Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211754 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 154 PM EDT THU MAY 21 2015 .SYNOPSIS...LOW PRESSURE WILL TRACK ACROSS CENTRAL NORTH CAROLINA TO THE COAST THIS AFTERNOON...THEN MOVE OFFSHORE TONIGHT AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE WEST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 130 PM THURSDAY... OVERVIEW: A SMALL AMPLITUDE WAVE TRACKING EAST INTO THE WESTERN PIEDMONT THIS MORNING WILL PROGRESS TO THE COASTAL PLAIN BY 18Z AND THE CAROLINA COAST BY 21-00Z. AN ATTENDANT LOW PRESSURE SYSTEM... CENTERED NEAR ROCK HILL SC (JUST SOUTH OF CHARLOTTE) AT 14Z... IS PROGGED TO TRACK EAST TO FLORENCE SC/LUMBERTON NC BY 18Z AND THE CAROLINA COAST BY 00Z THIS EVENING. FURTHER UPSTREAM...POTENT SHORTWAVE ENERGY CENTERED IN VICINITY OF NORTHERN IL AT 14Z WILL TRACK EASTWARD INTO THE OH VALLEY THIS AFTERNOON...PROGRESS THROUGH THE MID-ATLANTIC THIS EVENING...AND MOVE OFFSHORE THE MID-ATLANTIC COAST LATE TONIGHT. PRECIP: EXPECT THE BEST CHANCE FOR PRECIP BETWEEN 15-21Z ALONG AND NORTH OF THE HWY 64 CORRIDOR WHERE 925-850 MB WARM ADVECTION...WEAK DPVA...AND MARGINAL ELEVATED INSTABILITY (250-500 J/KG MUCAPE) SHOULD SUPPORT SCATTERED ELEVATED SHOWERS. IN THIS AREA (NORTHERN PIEDMONT/NE COASTAL PLAIN)...WEAK UPPER LEVEL FORCING AND SHALLOW/ MARGINAL INSTABILITY (CAPE SITUATED ALMOST ENTIRELY BELOW THE -10C ISOTHERM) SHOULD PRECLUDE THUNDER. THE EXCEPTION MAY BE IN THE NE COASTAL PLAIN WHERE DIURNAL TIMING OF APPROACHING DPVA AND DESTABILIZATION WILL BE BETTER. CONVECTIVE DEVELOPMENT REMAINS MORE UNCERTAIN SOUTH OF HWY 64. FORCING FOR ASCENT WILL BE GREATEST BETWEEN ROUGHLY 15-20Z AS THE SMALL AMPLITUDE WAVE AND ATTENDANT SFC LOW TRACK EAST IN VICINITY OF THE SC/NC BORDER INTO THE COASTAL PLAIN...HOWEVER...SUFFICIENT DESTABILIZATION /EROSION OF CINH/ MAY NOT OCCUR UNTIL EARLY AFTERNOON...AT WHICH POINT THE NARROW WARM SECTOR WILL MOST LIKELY BE CONFINED TO EASTERN PORTIONS OF THE SANDHILLS AND SE COASTAL PLAIN. WITH THIS IN MIND...WILL INDICATE THE BEST POTENTIAL FOR SFC-BASED CONVECTION BETWEEN 16-20Z FROM SCOTLAND/HOKE COUNTIES NORTHEAST TO WILSON/EDGECOMBE COUNTIES. TEMPS: MID/UPPER 60S FAR NORTHERN PIEDMONT (VA BORDER) TO LOW/MID 80S FAR SOUTH (NEAR SC BORDER). LOWS TONIGHT RANGING FROM THE LOWER 50S FAR NORTH TO UPPER 50S /NEAR 60F/ FAR SOUTH/SE. SEVERE: DEEP LAYER SHEAR RANGES FROM ~30 KT NEAR THE SC BORDER TO ~40 KT NEAR THE VA BORDER. AT 14Z...THE BEST LOW-LEVEL SHEAR (ON THE EASTERN PERIPHERY OF THE 925 MB LOW) WAS SHIFTING INTO EASTERN NC IN ADVANCE OF THE EASTWARD PROGRESSING 925 MB LOW...AND IS EXPECTED TO SHIFT FURTHER EAST TO THE CAROLINA COAST THIS AFTERNOON. EXPECT THE RELATIVE BEST POTENTIAL FOR AN ISOLD SEVERE STORM IN THE COASTAL PLAIN BETWEEN 16-20Z...PRIMARILY IN WAYNE/WILSON/EDGECOMBE COUNTIES WHERE ANY SFC-BASED CONVECTION DEVELOPING WITHIN THE NARROW WARM SECTOR WILL ENCOUNTER 1) GREATER DIURNAL DESTABILIZATION AND 2) INCREASINGLY FAVORABLE DEEP-LAYER SHEAR (WITH NORTHWARD EXTENT). PRIMARY HAZARD APPEARS TO BE DAMAGING WINDS...THOUGH MARGINALLY SVR HAIL COULD NOT BE RULED OUT WITH ANY ROTATING UPDRAFTS. ISOLD TOR POTENTIAL SHOULD BE CONFINED TO FAR EASTERN/COASTAL NC WHERE ENHANCED LOW-LEVEL SHEAR WILL BE PRESENT THIS AFTERNOON ON THE EASTERN PERIPHERY OF THE ADVANCING 925 MB LOW. -VINCENT && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
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AS OF 140 PM THURSDAY... THE UPPER LEVEL TROUGH WILL SHIFT OFF TO THE EAST ON FRIDAY AS A RIDGE BUILDS INTO THE MIDWEST. AT THE SURFACE...HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT. NW FLOW ALOFT WILL RESULT IN SUBSIDENCE BEHIND THE FRONT AND THUS DRY WEATHER IS EXPECTED. A SECONDARY PUSH OF COLD AIR INTO THE NORTHEAST PORTION OF THE AREA IS EXPECTED FRIDAY NIGHT. TEMPERATURES WILL BE A FEW TO SEVERAL DEGREES BELOW NORMAL FOR THIS TIME OF YEAR...COMFORTABLE MID 70S FOR HIGHS AND MID 50S FOR LOWS.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY NIGHT/...
