Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210300 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1000 PM EST THU NOV 20 2014 .SYNOPSIS...A DRY COLD FRONT WILL EXIT THE AREA LATE THIS EVENING BEFORE HIGH PRESSURE RETURNS FOR THE END OF THE WEEK. A LOW PRESSURE SYSTEM WILL APPROACH THE AREA ON SUNDAY...CAUSING MORE UNSETTLED CONDITIONS. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 PM THURSDAY... SURFACE COLD FRONT CROSSING CENTRAL NC AT 9 PM EXTENDING FROM WARRENTON-RALEIGH-ALBEMARLE. THIS FEATURE WILL CONTINUE TO SLIDE SEWD...EXITING THE SE COUNTIES AROUND MIDNIGHT OR SHORTLY THEREAFTER. LITTLE IN THE MANNER OF CLOUDS ASSOCIATED WITH THE FRONT. COLD AIR ADVECTION WILL BE INITIALLY OFFSET BY DOWNSLOPE COMPONENT OF LOW LEVEL FLOW. SHOULD START TO FEEL AFFECTS OF COLDER AIR MASS TOWARDS DAYBREAK. FORECAST MIN TEMPS IN THE UPPER 20S NW TO NEAR FREEZING SE APPEAR ON TARGET. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... AS OF 225 PM THURSDAY... HIGH PRESSURE OVER THE OHIO VALLEY WILL RIDGE INTO THE AREA ON FRIDAY...MOVING SOUTHWARD AND SETTLING OVER NC FRIDAY NIGHT. EXPECT SKIES TO REMAIN CLEAR AND THE WINDS TO RELAX SOME AS WELL AS THE HIGH RIDGES IN. THE REINFORCING SHOT OF COLD AIR WILL YIELD HIGHS ABOUT 10 DEGREES OR SO COOLER THAN THURSDAY...MID 40S NORTH TO LOW 50S SOUTH. THIS IS SUPPORTED BY A DECREASE IN THICKNESSES...WITH THE LOWEST VALUES ACROSS THE NORTHEAST WHERE HIGHS WILL BE LOWEST. WINDS WILL BE GENERALLY NORTH AND NORTHEASTERLY DURING THE DAY...VEERING OVERNIGHT AS THE HIGH BUILDS IN. WITH THE CLEAR SKIES AND CALM WINDS YIELDING GOOD RADIATIONAL COOLING CONDITIONS...EXPECT LOWS FRIDAY NIGHT GENERALLY IN THE MID 20S. -KC && .LONG TERM /SATURDAY THROUGH THURSDAY/... AS OF 320 PM THURSDAY... THE CORE OF THE HIGH WILL SETTLE OVER THE AREA EARLY SATURDAY AND THEN SHIFT EAST OFFSHORE DURING THE DAY. A STRONG MID-LEVEL INVERSION SUGGEST AND VERY WEAK MIXING SUGGEST TEMPS WONT GET ANYWHERE NEAR THEIR THICKNESS-CORRELATED VALUES...WITH GUIDANCE MOSTLY IN THE UPPER 40S NORTHEAST TO MID 50S SOUTHWEST. HIGH CLOUDS WILL BEGIN TO POUR IN SATURDAY EVENING AS A SYSTEM BEGINS TO LIFT OUT OF THE SOUTHERN PLAINS...WITH LOW LEVEL MOISTURE QUICKLY RETURNING AROUND THE OFFSHORE HIGH. SOUTHEASTERLY LOW-LEVEL FLOW AND ISENTROPIC LIFT SHOULD BE FOCUSED ACROSS SC AND INTO THE SOUTHWESTERN NC SATURDAY NIGHT...LEAVING NC DRY THROUGH SUNRISE SUNDAY. LOWS WILL BE MILDER...LIKELY ABOVE GUIDANCE IN THE MID TO UPPER 30S. SUNDAY AND SUNDAY NIGHT... SOUTH TO SOUTHEASTERLY FLOW REALLY RAMPS UP SUNDAY BETWEEN THE HIGH AND A LOW PRESSURE SYSTEM LIFTING FROM TEXAS TO THE GREAT LAKES. BASED ON THE ORIENTATION OF THE SURFACE HIGH...STRONG COLD AIR DAMMING IS NOT VERY LIKELY...THOUGH PRECIP OVER THE WESTERN PIEDMONT EARLY SUNDAY WILL LIKELY STABILIZE THAT AREA AND LEAD TO A IN-SITU WEDGE AIRMASS. WE SHOULD THEN SEE RAIN SPREAD ACROSS THE AREA TO THE NORTHEAST SUNDAY AFTERNOON...WITH THE HEAVIEST PRECIP SUNDAY EVENING INTO SUNDAY NIGHT AS A 50-60KT SOUTHERLY LLJ BRINGS AND A SFC/850MB WARM FRONT AND STRONG WARM ADVECTION ACROSS THE AREA. PW WILL WILL BE OVER 1.75 INCHES...2 SD ABOVE