Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 271753 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 153 PM EDT THU AUG 27 2015 .SYNOPSIS...A FRONT WILL LINGER NEAR THE CAROLINA COAST THROUGH THURSDAY. WEAK SURFACE HIGH PRESSURE WILL BUILD INTO THE REGION FOR FRIDAY AND SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1027 AM THURSDAY... CLOUD COVER... PARTICULARLY ACROSS THE EASTERN PART OF THE STATE... WILL HANG ON IN TO THE AFTERNOON HOURS AS THE AREA REMAINS UNDER THE INFLUENCE OF A MOIST LOW LEVEL NORTHEASTERLY FLOW. TEMPERATURES WILL SLOWLY RISE IN TO THE LOW TO MID 80S THIS AFTERNOON. FRONT IS LOCATED JUST OFFSHORE AT THIS TIME... AND ISOLATED TO SCATTERED SHOWER AND STORM ACTIVITY WILL CONTINUE TO BE POSSIBLE MAINLY IN THE SOUTHEASTERN PART OF THE AREA. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 330 AM THURSDAY... SUBTROPICAL RIDGE OVER THE SOUTHWESTERN ATLANTIC WILL BEGIN TO RETROGRADE TOWARDS THE SOUTHEASTERN STATES AS ELONGATED TROUGHINESS LINGERS FROM THE CENTRAL GULF NEWED INTO THE SOUTHERN APPALACHIANS. AT THE SURFACE...WEAK SURFACE HIGH WILL EXTEND SOUTH ACROSS THE MID- ATLANTIC STATES. UNDER INCREASING HEIGHTS ALOFT AND WEAK SFC HIGH PRESSURE ...FRIDAY LOOKS MOSTLY DRY ACROSS CENTRAL NC WITH RAIN CHANCES MAINLY CONFINED TO THE DIFFERENTIAL HEATING OVER MTNS AND FTHLS AND ALONG THE IMMEDIATE COAST INVOF WHERE THE SEABREEZE MAY BE ENHANCED BY NEARBY WEAKENING FRONTAL ZONE. HIGHS MAINLY IN THE MID 80S. LOWS FRIDAY NIGHT IN THE MID TO UPPER 60S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 355 AM THURSDAY... THE MODELS CONTINUE TO INDICATE THE SOUTHERN PORTION OF A POSITIVELY- TILTED AND STRONGLY MERIDIONAL TROUGH ALOFT STRETCHING FROM QUEBEC TO THE WESTERN GULF OF MEXICO THIS MORNING WILL BE LEFT BEHIND... CLOSE OFF...AND EVENTUALLY BECOME INCORPORATED INTO A RE-DEVELOPING TROUGH OVER THE LOWER-MID MS VALLEY BY EARLY NEXT WEEK. THE ASSOCIATED (DISCONTINUOUS) RETROGRESSION OF THE TROUGH IN THE MEAN...AND ACCOMPANYING WESTWARD EXPANSION OF A SUB-TROPICAL RIDGE ALONG THE SOUTHEAST US COAST...WILL BECOME AN IMPORTANT DEVELOPMENT FOR ERIKA AS IT TRACKS THROUGH THE CARIBBEAN ISLANDS. ANY ASSOCIATED TROPICAL MOISTURE OR AFFECTS ON CENTRAL NC WOULD LIKELY NOT OCCUR UNTIL EARLY NEXT WEEK...AND THAT IS OF COURSE CONDITIONAL UPON THE SYSTEM EVEN SURVIVING A HOSTILE ENVIRONMENT AS IT MOVES ON A WEST TO NORTHWEST TRACK DURING THE NEXT COUPLE OF DAYS. IN THE MEANTIME...A CANADIAN SURFACE HIGH --ONE THAT HAS SUPPORTED LOW TEMPERATURES IN THE 30S-40S FROM THE NORTHERN PLAINS TO THE UPPER MIDWEST IN RECENT DAYS-- WILL HAVE DRIFTED OFF THE MIDDLE ATLANTIC COAST BY SAT. THE ASSOCIATED DRY AIR MASS CHARACTERIZED INITIALLY BY PRECIPITABLE WATER VALUES AOB ONE INCH OVER CENTRAL NC WILL ONLY SLOWLY RECOVER AND LIKELY PROVE UNSUPPORTIVE OF CONVECTION SAT...EXCEPT OVER THE FAR SOUTHERN AND WESTERN PIEDMONT/AROUND THE SW PERIPHERY OF THE RIDGE...WHERE THE MODELS INDICATE 850-MB THETA-E WILL BE HIGHEST AND WHERE A CAPPING INVERSION ON GFS FORECAST SOUNDINGS WEAKENS FIRST. THE GFS/ECMWF ARE THEN IN GOOD AGREEMENT REGARDING THE EJECTION OF A DISTURBANCE FROM THE AFOREMENTIONED CLOSED LOW OVER THE GULF OF MEXICO; AND THIS FEATURE IS FORECAST TO TRACK THROUGH THE SOUTHERN AND CENTRAL APPALACHIANS SUN-SUN NIGHT. THE BEST OVERLAP OF ASSOCIATED FORCING FOR ASCENT AND RECOVERING DEEP MOISTURE WILL EXIST OVER THE PIEDMONT AND SANDHILLS...WHERE SCATTERED SHOWERS AND STORMS ARE EXPECTED BY SUN AFTERNOON. SOME OF THIS ACTIVITY COULD LINGER OVERNIGHT AS THE DISTURBANCE TRACKS THROUGH WESTERN NC. THE FORECAST FOR NEXT WEEK IS ENTIRELY DEPENDENT UPON THE EVOLUTION OF ERIKA...WHICH IF IT WERE TO HOLD TOGETHER...COULD THREATEN THE FL/SOUTHEAST US COAST EARLY-MID NEXT WEEK. IF AN ORGANIZED TROPICAL CYCLONE WERE TO APPROACH...CENTRAL NC WOULD INITIALLY LIKELY LIE IN A REGION OF SUBSIDENCE (AND WARMING) EARLY NEXT WEEK...WITH IMPROVING PRECIPITATION CHANCES WITH TIME...AS THE TC --OR AT LEAST TROPICAL MOISTURE AHEAD OF IT-- MOVES UP THE SOUTHEAST US COAST. REFERENCE NHC PRODUCTS FOR THE LATEST. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AS OF 152 PM THURSDAY... 24 HOUR TAF PERIOD: CONDITIONS ARE VFR ACROSS THE AREA AS EARLIER STRATUS HAS DISSIPATED. CONDITIONS ARE LIKELY TO REMAIN VFR AS THE REGION IS INFLUENCED BY HIGH PRESSURE OVER THE MID ATLANTIC. OUTLOOK: VFR CONDITIONS WILL CONTINUE AS HIGH PRESSURE MOVES OFF THE MID ATLANTIC COAST OVER THE WEEKEND. MAINLY DIURNAL SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE LATE IN THE WEEKEND INTO THE FIRST HALF OF NEXT WEEK AS MOISTURE INCREASES ACROSS THE AREA. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...30 SHORT TERM...CBL LONG TERM...26 AVIATION...30

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