE NORMAL THICKNESSES... AND GOOD INSOLATION FOR MUCH OF THE DAY... SUPPORTING HIGHS FROM 93 NORTH TO 99 SOUTH. LOWER DEWPOINTS WILL KEEP HEAT INDEX VALUES FROM GETTING TOO DANGEROUS... BUT STILL EXPECT WIDESPREAD VALUES AROUND 100-102 IN THE SOUTH AND EAST. LOWS WED NIGHT 68-74 WITH PARTLY CLOUDY SKIES AND SCATTERED SHOWERS AND A FEW STORMS PERSISTING OVERNIGHT. -GIH && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 315 PM TUESDAY... OVERALL THE SYNOPTIC PATTERN THROUGHOUT THE LONG TERM PERIOD WILL FEATURE RIDGING OVER THE SOUTH-CENTRAL/SOUTHWEST CONUS AND TROUGHING (WITH VARYING STRENGTHS) OVER THE EAST. GIVEN THIS UPPER LEVEL FLOW PATTERN...MUCH OF OUR WEATHER WILL BE DICTATED BY NUMEROUS SHORTWAVES (WHICH ARE IMPOSSIBLE TO ACCURATELY PREDICT THIS FAR OUT). TWO DISTURBANCES ARE PROGGED TO CROSS THE REGION DURING THE LATE THURSDAY INTO FRIDAY TIME FRAME. THE GFS AND ECMWF STILL DIFFER QUITE A BIT...LEADING TO A LOW CONFIDENCE FORECAST. WITH REGARDS TO THE FIRST WAVE THURSDAY NIGHT INTO EARLY FRIDAY...THE GFS IS WEAKER AND DISORGANIZED AND THE ECMWF/NAM ARE SIGNIFICANTLY STRONGER. THE GFS SHOWS A STRONGER WAVE LATE FRIDAY INTO EARLY SATURDAY...WHILE THE OTHER MODELS ARE MUCH WEAKER WITH THIS PARTICULAR FEATURE. REGARDLESS OF SOLUTIONS...PRECIP CHANCES ARE EXPECTED TO RAMP UP LATE THURSDAY INTO FRIDAY WITH THE APPROACH OF THE DEEPER SHORT WAVE/SURFACE FRONT BEFORE DECREASING LATE FRIDAY NIGHT INTO SATURDAY AS THE SECOND WAVE PUSHES THE FRONT EAST. GIVEN THE MODEL DIFFERENCES...PRECIP TIMING (STARTING AND ENDING) AND EXACT COVERAGE VARY...BUT THE SAME OVERALL TREND IS THERE. BY THE WEEKEND...BOTH MODELS ARE THEN IN FAIRLY GOOD AGREEMENT WITH THE FRONT BEING PUSHED TO OUR EAST...AND BECOMING NEARLY STATIONARY THERE. HIGH PRESSURE WILL BUILD IN AND THIS SHOULD RESULT IN A MOSTLY DRY FORECAST...WITH ONLY SOME ISOLATED DIURNAL TYPE ACTIVITY...MOSTLY ACROSS THE EAST IN CLOSER PROXIMITY TO THE BOUNDARY. THE HIGH WILL BEGIN TO SHIFT OFFSHORE EARLY NEXT WEEK AND THEREFORE PRECIP CHANCES WILL SLOWLY BEGIN TO INCREASE. TEMPS WILL BE RATHER WARM TO START THE PERIOD (HIGHS IN THE LOW/MID 90S...LOWS IN THE LOW/MID 70S)...BUT BY THE WEEKEND THEY SHOULD FALL SOME BEHIND THE FRONT (HIGHS IN THE MID/UPPER 80S...LOWS IN THE MID/UPPER 60S). && .AVIATION /06Z WEDNESDAY THROUGH SATURDAY/... AS OF 310 AM WEDNESDAY... MAINLY VFR CONDITIONS EXPECTED TODAY...ALTHOUGH AN ISOLATED SHOWER OR TSTM IS POSSIBLE DURING THE LATE AFTERNOON AND EVENING WITH THE FRONT DROPPING SOUTH...WHICH COULD BRIEFLY REDUCE FLT CONDITIONS TO MVFR OR IFR. LOOKING BEYOND THE 24 HOUR TAF PERIOD...ISOLD TO SCATTERED SHOWERS AND TSTMS WILL BE POSSIBLE EACH DAY...UNTIL HIGH PRESSURE BUILDS OVER THE REGION LATER THIS WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RAH NEAR TERM...RAH SHORT TERM...HARTFIELD LONG TERM...KRD AVIATION...RAH

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