Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240531 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 130 AM EDT THU JUL 24 2014 .SYNOPSIS...A COLD FRONT WILL PUSH SOUTHEASTWARD THROUGH THE REGION LATE TODAY THROUGH TONIGHT. THIS FRONT WILL STALL OUT NEAR THE SOUTH CAROLINA BORDER ON FRIDAY... AS WEAK HIGH PRESSURE BUILDS IN FROM THE NORTH. THIS FRONT WILL THEN WEAKEN AND HEAD BACK NORTH OF THE AREA OVER THE WEEKEND. && .NEAR TERM /THROUGH THURSDAY/... AS OF 922 PM WEDNESDAY... BULK OF ISOLATED TO SCATTERED CONVECTION HAS DIMINISHED/DISSIPATED WITH LOSS OF HEATING. 00Z ANALYSIS DEPICTS A MOISTURE-RICH AIR MASS IN PLACE AS PRECIPITABLE WATER VALUES HOVER BETWEEN 1.8 TO 2 INCHES. WATER VAPOR IMAGERY DEPICTS A WEAKENING SHEAR AXIS STRETCHING FROM THE LOWER MS VALLEY INTO THE NORTHERN MID ATLANTIC. A WELL DEFINED VORT MAX AND ATTENDANT SHEAR AXIS WAS DIVING SEWD ACROSS THE WESTERN GREAT LAKES THIS EVENING. THE FORMER SHEAR AXIS AND ASSOCIATED SFC TROUGH WILL BE IN CLOSE ENOUGH PROXIMITY OVERNIGHT TO TRIGGER ISOLATED TO SCATTERED CONVECTION OVER THE NORTHERN PIEDMONT. ELSEWHERE...COULD SEE AN ISOLATED SHOWER OR STORM ABOUT ANYWHERE DUE TO OLD OUTFLOW BOUNDARIES AND A CONDITIONALLY UNSTABLE MOIST AIR MASS. MIN TEMPS GENERALLY NEAR 70-LOWER 70S. THE APPROACH OF THE GREAT LAKES VORT MAX AND ATTENDANT SHEAR AXIS EARLY THURSDAY WILL AID TO REINVIGORATE THE STALLED BOUNDARY IMMEDIATELY TO OUR NW. SHOULD SEE SCATTERED CONVECTION DEVELOP BY MID-LATE MORNING OVER THE PIEDMONT COUNTIES WITH CONVECTION DEVELOPING/SPREADING OVER THE REMAINDER OF THE FORECAST AREA THURSDAY AFTERNOON. BEST SHEAR/INSTABILITY PARAMETERS WILL RESIDE OVER THE NORTHERN PIEDMONT-NORTHERN COASTAL PLAIN SO THIS AREA WILL HAVE THE BETTER CHANCE OF SEEING ORGANIZED CONVECTION...MAINLY IN THE FORM OF BROKEN CONVECTIVE SEGMENTS WITH MAIN WEATHER HAZARD BEING LOCALLY DAMAGING WIND GUSTS. POTENTIAL FOR INDIVIDUAL STORMS TO TRACK REPEATEDLY ACROSS A PARTICULAR LOCATION FOR A COUPLE HOURS AS THE SURFACE FRONT WILL BE SLOWED/BLOCKED BY AN AREA OF HIGH PRESSURE OFFSHORE. CONSIDERING HOW MOIST THE AIR MASS IS...LOCALLY HEAVY/EXCESSIVE RAINFALL WILL BE AN ISSUE...ESPECIALLY IN URBANIZED LOCATIONS. MAX TEMPS THURSDAY WILL BE HAMPERED BY CONSIDERABLE CLOUDINESS AND SCATTERED-NUMEROUS SHOWERS/T-STORMS. CURRENT FORECAST OF MID 80S NW TO LOWER 90S SE APPEARS ON TARGET. IF CONVECTION STARTS FIRING IN THE PIEDMONT BY 10 AM-12PM...HOWEVER...COULD SEE MAX TEMPS 3-4 DEGREES COOLER. && .SHORT TERM /THURSDAY NIGHT/... AS OF 315 PM WEDNESDAY... THE UPPER TROF WILL BE BLOCKED BY HIGH PRESSURE OFFSHORE...AND THE COLD FRONT WILL CORRESPONDINGLY SLOW AND THEN STALL AS IT REACHES THE COAST FRIDAY MORNING. AS SUCH...POPS WILL FALL OFF TO SLIGHT CHANCE WEST OF I95 BY MIDNIGHT...WITH LINGERING CHANCES IN THE EAST THROUGH MORNING. MODEST FLOW OF COOLER AND DRIER AIR INTO THE NORTHWEST WILL PRODUCE OVERNIGHT MINS IN THE MID 60S...WITH MINS OVER THE EAST STILL IN THE LOW 70S. