Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 302352 RRA AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 752 PM EDT SAT AUG 30 2014 .SYNOPSIS...DEEP HIGH PRESSURE WILL EXTEND OVER THE REGION THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 740 PM SATURDAY... THE LATEST SURFACE ANALYSIS SHOWED A SLACK GRADIENT OVER CENTRAL NORTH CAROLINA. RADAR IMAGERY SHOWED THE SEA BREEZE HAD MOVED WELL INLAND...MOVING NORTH THROUGH THE TRIANGLE AND HEADED TOWARD INTERSTATE 40/85. THE SPC MESOANALYSIS SHOWED MLCAPE AROUND 1500J/KG...THOUGH DESPITE THE INSTABILITY SHEAR WAS VERY WEAK AND THERE WAS JUST ENOUGH LIFT TO PRODUCE ISOLATED SHOWERS. TOTAL LIFT AND CONVECTIVE DEVELOPMENT COULD ALSO BE FURTHER INHIBITED BY AN AXIS OF VERY DRY MID-LEVEL AIR NOTED ON WATER VAPOR OVER CENTRAL NORTH CAROLINA. DIURNALLY...THE SHOWERS SHOULD DIMINISH THIS EVENING ESPECIALLY AS AN AXIS OF LOWER PRECIPITABLE WATER VALUES...NEAR NORMAL AT ABOUT 1.3 INCHES...IS FORECAST BY THE RAP TO MOVE EAST FROM THE FOOTHILLS AND FAR WESTERN PIEDMONT OVERNIGHT...WITH K INDICES FALLING INTO THE TEENS AS BUFR SOUNDINGS FROM THE GFS AND NAM ALONG WITH RAP SOUNDINGS SHOW AN OVERALL STABLE AIR MASS THEN. OVERNIGHT LOW TEMPERATURES HAVE WARMED ON THE MAV MOS GUIDANCE FROM 12Z TO 18Z...CLOSER TO THE MET MOS GUIDANCE WHICH HAS APPARENTLY PERFORMED A LITTLE BETTER OVER THE LAST DAY OR TWO. STILL...THE BASIC FORECAST FOR MINIMUM TEMPERATURES REMAINS THE SAME...MOSTLY WITHIN A DEGREE OR TWO OF 70. SOME LOW CLOUDS ARE POSSIBLE LATE TONIGHT PARTICULARLY AS NOTED ON NAM BUFR SOUNDINGS AND THE SREF PROBABILISTIC GUIDANCE...AND ALLUDED TO MORE ON THE GFS 18Z MOS GUIDANCE OUTPUT FROM ITS EARLIER...MORE OPTIMISTIC 12Z GUIDANCE. 925MB WINDS SEEM A LITTLE HIGH FOR FOG IN MOST PLACES...TO 20KT TOWARD THE TRIAD LATE TONIGHT...BUT THE LOWER VALUES OF 10 TO 15KT TOWARD INTERSTATE 95 ALONG WITH EXPECTED DEW POINTS IN THE LOWER 70S COULD ALLOW A LITTLE MORE NOTICEABLE FOG IN PATCHES TOWARD THERE LATE. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 230 PM SATURDAY... A SHORT WAVE TROUGH OVER THE MS RIVER VALLEY TO START THE DAY WILL LIFT TO THE NORTHEAST INTO THE OH VALLEY THROUGH SUNDAY NIGHT. HOWEVER...ITS ASSOCIATED ENERGY AND DEEP MOISTURE PLUME (EMANATING FROM THE GULF) WILL LARGELY REMAIN WEST AND NORTH OF CENTRAL NC. IN ADDITION...THE SUBTROPICAL RIDGE CENTERED OVER THE SOUTHEAST COAST SHOULD ALSO HELP KEEP THE BETTER RAIN CHANCES WEST OF THE AREA. THEREFORE...WILL CONTINUE THE FORECAST THINKING OF ONLY ISOLATED TO WIDELY SCATTERED SHOWERS/STORMS...WITH THE BEST CHANCES ACROSS THE WEST DUE TO THE PROXIMITY OF THE ABOVE FEATURES. TEMPS WILL CONTINUE TO BE ABOVE NORMAL...WITH HIGHS GENERALLY IN THE LOWER 90S AND OVERNIGHT LOWS AROUND 70 DEGREES. && .LONG TERM /MONDAY THROUGH SATURDAY/... AS OF 200 PM SATURDAY... WITH ROUGHLY 3 WEEKS OF SUMMER REMAINING (AUTUMN EQUINOX IS SEPT 23)...THE WESTWARD EXPANSION OF THE SUBTROPICAL RIDGE ACROSS MUCH OF THE SOUTHERN CONUS...WITH THE MAIN BELT OF WESTERLIES RETREATING NORTHWARD ALONG THE US-CANADA BORDER WILL RESULT IN THE FIRST PROLONGED PERIOD OF SUMMERTIME HEAT AND CONVECTIVE RAIN CHANCES THAT CENTRAL NC HAS SEEN THIS SEASON. AFTERNOON THICKNESSES ARE PROGGED TO RUN 25 TO 30 METERS ABOVE CLIMATOLOGY...WHICH SHOULD SUPPORT DAYTIME HIGHS RANGING FROM 90 TO 95F WITH LOWS IN THE UPPER 68 TO 74F. A LOW AMPLITUDE TROUGH MOVING EASTWARD ACROSS THE NORTHEAST AND MID- ATLANTIC STATES WILL TEMPORARILY FLATTEN THE UPPER ANTICYCLONE LONG ENOUGH TO ALLOW A WEAK SURFACE FRONT TO APPROACH NC FROM THE NORTH...BUT RECENT MODEL TRENDS OVER THE LAST COUPLE OF DAYS REALLY WASHES OUT THE FRONT TO OUR NORTH DURING THE LATE WEDNESDAY/THURSDAY PERIOD. AS SUCH...GRIDDED DATABASE WILL CONTINUE TO EXHIBIT DIURNALLY DRIVEN CONVECTION ISOLATED TO WIDELY SCATTERED STORMS EACH AFTERNOON...FIRING WITHIN A MODERATELY UNSTABLE AIRMASS ALONG A LEE SIDE SURFACE TROUGH. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 751 PM SATURDAY... VFR CONDITIONS WILL CONTINUE THROUGH THE EVENING. LOW LEVEL MOISTURE REMAINS HIGH ACROSS THE AREA WITH LIGHT SURFACE WINDS... AND IFR CONDITIONS WITH STRATUS... AND POSSIBLY SOME PATCHY FOG.... ARE EXPECTED TO DEVELOP IN THE EARLY MORNING HOURS SUNDAY AT KRDU...KRWI...AND KFAY... WHERE DEWPOINTS ARE HIGHEST. MVFR CONDITIONS ARE POSSIBLE AT KGSO AND KINT. CONDITIONS WILL RETURN TO VFR AFTER 12Z SUNDAY... WITH A FEW SHOWERS/THUNDERSTORMS POSSIBLE IN THE AFTERNOON. OUTLOOK...A SUMMERTIME PATTERN WILL PERSIST THROUGH EARLY/MID NEXT WEEK...WITH ISOLATED TO SCATTERED AFTERNOON/EVENING CONVECTION AND A POTENTIAL FOR EARLY MORNING FOG/STRATUS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...GIH NEAR TERM...DJF SHORT TERM...KRD LONG TERM...CBL AVIATION...SEC/KRD

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