Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281526 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1126 AM EDT SUN JUL 28 2014 .SYNOPSIS...A STRONG COLD FRONT WILL CROSS THE AREA THIS AFTERNOON... BRINGING NOTICEABLY COOLER AND LESS HUMID AIR INTO THE AREA. HIGH PRESSURE BUILDS OVER MUCH OF THE REGION FOR TUESDAY INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1120 AM MONDAY... HARD TO IMAGINE THAT SUCH STRONG DYNAMICS AND THE PASSAGE OF A SURFACE FRONT IN LATE JULY WOULD RESULT IN SO LITTLE RAINFALL FOR CENTRAL NC...AND THAT WHAT LITTLE RAIN THAT DID OCCUR RESULTED FROM AN MCV WELL DOWNSTREAM OF THE STRONGEST FORCING FOR ASCENT WITH THE UPPER TROUGH AND ACCOMPANYING LOW LEVEL FRONTAL ZONE. OVERWHELMING NOCTURNAL CINH FOLLOWED THIS MORNING BY DOWNSLOPE FLOW HAS SIMPLY PROVEN TOO GREAT TO OVERCOME. MOISTURE CHANNEL AND BLENDED TPW IMAGERY INDICATE DEEP DRYNESS...AND CAPPING/STABILITY PER PROXIMITY RAOBS AWAY FROM COASTAL AREAS...HAS ENVELOPED ALL BUT SE NC THIS MORNING. PRECIPITATION CHANCES FOR THE REMAINDER OF TODAY WILL CONSEQUENTLY NOW BE CONFINED TO THE SOUTHERN SANDHILLS AND SOUTHERN AND CENTRAL COASTAL PLAIN...INVOF AND AHEAD OF A SFC TROUGH/FRONT THAT WILL BECOME BETTER DEFINED FROM NEAR THE NC OUTER BANKS TO THE SANDHILLS TO THE SC UPSTATE...AS DRY AIR IN THE 850-925 MB LAYER IS IMPARTED ON THE SFC WITH HEATING/MIXING. THESE AREAS WILL BE ON THE NW EDGE OF MODERATE INSTABILITY FORECAST TO DEVELOP OVER COASTAL AREAS...FUELED BY KMHX 12Z-OBSERVED MID LEVEL LAPSE RATES IN EXCESS OF 7 C/KM. IN ADDITION...A BELT OF STRONG (40-50 KT) MID LEVEL FLOW OBSERVED FROM THE NORTHERN PLAINS- TN VALLEY-NC COAST WILL PROVIDE AMPLE DEEP LAYER SHEAR... CHARACTERIZED BY LONG AND STRAIGHT FORECAST HODOGRAPHS AT KFAY AND KILM THROUGH 00Z - SUPPORTIVE OF A CONDITIONAL SVR RISK OF DAMAGING WIND GUSTS AND LARGE HAIL (LIKELY FROM SPLITTING SUPERCELLS PROVIDED STORMS CAN BOTH DEVELOP AND NOT SUCCUMB TO ENTRAINMENT OF THE AFOREMENTIONED DRY AIR ALOFT). HOWEVER...THIS PROBABILITY OF STORMS FORMING AND THRIVING IN THE RAH CWFA IS RELATIVELY LOW - ONLY AROUND 20 PERCENT. OTHERWISE...A RELATIVELY TIGHT MSL PRESSURE GRADIENT ABOUT THE SFC FRONT WILL GENERATE A BREEZY GENERALLY WESTERLY SFC WIND (WNW OVER THE PIEDMONT TO WSW OVER THE SANDHILLS AND COASTAL PLAIN)...WITH GUSTS UP TO 20-25 MPH. LOW LEVEL THICKNESS VALUES AROUND 1425 METERS SUPPORT HIGH TEMPERATURES IN THE MID-UPPER 80S NW TO LOWER-MID 90S SE. LOWS GENERALLY WITHIN A FEW DEGREES EITHER SIDE OF 65. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... AS OF 240 AM MONDAY... UPPER LEVEL TROUGHING WILL STAY IN PLACE OVER THE EAST COAST THROUGHOUT THE SHORT TERM PERIOD...WHILE AT THE SURFACE COOL...CANADIAN HIGH PRESSURE WILL GRADUALLY SETTLE EAST OVER THE EAST COAST...KEEPING THE FRONT OFFSHORE. ALL OF THIS WILL LEAD TO BELOW NORMAL TEMPS...WITH HIGHS GENERALLY IN THE LOW/MID 80S AND OVERNIGHT LOWS IN THE LOW/MID 60S...POSSIBLY EVEN SOME UPPER 50S IN THE NORMAL COOLER SPOTS. IN ADDITION...MOSTLY DRY CONDITIONS ARE EXPECTED THROUGH AT LEAST THURSDAY AS NORTHWESTERLY FLOW ALOFT MAINTAINS A DRY COLUMN...WITH PWAT VALUES PROGGED TO HOVER JUST ABOVE 1 INCH. && .LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 240 AM MONDAY... BY LATE IN THE WEEK AND ESPECIALLY INTO THE WEEKEND...THE HIGHLY AMPLIFIED RIDGE OVER THE ATLANTIC WILL SHIFT WESTWARD...NUDGING THE UPPER LEVEL TROUGH BACK TOWARDS THE MS RIVER VALLEY. AS A RESULT...THE LINGERING FRONT/INVERTED TROUGH WILL WILL ALSO MOVE CLOSER TO THE COAST...AND LIKELY INLAND BY THE LATTER HALF OF THE WEEKEND. IN ADDITION...MOISTURE WILL GRADUALLY INCREASE (PWATS RISING BACK OVER 1.5 INCHES BY SATURDAY...THEN APPROACHING 2 INCHES BY SUNDAY) AS FLOW ALOFT BECOMES MORE SOUTHWESTERLY. AS A RESULT OF ALL OF THIS...WILL SHOW PRECIP CHANCES GRADUALLY INCREASING INTO THE 30-40 PERCENT RANGE BY SUNDAY. HIGH TEMPS WILL STILL BE IN THE LOW/MID 80S...WITH OVERNIGHT LOWS IN THE LOW/MID 60S. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... AS OF 730 AM MONDAY... DRIER AIR WILL ALOFT AND AT THE SURFACE WILL CONTINUE TO SPREAD WEST TO EAST INTO CENTRAL NORTH CAROLINA THROUGH THE DAY ON MONDAY AS A STRONG COLD FRONT CROSSES THE AREA. THIS SHOULD SHIFT THE FOCUS FOR CONVECTIVE INITIATION ACROSS SOUTHEASTERN NC. LATEST HI-RES CONVECTIVE ALLOWING MODELS HAVE ALL RE-DEVELOPMENT WELL EAST OF KFAY AND KRWI AND THUS DO NOT PLAN ON CARRYING ANY MENTION OF THUNDER WITH THE 12Z ISSUANCE. AS SUCH...EXPECT VFR CONDITIONS WITH DAYTIME MIXING RESULTING IN WESTERLY WIND GUSTS TO AROUND 20KTS. BEYOND THE 24 HOUR TAF PERIOD...VFR CONDITIONS SHOULD PREVAIL FOR MUCH OF THE REST OF THE WORK WEEK...WITH INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS FROM FRIDAY INTO THE WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...MWS SHORT TERM...KRR LONG TERM...KRR AVIATION...CBL

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