Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 191443 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 943 AM EST FRI DEC 19 2014 .SYNOPSIS...HIGH PRESSURE CENTERED OVER THE MID MISSISSIPPI RIVER VALLEY WILL GRADUALLY EXTEND INTO THE CAROLINAS TODAY. A WEAK STORM SYSTEM WILL DEVELOP OVER THE TEXAS GULF COAST TODAY... THEN TRACK EASTWARD ACROSS THE SOUTHEAST STATES ON SATURDAY. WEAK HIGH PRESSURE WILL BRIEFLY EXTEND ACROSS CENTRAL NC ON SUNDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 943 AM FRIDAY... TODAY...AS EXPECTED...EARLIER CLOUDINESS HAS DISSIPATED AND SKIES HAVE CLEARED OUT NICELY OVER CENTRAL NC. EXPECT THIS TO CONTINUE FOR THE NEXT SEVERAL HOURS BEFORE SOME HIGHER CLOUDS COULD BEGIN TO CREEP IN LATER THIS AFTERNOON. PLUS OR MINUS 5 KT WINDS THIS MORNING GENERALLY OUT OF THE NORTH NORTHWEST. THESE COULD VEER AROUND TO NORTH OR NORTH NORTHEASTERLY AS THE MORNING PROGRESSES. OTHERWISE COOL AIRMASS IN PLACE WILL KEEP TEMPERATURES DOWN A BIT BELOW NORMAL WITH MAX TEMPS IN THE LOWER 50S NORTH TO MID 50S SOUTH. -ELLIS TONIGHT...A S/W LIFTING E-NE FROM THE SOUTHERN PLAINS WILL ADVANCE EAST ACROSS THE LOWER MS VALLEY TONIGHT. WARM AIR ADVECTION AHEAD OF THIS SYSTEM WILL INCREASE MOISTURE ACROSS OUR REGION...RESULTING IN THICKENING CLOUD COVERAGE FROM THE WEST-SW. MODEST ISENTROPIC UPGLIDE MAY CAUSE PATCHES OF LIGHT RAIN TO DEVELOP OVER THE FAR WESTERN-SOUTHERN PIEDMONT PRIOR TO DAYBREAK. MIN TEMPS GENERALLY IN THE LOW-MID 30S THOUGH SOME PLACES IN THE WEST AND SOUTHWEST WILL SEE MIN TEMPS OCCUR SHORTLY AFTER MIDNIGHT...WITH TEMPS HOLDING STEADY THEREAFTER DUE TO THE THICKENING CLOUDS. -WSS
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&& .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 315 AM FRIDAY... S/W CROSSING THE DEEP SOUTH EARLY SATURDAY WILL SPREAD MOISTURE INTO CENTRAL NC. BEST LIFT THROUGH THE COLUMN ASSOCIATED WITH SPEED CONVERGENCE AT 700MB AND MODEST HEIGHT FALLS IN THE MID LEVELS. THE MODEL GUIDANCE HAS BEEN TRENDING DRIER COMPARED TO 48-72 HOURS AGO WITH SOME NEAR TERM MODELS NOW SUGGESTING LITTLE IF ANY MEASURABLE PRECIP OVER THE NORTHERN PIEDMONT. WILL NEED TO MONITOR THE DEVELOPING RAIN SHIELD OVER THE LOWER MS VALLEY TODAY...AND THE TN VALLEY/DEEP SOUTH TONIGHT. PER LATEST MOISTURE PROFILES AND LIFT...FELL THAT A FEW HUNDREDTHS PROBABLE ACROSS THE PIEDMONT SATURDAY MORNING. THUS HAVE ADJUSTED POPS BACK INTO THE LIKELY CATEGORY OVER THE NW PIEDMONT AND MAINTAINED A LIKELY POPS IN THE SOUTH. FOR AREAS NORTH AND EAST OF RDU..CONTINUED CHANCE POPS. AGAIN...WHAT PRECIP THAT OCCURS WILL BE LIGHT WITH AMOUNTS VARYING BETWEEN A TRACE TO LESS THAN A TENTH OF AN INCH. NAM AND GFS BUFKIT SOUNDINGS SUGGEST A BRIEF OPPORTUNITY FOR MIXED PRECIP IN THE NW PIEDMONT AROUND DAYBREAK...COINCIDING WITH THE BEST LIFT. THE GFS AND NAM HAVE TRENDED SLIGHTLY COOLER WITH PARTIAL THICKNESSES SUGGESTING A RAIN/SNOW MIX POSSIBLE IN THE TRIAD AND POSSIBLY THE ROXBORO AREAS...MAINLY WHEN HEAVIER