Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 161808 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 207 PM EDT THU APR 16 2015 .SYNOPSIS...CHILLY HIGH PRESSURE WILL EXTEND INTO THE CAROLINAS AND VIRGINIA FROM THE NORTHEAST THROUGH TONIGHT. A WEAK AREA OF LOW PRESSURE WILL DEVELOP OFF THE SOUTHEAST U.S. COAST TODAY AND DRIFT NORTHEAST AND AWAY FROM THE REGION ON FRIDAY. WEAK HIGH PRESSURE WILL EXTEND INTO THE AREA LATE FRIDAY INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM THURSDAY... VERY WELL DEFINED WEDGE FRONT ASSOCIATED WITH A HYBRID COLD AIR DAMMING EVENT SHOWING UP NICELY IN OBSERVATIONS. TO THE SOUTHEAST...A COASTAL LOW IS DEVELOPING OFF THE COAST OF SC AND FURTHER ENHANCING THE WEDGE BOUNDARY. THIS WILL MAKE TEMPERATURE FORECASTS VERY TRICKY TODAY AS A VERY STRONG GRADIENT WILL BE PRESENT FROM WEST TO EAST WITH VERY COOL HIGHS IN THE WEST AND POTENTIALLY QUITE A BIT WARMER HIGHS IN THE EAST. FOR NOW HAVE MID 50S IN THE WEST AND UPPER 60S IN THE EAST BUT BY LATE IN THE AFTERNOON THIS COULD VERY WELL PAN OUT TO BE LOWER 50S IN THE WEST AND LOWER TO MID 70S IN THE EASTERN TIER OF COUNTIES. PRECIPITATION CONTINUES ACROSS THE CENTRAL PIEDMONT AND THE NORTHEASTERN COUNTIES AIDED BY ISENTROPIC LIFT AND SOME UPPER LEVEL DIVERGENCE AS WE SIT UNDER THE LEFT EXIT REGION OF A 250 MB JET. PRECIPITATION SHOULD BEGIN TO TREND DOWNWARD HOWEVER AS ISENTROPIC LIFT WEAKENS AND SOME VERY DRY MID-LEVEL AIR TO THE NORTHEAST TRIES TO WORK SOUTHWESTWARD INTO THE CWA. THIS IS VERY EVIDENT ON THE SOUNDINGS WHERE THE KMHX SOUNDING HAS A 5 DEGREE DEWPOINT DEPRESSION AT 850 MB AND THE KWAL SOUNDING HAS A 33 DEGREE DEWPOINT DEPRESSION. AS PRECIPITATION MOVES NORTHEAST...COMPOSITE RADAR SHOWS EVAPORATION OF THE PRECIPITATION...MOST LIKELY CAUSED BY THE MID LEVEL DRY AIR. AS FAR AS CONVECTIVE ALLOWING MODELS ARE CONCERNED...ONLY ONE REALLY HAS A HANDLE OF THE CURRENT MODE OF PRECIP AND THAT IS THE HRRR WHICH DEPICTS THE CURRENT PATTERN VERY WELL. GOING INTO THIS AFTERNOON THE RAIN OVER THE CENTRAL PART OF THE CWA PUSHES NORTHEAST AND CHANCES ELSEWHERE DIMINISH THROUGH THE AFTERNOON TO JUST A FEW PATCHES OF DRIZZLE OR LIGHT RAIN BY THIS EVENING. CLOUDS SHOULD REMAIN OVERNIGHT...THUS MODERATING LOWS...MAINLY LOW TO MIDDLE 50S NW TO SE. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 317 AM THURSDAY... FRIDAY SHOULD SEE THE BEGINNING OF A SLOW IMPROVEMENT IN SKY CONDITION AND TEMPS. DEVELOPING (THOUGH WEAK) NW FLOW IN THE MID- UPPER LEVELS WILL BEGIN TO SCOUR THE CAD AIR MASS FROM ALOFT. STILL...RESIDUAL LOW LEVEL MOISTURE WILL REMAIN HIGH ENOUGH TO PRODUCE EXTENSIVE CLOUDINESS IN THE MORNING WITH SOME PARTIAL BREAKS DEVELOPING IN THE AFTERNOON. THIS HEATING ALONG WITH THE PASSAGE OF A WEAK MID LEVEL TROUGH MAY PROVIDE ENOUGH LIFT TO GENERATE AN ISOLATED SHOWER OR THUNDERSTORM ACROSS CENTRAL NC. TEMPS WILL BEGIN TO RECOVER FRIDAY THOUGH IF CLOUDS STICK AROUND A LOT LONGER THAN EXPECTED...MAX TEMPS MAY END UP BEING 3-5 DEGREES COOLER THAN CURRENTLY FORECAST...ESPECIALLY ACROSS THE NORTHERN PIEDMONT. MAX TEMPS FRIDAY LOW-MID 70S. FRIDAY NIGHT..PARTIAL CLEARING MAY LEAD TO THE DEVELOPMENT OF FOGGY CONDITIONS AFTER MIDNIGHT. MIN TEMPS 55-60. