Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250743 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 340 AM EDT SAT APR 25 2015 .SYNOPSIS...A WARM FRONT WILL MOVE INTO THE AREA AND STALL TODAY. AN AREA OF LOW PRESSURE WILL APPROACH FROM THE WEST THIS EVENING AND CROSS THE AREA OVERNIGHT...FOLLOWED BY A COLD FRONT ON SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 340 AM SATURDAY... HIGH CLOUDS CONTINUE TO THICKEN ACROSS THE AREA THIS MORNING AHEAD OF A SHORTWAVE AND ASSOCIATED LOW PRESSURE MOVING INTO THE MID- MISSISSIPPI VALLEY REGION. AN AREA OF RAIN DRIVEN BY WARM ADVECTION IS MOVING THROUGH THE LOWER TENNESSE VALLEY REGION AND WILL ENCROACH UPON THE WESTERN PIEDMONT AFTER SUNRISE...THOUGH THE ATMOSPHERE OVER CENTRAL IS VERY DRY WITH PW AROUND A QUARTER OF AN INCH ON THE 00Z KGSO RAOB. VIRGA SHOULD GIVE WAY TO A WIDESPREAD LIGHT RAIN IN THE WEST BY MID-MORNING AND CONTINUE TO THE EAST THROUGH EARLY AFTERNOON. THE CHANCE OF THUNDER LOOKS PRETTY LOW WITH THE INITIAL BAND OF PRECIP DUE TO WEAK LAPSE RATES AND LIMITED HEATING. A WARM FRONT WORKING NORTH THROUGH SC THIS AFTERNOON SHOULD END UP SOMEWHERE ACROSS SOUTHERN NC THIS EVENING...WITH ITS NORTHWARD PUSH HAMPERED BY THE LIGHT RAIN AND RESULTING COOL POOL OVER THE PIEDMONT. MEANWHILE...A DRY SLOT WILL SPREAD ACROSS THE REGION...BRINGING THE INITIAL PRECIP TO AN END BUT ALSO CREATING SOME POTENTIAL INSTABILITY WHICH WOULD HELP STEEPEN MID-LEVEL LAPSE RATES THIS EVENING AS THE REMNANTS OF THE AFOREMENTIONED SHORTWAVE AND ASSOCIATED 60-80M HEIGHT FALLS CROSS THE AREA. FORECAST SOUNDINGS SHOW THE INCREASE IN AT LEAST SOME WEAK MUCAPE ACROSS SOUTHERN NC BY 00Z. WITH STRONG WESTERLIES ALOFT AND 50-60KT OF BULK SHEAR...THE BIGGEST QUESTION WILL THEN BE THE COVERAGE OF CONVECTION APPROACHING FROM THE NORTHWEST AND WHETHER OR NOT WILL CAN BECOME SURFACE BASED...AND LATEST MODEL GUIDANCE SUGGESTS SBCAPE WILL BE NEGLIGIBLE. CURRENTLY...FORECAST CONFIDENCE IS LOW REGARDING SEVERE WEATHER...BUT THERE APPEARS TO BE ENOUGH POTENTIAL TO ADD A CHANCE OF THUNDER ACROSS THE SOUTH AND ADD SOME WORDING TO THE HWO. LATEST MODEL RUNS SHOW A LITTLE BETTER AGREEMENT REGARDING QPF...WITH THE BETTER POTENTIAL FOR A THIRD TO A HALF INCH ACROSS THE SOUTH IN CLOSER PROXIMITY TO THE WARM FRONT. AS FOR TEMPS...THE CURRENT FORECAST LOOKS PRETTY GOOD IN SHOWING A STRONG GRADIENT FROM WEST TO EAST BASED OF THE TIMING OF PRECIP AND ANTICIPATED IN-SITU DAMMING....WITH LOW/MID 50S WEST AND LOW/MID 60S EAST. TEMPS WILL ONLY FALL A FEW DEGREES TONIGHT AS MOST OF THE AREA REMAINS SOCKED IN WITH ABUNDANT LOW CLOUDS AND SOME AREAS OF FOG...UPPER 40S NORTH TO MID 50S SOUTH. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 340 AM SATURDAY... THE DEAMPLIFYING SHORTWAVE FROM SATURDAY NIGHT AND THE ASSOCIATED SURFACE LOW WILL MOVE EAST OF THE AREA ALONG WITH EARLY SUNDAY BUT WILL BE FOLLOWED BY ANOTHER WAVE ROUNDING THE UPPER LOW WOBBLING EAST ACROSS NEW ENGLAND. A STRONG 850MB FRONT DRAPED ACROSS THE OHIO VALLEY AND MID-ATLANTIC STATES WILL PUSH SOUTH ACROSS NC SUNDAY AFTERNOON...WHICH SHOULD HELP TO ERODE THE LINGER DAMMING COOL POOL AND LOW CLOUDS...BUT IT MAY NOT BE EARLY ENOUGH TO ALLOW FOR MUCH HEATING BEFORE SUNSET. THUS...HIGHS ARE EXPECTED TO AGAIN BE WELL BELOW NORMAL IN THE UPPER 50S AND 60S FOR MUCH OF THE AREA...WITH SOME 70S POSSIBLE ACROSS THE FAR SOUTH. WILL MAINTAIN A CHANCE OF SHOWERS WITH THE FRONT ON SUNDAY...ENDING SUNDAY EVENING. LOWS SUNDAY NIGHT IN THE 40S. && .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 300 PM FRIDAY... SUNDAY: EXPECT WARM MOIST WEST-SOUTHWESTERLY FLOW TO START THE PERIOD...WITH THE RETREATING WARM FRONT INVOF THE NC/VA BORDER. AN UPPER LEVEL SHORTWAVE WILL TRAVERSE THE REGION DURING THE DAY SUNDAY. AT THE SURFACE...A WEST-EAST ORIENTED LOW OVER THE CAROLINAS WILL SLOWLY BE PUSHED SOUTH AND EAST AS A COLD FRONT SLIDES THROUGH THE REGION. EXPECT SOME RAIN TO MOVE THROUGH CENTRAL NC FROM NORTH TO SOUTH AHEAD OF THE FRONT...ENDING LATE SUNDAY EVENING...ALTHOUGH THE EXACT TIMING REMAINS UNCERTAIN. THE 12Z GFS SOLUTION IS CLOSE TO THE 00Z ECMWF SOLUTION WITH RESPECT TO TIMING OF THE FRONT...THE 12Z CANADIAN LAGS 6-12 HOURS BEHIND. WILL CONTINUE TO LEAN MORE TOWARD THE ECMWF...WITH THE FRONT MAKING ITS WAY THROUGH THE AREA BY SUNDAY NIGHT. HIGHS WILL DEPEND ON THE TIMING OF THE FRONT AND IF AND HOW MUCH SKIES CLEAR ACROSS THE SOUTH DURING THE DAY. FOR NOW...EXPECT A WIDE RANGE OF HIGHS...MID 50S NORTH TO POTENTIALLY LOW 70S SOUTH. SUNDAY NIGHT THROUGH TUESDAY NIGHT: AS PREVIOUSLY STATED...THE RAIN SHOULD BE OUT OF THE REGION BY SUNDAY NIGHT...AND EXPECT THE WEATHER TO REMAIN DRY THROUGH TUESDAY NIGHT UNDER NW FLOW AND SUBSIDENCE ALOFT. AT THE SURFACE...COLD BUT WEAKENING HIGH PRESSURE WILL GRADUALLY BUILD INTO THE AREA THROUGH THE PERIOD. HIGHS WILL GENERALLY BE IN THE MID 60S TO LOW 70S...LOWS IN THE LOW TO MID 40S. WEDNESDAY AND THURSDAY: THERE IS QUITE A BIT