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AS OF 150 PM THURSDAY... THE UPPER LEVEL RIDGE OVER THE MIDWEST WILL MOVE EASTWARD ON SATURDAY AND REMAIN OVER THE SOUTHEAST U.S. THROUGH THE PERIOD. THE SURFACE HIGH CENTERED OVER THE MID ATLANTIC COAST SATURDAY MORNING WILL SHIFT OFFSHORE BUT CONTINUE TO RIDGE INTO THE CAROLINAS THROUGH WEDNESDAY. FOR NOW...EXPECT SATURDAY THROUGH TUESDAY NIGHT TO REMAIN DRY AND MAINLY CLEAR...WITH THICKNESSES (AND THUS TEMPERATURES) INCREASING STEADILY THROUGH THE WEEK. THE RETURN FLOW AROUND THE HIGH WILL START ADVECTING IN MORE WARM MOIST AIR INTO THE REGION MID- WEEK...INCREASING PRECIP CHANCES AND CLOUD COVER...ESPECIALLY IN THE WEST WHERE THE MOIST FLOW IMPINGES ON THE TERRAIN. UPPER LEVEL DISTURBANCES MAY ALSO HELP GET SOME SHOWERS GOING...HOWEVER THE BEST CHANCES WILL BE ACROSS THE WESTERN HALF OF THE AREA WEDNESDAY AND THURSDAY AFTERNOONS. HIGHS SATURDAY IN THE MID 70S NE TO AROUND 80 DEGREES SW WILL INCREASE 2-3 DEGREES PER DAY THROUGH TUESDAY WHERE THEY WILL LEVEL OFF IN THE UPPER 80S ACROSS THE AREA. LOWS SATURDAY NIGHT WILL BE MOST COMFORTABLE...LOW TO MID 50S...INCREASING INTO THE 60S FOR THE REMAINDER OF THE PERIOD.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AS OF 130 PM THURSDAY... 24-HR TAF PERIOD: IFR CEILINGS AT INT/GSO WILL GRADUALLY IMPROVE TO MVFR LATE THIS AFTERNOON...FOLLOWED BY VFR THIS EVENING AS A DRIER AIRMASS ADVECTS INTO CENTRAL NC FROM THE NW IN THE WAKE OF A LOW PRESSURE SYSTEM TRACKING EAST TOWARD THE CAROLINA COAST. FURTHER EAST AT RDU/FAY/RWI...MVFR CEILINGS AND SHOWERS/STORMS ARE EXPECTED THROUGH ~21Z THIS AFTERNOON. ONCE CONVECTION CLEARS A GIVEN TERMINAL AND PASSES TO THE EAST...A SHORT PERIOD (1-3 HR) OF MVFR/IFR CEILINGS WILL BE POSSIBLE AS LOW CEILINGS NORTH OF THE WARM FRONT ADVECT SOUTHEASTWARD. VFR CONDITIONS WILL RETURN THIS EVENING (~00Z) FROM WEST/NW TO EAST/SE AS THE SFC LOW TRACKS OFFSHORE AND A DRIER AIRMASS ADVECTS INTO THE REST OF CENTRAL NC. LOOKING AHEAD: VFR CONDITIONS WILL PREVAIL THROUGH EARLY NEXT WEEK IN ASSOC/W HIGH PRESSURE. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...RAH LONG TERM...RAH AVIATION...VINCENT

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