Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 020746 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 246 AM EST MON MAR 2 2015 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH THIS AFTERNOON THROUGH TONIGHT...IN THE WAKE OF A COLD FRONTAL PASSAGE THIS MORNING. HIGH PRESSURE WILL SHIFT OFFSHORE DURING THE DAY TUESDAY AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST FROM THE CENTRAL PLAINS INTO THE GREAT LAKES.
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&& .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 130 AM MONDAY... TODAY: A COLD FRONT...APPROACHING THE WESTERN SLOPES OF THE SOUTHERN APPALACHIANS PER 06Z OBSERVATIONS...WILL PROGRESS SOUTHEAST AND THEN SOUTHWARD ACROSS CENTRAL NC LATER THIS MORNING THROUGH EARLY THIS AFTERNOON. DRYING ALOFT ASSOC/W SPEEDY WESTERLY FLOW (30+ KT DOWN TO 950 MB) HAS REDUCED CLOUD COVER ALOFT AND INCREASED RADIATIONAL COOLING AT THE SURFACE OVER CENTRAL NC. DECREASING CLOUD COVER ALOFT...IN THE PRESENCE OF LINGERING SURFACE MOISTURE FROM RECENT RAINFALL AND RESIDUAL SNOWPACK...HAS LED TO THE DEVELOPMENT OF LOW STRATUS AND FOG AREA-WIDE...WITH CEILINGS 100-300 FT AGL AND VISBYS FALLING INTO THE 1/4SM TO 2 SM RANGE AS PF 06Z. IF CURRENT TRENDS PERSIST...A DENSE FOG ADVISORY MAY BE NEEDED SHORTLY FOR MOST IF NOT ALL OF CENTRAL NC. EXPECT CLEARING OF FOG AND LOW STRATUS TO TAKE A WHILE TODAY...NOT UNTIL THE DRIER/COOLER AIRMASS BEHIND THE COLD FRONT ADVECTS SOUTHWARD INTO THE REGION (AFTER NOON)...AND FULL CLEARING MAY NOT BE ACHIEVED IN ALL LOCATIONS BY SUNSET. EXPECT HIGHS IN THE LOW TO MID 50S. TONIGHT: THOUGH DECREASED CLOUD COVER SHOULD BE PRESENT FOR A PERIOD THIS EVENING...LOW CEILINGS WILL RE-DEVELOP AFTER MIDNIGHT IN ASSOC/W SOUTHERLY RETURN FLOW /WARM ADVECTION/ AS THE LOW-LEVEL RIDGE SHIFTS QUICKLY OFFSHORE. IN ADDITION TO STRENGTHENING WARM ADVECTION...DPVA IN THE FORM OF FAST-MOVING/SMALL AMPLITUDE SHORTWAVE ENERGY IS EXPECTED TO BE PRESENT BETWEEN 06-12Z TUE... AND LIGHT PRECIP WILL BE POSSIBLE IN THE WESTERN PIEDMONT AND WESTERN PORTIONS OF THE SANDHILLS BY SUNRISE TUE. DUE TO THE PROGRESSIVE NATURE OF THE HIGH BUILDING INTO THE REGION LATER TODAY...THE AIRMASS IN PLACE TUE MORNING WILL BE LESS CAPABLE OF SUPPORTING MIXED PTYPE THAN IN THE PREVIOUS EVENT. NEVERTHELESS...A NUISANCE PERIOD OF LIGHT PL/FZRA CANNOT BE RULED OUT ACROSS ALONG AND WEST OF THE HWY 1 CORRIDOR AROUND SUNRISE TUE MORNING. GIVEN ABOVE NORMAL UNCERTAINTY WITH REGARD TO THE QUALITY OF THE ANTECEDENT AIRMASS AND EVOLUTION OF PRECIPITATION TUE MORNING...THE FORECAST WILL SIMPLE REFLECT A CHANCE OF LIGHT RAIN BETWEEN MIDNIGHT-SUNRISE FROM THE TRIANGLE WESTWARD. EXPECT LOWS IN THE LOWER TO MID 30S. -VINCENT
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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AS OF 200 AM MONDAY... TUE: A PRONOUNCED COLD AIR DAMMING WEDGE WILL BE IN PLACE TUE...WITH PERIODS OF DRIZZLE OR LIGHT RAIN POSSIBLE THROUGHOUT THE DAY IN ASSOC/W MODEST (ALBEIT STEADY) WARM ADVECTION...THOUGH LITTLE IF ANY UPPER LEVEL FORCING IS ANTICIPATED AT THIS TIME. EXPECT HIGHS WELL BELOW NORMAL IN THE LOWER/MID 30S (NW) TO MID/UPPER 30S ELSEWHERE. TEMPS COULD VARY A GOOD 4-7F FROM THIS FORECAST IF LIGHT PRECIP (AND ASSOC EVAP COOLING) DO NOT OCCUR AS ANTICIPATED. TUE NIGHT: LOWS WED MORNING WILL LIKELY OCCUR AT MIDNIGHT IN MOST AREAS. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD TOWARD CENTRAL NC TUE NIGHT...HOWEVER...GIVEN AN UNAMPLIFIED PATTERN...RELATIVELY WEAK MSLP/HEIGHT GRADIENT AND THE LACK OF A WELL DEFINED UPSTREAM CYCLONE...IT SHOULD BE DIFFICULT FOR THE WARM FRONT TO MAKE MUCH PROGRESS THROUGH THE CAD WEDGE IN PLACE ACROSS CENTRAL NC. SLOW/STEADY PROGRESS INTO THE SANDHILLS AND COASTAL PLAIN SHOULD RESULT IN RISING TEMPS AFTER MIDNIGHT IN MOST LOCATIONS...THOUGH PERHAPS REMAINING STEADY IN THE MID/UPPER 30S ACROSS THE N/NW PIEDMONT WITH ONLY A SLIGHT RISE TO NEAR 40F IN THE TRIANGLE BY SUNRISE WED. SOUTHERN PORTIONS OF THE SANDHILLS AND COASTAL PLAIN ARE MOST LIKELY TO SEE TEMPERATURES RISING INTO THE MID/UPPER 40S AND PERHAPS LOWER 50S BY SUNRISE WED. -VINCENT
