Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251703 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 103 PM EDT TUE AUG 25 2015 .SYNOPSIS...
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A STALLED FRONT WILL PERSIST IN VICINITY OF THE CAROLINA COAST THROUGH THE DURATION OF THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 100 PM TUESDAY... CYCLONIC FLOW ALOFT WILL PREVAIL OVER THE MID-ATLANTIC AND CAROLINAS THROUGH TONIGHT...EQUATORWARD OF AN UNSEASONABLY STRONG UPPER LEVEL LOW STALLED ALONG THE NORTHERN PERIPHERY OF THE GREAT LAKES IN SOUTHERN ONTARIO. A COLD FRONT PROGRESSING INTO THE COASTAL PLAIN THIS MORNING WILL STALL IN VICINITY OF THE CAROLINA/SOUTHEAST COAST THIS AFTERNOON INTO TONIGHT. PRECISELY WHERE THE FRONT WILL BE LOCATED THIS EVE/TONIGHT REMAINS DIFFICULT TO ASCERTAIN GIVEN THAT A WEAK WAVE OF LOW PRESSURE WILL DEVELOP ALONG THE BOUNDARY AS IT APPROACHES STALLED SHORTWAVE ENERGY ALONG THE SOUTHEAST COAST...AMIDST WEAK SYNOPTIC HEIGHT FALLS /STRENGTHENING CYCLONIC FLOW ALOFT/. ADDITIONALLY...CONVECTION /OUTFLOW/ AND DIFFERENTIAL HEATING THIS AFTERNOON MAY ALSO INFLUENCE THE POSITION OF THE FRONT. GIVEN THE LATEST OBSERVATIONAL DATA...EXPECT DRY CONDITIONS ALONG/WEST OF HWY 1 (TRIANGLE WESTWARD)...WITH A POTENTIAL FOR ISOLD/SCT CONVECTION TO THE EAST...PRIMARILY IN THE SOUTHEAST COASTAL PLAIN. EXPECT COOLER HIGHS IN THE MID TO UPPER 80S DEPENDING ON CLOUD COVER AND CONVECTION/OUTFLOW. A DIURNAL WANE IN CONVECTIVE COVERAGE IS EXPECTED AFTER SUNSET...THOUGH SOME POTENTIAL FOR ISOLD CONVECTION WILL PERSIST OVERNIGHT IN VICINITY OF THE STALLED FRONTAL ZONE/WEAK SURFACE LOW...PRIMARILY IN THE SOUTHEAST COASTAL PLAIN. LOWS RANGING FROM THE LOWER 60S IN THE N/NW PIEDMONT TO THE UPPER 60S /NEAR 70F/ IN THE FAR SE COASTAL PLAIN. -VINCENT
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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AS OF 100 PM TUESDAY... LITTLE CHANGE IN THE OVERALL PATTERN IS EXPECTED ON WED...WITH THE UNSEASONABLY STRONG UPPER LEVEL LOW STALLED NORTH OF THE GREAT LAKES...CYCLONIC FLOW ALOFT ALONG THE EASTERN SEABOARD...AND A STALLED FRONTAL ZONE IN VICINITY OF THE CAROLINA/SOUTHEAST COAST. AS A RESULT...EXPECT CONDITIONS ON WED TO BE SIMILAR TO TODAY...WITH THE BEST POTENTIAL FOR CONVECTION IN COASTAL/FAR-EASTERN NORTH CAROLINA. WILL KEEP PRECIP CHANCES GENERALLY CONFINED TO THE FAR SE COASTAL PLAIN COUNTIES (I.E. CUMBERLAND/SAMPSON/WAYNE). ADDITIONAL SHORTWAVE ENERGY DIGGING SOUTHEAST ALONG THE WESTERN PERIPHERY OF THE STALLED UPPER LOW IS PROGGED TO PROGRESS INTO THE CENTRAL APPALACHIANS LATE WED NIGHT...AND IT IS POSSIBLE THAT THE FRONTAL ZONE SHIFTS FURTHER INLAND (ALONG WITH A POTENTIAL FOR PRECIP) AFTER MIDNIGHT AS LOW-LEVEL WIND/HEIGHT FIELDS RESPOND TO THE APPROACHING SHORTWAVE. FORECAST CONFIDENCE REMAINS LOW WITH REGARD TO THE EVOLUTION/TIMING OF THE APPROACHING WAVE...THE STALLED FRONTAL ZONE...AND WHETHER AN INLAND SHIFT IN PRECIPITATION WILL OCCUR (AS THE GFS SUGGESTS) OR PRECIPITATION REMAINS ALONG THE COAST (AS THE NAM SUGGESTS). -VINCENT
