Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220733 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 333 AM EDT WED OCT 22 2014 .SYNOPSIS....AN UPPER LEVEL LOW WILL SETTLE SOUTHEAST ACROSS SOUTHEASTERN VA AND NORTHEASTERN NC THIS MORNING...THEN MOVE OFFSHORE TODAY. ASSOCIATED COASTAL LOW PRESSURE WILL DEVELOP AND LIFT UP THE MIDDLE ATLANTIC COAST THROUGH THURSDAY...WHILE HIGH PRESSURE OTHERWISE BUILDS IN FROM THE WEST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 320 AM WEDNESDAY... AN UPPER LOW WILL DEVELOP/AMPLIFY SOUTHEASTWARD FROM WEST-CENTRAL VA THIS MORNING TO JUST OFFSHORE THE NC/VA COAST THIS AFTERNOON. THE CENTER OF THE ASSOCIATED STRONGEST MID LEVEL HEIGHT FALLS...ON THE ORDER OF 100 M/12 HR...WILL SETTLE ACROSS EAST-CENTRAL NC THROUGH 12Z. THIS FORCING FOR ASCENT...IN CONJUNCTION WITH THE ARRIVAL OF THE COLD POOL/STEEPENING LAPSE RATES ALOFT...HAS SUPPORTED THE MAINTENANCE OF AN AREA OF SHOWERS INTO THE RAH NE PIEDMONT AND NORTHERN COASTAL PLAIN THIS MORNING. THESE SHOWERS...AND CLOUDINESS...WILL BOTH BECOME ENHANCED WITH DIURNAL HEATING OWING TO THE PRESENCE OF THE COLD TEMPERATURES/STEEP LAPSE RATES ALOFT ASSOCIATED WITH THE UPPER LOW - THE FORMER IN EXCESS OF MINUS 20 C AND THE LATTER BETWEEN 6.5-7 C/KM...THROUGH EARLY-MID AFTERNOON. SHOWERS SHOULD THEN MOVE EAST AND NORTHEAST OF THE RAH CWFA AS THE UPPER LOW MAKES A TURN/LIFTS UP THE MIDDLE ATLANTIC COAST BY LATE AFTERNOON-EVENING. PARTLY TO MOSTLY SUNNY ELSEWHERE TODAY. IT WILL ALSO BE COOLER AND BREEZY...WITH NORTHWESTERLY DAYTIME WIND GUSTS UP TO 25 MPH OWING TO THE DEEPENING OF A COASTAL LOW ACCOMPANYING THE UPPER ONE...WITH HIGHS IN THE 60S. CLEARING AREA-WIDE AND SIMILARLY COOLER TONIGHT...WITH A CONTINUED LIGHT NW WIND AND LOWS RANGING FROM THE UPPER 30S OVER THE SOUTHERN AND WESTERN PIEDMONT...TO MIDDLE 40S OVER THE COASTAL PLAIN. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
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AS OF 330 AM WEDNESDAY... THE COASTAL AND UPPER LOWS WILL CONTINUE TO LIFT SLOWLY UP THE MIDDLE ATLANTIC COAST...WHILE HEIGHT RISES ALOFT AND ASSOCIATED SUBSIDENCE SPREAD EAST ACROSS NC THU. A NOTICEABLE NW BREEZE WILL LINGER THROUGH THE DAY...WITH GUSTS AROUND 20 MPH THROUGH MID-AFTERNOON... STRONGEST OVER THE NE PIEDMONT AND NORTHERN COASTAL PLAIN. DESPITE SUNNY OR MOSTLY SO CONDITIONS...TEMPERATURES WILL REMAIN COOL IN THE 60S...TO AROUND 70 OVER THE SOUTHERN PIEDMONT AND SANDHILLS. AN ELONGATED UPPER TROUGH OVER THE ROCKIES THIS MORNING...ONE SPANNING BOTH THE NORTHERN AND SOUTHERN STREAMS...WILL MOVE EAST AND INTO THE TN VALLEY AND GULF COAST STATES THU NIGHT. MID-HIGH CLOUDS ASSOCIATED WITH THE SOUTHERN STREAM COMPONENT WILL INCREASE THU NIGHT...WITH LOWS MOSTLY IN THE LOWER TO MIDDLE 40S.