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 320 AM THURSDAY... SATURDAY AND SATURDAY NIGHT: MID LEVEL S/W RIDGING WILL LARGELY KEEP CENTRAL NC DRY ON SATURDAY AND SATURDAY NIGHT. HOWEVER... WITH AND EASTERLY TO SOUTHEASTERLY SURFACE FLOW DEVELOPING LATE SATURDAY ALONG WITH DAYTIME HEATING CANT COMPLETELY RULE OUT SOME AFTERNOON SHOWERS AND STORMS ACROSS FAR EASTERN PORTIONS OF THE AREA WHERE LOW LEVEL CONVERGENCE MAY BE ENHANCED SOME ALONG PERHAPS A SEABREEZE. THUS... WILL GO WITH A SLIGHT CHANCE FOR SHOWERS AND STORMS ACROSS OUR FAR EASTERN COUNTIES FOR SATURDAY AFTERNOON. WITH SKIES NOW EXPECTED TO BE AT LEAST PARTLY SUNNY AT TIMES WILL RAISE HIGH TEMPS A DEGREE OR TWO INTO THE UPPER 70S NW TO LOWER 80S SE. THE LATEST GFS/ECMWF/NAM NOW SHOW THE ONSET OF PRECIP DELAYED A GOOD 6 TO 12 HOURS FROM PREVIOUS FORECASTS. THUS... WILL NOT INTRODUCE POPS UNTIL CLOSE TO DAYBREAK... FIRST IN THE WEST THEN SPREADING EAST THROUGH THE DAY ON SUNDAY. WITH INCREASING SOUTHERLY LOW LEVEL FLOW AND CLOUD COVER ON SATURDAY NIGHT/EARLY SUNDAY MORNING EXPECT LOW TEMPS WILL ABOVE NORMAL... GENERALLY RANGING FROM THE MID 50S IN THE FAR NE (WHERE WE MAY SEE SOME CLEARING BRIEFLY WITH THE LOSS OF HEATING AND PRIOR TO THE INCREASING OF MID AND HIGH LEVEL CLOUDS COVER) TO GENERALLY NEAR 60 ELSEWHERE. SUNDAY THROUGH MONDAY NIGHT: GOOD MOISTURE TRANSPORT IS EXPECTED ON SUNDAY INTO SUNDAY NIGHT AS CLOSED LOW INVOF THE FOUR CORNERS REGION (CURRENTLY) SHIFT EASTWARD AND OPENS WHILE COMBINING WITH A NORTHERN STREAM TROUGH TO AMPLIFY THE MID/UPPER LEVEL FLOW ACROSS THE CENTRAL AND EASTERN PART OF THE COUNTRY LATE WEEKEND INTO EARLY NEXT WEEK. THIS WILL HELP TO DRIVE A LEAD DEEP MOIST AXIS THROUGH CENTRAL NC LATE SUNDAY THROUGH EARLY MONDAY MORNING. WITH STRONG SOUTHERLY LOW LEVEL FLOW WITH THIS SYSTEM AND EXCELLENT MOISTURE TRANSPORT WE SHOULD SEE A LARGE BAND OF SHOWER/ISOLATED STORMS AND HEAVY RAIN MOVE THROUGH CENTRAL NC LATE SUNDAY INTO SUNDAY NIGHT... WITH A MAIN THREAT OF HEAVY RAIN. ALTHOUGH GIVEN THE STRONG LOW LEVEL WIND FIELDS CAN COMPLETELY RULE OUT AT LEAST A STRONG WIND GUST OR TWO. BUT GIVEN THE RATHER WEAK INSTABILITY AND POOR DIURNAL TIMING FOR THE MOST PART ANY SEVERE THREAT SHOULD REMAIN LOW. HIGHS SHOULD BE COOLER SUNDAY WITH THE INCREASE IN CLOUDS AND EVENTUALLY PRECIP LATE IN THE DAY...EXPECT HIGHS TO BE IN THE MID TO UPPER 60S NW (WHERE WE COULD SEE A BRIEF CAD AIRMASS DEVELOP) TO THE MID 70S SE/E (MAYBE