Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220455 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1250 AM EDT TUE JUL 22 2014 .SYNOPSIS...
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AN UPPER LEVEL LOW PRESSURE SYSTEM WILL REMAIN OVER THE GULF COAST STATES THROUGH MIDWEEK... RESULTING IN A MOIST FLOW OFF THE ATLANTIC INTO NORTH CAROLINA. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTH LATE WEDNESDAY... THEN SETTLE SOUTHWARD THROUGH NORTH CAROLINA ON THURSDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 910 PM MONDAY... ONLY ISOLATED SHOWERS REMAIN IN THE WELL TURNED OVER BOUNDARY LAYER. ALTHOUGH IT CONTINUED TO BE EXTREMELY MOIST WITH DEW POINTS IN THE 70S... CONDITIONS HAD GREATLY STABILIZED BY EARLIER CONVECTION AND THE ONSET OF CONVECTIVE INHIBITION. CONVECTION IS EXPECTED TO REMAIN POSSIBLE... BUT MAINLY DIURNALLY DRIVEN - THEREFORE THE PREVIOUS FORECAST OF ISOLATED TO SCATTERED SHOWERS OVERNIGHT WILL CONTINUE. THE EASTERLY FLOW WILL ALSO CONTINUE TO ENSURE THAT THE DEW POINTS REMAIN HIGH... WITH A HIGH LIKELIHOOD OF LOW STRATUS OVERNIGHT. LOWS IN THE LOWER 70S. && .SHORT TERM /TUESDAY THROUGH FRIDAY NIGHT/... AS OF 305 PM MONDAY... PRECIPITABLE WATER REMAINS HIGH AS WE KICK OFF THE DAY WITH IN-SITU DAMMED AIRMASS ACROSS THE AREA. GUIDANCE HIGHS TOMORROW ON THE GFS REACH THE LOW 90S...WHICH IS QUESTIONABLE GIVEN MORNING LOW CLOUDINESS AND EAST TO NORTHEAST SURFACE FLOW. WILL TREND TOWARDS MID 80S WITH MOSTLY CLOUDY SKIES. POP-WISE... THE UPPER LOW WILL RETROGRADE BACK TO THE MISSISSIPPI DELTA AREA BY LATE TUESDAY...MAINTAINING A CHANCE OF MAINLY DIURNAL CONVECTION...ESPECIALLY IN THE SOUTHWEST. DEEPER RIDGING WILL RETROGRADE INTO THE AREA TUESDAY NIGHT... VEERING THE LOW LEVEL FLOW...WEAKENING THE ISENTROPIC LIFT TO ONLY SLIGHT CHANCE POPS. WITH NO AIR MASS CHANGE...MINS AGAIN WILL BE AROUND 70. AN UPPER LEVEL TROUGH WILL DIVE FROM THE WESTERN GREAT LAKES REGION WEDNESDAY INTO THE SOUTHERN APPALACHIANS BY THURSDAY MORNING. THE ASSOCIATED COLD FRONT WILL STAY WEST OF THE APPALACHIANS THROUGH WEDNESDAY EVENING. THE AIR MASS ACROSS CENTRAL NC ON WEDNESDAY AFTERNOON WILL BE WARM AND UNSTABLE WITH WEAK TO MODERATE INSTABILITY VALUES OF AROUND 1000-2000 J/KG. THE AIR MASS WILL BE MOIST WITH PRECIPITABLE WATER VALUES OF 1.75 TO 2.0 INCHES. CONVECTIVE COVERAGE IS NOT EXPECTED TO BE OVERWHELMING AND LIKELY MOST FOCUSED ACROSS THE COASTAL PLAIN...EAST OF THE PIEDMONT TROUGH AND TO THE WEST ACROSS THE HIGHER TERRAIN. HIGH TEMPERATURES IN THE 88 TO 92 RANGE ARE SUPPORTED BY CONSENSUS THICKNESS VALUES AND IN BETWEEN THE WARMER MAV AND COOLER MET GUIDANCE. SCATTERED CONVECTION IS APT TO CONTINUE IN THE EARLY EVENING HOURS AND THEN BECOME ISOLATED OVERNIGHT...AGAIN THE BEST COVERAGE IS EXPECTED ACROSS THE COASTAL PLAIN AND PERHAPS MORE SO IN THE WESTERN PIEDMONT CLOSER TO THE UPPER TROUGH AND AS CONVECTION INITIATED NEAR THE MOUNTAINS MOVES EAST. OVERNIGHT LOWS SHOULD BE MODERATED BY CLOUD COVER AND SOME MIXING AHEAD OF THE APPROACHING WITH LOWS IN THE LOWER 70S. THE UPPER TROUGH REACHES THE SOUTHERN APPALACHIANS ON THURSDAY MORNING AS THE COLD FRONT SLOWLY MOVES FROM THE FOOTHILLS INTO THE PIEDMONT DURING THE MORNING AND AFTERNOON. THE AIR MASS ACROSS CENTRAL NC IS POSSIBLY EVEN MORE MOIST THAN ON WEDNESDAY WITH PRECIPITABLE WATER VALUES AROUND OR IN EXCESS OF 2 INCHES. EXPECT A GOOD AMOUNT OF CLOUD COVER WHICH MAY LIMIT INSTABILITY A BIT. THE APPROACHING TROUGH WILL RESULT IN STRONGER FLOW ALOFT AND BULK SHEAR VALUES WILL INCREASE INTO THE 20-30 KTS RANGE AND SUPPORT MORE CONVECTIVE STORM ORGANIZATION AND A SLIGHTLY ELEVATED SEVERE THREAT. POPS HAVE BEEN INCREASED TO THE HIGH CHANCE