Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 160305 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1105 PM EDT MON SEP 15 2014 .SYNOPSIS...A COLD FRONT APPROACHING THE REGION FROM THE WEST TONIGHT WILL TRACK SLOWLY SOUTHWARD THROUGH THE CAROLINAS TUESDAY INTO TUESDAY NIGHT. THE FRONT WILL GRADUALLY MOVE OFFSHORE THE SOUTHEAST COAST ON WEDNESDAY AND THURSDAY AS HIGH PRESSURE STRENGTHENS OVER THE GREAT LAKES AND EXTENDS SOUTHWARD THROUGH THE MID ATLANTIC. && .NEAR TERM /OVERNIGHT/... AS OF 1045 PM MONDAY... OVERVIEW: CENTRAL NC IS SITUATED ON THE NORTHEAST PERIPHERY OF A GULF COAST RIDGE...AT THE SOUTHERN FRINGE OF THE WESTERLIES IN BROAD CYCLONIC FLOW ALOFT. 02Z WV IMAGERY AND RAP DATA INDICATED SMALL AMPLITUDE SHORTWAVE ENERGY OVER EASTERN TN AND FAR SOUTHWESTERN NC. PRECIPITATION: COMPACT DPVA IN THE PRESENCE OF LOW-LEVEL MOISTENING/ WARM ADVECTION AND RESULTING DESTABILIZATION ALLOWED CONVECTION TO BLOSSOM OVER THE MOUNTAINS/FOOTHILLS BETWEEN 21-00Z. THIS ACTIVITY HAS PERSISTED AND PROGRESSED EASTWARD TO THE YADKIN RIVER BY 03Z AND APPEARS TO BE EITHER 1) ELEVATED OR 2) HIGH-BASED WITH CONVECTIVE CEILINGS AT 7-10 KFT AND OBSERVATION SITES REPORTING SPRINKLES/LIGHT RAIN WITH 7-10SM VISBYS AS PRECIP FALLS THROUGH A DRY MID-LEVEL AIRMASS (AS SEEN ON THE 00Z GSO SOUNDING). THIS ACTIVITY WILL TRACK EAST TOWARD THE HWY 1 CORRIDOR THROUGH 06Z IN ASSOC/W THE APPROACHING SHORTWAVE...THOUGH IT WILL ENCOUNTER AN INCREASINGLY UNFAVORABLE THERMODYNAMIC ENVIRONMENT AND THUS APPEARS LIKELY TO WEAKEN WITH EASTWARD PROGRESSION. WILL INDICATE A SLIGHT TO LOW CHANCE OF SHOWERS/SPRINKLES THROUGH 06Z WEST OF I-95...WITH THE BEST CHANCE IN THE WESTERN PIEDMONT. -VINCENT && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY... FOR TUE/TUE NIGHT: THE WEAK SURFACE TROUGH WILL BE IN PLACE OVER ERN NC TUE MORNING... AND WILL EXTEND A SLIGHT CHANCE OF SHOWERS IN THE SOUTHEAST INTO TUE TO REFLECT THE TROUGH`S PRESENCE AND THE DEPARTING MID LEVEL WAVE. WITH SUBSEQUENT NORTHWESTERLY DOWNSLOPE 925-850 MB FLOW... WE SHOULD THEN BE FAIRLY DRY FOR SEVERAL HOURS... UNTIL THE NEXT MID LEVEL VORTICITY MAX AND ACCOMPANYING STRONGER SURFACE COLD FRONT APPROACH FROM THE NW BY EARLY-MID AFTERNOON. SURFACE-925 MB LOW PRESSURE ALONG THIS FRONT WILL APPROACH FROM THE NW AND BECOME BETTER DEFINED AS IT CROSSES THE MOUNTAINS INTO THE PIEDMONT OF NC DURING THE AFTERNOON. MODELS SHOW A POCKET OF 6+ C/KM MID LEVEL LAPSE RATES CROSSING SRN NC LATE TUE ALONG WITH NEGATIVE LI VALUES. MUCAPE SHOULD PEAK AT JUST 750-1500 J/KG FOCUSED ON THE SOUTHEAST... AND DEEP LAYER SHEAR IS MARGINAL AT ABOUT 20-25 KTS... BUT THESE NUMBERS COMBINED WITH LOW LEVEL MASS CONVERGENCE SHOULD STILL SUPPORT SCATTERED SHOWERS AND ISOLATED STORMS LATE TUE AFTERNOON THROUGH TUE NIGHT. CONFIDENCE IN THE COVERAGE AND PLACEMENT IS NOT GREAT HOWEVER... AS THERE IS LITTLE AGREEMENT IN QPF AND POPS AMONG THE NAM/GFS/ECMWF. BUT GENERALLY EXPECT THE BEST COVERAGE TO BE IN THE SOUTHEAST CWA... WHERE MOISTURE TRANSPORT AND INSTABILITY WILL BE BEST... FROM LATE AFTERNOON THROUGH THE EVENING... TAPERING DOWN TO ISOLATED SHOWERS OVERNIGHT. THICKNESSES ADJUSTED FOR CLOUDS