PRECIP INTENSITY IS OCCURRING. WHILE BULK OF PRECIP WILL BE LIQUID...CANNOT RULE OUT THE POSSIBILITY OF SOME SNOW MIXED IN AT TIMES NORTH OF TEH I-85/40 CORRIDOR IN THE TRIAD. HIGH TEMPS SATURDAY DEPENDENT UPON EXTENT OF PRECIP SATURDAY AND WHETHER PRECIP DOES DIMINISH SATURDAY AFTERNOON. HAVE ADJUSTED MAX TEMPS UP A DEGREE OR TWO. HAVE LEANED TOWARD A DRIER FORECAST FOR SATURDAY NIGHT AS SUBSIDENCE IN THE WAKE OF THE DEPARTING S/W SHOULD END THE THREAT OF PRECIP ACROSS THE REGION BY LATE SATURDAY...AND MORE SO SATURDAY EVENING WITH SOME DECREASE IN CLOUDS POSSIBLE AFTER SUNSET. IF ENOUGH CLEARING OCCURS...MAY SEE POCKETS OF FOG DEVELOP AFTER MIDNIGHT. IN ANTICIPATION OF SOME PARTIAL CLEARING...HAVE LOWERED MIN TEMPS A FEW DEGREES FROM THE PREVIOUS FORECAST (LOW-MID 30S). && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 320 AM FRIDAY... SUNDAY: SURFACE HIGH PRESSURE WILL CONTINUE TO EXTEND SOUTHWARD INTO THE AREA FROM NEW ENGLAND ON SUNDAY... WHILE BRIEF MID LEVEL S/W RIDGING BUILDS ACROSS CENTRAL NC. HOWEVER... THE NEXT SOUTHERN STREAM S/W DISTURBANCE WILL BEGIN TO SPREAD CLOUD COVER NORTHEASTWARD FROM THE GULF OF MEXICO AND INTO OUR REGION. THIS WILL YIELD PARTLY SUNNY SKIES DURING THE MID MORNING BECOMING MOSTLY CLOUDY BY LATE DAY INTO THE EVENING. AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO BE NEAR NORMAL. THUS... GIVEN WE SHOULD SEE SOME SUN ON SUNDAY EXPECT HIGH TEMPS WILL BE NEAR NORMAL... FROM AROUND 50 N TO LOWER 50S SOUTH. SUNDAY NIGHT THROUGH WEDNESDAY: THE AFOREMENTIONED SOUTHERN STREAM S/W DISTURBANCE WILL LIFT NORTHEASTWARD OUT FROM THE GULF COAST STATES ON SUNDAY NIGHT INTO MONDAY MORNING... SPREADING WIDESPREAD RAIN ACROSS ALL OF CENTRAL NC AS ISENTROPIC LIFT RAMPS UP. WITH A 1030 MB SURFACE HIGH STILL EXTENDING SOUTHWARD INTO OUR AREA AS IT EVER SO SLOWLY SHIFTS EASTWARD EXPECT WE WILL SEE A PRONOUNCED DAMMING EVENT DEVELOP.... WITH TEMPS FALLING INTO THE UPPER 30S MONDAY MORNING ACROSS THE NORTHWEST PIEDMONT AND HARDLY MOVING FOR THE NEXT DAY OR SO. HOWEVER... BOTH THE GFS AND ECMWF CONTINUE TO DEPICT AN ALL RAIN EVENT ACROSS THE AREA. WITH THE SURFACE LOW EXPECTED TO LIFT NORTH-NORTHEASTWARD ALONG THE COAST ON MONDAY... THINK WE COULD SEE OUR COASTAL PLAIN COUNTIES WARM UP A LITTLE BIT MONDAY... BEFORE THE COLD AIR PUSHES FURTHER EAST AGAIN AS THE SURFACE LOW MOVES TO THE NORTH AND EAST OF NC ON MONDAY NIGHT. AS THIS HAPPENS THE MORE SUBSTANTIAL PRECIP WILL COME TO AN END... WITH ONLY LINGERING AREAS OF LIGHT RAIN AND DRIZZLE REMAINING. LOWS MONDAY MORNING ARE EXPECTED TO BE IN THE UPPER 30S NW TO LOWER 40S SE. HIGHS MONDAY WILL BE TRICKY... FOR NOW WILL GO WITH HIGHS RANGING FROM THE UPPER 30S/NEAR 40 NW TO THE MID 50S FAR E/SE. A NORTHERN STREAM DISTURBANCE WILL HAVE FORMED A DEEP TROUGH BY TUESDAY MORNING WITH STACKED LOW PRESSURE OVER THE UPPER MIDWEST. BOTH THE GFS AND ECMWF ARE IN GOOD AGREEMENT IN SHOWING THE DEEP ASSOCIATED TROUGH AXIS SHIFTING EASTWARD ON TUESDAY INTO WEDNESDAY