EVEN A FEW UPPER 70S SE). LOWS MONDAY MORNING SHOULD BE WARM FOR THIS TIME OF YEAR... EXPECT LOWS IN THE LOWER TO MID 60S. THE MAIN SURFACE COLD FRONT SHOULD MOVE THROUGH THE REGION LATE MONDAY INTO MONDAY EVENING. WHILE THE STRONGER MID AND LOW LEVEL FLOW WILL HAVE PUSHED TO THE EAST... WE SHOULD SEE INSTABILITY INCREASE AS SOME DRIER MID LEVEL AIR WORKS INTO THE AREA FROM THE SOUTHWEST ON MONDAY MORNING/AFTERNOON. THIS SHOULD HELP TO YIELD AT LEAST SOME DESTABILIZATION AHEAD OF THE FRONT ON MONDAY RESULTING IN ISOLATED TO SCATTERED SHOWER AND STORMS MONDAY AFTERNOON/EVENING IN ADVANCE OF THE FRONT... WITH POSSIBLY A FEW STRONG TO MAYBE SEVERE STORMS (AS DEEP LAYER SHEAR WILL STILL BE AROUND 25 TO 35 KTS). BEST CHANCE OF ANY SVR AT THIS TIME (KEEP IN MIND WE ARE STILL A WAYS OUT IN TIME) WOULD BE ACROSS EASTERN PORTIONS OF THE AREA. HIGHS MONDAY ARE EXPECTED TO BE IN THE 70S TO LOWER 80S EAST/SOUTHEAST. LOWS TUESDAY MORNING RANGING FROM THE MID 50S NW TO AROUND 60 SE. TUESDAY THROUGH WEDNESDAY: DRIER WEATHER IS EXPECTED BEHIND THE FRONT ON TUESDAY AND WEDNESDAY... WITH A MUCH DRIER AIRMASS ADVECTING INTO THE REGION. HIGH TEMPS SHOULD BE NEAR NORMAL GENERALLY IN THE 70S... WITH LOWS IN THE 40S AND 50S. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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AS OF 205 PM THURSDAY... 24 HOUR TAF PERIOD: VARIABLE CONDITIONS ACROSS THE CWA RIGHT NOW AS PREDOMINANTLY IFR CEILINGS AND MVFR VISIBILITIES HAVE OVERSPREAD THE SOUTHWESTERN COUNTIES...MVFR CONDITIONS OVER THE NW PIEDMONT ARE SETTLING BACK IN AND VFR TO THE EAST. WHILE CONDITIONS WILL VARY THIS AFTERNOON BASED ON CLOUD COVER AND PLACEMENT OF PRECIPITATION THERE WILL BE AN OVERALL TREND OF IMPROVING IN THE EAST THIS AFTERNOON AND HOLDING STEADY IN THE WEST WHERE THE CAD WEDGE HAS MORE INFLUENCE. OVERNIGHT TONIGHT EXPECT CEILINGS TO GO DOWN TO AT LEAST IFR LEVELS IN MOST LOCATIONS. THIS WILL HAPPEN EARLIER IN THE WEST AND LATER IN EAST. CONVERSELY...AFTER SUNRISE FRIDAY EXPECT EASTERN SITES TO RECOVER TO VFR FASTER THAN WESTERN SITES WHICH COULD HOLD MVFR THROUGH THE END OF THE TAF PERIOD. MOSTLY NNE WINDS AT THIS TIME AT 5-10 KTS BUT AS COASTAL LOW DEVELOPS OFF OF NC...BIGGER EASTWARD COMPONENT COMING IN...CURRENTLY NOTED AT KRWI. BIGGEST THREAT TO CEILINGS OVERNIGHT WILL BE LOW CEILINGS WITH VISIBILITIES SECONDARY. RAIN SHOULD TAPER OFF AFTER SUNSET. ONCE THAT HAPPENS SHOULD BE DRY THROUGH THE END OF THE TAF PERIOD. LONG TERM: RETURN TO MAINLY VFR CONDITIONS FRIDAY AFTERNOON THROUGH SATURDAY. CHANCE FOR ADVERSE CONDITIONS WITH A COLD FRONT SUNDAY INTO MONDAY AND THEN IMPROVING CONDITIONS FOR MIDWEEK NEXT WEEK.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...ELLIS SHORT TERM...WSS LONG TERM...BSD AVIATION...ELLIS

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