AND POSSIBLE SHOWERS LATE SUPPORT HIGHS FROM 82 TO 86. LOWS 60-65 TUE NIGHT AS COOLER AND DRIER AIR STARTS TO FILTER IN POST-FRONT FROM THE NNW. -GIH WEDNESDAY AND WEDNESDAY NIGHT...WESTERLY FLOW ALOFT WILL INDUCE PROGRESSIVE TOP DOWN DRYING THROUGH WEDNESDAY NIGHT...LESSENING THE DEPTH OF MOISTURE...WHILE NORTHEAST LOW LEVEL FLOW MAINTAINS MOISTURE THROUGH ABOUT 5KFT THROUGH THURSDAY MORNING. A SHORT WAVE WILL BE MOVING ACROSS THE SOUTHERN PERIPHERY OF THE AREA ON WEDNESDAY...ACCOMPANIED BY AN H85 WAVE THAT WILL ENHANCE LIFT VIA CONVERGENCE AND WEAK ISENTROPIC LIFT AT THE TOP OF THE MOISTURE COLUMN. HENCE WILL MAINTAIN A CHANCE POP FOR SHOWERS ACROSS THE SOUTH AND A SLIGHT CHANCE ACROSS THE NORTH THROUGH WEDNESDAY... DIMINISHING TO A LINGERING SLIGHT CHANCE IN THE EAST INTO THURSDAY. COOL AIR ADVECTION WILL COMMENCE LATE DAY AS THE SHORT WAVE PASSES AND WITH THE DAMPNESS AND CHANCE OF SHOWERS...HIGHS WEDNESDAY WILL RANGE FROM 75 TO 80...WITH SOME LOWER 70S POSSIBLE ACROSS THE NORTHEAST WHERE COOL AIR WILL ARRIVE A LITTLE SOONER. LOWS WEDNESDAY NIGHT WILL BE MAINLY IN THE UPPER 50S. -MLM && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 245 PM MONDAY... A LONG WAVE TROF SETS UP ACROSS THE EASTERN CONUS BY LATE WEEK... CONCURRENT WITH STRONG HIGH PRESSURE BUILDING INTO EASTERN CANADA AND DOWN THE EAST COAST ON FRIDAY WITH THE RESULTING DAMMING SCENARIO LINGERING THROUGH THE WEEKEND. LOW AMPLITUDE MID LEVEL RIDGING SHOULD INHIBIT PRECIP CHANCES THROUGH THE WEEKEND...WHILE THE PROLONGED EAST TO NORTHEAST LOW LEVEL FLOW OFF THE ATLANTIC WILL SUPPRESSES HIGH TEMPS INTO THE LOW AND MID 70S THROUGH SATURDAY. A STRONG TROF MOVING ACROSS THE MIDWEST WILL NUDGE THE SURFACE HIGH FURTHER OFFSHORE. THE WEAKENED FLOW WILL ALLOW THE AIRMASS TO MODERATE ON SUNDAY...WITH HIGHS MOSTLY IN THE UPPER 70S. FLOW VEERS TO SOUTHWEST BY MONDAY AHEAD OF THE UPPER TROF AND SURFACE FRONT...WITH INCREASING MOISTURE IN THE RESULTING RETURN FLOW AND A CHANCE OF SHOWERS BY LATE DAY MONDAY. HIGHS MONDAY WILL BE WITHIN A DEGREE OR TWO OF 80. MORNING LOWS THROUGH THE PERIOD WILL BE MOSTLY FROM 55 TO 60 DEGREES. -MLM && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS OF 750 PM MONDAY... 24 HOUR TAF PERIOD: MVFR CONDITIONS HAVE HELD ON AT MOST LOCATIONS THIS EVENING AND WILL CONTINUE TO DO SO OVERNIGHT TONIGHT WITH THE POSSIBILITY OF IFR/LIFR CEILINGS DURING THE OVERNIGHT HOURS AND JUST BEFORE SUNRISE. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT AS A WEAK SHORTWAVE CROSSES THE AREA FROM THE WEST. A FEW SPRINKLES CANT BE RULED OUT..ESPECIALLY IN THE TRIAD. CONDITIONS SHOULD GRADUALLY IMPROVE TO VFR AS MOISTURE DECREASES ON TUESDAY WITH SOME CLOUDS IN THE 3-5 KFT LAYER. THERE WILL BE A SLIGHT CHANCE FOR RAIN OR ISOLATED THUNDER IN THE SOUTH AND EAST LATE TUESDAY AFTERNOON INTO THE EVENING HOURS. LONG TERM: A GENERALLY DRIER PERIOD WILL ROUND OUT THE END OF THE WEEK WITH SLIGHT CHANCES FOR SOME AFTERNOON SHOWERS WEDNESDAY BUT GENERALLY VFR CONDITIONS PREVAILING. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...HARTFIELD/MLM LONG TERM...MLM AVIATION...ELLIS

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