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 320 AM WEDNESDAY... THE EXPANSIVE UPPER LOW OVER THE NEW ENGLAND COAST ON THURSDAY WILL CONTINUE ON OFF TO THE NORTHEAST FRIDAY...WHILE A DISTURBANCE CROSSING THE MIDWEST DIVES SOUTHEAST TOWARD OUR AREA. BOTH THE GFS AND ECMWF DEPICT THIS DISTURBANCE A RELATIVELY COMPACT VORT CENTER BY THE TIME IT CROSSES NC FRIDAY NIGHT. HOWEVER...DESPITE THE STRONG DCVA ASSOCIATED WITH THIS FEATURE...WEST-NORTHWESTERLY FLOW WILL LIMIT DEEP MOISTURE AND THE ONLY ANTICIPATED SENSIBLE IMPACT IS SOME MID/HIGH CLOUDS ASSOCIATED WITH A STRENGTHENING UPPER JET OVER THE SOUTHEAST US. HIGHS WILL BE IN THE UPPER 60S TO LOWER 70S...WITH OVERNIGHT LOWS IN THE MID 40S. HIGH PRESSURE WILL INCH EASTWARD FROM THE MID-SOUTH SATURDAY AND SUNDAY...SETTLING OVER NC/VA ON MONDAY. MODELS SHOW A WEAK BACKDOOR FRONT..ATTENDANT TO SHORTWAVE CROSSING NEW ENGLAND... SLIPPING INTO THE AREA EARLY SUNDAY. THIS...ALONG WITH SHALLOW MIXING BENEATH THE HIGH PRESSURE ON MONDAY...MAY BE ENOUGH TO KEEP TEMPS SLIGHTLY COOLER THAN THE GRADUAL RISE OF THICKNESSES INTO THE 1360-1370M RANGE WOULD SUGGEST. HIGHS ARE EXPECTED TO BE IN THE UPPER 60S TO LOWER 70S. THE HIGH WILL THEN SHIFT OFFSHORE TUESDAY AS THE UPPER RIDGE AXIS SLIDES OVERHEAD. THIS WILL ALLOW TEMPS TO MODERATE A LITTLE MORE TOWARD MIDWEEK AS A SOUTHERLY WIND DEVELOPS AHEAD OF A FRONTAL ZONE CROSSING THE CENTRAL US. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 220 AM WEDNESDAY... THE PASSAGE OF A STRONG UPPER LEVEL LOW ACROSS SOUTHEASTERN VA AND NORTHEASTERN NC THROUGH EARLY AFTERNOON WILL RESULT IN VICINITY/ SCATTERED SHOWERS AT KRWI THROUGH AROUND 20Z...AND PERHAPS AS FAR WEST AS KRDU AS THE BRUNT OF THE LIFT ASSOCIATED WITH THE UPPER LOW ARRIVES THROUGH 12Z. AFTER AN INITIAL BAND OF ALTOCUMULUS PASSES KFAY DURING THE NEXT FEW HOURS...SKIES WILL BE MOSTLY CLEAR AT KFAY AND AT TRIAD TERMINALS. MEANWHILE IN CLOSER PROXIMITY TO THE AFOREMENTIONED UPPER LEVEL LOW AT KRDU AND ESPECIALLY KRWI...VARIABLY CLOUDY CONDITIONS WILL OCCUR THROUGH THIS AFTERNOON...WITH CEILINGS/CLOUD BASES MOSTLY BETWEEN 4000-8000 FT...AND TOPS IN SHOWERS UP TO 17 THOUSAND FT. OTHERWISE...A STEADY WNW TO NW SURFACE WIND...WITH AN OCCASIONAL GUST INTO THE MID-UPPER TEENS KTS...WILL CONTINUE AS COLDER AIR MOVES IN BEHIND THE FRONT THIS MORNING. NW WINDS WILL INCREASE INTO THE LOW-MID TEENS KTS WITH PEAK GUSTS IN THE LOWER 20S KTS...ONCE DIURNAL HEATING/MIXING COMMENCES BY 15Z...AND IN RESPONSE TO A TIGHTENING MSL PRESSURE GRADIENT AROUND DEVELOPING COASTAL LOW PRESSURE ALONG THE MIDDLE ATLANTIC COAST. OUTLOOK: BREEZY NW WINDS AGAIN THU. OTHERWISE...VFR...UNDER THE INFLUENCE OF HIGH PRESSURE FORECAST TO REMAIN SITUATED JUST WEST OF THE APPALACHIANS...WHICH WILL RESULT IN A DRY WEST TO NORTHWEST WIND IN CENTRAL NC...THROUGH THE NEXT SEVERAL DAYS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...MWS LONG TERM...BLS AVIATION...MWS

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