WHILE TAKING ON MORE OF A NEGATIVE TILT... WITH THE ASSOCIATED SURFACE FRONT AND POSSIBLE TRIPLE POINT LOW MOVING ACROSS CENTRAL NC ON WEDNESDAY MORNING INTO THE EARLY AFTERNOON (AS IT STANDS NOW... STILL SEVERAL DAYS OUT THOUGH). QUESTIONS REMAIN AS TO WHERE A POSSIBLE TRIPLE POINT LOW MAY FORM THOUGH... AS FINER DETAILS LIKE THIS ARE HARD TO NAIL DOWN THIS FAR OUT IN THE FORECAST. HOWEVER... WITH THE POTENTIAL FOR A RETREATING CAD BOUNDARY AND STRENGTHENING LOW LEVEL WIND FIELD... WE WILL NEED TO KEEP AN EYE ON HOW THIS SYSTEM DEVELOPS. THIS WOULD BE A HSLC TYPE OF SYSTEM. GIVEN THE TIME OF YEAR IT IS QUITE HARD TO GET THE NEEDED INSTABILITY FOR POSSIBLE SEVERE STORMS THOUGH. AS THE FRONT APPROACHES AND MOVES THROUGH THE AREA ON WEDNESDAY MORNING INTO THE AFTERNOON WE SHOULD SEE A BAND OF RAIN/SHOWERS ALONG AND IN ADVANCE OF IT... WITH THINGS DRYING OUT QUICKLY BEHIND THE EFFECTIVE FRONT ON WEDNESDAY AFTERNOON. HIGHS ON TUESDAY WILL BE TRICKY AND DEPEND ON HOW MUCH THE CAD BOUNDARY RETREATS. FOR NOW WILL GO WITH HIGHS IN THE MID 40S NW TO AROUND 60S SE. TEMPS BY WEDNESDAY MORNING WILL NOT FALL MUCH... WITH LOWS WEDNESDAY MORNING IN THE MID 40S NW TO MID 50S SE/E. HIGHS WEDNESDAY IN THE 50S TO AROUND 60. WEDNESDAY NIGHT THROUGH THURSDAY: WE SHOULD SEE RAPID CLEARING ON WEDNESDAY NIGHT AND CONTINUING INTO THURSDAY... WITH A RETURN TO QUITE WEATHER. LOWS THURSDAY MORNING ARE EXPECTED TO BE IN THE 30S... WITH HIGHS THURSDAY AFTERNOON NEAR NORMAL IN THE UPPER 40S TO LOWER 50S. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 635 AM FRIDAY... HIGH PRESSURE CENTERED OVER THE LOWER OH VALLEY WILL GRADUALLY EXTEND INTO CENTRAL NC THROUGH EARLY THIS EVENING. PATCHES OF MID LEVEL CLOUDS WITH BASES 6000-8000FT WILL CROSS THE REGION THROUGH MID MORNING. OTHERWISE VFR CONDITIONS WILL PERSIST. FEWER CLOUDS ANTICIPATED LATER THIS MORNING THROUGH THE AFTERNOON WITH LIGHT AND VARIABLE SURFACE WINDS. A LOW PRESSURE SYSTEM WILL ADVANCE TOWARD CENTRAL NC LATER TONIGHT AND CROSS THE REGION SATURDAY. AREAS OF LIGHT RAIN WILL DEVELOP TOWARD DAYBREAK SATURDAY AND CROSS CENTRAL NC SATURDAY MORNING THROUGH EARLY AFTERNOON. THE LIGHT RAIN FALLING THROUGH THE LOWER LEVELS OF THE ATMOSPHERE WILL AID TO MOISTEN THIS LEVEL...LEADING TO THE POTENTIAL FOR PATCHES OF MVFR CEILINGS...MAINLY IN THE 14Z-20Z SATURDAY TIME FRAME. WINDS EXPECTED TO REMAIN LIGHT AND VARIABLE. VFR CONDITIONS EXPECTED SATURDAY NIGHT INTO SUNDAY AS WEAK HIGH PRESSURE EXTENDS ACROSS THE AREA. ANOTHER LOW PRESSURE SYSTEM...THIS ONE STRONGER THAN THE SATURDAY SYSTEM...WILL BEGIN TO AFFECT CENTRAL NC SUNDAY NIGHT INTO SUNDAY...LEADING TO A PERIOD OF WIDESPREAD MVFR/IFR CEILINGS AND AREAS OF RAIN. THE RAIN WILL DIMINISH ACROSS THE REGION BY MONDAY NIGHT THOUGH MVFR/IFR CEILINGS WILL PERSIST MONDAY NIGHT INTO TUESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...ELLIS/WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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