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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AS OF 250 PM SUNDAY... BY OR SHORTLY AFTER SUNRISE WED...TEMPS WILL BE IN THE 50S ACROSS OUR ENTIRE CWA. WITH FROPA DURING THE AFTERNOON...WE COULD SEE TEMPS RISE WELL INTO THE 60S DURING THE MORNING...PERHAPS BREAKING THE 70 DEGREE MARK ACROSS OUR SE ZONES. AS FOR RAIN CHANCES...LOOK FOR POPS TO INCREASE FROM NW TO SE THRU THE DAY WED...WHILE IT STILL LOOKS LIKE THE BULK OF THE PRECIP WILL BE FOUND RIGHT ALONG OR JUST BEHIND THE FRONT...WHICH WILL LINGER WEDNESDAY NIGHT THROUGH MUCH OF THE DAY THURSDAY AS MIDLEVEL FLOW BECOMES PARALLEL TO THE FRONT...AND A STEADY FETCH OF DEEP MOISTURE IS TRANSPORTED OVERTOP A COOLING POST- FRONTAL LOW LEVEL AIRMASS. SPEAKING OF THE COOLING LOW LEVEL AIRMASS...LOW LEVEL THICKNESSES ARE PROGGED TO PLUMMET IN THE WAKE OF THE FRONT...FROM ~1380M 00Z THU TO ~1265M BY 10Z THU. SOME OF THE GUIDANCE SUGGESTS TEMPS MAY HOLD IN THE 20S DURING THE DAY THU! GIVEN THE AFOREMENTIONED LINGERING MOISTURE PLUME...ASSUMING THIS MODEL SOLUTION HOLDS...ITS BEGINNING TO LOOK A LITTLE MORE LIKELY THAT WE MAY BE DEALING WITH SOME SORT OF WINTER P-TYPE EVENT DURING THE DAYTIME THURSDAY. THE MAIN QUESTION IS HOW MUCH...AS QPF PROGS STILL VARY QUITE A BIT...WITH GFS QPF ROUGHLY TWICE AS MUCH AS THE ECMWF DURING THE 12Z THU TO 00Z FRI PERIOD. PLEASE STAY TUNED! LATEST GFS AND ECMWF ARE IN BETTER AGREEMENT DURING THE LATE-WEEK AND WEEKEND TIMEFRAME...WITH THE OPERATIONAL RUNS BOTH SHOWING THE MOISTURE PLUMES PUSHING SOUTH OF OUR CWA BY 06Z FRIDAY...THEN DRY WEATHER FOR OUR CWA FRIDAY THROUGH SATURDAY WITH HIGH PRESSURE BUILDING OVER THE AREA. LOW LEVEL THICKNESS PROGS RECOVER QUITE QUICKLY DURING THIS TIME...BUT THAT MAY NEED ADJUSTMENT DEPENDING ON WHAT HAPPENS THURSDAY.
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&& .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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AS OF 200 AM MONDAY... 24-HR TAF PERIOD: LIFR/VLIFR CONDITIONS WITH DENSE FOG AND/OR LOW CEILINGS WILL PREVAIL THROUGH ~15Z...IMPROVING TO IFR/MVFR BY 18Z AND MVFR TO POSSIBLY VFR BY 21-00Z AS DRY HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTH. IMPROVEMENT WILL BE SHORT-LIVED... HOWEVER...WITH MVFR/IFR CEILINGS RETURNING BETWEEN MIDNIGHT AND SUNRISE TUE MORNING AS THE SFC HIGH MOVES QUICKLY OFFSHORE... SOUTHERLY RETURN FLOW DEVELOPS IN THE LOWER LEVELS...AND AN UPPER LEVEL DISTURBANCE APPROACHES FROM THE WEST. LOOKING AHEAD: ADVERSE AVIATION CONDITIONS (IFR/LIFR CEILINGS AND RAIN) ASSOC/W A PRONOUNCED COLD AIR DAMMING WEDGE WILL PREVAIL TUE... WITH SOME IMPROVEMENT IN CEILINGS POSSIBLE AT SOUTHERN TERMINALS LATE TUE NIGHT AS A WARM FRONT LIFTS NORTHWARD THROUGH THE CAROLINAS. ADVERSE AVIATION CONDITIONS ARE LIKELY TO PREVAIL THE REMAINDER OF THE WEEK. -VINCENT
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&& $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...RAH AVIATION...VINCENT

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