OF DIVERGENCE BETWEEN THE MODELS DURING THIS PART OF THE FORECAST...THUS THERE IS NOT A LOT OF CONFIDENCE WITH RESPECT TO TIMING AND INTENSITY OF VARIOUS FEATURES. GENERALLY SPEAKING THOUGH...EXPECT A SURFACE LOW TO DEVELOP OVER THE GULF COAST ON WEDNESDAY AND SLOWLY MOVE EAST- NORTHEAST TOWARD THE CAROLINAS THROUGH THURSDAY. ALOFT...THOUGH THERE IS UNCERTAINTY ON WHETHER IT WILL BE CUTOFF OR OPEN...EXPECT AN UPPER LEVEL LOW TO DEVELOP OVER OK/TX ON TUESDAY AND MOVE EAST TOWARD THE CAROLINAS TUESDAY NIGHT/EARLY WEDNESDAY. THE ECMWF SEEMS TO BE MORE INTENSE/AMPLIFIED AND QUICKER MOVING INTO THE AREA THAN THE GFS AT THIS TIME. REGARDLESS...EXPECT INCREASING RAINFALL CHANCES BEGINNING LATE TUESDAY NIGHT/WEDNESDAY MORNING THROUGH THURSDAY AND POSSIBLY THURSDAY NIGHT. WITH THE LOW LEVEL FLOW DEPENDENT ON THE POSITION OF THE LOW...AND THE TEMPERATURES DEPENDENT ON THE LOW LEVEL FLOW...THERE IS A HIGH DEGREE OF UNCERTAINTY IN THE TEMPERATURES FOR WEDNESDAY AND THURSDAY AND THERE COULD QUITE POSSIBLY BE A LARGE RANGE OF TEMPERATURES FROM NW TO SE ACROSS THE AREA. HIGHS IN THE MID 60S TO NEAR 70 DEGREES AND LOWS UPPER 40S TO LOW 50S. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 145 AM SATURDAY... VFR CONDITIONS EARLY THIS MORNING WITH JUST INCREASING MID AND HIGH CLOUDS THROUGH 12Z. AN AREA OF RAIN ASSOCIATED WITH WARM ADVECTION ACROSS THE LOWER TENNESSE VALLEY REGION WILL MOVE INTO THE WESTERN PIEDMONT BETWEEN 12Z AND 15Z...THOUGH THE RAIN SHOULD BE LIGHT INITIALLY GIVEN HOW DRY THE AIRMASS IS OVER CENTRAL NC THIS MORNING. CEILINGS WILL STEADILY LOWER TO MVFR FROM WEST TO EAST BY LATE MORNING AND EARLY AFTERNOON...FOLLOWED BY IFR CONDITIONS ARE THE RAIN BECOMES MORE WIDESPREAD. A WARM FRONT IS FORECAST TO LIFT INTO THE SOUTHERN PORTIONS OF THE AREA...POSSIBLY APPROACHING KFAY DURING THE AFTERNOON. THIS MAY OFFER SOME SUPPORT FOR AN ISOLATED THUNDERSTORM FROM KRCZ TO KFAY DURING THE LATE AFTERNOON AND EVENING HOURS. THE PROBABILITY OF THUNDERSTORMS IS MUCH LOWER TO THE NORTH. POOR AVIATION CONDITIONS WILL CONTINUE OVERNIGHT AS CEILINGS ARE LIKELY TO LOWER TO LIFR AND SOME AREAS OF FOG DEVELOP OUTLOOK... ADVERSE AVIATION CONDITIONS ARE EXPECTED TO CONTINUE INTO LATE SUNDAY BEFORE IMPROVING BY MONDAY. THE NEXT CHANCE OF SUB-VFR CONDITIONS WILL BE MIDWEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...22 NEAR TERM...22 SHORT TERM...22 LONG TERM...KCP AVIATION...22

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