Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 271333 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 933 AM EDT MON OCT 27 2014 .SYNOPSIS...
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HIGH PRESSURE WILL DRIFT OVERHEAD TODAY AND MOVE OFFSHORE BY THIS EVENING. THE HIGH PRESSURE WILL DRIFT EAST INTO BERMUDA-HIGH POSITION THROUGH MID-WEEK AND RESULT IN WARM SOUTHWEST FLOW UNTIL A COLD FRONT CROSSES CENTRAL NC WED INTO WED EVENING.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 933 AM MONDAY... DEEP LAYER RIDGING AND RESULTANT SUBSIDENCE WILL RULE ACROSS THE CAROLINAS TODAY AS SHORTWAVE RIDGE OVER THE TN AND OHIO VALLEY MIGRATES AND AMPLIFY EAST INTO THE MIDDLE ATLANTIC REGION TODAY. LOW PWAT AIR OF 0.50" OR LESS WILL ALLOW FOR UNLIMITED SUNSHINE WITH FCST THICKNESSES FORECAST TO BE VERY SIMILAR TO YESTERDAY. HIGHS IN THE UPPER 70S TO LOWER 80S. TONIGHT: UNDER A SCATTERED THIN LAYER OF CIRRUS CLOUDS....THE DRY AIR MASS WILL LIKELY COOL QUICKLY THIS EVENING AS THE BL DECOUPLES AND LIGHT SSW SURFACE WINDS BECOME CALM...PARTICULARLY IN CLOSER PROXIMITY TO THE OFFSHORE-DEPARTING SURFACE HIGH OVER THE COASTAL PLAIN AND EASTERN PIEDMONT. MIN TEMPS LIKELY BOTTOMING OUT IN THE UPPER 40S TO LOWER 50S.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 330 AM MONDAY... WARM SW FLOW WILL STRENGTHEN TUE AND MIXING HEIGHTS WILL DEEPEN TUE...IN A TIGHTENING MSLP/HEIGHT GRADIENT DOWNSTREAM OF A COLD FRONT THAT WILL APPROACH FROM THE WEST AND BE FORECAST TO LIE INVOF THE APPALACHIAN WEST SLOPES BY 12Z WED. WARMER CONDITIONS WILL CONSEQUENTLY PREVAIL...WITH CONTINUED SUNNY OR MOSTLY SO CONDITIONS....AND HIGHS IN THE LOWER TO MIDDLE 80S. AREAS OF LOW STRATUS ARE APT TO DEVELOP AND SPREAD NORTH LATE TUE NIGHT-EARLY WED...MAINLY OVER THE COASTAL PLAIN...AS MOISTURE ALSO INCREASES IN THE STRENGTHENING SSW FLOW. MID- HIGH CLOUDS WILL OTHERWISE STEADILY INCREASE FROM THE WEST ESPECIALLY LATE...WITH MILDER LOWS AMIDST SSW STIRRING IN THE 55-60 DEGREE RANGE. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 245 AM MONDAY... ...FIRST POSSIBLE FROST OF THE SEASON THIS WEEKEND... WEDNESDAY THROUGH THURSDAY: A FRONTAL SYSTEM WILL APPROACH THE AREA ON WEDNESDAY ASSOCIATED WITH A LOW PRESSURE SYSTEM OVER WESTERN QUEBEC. THE UPPER LEVEL RIDGE THAT HAD BROUGHT US THE UNSEASONABLY WARM WEATHER WILL MOVE OFFSHORE...REPLACED BY AN EASTERN CONUS TROUGH THAT WILL SET THE STAGE FOR A COOLING TREND FOR THE END OF THE WEEK. TIMING IS GENERALLY GOOD FOR A FRONTAL PASSAGE WEDNESDAY EVENING OR EARLY THURSDAY MORNING. THE CURRENT RUN OF THE GFS IS SLIGHTLY FASTER THAN THE ECMWF. THERE IS NOT A LOT OF MOISTURE WITH THIS SYSTEM AND EVEN LESS INSTABILITY. SHEAR