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 325 AM TUESDAY... THU/THU NIGHT: THE FRONTAL ZONE IS EXPECTED TO SIT ALONG THE SRN NC COAST EARLY THU... PIVOTING TO A MORE SW-NE ORIENTATION AS SURFACE HIGH PRESSURE SLIDES FROM THE GREAT LAKES EARLY THU EASTWARD TO THE INTERIOR MIDATLANTIC THROUGH THU NIGHT... WHILE BUILDING DOWN INTO NC. THE GFS DEPARTS FROM THE NAM/ECMWF IN HOLDING MUCH HIGHER PW VALUES WESTWARD WELL INTO NC WHILE THE NAM/ECMWF KEEP ABOVE-NORMAL PW JUST NEAR THE COAST... AND ACCORDINGLY THE GFS GENERATES PRECIP WELL INLAND IN CONTRAST TO THE OTHER DRIER MODELS. PREFER THE DRIER SOLUTION BASED ON THE STRENGTH OF THE TROUGH AXIS SHIFTING EASTWARD THROUGH THE ST LAWRENCE VALLEY/CANADIAN MARITIMES AND DRIVING THE DRIER AIR MASS INTO NC. WILL KEEP LOW RAIN CHANCES IN JUST THE SE CWA... PRIMARILY IN THE AFTERNOON/EARLY EVENING. THICKNESSES AS WELL AS THE WARMER NAM-BASED GUIDANCE SUPPORT HIGHS OF 84-89. FRI-MON: AS SHORTWAVE ENERGY LIFTS OVER AND OFF THE ERN CANADA COAST WHILE WEAKER WAVES BEHIND IT CROSS QUEBEC KEEPING THE NRN STREAM FLAT... THE SOUTHERN PORTION OF THE TROUGH HOLDS BACK AS A VERY WEAK AND BAGGY SHEAR AXIS THROUGH THE SRN APPALACHIANS DOWN TO THE CENTRAL GULF COAST. THE ONCE-COOL SURFACE HIGH IS EXPECTED TO SHIFT EAST OFF THE COAST WITH MODIFICATION OF THE RIDGE DOWN THROUGH WRN NC... LEADING TO A WESTWARD DRIFT OF THE INCREASINGLY-DIFFUSE FRONTAL ZONE... AND RISING PW FURTHER INLAND WITH TIME. POTENT ENERGY NOW ASSOCIATED WITH THE MONSOON ACTIVITY OVER THE DESERT SOUTHWEST WILL TRACK AROUND THE ANTICYCLONE THROUGH THE CENTRAL PLAINS BEFORE SHEARING OUT FROM THE CENTRAL MISS VALLEY INTO THE SRN GREAT LAKES... HELPING TO REESTABLISH THE WEAK SHEAR AXIS JUST TO OUR WEST. THIS WILL KEEP CENTRAL NC IN A SOUTHERLY/SOUTHWESTERLY BUT VERY WEAK FLOW REGIME DOMINATED BY SLOW WESTWARD EXPANSION OF THE MID LEVEL RIDGE OVER THE ATLANTIC WELL OFF THE SE COAST. SUCH FLOW MAY DRAW BAHAMIAN TROPICAL MOISTURE INTO OUR REGION HEADING INTO MON... CAUSING AN UPTICK IN PRECIP CHANCES... ALTHOUGH WILL KEEP THEM ON THE LOW SIDE FOR NOW GIVEN THE UNCERTAINTY AND THE POSSIBILITY THAT THE OFFSHORE RIDGE MAY BE STRONG ENOUGH TO SUPPRESS PRECIP OVER CENTRAL/ERN NC. WILL TREND TEMPS FROM SLIGHTLY BELOW NORMAL ON FRI TO SLIGHTLY ABOVE NORMAL BY MON AS THE RESIDENT AIR MASS MODIFIES. -GIH && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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AS OF 100 PM TUESDAY... 24 HOUR TAF PERIOD: SUB-VFR CONDITIONS ASSOC/W SCATTERED CONVECTION WILL BE POSSIBLE AT THE FAY TERMINAL TODAY IN ASSOC/W A SLOW MOVING COLD FRONT THAT WILL STALL OVER FAR EASTERN PORTIONS OF THE CAROLINAS THIS AFTERNOON THROUGH TONIGHT. CHANCES FOR CONVECTION SHOULD DIMINISH THIS EVENING/TONIGHT. MVFR/IFR CEILINGS MAY DEVELOP DURING THE PRE-DAWN HOURS WED MORNING AT THE FAY/RWI TERMINALS... PARTICULARLY THE FAY TERMINAL IN CLOSER VICINITY TO THE STALLED FRONTAL ZONE. FURTHER WEST AT THE INT/GSO/RDU TERMINALS...VFR CONDITIONS AND A LIGHT NORTHERLY WIND ARE EXPECTED TO PREVAIL THROUGH THE TAF PERIOD. LOOKING AHEAD: A POTENTIAL FOR CONVECTION AND LOW CEILINGS WILL PERSIST AT FAY/RWI (PARTICULARLY FAY) THROUGH THE REMAINDER OF THE WEEK AS A WEAK WAVE OF LOW PRESSURE DEVELOPS AND PERSISTS ALONG THE STALLED FRONT IN VICINITY OF THE SOUTHEAST COAST. -VINCENT
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...HARTFIELD AVIATION...VINCENT

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