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 235 PM WEDNESDAY... NWP GUIDANCE IS RELATIVELY CONSISTENT IN BRINGING THE SURFACE COLD FRONT TO THE COASTAL PLAIN OF THE CAROLINAS BY 12 UTC FRIDAY AS THE UPPER LEVEL TROUGH AXIS CROSSES THE APPALACHIANS. THE UPPER LEVEL TROUGH AXIS MAKES LIMITED PROGRESS EAST ON FRIDAY AS THE NEXT SHORTWAVE TROUGH OVER THE OH VALLEY EARLY FRIDAY SPLITS WITH ONE PIECE OF ENERGY MOVING EAST INTO THE NORTHEAST AND THE OTHER DROPS TOWARD THE SAVANNAH RIVER VALLEY. THE FRONT DRIFTS SOUTH AND BRIEFLY STALLS BEFORE MOVING NORTH INTO THE MID ATLANTIC AS A WARM FRONT SATURDAY. DEEP MOISTURE DECREASES ON FRIDAY COMPARED TO THURSDAY WITH THE BULK OF THE MOISTURE CONFINED TO THE 925 TO 700 MB LAYER IN A REGION OF RELATIVELY STEEP LAPSE RATES. THIS PATTERN SUGGESTS THE BEST CONVECTIVE COVERAGE ON FRIDAY WILL BE ACROSS THE FAR SOUTHEAST PIEDMONT AND ESPECIALLY THE COASTAL PLAIN AND EASTERN SANDHILLS FRIDAY AFTERNOON AND EVENING. POPS IN THE SLIGHT CHANCE TO LOW CHANCE RANGE SHOULD SUFFICE. HIGHS ON FRIDAY WILL RANGE IN THE MID TO UPPER 80S. PARTLY CLOUDY SKIES ARE EXPECTED FRIDAY NIGHT WITH LOWS IN THE MID 60S TO NEAR 70. SATURDAY WILL FEATURE PARTLY CLOUDY SKIES WITH THE BULK OF THE CONVECTION SUPPRESSED TOWARD THE COAST. THERE IS JUST A LIMITED THREAT OF PRECIPITATION IN CENTRAL NC WITH THE BEST CHANCE OF STORMS ON SATURDAY ACROSS THE EASTERN COASTAL PLAIN WITH ONLY SLIGHT CHANCE POPS WARRANTED. SATURDAY SHOULD FEATURE THE FAIRER WEATHER OF THE WEEKEND WITH VERY LIMITED PRECIPITATION COVERAGE AND NEAR SEASONABLE TEMPERATURES. TEMPERATURES WILL MODERATE A BIT ON SATURDAY WITH HIGHS IN THE 87 TO 92 RANGE. THE NEXT UPPER TROUGH APPROACHES FROM THE NORTHWEST ON SUNDAY WITH A COLD FRONT DROPPING ACROSS THE OH VALLEY. A LEE TROUGH AHEAD OF THE FRONT ACROSS THE PIEDMONT OF VA AND THE CAROLINAS IS EXPECTED TO BECOME CONVECTIVELY ACTIVE DURING THE AFTERNOON AND EVENING WITH SCATTERED CONVECTION. THE SOUTHERLY FLOW AHEAD OF THE UPPER TROUGH... COMBINED WITH DEEP MIXING WILL RESULT IN HIGHS IN THE LOWER 90S. THE UPPER TROUGH AXIS AND COLD FRONT WILL CROSS CENTRAL NC ON MONDAY WITH GOOD CONVECTIVE COVERAGE ANTICIPATED. WILL INCREASE POPS INTO THE HIGH CHANCE RANGE. WITH THE APPROACHING TROUGH...THE LOW AND MID LEVEL FLOW INCREASES WITH BULK SHEAR VALUES OF 30-40 KTS EXPECTED SUGGESTING SOME HIGH-BASED STORM ORGANIZATION IS POSSIBLE. SLIGHTLY COOLER TEMPERATURES ARE EXPECTED ON MONDAY WITH THE CLOUD COVER AND PRECIPITATION...HIGHS SHOULD RANGE IN THE 86 TO 91 