Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281858 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 258 PM EDT SUN JUL 28 2014 .SYNOPSIS...A STRONG COLD FRONT WILL MOVE OFF THE NC COAST THIS EVENING...THEN STALL OFFSHORE TUESDAY. CANADIAN HIGH PRESSURE WILL OTHERWISE EXPAND ACROSS THE CAROLINAS AND MIDDLE ATLANTIC THROUGH MID-WEEK. && .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 AND TUESDAY NIGHT/...
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AS OF 255 PM MONDAY... BENEATH AND WEST OF CYCLONIC FLOW ALOFT WITHIN A MID-UPPER TROUGH AXIS NEAR 85W...CANADIAN HIGH PRESSURE WILL EXTEND SOUTHEASTWARD INTO THE MIDDLE ATLANTIC AND CAROLINAS TUE AND TUE NIGHT. COOLER AIR CHARACTERIZED BY H85 TEMPERATURES AROUND 13C...WHICH WAS ALREADY ON THE DOORSTEP OF THE RAH CWFA/AT KRNK AND KBNA AT 12Z MON...WILL HAVE FULLY OVERSPREAD CENTRAL NC THIS PERIOD - SUPPORTIVE OF HIGH TEMPERATURES IN THE LOWER TO MIDDLE 80S. WITH DEWPOINTS EXPECTED IN THE 50S BASED ON UPSTREAM OBSERVATIONS OVER THE OH VALLEY...THE COMBINATION OF LOW RH AND MILD TEMPERATURES WILL FEEL FAR FROM LATE JULY. LOW LEVEL THICKNESS VALUES OF AROUND 1380 METERS OR SO AT 12Z WED FAVORS LOWS IN THE UPPER 50S TO AROUND 60 DEGREES ON AVG.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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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. 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.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 150 PM MONDAY... A COLD FRONT NEAR KFAY WILL SETTLE SOUTHEASTWARD AND OUT OF THE RAH FORECAST AREA THROUGH SUNSET. WHILE THERE REMAINS A VERY SLIGHT CHANCE OF A SHOWER OR STORM AT KFAY WITH THE PASSAGE OF THE FRONT DURING THE NEXT FEW HOURS...IT IS MORE LIKELY THAT ANY SUCH STORM DEVELOPMENT WILL OCCUR ALONG COASTAL/SE NC WHERE LOW AND DEEP LAYER MOISTURE IS (MARGINALLY) MORE SUPPORTIVE. OTHERWISE...A BREEZY WESTERLY WIND WILL GRADUALLY VEER TO NW...AND SUBSIDE AROUND SUNSET...WITH LIGHT NW WINDS EXPECTED OVERNIGHT. DIURNAL CUMULUS SHOULD LIKEWISE DIMINISH AROUND SUNSET...THOUGH THE PASSAGE OF A TRAILING MID LEVEL TROUGH OVERNIGHT COULD PRODUCE A FEW PATCHES OF HIGH STRATOCUMULUS OR LOW ALTOCUMULUS PER UPSTREAM/OH VALLEY OBSERVATIONS...AND NWP GUIDANCE. PREDOMINATELY VFR CONDITIONS SHOULD OTHERWISE PREVAIL THROUGH MOST OF THE FORECAST PERIOD...AS CANADIAN HIGH PRESSURE BECOMES CENTERED OVER THE TN VALLEY AND CENTRAL APPALACHIANS THROUGH MID-WEEK...THEN YIELDS TO AN INVERTED SURFACE TROUGH AND SMALL CHANCE OF A SHOWER OR STORM BY FRI-SAT. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...MWS LONG TERM...KRR AVIATION...MWS

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