Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 200510 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 110 AM EDT WED AUG 20 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES IN NORTHWEST FLOW ALOFT WILL CROSS THE REGION THIS WEEK. A BACK DOOR COLD FRONT IS FORECAST TO SLIP INTO THE AREA OVER THE WEEKEND. && .NEAR TERM /OVERNIGHT/... AS OF 925 PM TUESDAY... WITH LOSS OF HEATING AND WEAKENING SUPPORT ALOFT AS SC VORT MAXIMUM DRIFTS EAST...BULK OF CONVECTION AS DIMINISHED ACROSS CENTRAL NC AT MID-EVENING. ISOLATED SHOWERS CONTINUE TO PERSIST OVER THE WESTERN PIEDMONT ALONG A LOW LEVEL THETA-E GRADIENT WITH SOME WEAK SUPPORT ALOFT FROM A VORT MAX CROSSING THE HIGHLANDS OF WV/VA. SCATTERED CONVECTION NOW OCCURRING IN THE VICINITY OF ROANOKE, VA MAY FOLLOW ALONG THE SFC THETA-E GRADIENT AND DRIFT INTO THE NW PIEDMONT COUNTIES AFTER MIDNIGHT. OTHERWISE ABUNDANT LOW LEVEL MOISTURE AND A LIGHT-CALM WIND REGIME SHOULD ALLOW AREAS OF LOW CLOUDS AND/OR FOG TO DEVELOP LATE THIS EVENING OR OVERNIGHT. THINK LOW CLOUDS WILL BE MORE PREVALENT VERSUS FOG AS SURFACE GROUND QUITE WARM FROM HEATING EARLIER TODAY. MIN TEMPS NEAR 70-LOWER 70S. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 310 PM TUESDAY... NORTHWESTERLY FLOW ALOFT CONTINUES ON WEDNESDAY...WITH MODELS SHOWING A DISTURBANCE CURRENTLY ASSOCIATED WITH CONVECTION OVER SOUTHERN ILLINOIS SINKING SOUTH AND CROSSING VA/NORTHERN NC DURING THE DAY. AFTER THE EROSION OF ANY MORNING STRATUS...CONDITIONS ARE ARE EXPECTED TO BE SIMILAR TODAY WITH GUIDANCE GIVING HIGHS IN THE UPPER 80S/LOWER 90S. DEWPOINTS MAY MIX OUT A LITTLE MORE INT HE WESTERN PIEDMONT WITH MORE NORTHWESTERLY FLOW...BUT 1000-1500 J/KG OF MLCAPE IS STILL EXPECTED IN THE EAST. SHEAR WILL AGAIN BE WEAK AND THE SEVERE THREAT IS RELATIVELY LOW. LOWS IN THE UPPER 60S AND LOWER 70S. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 240 PM TUESDAY... EXPECT A MERIDIONAL UPPER LEVEL PATTERN...WITH RIDGING OVER THE MIDWEST AND TROUGHING ALONG THE NE AND ATLANTIC COAST THROUGH THE PERIOD. THIS WILL RESULT IN NORTHWESTERLY FLOW ALOFT OVER CENTRAL NC. THE GFS AND ECMWF BOTH INDICATE THE CHANCE FOR SHOWERS AND STORMS THROUGHOUT THE PERIOD AS A SERIES OF SHORT WAVES MOVE OVER THE AREA AROUND THE BASE OF THE UPPER LEVEL TROUGH. ALTHOUGH THE CONVECTION SHOULD BE DIURNAL IN NATURE...COVERAGE AND LOCATION ARE STILL FAIRLY UNCERTAIN AT THIS TIME. AT THE SURFACE...EXPECT A TROUGH TO LINGER ALONG THE COAST...WITH WEAK RIDGING TO THE NORTH- NORTHWEST. THE LATEST GFS STILL PUSHES A BACKDOOR COLD FRONT INTO THE NE PORTIONS OF THE AREA THIS WEEKEND...RESULTING IN HIGHS 80-85 DEGREES ACROSS THE NORTH AND 85-90 DEGREES ACROSS THE SOUTH FOR SATURDAY THROUGH MONDAY. THE ADVECTION OF WARM MOIST AIR FROM THE GULF AROUND THE HIGH AND THE RESULTING SUBSIDENCE IN THE LEE OF THE MOUNTAINS COULD MEAN INCREASING TEMPERATURES FOR THE MIDDLE OF NEXT WEEK. ALSO...THE GFS INCREASES PWAT VALUES FROM AROUND 1.5 TO AROUND 2 INCHES THROUGH THE WEEKEND...BEFORE DECREASING AGAIN TO NEAR 1.5 INCHES. THUS...EXPECT THE CONVECTION OVER THE WEEKEND TO BE CAPABLE OF PRODUCING SOME LOCALLY HEAVY RAINFALL. OVERNIGHT LOW TEMPS SHOULD GRADUALLY DECREASE...FROM THE LOW TO MID 70S THURSDAY NIGHT TO THE MID TO UPPER 60S SUNDAY AND MONDAY NIGHTS. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 110 AM WEDNESDAY... SKIES HAVE CLEARED OFF THIS EVENING. AREA METARS ARE ALREADY REPORTING 2 TO 3 DEGREE DEWPOINT DEPRESSIONS. COMBINED WITH LIGHT WINDS...THIS ALLOW FOR THE DEVELOPMENT OF MOSTLY MVFR FOG. NORTHERN COASTAL PLAIN/NORTHEAST PIEDMONT(KRWI AND KRDU)COULD ALSO SEE SOME STRATUS ADVECT INTO THE AREA AS N-NELY FLOW DEVELOPS. EXPECT CONDITIONS TO IMPROVE TO VFR BETWEEN 14-15Z. SHORTWAVE DISTURBANCES TRAVERSING THE REGION WILL ONCE AGAIN FUEL ISOLATED TO SCATTERED CONVECTION THIS AFTERNOON/EVENING... WITH THE HIGHEST PROBABILITY ACROSS THE NORTHERN TAF SITES. HOWEVER... CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE ANY MENTION OF CONVECTION IN THE TAFS AT THIS TIME. OUTLOOK... EARLY MORNING STRATUS/FOG...ALONG WITH AFTERNOON SHOWERS AND STORMS WILL BE POSSIBLE EACH DAY THIS WEEK INTO THE WEEKEND.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLS NEAR TERM...WSS SHORT TERM...BLS LONG TERM...KC AVIATION...CBL/BLS

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