Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220534 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 135 AM EDT FRI AUG 22 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL DIVE SOUTHEAST INTO OUR REGION FROM THE OHIO VALLEY AND MIDWEST. A COLD FRONT LOCATED ACROSS THE MID ATLANTIC ON FRIDAY WILL MOVE SOUTH THROUGH THE AREA OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1040 PM WEDNESDAY... LACK OF A LOW LEVEL FOCUS OR BOUNDARY ALONG WITH INCREASING CINH WITH LOSS OF HEATING ALLOWED CONVECTION APPROACHING FROM THE NW TO DIE OFF ALONG THE NC/VA BORDER THIS EVENING. THIS OCCURRED EVEN THOUGH DEW POINTS HAD COME UP INTO THE MID 70S TO NEAR 80 (PW`S IN EXCESS OF 1.7 INCHES ALSO NOTED) AT GSO AND MHX. THERE COULD STILL BE AN ISOLATED SHOWER OR STORM OVERNIGHT DUE TO THE RESIDUAL OUTFLOW TO CREATE LIFT... YET NOTHING ORGANIZED IS EXPECTED. MOSTLY CLOUDY SKIES BECOMING PARTY CLOUDY. VERY OPPRESSIVE WITH LOWS IN THE 70S. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 235 PM THURSDAY... FRIDAY WILL BE ANOTHER DAY WITH NORTHWESTERLY FLOW ALOFT...SURFACE TROUGHING IN THE EAST...AND THE POTENTIAL FOR A DISTURBANCE OR TWO TO CROSS THE AREA. THE MAIN DISTURBANCES IN QUESTION ARE LIKELY ASSOCIATED WITH CONVECTION OVER THE UPPER MIDWEST...AND ARE PROGGED TO MOVE SOUTHEAST ACROSS THE AREA LATE FRIDAY AFTERNOON. TIMING OF SUCH A FEATURE IS STILL TOUGH THIS FAR OUT...SO CONFIDENCE IN ITS ADDITIONAL SUPPORT FOR AFTERNOON CONVECTION IS LOW. DEEP MIXING IS EXPECTED AGAIN DURING THE AFTERNOON...WHICH WILL TEMPER INSTABILITY A LITTLE IN THE WEST WHERE DEWPOINTS SHOULD DROP BACK INTO THE MID 60S. THERMAL PROFILES ARE RELATIVELY SIMILAR TO TODAY...SO MLCAPE SHOULD AGAIN RANGE FROM LESS THAN 1000 J/KG IN THE WEST TO OVER 1500 J/KG IN THE EAST. A BELT OF STRONGER WESTERLIES OVER THE CENTRAL APPALACHIANS WILL LIKELY ENHANCE CONVECTION OVER VA...AND SOME OF THIS ACTIVITY MAY DRIFT SOUTH INTO THE NORTHERN PORTIONS OF THE CWA BY FRIDAY EVENING...SO WILL HAVE THE HIGHEST CHANCE POPS ACROSS THE NORTH...WHILE AREAS IN SOUTHERN PIEDMONT MAY STAY DRY. H85 TEMPS ARE FORECAST TO BE ABOVE 20C AGAIN FRIDAY AND WITH DEEP MIXING RESULTS IN MID TO POSSIBLY UPPER 90S. DEWPOINTS ARE FORECAST TO MIX OUT A LITTLE MORE IN THE EAST THAN TODAY...THOUGH ONLY SLIGHTLY...SO HEAT INDEX VALUES SHOULD AGAIN HOLD AROUND 100F IN THE SOUTHEAST. DEPENDING ON HOW MUCH CONVECTION THERE IS TO THE NORTH FRIDAY EVENING...THERE IS THE POTENTIAL FOR A WEAK EFFECTIVE FRONT INTO THE NORTHERN COASTAL PLAIN FRIDAY NIGHT...NECESSITATING POPS THROUGH THE OVERNIGHT HOURS. LOWS IN THE UPPER 60S TO LOWER 70S. && .LONG TERM /SATURDAY THROUGH THURSDAY/... AS OF 145 PM THURSDAY... THE LONG TERM PERIOD REMAINS CHARACTERIZED BY A BUILDING UPPER RIDGE ACROSS THE MISSISSIPPI RIVER VALLEY