CATEGORY. MAX TEMP GUIDANCE IS EVEN WARMER COMPARED TO WEDNESDAY WITH THE WARMER MAV GUIDANCE SUGGESTING S HIGHS IN THE 94-95 RANGE AT RDU AND FAY. NOT READY TO GO THAT HIGH BUT WE HAVE INCREASED MAX TEMPS A BIT AND IF CLOUDS COVER IS LESS THAN EXPECTED...WARMER TEMPERATURES AND INCREASED INSTABILITY CAN BE EXPECTED. THE THUNDERSTORM THREAT CONTINUES INTO THURSDAY EVENING WITH THE BEST COVERAGE IN THE EAST. HIGHS THURSDAY SHOULD RANGE IN THE 88 TO 93 RANGE WITH LOWS IN THE UPPER 60S TO LOWER 70S. THE FRONT SLOWLY CLEARS CENTRAL NC FRIDAY AFTERNOON AND THEN STALLS ALONG THE NC COAST AND EXTENDS BACK INTO CENTRAL SC BY LATE FRIDAY NIGHT. A CONTINUED THREAT OF SHOWERS AND THUNDERSTORMS PERSISTS ON FRIDAY WITH THE GREATEST CHANCES ACROSS THE COASTAL PLAIN. HIGHS WILL BE NOTICEABLY COOLER THAN ON THURSDAY WITH FRIDAY MAXES IN THE MID TO UPPER 80S. LOWS WILL RANGE IN THE MID 60S TO THE NORTHWEST AND UPPER 60S TO THE SOUTHEAST. -BLAES && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 320 PM MONDAY... THE COLD FRONT LINGERS SOUTH OF OUR AREA ON SATURDAY WITH HIGH PRESSURE EXTENDING INTO THE REGION. SATURDAY SHOULD BE THE BETTER DAY OF THE WEEKEND WITH A LIMITED THREAT OF CONVECTION...MAINLY ACROSS THE SOUTHWESTERN PIEDMONT...SANDHILLS AND SOUTHERN COASTAL PLAIN DURING THE TYPICAL AFTERNOON/EVENING PERIOD. ANOTHER UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT APPROACHES ON SUNDAY AND BRINGS AN INCREASED THREAT OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS. GUIDANCE DIFFERS ON MONDAY WITH THE ECMWF BRINGER THE UPPER TROUGH THROUGH FASTER THAN THE GFS...FOR NOW WILL OPT FOR THE DRIER ECMWF SOLUTION AND DECREASE POPS FOR MONDAY. TEMPERATURES DURING THE LONG TERM RETURN TO MORE SEASONABLE VALUES WITH HIGHS IN THE MID 80S TO AROUND 90 AND MORNING LOWS IN THE UPPER 60S TO LOW 70S. -BLAES && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 1250 AM TUESDAY... ABOVE-AVERAGE CONFIDENCE IN PREVAILING IFR TO LIFR CONDITIONS UNTIL AROUND 12Z OR 13Z AT ALL TAF AIRFIELDS. CIGS AND VSBYS CURRENTLY SIT AT VFR OR MVFR... BUT CIGS ARE EXPECTED TO DROP TO IFR/LIFR BY 07Z OR 08Z... WITH MAINLY MVFR VSBYS. CIGS SHOULD RISE SLOWLY TO MVFR BY 15Z WITH VSBYS CLIMBING TO VFR... THEN MVFR CIGS SHOULD RISE TO VFR BY 17Z OR 18Z. ISOLD SHOWERS THROUGH MID MORNING WILL LIKELY GIVE WAY TO GREATER COVERAGE OF SHOWERS AND STORMS AS INSTABILITY INCREASES WITH RISING AND DEEPENING MOISTURE... ALTHOUGH AS WAS THE CASE YESTERDAY... THE DIFFICULTY LIES IN TRYING TO DETERMINE WHICH SITE WILL SEE THE BEST CHANCE FOR SHOWERS/STORMS. IT LOOKS LIKE FAY COULD SEE THE FIRST DEVELOPMENT OF SHOWERS/STORMS BY THE NOON HOUR... WITH ACTIVITY THEN SPREADING TO THE NORTH AND NW TO THE REST OF THE TAF SITES AND INCREASING IN COVERAGE THROUGH THE EARLY/MID AFTERNOON. OVERALL COVERAGE SHOULD BE A LITTLE LESS THAN WE SAW MONDAY. CIGS SHOULD HEAD BACK DOWN TO MVFR AFTER SUNDOWN. LOOKING BEYOND 06Z EARLY WEDNESDAY MORNING... WITH DEW POINTS STILL HIGH... IFR CONDITIONS ARE LIKELY ONCE AGAIN AFTER 08Z AT ALL SITES... LASTING THROUGH 13Z WED MORNING. THE FRONTAL ZONE ACROSS ERN NC WILL HAVE DISSIPATED WITH SURFACE WINDS MAINLY FROM THE SW WED AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND SLIGHTLY DRIER AIR... SO CLOUD BASES SHOULD RISE TO VFR BY 15Z WED MORNING. VFR CONDITIONS ARE LIKELY TO HOLD THROUGH FRONTAL PASSAGE ON THU (ALTHOUGH SUB-VFR CONDITIONS WITHIN STORMS ARE POSSIBLE THU AFTERNOON/EVENING). EXPECT VFR CONDITIONS TO LAST THROUGH SAT WITH WEAK HIGH PRESSURE BUILDING IN. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...32 SHORT TERM...BLAES LONG TERM...BLAES/DJF AVIATION...HARTFIELD

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