NORMAL...WITH A DEEP WARM RAIN LAYER...SO THE POTENTIAL FOR SOME LOCALLY HEAVY RAINFALL MAY EXIST ACROSS EASTERN AREAS. MODELS ALSO SHOW CONVECTION MOVING FROM THE GULF COAST TOWARD COASTAL CAROLINA...WHICH LEADS TO SOME UNCERTAINTY IN THE QPF FORECAST...WITH MODELS CURRENTLY SHOWING AROUND AN INCH AREAWIDE. SEVERE WEATHER POTENTIAL WILL BE LIMITED BY 1) MOIST ADIABATIC PROFILES AND THE LACK OF INSTABILITY...AND 2) THE MAIN DYNAMIC FORCING LIFTING WELL WEST OF THE MOUNTAINS. HOWEVER...BASED ON THE INTENSITY OF THE LLJ/WARM ADVECTION...WOULDNT BE SURPRISED IF THE MODELS ARE UNDERDOING INSTABILITY A BIT...ESPECIALLY ELEVATED WITH CRUX OF THE WARM ADVECTION ACROSS THE SOUTHEAST SUNDAY EVENING/NIGHT. FORECAST SOUNDINGS SHOW LITTLE POTENTIAL FOR ANY (NEAR)SURFACE BASED INSTABILITY...AND IF THERE IS A POTENTIAL FOR SEVERE WEATHER IT SHOULD BE CONFINED TO THE FAR SOUTHEAST. WILL LEAVE THUNDER OUT FOR NOW GIVEN THE UNCERTAINTY IN INSTABILITY. TEMPS WILL LIKELY HOLD STEADY IN THE LOW-MID 50S IN THE WEDGE AIRMASS TO LOWER 60S IN THE EAST SUNDAY EVENING...RISING WELL INTO THE 60S SUNDAY NIGHT AS THE WARM FRONT MOVES THROUGH AND THEN INTO THE UPPER 60S/LOWER 70S ON MONDAY. MONDAY THROUGH THURSDAY... THE DEEP MOIST AXIS WILL SHIFT EAST TO THE COAST ON MONDAY...WITH SOUTHWESTERLY FLOW ALOFT. THERE IS A BIT OF UNCERTAINTY REGARDING ADDITIONAL ENERGY WITHIN THE BASE OF THE LONGWAVE TROUGH AND HOW THAT WILL EVOLVE. THE GFS SHOWS ANOTHER WAVE MOVING UP THE APPALACHIANS ON TUESDAY AND SPITS OUT A LITTLE QPF...WHILE THE ECMWF MAINTAINS AN ELONGATED...POSITIVELY TILED TROUGH THAT FINALLY EJECTS EAST ON WEDNESDAY. WILL SHOW A SLOW DOWNWARD TREND IN POPS FROM WEST TO EAST ON TUESDAY AND WEDNESDAY AS TEMPS HEAD BACK BELOW NORMAL LATE NEXT WEEK. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 650 PM THURSDAY... 24-HOUR TAF PERIOD: A DRY COLD FRONT WILL CROSS THE REGION THIS EVENING. SURFACE HIGH PRESSURE WILL BUILD INTO THE AREA BEHIND THE FRONT AND SETTLE ACROSS THE REGION BY FRIDAY EVENING. THIS WILL RESULT IN CONTINUED VFR CONDITIONS (HIGH CONFIDENCE). LIGHT WEST- SOUTHWESTERLY WINDS WILL BECOME NORTHWESTERLY TO NORTHERN OVERNIGHT INTO FRIDAY. WINDS OVERNIGHT WILL BE 05/06 KTS OR LESS... WITH WIND SPEED GENERALLY ONLY INCREASING TO 06 TO 10 KTS BY MID FRIDAY MORNING. HOWEVER... WE COULD SEE A BRIEF PERIOD OF WIND GUSTS TO AROUND 15-17 KTS AT KRDU/KFAY/KRWI FRIDAY MORNING... BEFORE THE FASTER FLOW ALOFT PUSHES TO THE EAST OF THE AREA. LOOKING AHEAD: THE NEXT THREAT TO AVIATION CONDITIONS WILL BE WITH A LOW PRESSURE SYSTEM APPROACHING AND MOVING THROUGH THE AREA SUNDAY INTO MONDAY...YIELDING INCREASING CLOUD COVER AND PRECIPITATION CHANCES. CONDITIONS COULD REMAIN BELOW VFR UNTIL THE COLD FRONTAL PASSAGE...EITHER MONDAY NIGHT OR EARLY TUESDAY. WINDS WILL LIKELY BECOME GUSTY AS THE FRONT APPROACHES AND MOVES THROUGH THE REGION. && .CLIMATE... RECORD LOW: GSO RDUFAY SAT 11/22 - 13 IN 1914 21 IN 2008 20 IN 2000 && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...ELLIS NEAR TERM...WSS SHORT TERM...KC LONG TERM...BLS AVIATION...BSD/KC CLIMATE...RAH

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