RANGE WITH LOWS MONDAY MORNING IN THE 69 TO 74 RANGE. THE LARGE AMPLITUDE UPPER LEVEL TROUGH SLOWLY MOVES EAST ON TUESDAY WITH THE COLD FRONT PROGGED TO MOVE INTO THE COASTAL PLAIN MONDAY NIGHT AND SLOWLY PUSH TOWARD THE COAST ON TUESDAY. COOL HIGH PRESSURE BUILDS INTO THE REGION WITH ANY PRECIPITATION ON TUESDAY LIKELY CONFINED TO THE COASTAL PLAIN AND POINTS EAST. MAINLY DRY CONDITIONS ARE EXPECTED ON WEDNESDAY BUT IT IS WORTH NOTING THAT THE GFS/ECMWF BOTH INDICATE THE STALLED FRONT NEAR THE COAST MAY TRY TO WORK WEST. FOR NOW WILL INCLUDE A DRY FORECAST. THE MUCH COOLER AIR MASS WITH LOW LEVEL THICKNESS VALUES FALLING INTO THE 1375-1390M RANGE FOR TUESDAY AND WEDNESDAY MORNINGS. THIS WOULD SUPPORT LOWS IN THE 60S AND PERHAPS UPPER 50S IN THE TRIAD OR NEAR THE VA BORDER ON WEDNESDAY MORNING WITH HIGHS OF 79-86. -BLAES && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 130 AM THURSDAY... VFR CONDITIONS ARE LIKELY TO DOMINATE THROUGH DAYBREAK AT ALL TAF SITES. A LIGHT BUT STEADY SURFACE BREEZE FROM THE SW WILL KEEP THE LOW LEVELS STIRRED AND INHIBIT MOST FOG DEVELOPMENT... BUT A SHORT PREDAWN PERIOD (UNDER 2 HRS) OF MVFR FOG IS NOT OUT OF THE QUESTION. CURRENTLY ANY CLOUD COVER OVER CENTRAL NC IS LIMITED TO HIGH CLOUDS BASED ABOVE 10 000 FT AGL MAINLY IN THE NW... AND WHILE CIGS WILL BE DROPPING AHEAD OF THE COLD FRONT APPROACHING FROM THE NW... THEY SHOULD STAY VFR THROUGH 13Z. SCATTERED TO NUMEROUS SHOWERS AND STORMS ARE EXPECTED NEAR INT/GSO STARTING AROUND 13Z OR 14Z... AND THESE COULD GENERATE MVFR CIGS/VSBYS AND ENHANCED WIND GUSTS. THESE SHOWERS/STORMS ARE THEN EXPECTED TO AFFECT RDU AND RWI STARTING AROUND 14Z OR 15Z... AND FAY STARTING AT 17Z OR 18Z. TOUGH CALL ON WHEN THE STORM THREAT WILL EXIT TAF SITES... BUT VFR CONDITIONS SHOULD RETURN SOON AFTER 22Z AT GSO... 00Z AT RDU/RWI... AND PROBABLY NOT UNTIL AFTER 04Z AT FAY. LOOKING BEYOND 06Z EARLY FRI MORNING... SURFACE WINDS WILL REMAIN FAIRLY LIGHT LATE TONIGHT BUT SHIFT AROUND QUICKLY FROM WSW TO NNE AS THE FRONT PUSHES SOUTHEAST THROUGH NC. THE FRONT WILL LIKELY SLOW DOWN ENOUGH OVER SE NC TO KEEP A CHANCE OF SUB-VFR SHOWERS/STORMS AT FAY THROUGH FRI AFTERNOON... BUT OTHERWISE VFR CONDITIONS ARE EXPECTED FRI-SAT AS HIGH PRESSURE NOSES IN FROM THE NORTH. THIS FRONT WILL SHIFT BACK NORTH AND DISSIPATE OVER THE WEEKEND WITH A SURFACE TROUGH REFORMING OVER CENTRAL NC. AN UPPER LEVEL DISTURBANCE AND ACCOMPANYING COLD FRONT WILL MOVE IN FROM THE NORTHWEST ON SUNDAY... POTENTIALLY BRINGING ANOTHER ROUND OF SHOWERS/STORMS LATE SUNDAY INTO MONDAY. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS..HARTFIELD NEAR TERM...WSS SHORT TERM...MLM LONG TERM...BLAES AVIATION...HARTFIELD

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