VALUES WILL BE DECENT IN THE 0-6 KM RANGE...BUT THE UPPER LEVEL JET DYNAMICS ARE FAIRLY WEAK FOR THIS TIME OF YEAR. THEREFORE ONLY EXPECTING LIGHT SHOWERS WITH THE FRONTAL PASSAGE WITH QPF VALUES PLUS OR MINUS A TENTH OF AN INCH. TEMPERATURES WEDNESDAY SHOULD STILL ACHIEVE MID 70S TO LOW 80S AS FROPA WILL BE LATER IN THE DAY. WITH CLOUDS STILL AROUND WEDNESDAY NIGHT EXPECT LOWS TO ONLY MAKE IT DOWN TO THE MID 40S NW TO MID 50S SE. THESE COULD EVEN BE HIGHER IF THE SLOWER TIMING OF THE ECMWF VERIFIES. THE FRONT WILL CONTINUE SOUTHEASTWARD ON THURSDAY AND GRADUAL CLEARING WILL OCCUR BEHIND THE FRONT. COLD AIR ADVECT WILL BEGIN IN EARNEST WITH MAX TEMPS ONLY REACHING THE LOW 60S NORTH TO UPPER 60S SOUTH. THURSDAY NIGHT THROUGH SUNDAY: A COLD AND DRY PERIOD WILL BEGIN THURSDAY NIGHT AS THE UPPER LEVEL TROUGH BEGINS TO DEEPEN AND A STRONG UPPER LEVEL LOW MOVES THROUGH THE GREAT LAKES AND INTO WESTERN NY. AS COLD AIR ADVECTION CONTINUES AND THICKNESS VALUES DROP...MAX TEMPERATURES WILL SUFFER...5-10 DEGREES BELOW NORMAL IN THE NORTH TO NEAR NORMAL HIGHS IN THE SOUTH (LOW TO UPPER 60S). LOWS WILL DROP INTO THE UPPER 30S TO LOW 40S BY SATURDAY MORNING. AS THE AXIS OF THE UPPER LEVEL TROUGH APPROACHES NC...A SURFACE HIGH TO THE WEST OF THE APPALACHIANS WILL SET UP NORTHERLY SURFACE FLOW AND HELP TO DROP TEMPS FURTHER THIS WEEKEND WITH HIGHS ONLY IN THE 50S AND THE FIRST FROST OF THE SEASON VERY POSSIBLE ON SUNDAY MORNING. WHILE SKIES WILL CLEAR...THE SURFACE WINDS MAY HELP TO KEEP TEMPERATURES UP SLIGHTLY FROM POTENTIAL LOWS SUGGESTED BY THICKNESS VALUES WITH OPTIMAL RADIATIONAL COOLING CONDITIONS. EXPECT LOW TO MID 30S OVER MUCH OF THE AREA SUNDAY MORNING. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... AS OF 605 AM MONDAY... UNDER THE INFLUENCE OF DRY AND SUBSIDENT RIDGING ALOFT AND AT THE SURFACE...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. CALM TO LIGHT AND VARIABLE WINDS WILL GRADUALLY VEER TO SSW BY THIS AFTERNOON...PARTICULARLY AT WESTERN SITES...IN RETURN FLOW AROUND THE OFFSHORE-DRIFTING SURFACE HIGH. OUTLOOK: STRONG RADIATIONAL COOLING AND SHALLOW MOISTURE JUST ABOVE THE SURFACE MAY RESULT IN PATCHY VISIBILITY RESTRICTIONS EARLY TUE...MOST LIKELY AT KRWI. STRENGTHENING SSW FLOW...AND ASSOCIATED MOISTURE ADVECTION AHEAD OF AN APPROACHING COLD FRONT...WILL ALSO RESULT IN A CHANCE OF LOW STRATUS EARLY WED MORNING. THEN THE COLD FRONT...AND ACCOMPANYING CHANCE OF SHOWERS AND SUB-VFR CONDITIONS...WILL MOVE EAST ACROSS CENTRAL NC WED...INTO WED EVENING AT EASTERN SITES. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...CBL/MWS SHORT TERM...MWS LONG TERM...ELLIS AVIATION...MWS

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