WITH A DEEPENING UPPER TROUGH OFF THE EAST COAST...RESULTING IN A NORTHWEST UPPER FLOW REGIME ACROSS CENTRAL NORTH CAROLINA. AT THE SURFACE...A BACKDOOR COLD FRONT WILL MOVE SOUTH THROUGH THE AREA ON SATURDAY. DEEP MOISTURE WILL REMAIN ENTRENCHED OVER THE REGION THROUGH THE FIRST HALF OF THE WEEKEND. AS SUCH...THE BEST CHANCE OF PRECIPITATION WILL BE ON SATURDAY GIVEN THE SURFACE BOUNDARY AND POTENTIAL ADDITIONAL SUPPORT FROM DISTURBANCES ALOFT WITHIN THE NORTHWEST FLOW. THE UPPER TROF AXIS SHIFTS FURTHER OFFSHORE...ALLOWING DRIER AIR TO SURGE SOUTH AT THE MID LEVELS...WITH DEEPER MOISTURE SUPPRESSED SOUTHWEST OF THE AREA SUNDAY THROUGH THE MIDDLE OF NEXT WEEK. THE UPPER RIDGE WILL SHIFT EAST TO FURTHER AID IN DAMPENING CONVECTION AS WELL...SO PRECIP CHANCES WILL BE MINIMAL FROM MONDAY THROUGH THURSDAY. LOW LEVEL THICKNESS VALUES WILL GRADUALLY FALL THROUGH EARLY NEXT WEEK AS THE UPPER TROUGH DEEPENS DOWN THE WESTERN ATLANTIC. IN ADDITION...NORTHEASTERLY SURFACE FLOW WILL PERSIST AS HIGH PRESSURE RIDGES INTO THE AREA FROM THE NORTHEAST. ALL OF THIS WILL RESULT IN BELOW NORMAL TEMPS...WITH MID 80S TO NEAR 90 DEGREES ON SATURDAY FALLING INTO THE UPPER 70S TO LOW/MID 80S SUNDAY THROUGH TUESDAY. TEMPS WILL BEGIN TO MODERATE WEDNESDAY INTO THURSDAY AS THE UPPER RIDGE SHIFTS EAST. OVERNIGHT LOWS THIS WEEKEND WILL BE IN THE UPPER 60S TO LOWER 70S...WITH MID TO UPPER 60S MONDAY MORNING AND FOR THE REMAINDER OF THE WEEK. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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AS OF 135 AM FRIDAY... 24-HR TAF PERIOD: AS DEBRIS CLOUD COVER SCATTERS OUT...MOSTLY MVFR VFR FOG AND/OR LOW CEILINGS ARE EXPECTED TO DEVELOP OVERNIGHT GIVEN VERY MUGGY/HUMID AIRMASS. THE EXCEPTION WILL BE AT FOG-PRONE KRWI...WHERE A BRIEF PERIOD OF LIFR TO IFR CONDITIONS ARE POSSIBLE. VFR CONDITIONS SHOULD RETURN BY 13Z TO 14Z. SHORTWAVE DISTURBANCES MOVING INTO THE AREA WITHIN THE NW FLOW ALOFT WILL SUPPORT SHOWERS AND STORMS THIS AFTERNOON AND EVENING...WITH THE BEST CHANCE AT THE RDU/RWI TERMINALS. ITS POSSIBLE THAT CONVECTION COULD PERSIST WELL INTO OVERNIGHT HOURS...ESPECIALLY ACROSS THE NE AS A COLD FRONT ATTEMPTS TO DROP SOUTH INTO THE AREA. LOOKING AHEAD: DIURNAL CONVECTION IS EXPECTED AGAIN ON SAT... ENHANCED BY THE PASSAGE OF A BACK DOOR COLD FRONT FROM THE NORTH/NE SAT EVE/NIGHT. WIDESPREAD IFR CEILINGS ARE EXPECTED IN THE WAKE OF THE BACKDOOR COLD FRONT SAT NIGHT/SUN MORNING...POSSIBLY PERSISTING THROUGH THE DAY AND INTO SUN NIGHT. DRY SURFACE HIGH PRESSURE BUILDING DOWN THE MID-ATLANTIC SEABOARD WILL SECURE DRY VFR CONDITIONS THROUGH EARLY NEXT WEEK.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...PWB SHORT TERM...BLS LONG TERM...MLM AVIATION...CBL/VINCENT

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