Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291954 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 320 PM EDT WED OCT 29 2014 .SYNOPSIS...HIGH PRESSURE IN THE WAKE OF THE COLD FRONTAL PASSAGE THIS EVENING WILL BUILD INTO THE AREA THROUGH FRIDAY. A POTENT UPPER LEVEL LOW CROSSING THE REGION ON SATURDAY AND ASSOCIATED STRONG CYCLOGENESIS OFF THE MID ATLANTIC COAST WILL RESULT IN WET BLUSTERY CONDITIONS FRIDAY NIGHT AND SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 258 PM WEDNESDAY... SURFACE COLD FRONT..WHICH CURRENTLY EXTENDS ALONG A LINE FROM MT AIRY TO ASHEVILLE...HAS MOVED VERY LITTLE...IF ANY...OVER THE PAST SEVERAL HOURS WHILE ASSOCIATED BAND OF PRECIP HAS PRETTY MUCH HIT THE SKIDS. EXPECTED FROPA TIMING IN THE NW PIEDMONT BETWEEN 20- 22Z...THE TRIANGLE BETWEEN 22-00Z...AND THE COASTAL PLAIN AND EASTERN SANDHILLS BETWEEN 00-03Z(~3 HOURS SLOWER THAN WHAT MODELS WERE SHOWING THIS TIME YESTERDAY). WHILE RECENT RADAR TRENDS LEAVE LITTLE TO GET EXCITED ABOUT...ANA- FRONTAL REDEVELOPMENT IS LIKELY AS THE DIVERGENT RIGHT ENTRANCE OF A JET STREAK IN THE NORTHERN STREAM SPREADS EAST ACROSS CENTRAL NC AND PROVIDES DEEPER/COUPLED ASCENT ATOP THE FRONTAL CIRCULATION THIS AFTERNOON. DESPITE THE COUPLED FORCING...WEAK LAPSE RATES AND ASSOCIATED INSTABILITY WILL OTHERWISE HINDER PRECIPITATION INTENSITY. INITIALLY...CLOUDINESS WILL LINGER BEHIND THE FRONT THROUGH THIS EVENING...BUT CLEARING WILL EVENTUALLY SPREAD EAST OVERNIGHT. CAA-DRIVEN LOWS MOSTLY BETWEEN 45 TO 55 DEGREES. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 250 PM WEDNESDAY... LEAD SHORTWAVE ENERGY OVER THE NORTHERN ROCKIES WILL EJECT SEWD ACROSS THE CENTRAL US AND INTO THE SOUTHERN APPALACHIANS BY DAYBREAK FRIDAY...WITHIN THE EVOLVING LONG WAVE TROUGH ACROSS THE EASTERN US IMPELLED BY THE VIGOROUS SHORTWAVE TROUGH DIVING SEWD OUT OF EASTERN MANITOBA. DRY TRANQUIL WEATHER AND MOSTLY SUNNY/CLEAR SKIES WILL PREVAIL THROUGH THE DAY ON THURSDAY...WITH PERHAPS AN INCREASE IN HIGH CLOUDS LATE THURSDAY NIGHT IN RESPONSE TO UPSTREAM HEIGHT FALLS AND VEERING SWLY FLOW ALOFT. MODEST COLD AIR ADVECTION IN THE WAKE OF THE TONIGHTS FROPA WILL YIELD SLIGHTLY BELOW NORMAL TEMPERATURES FOR LATE OCTOBER. HIGHS 63 TO 68. LOWS IN THE LOWER 40S...WITH SOME UPPER 30S POSSIBLE IN THE TYPICALLY COOLER LOCATIONS. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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AS OF 320 PM WEDNESDAY... ...ANOMALOUS PATTERN ON SATURDAY WILL BRING CHILLY, WINDY AND RAW CONDITIONS TO CENTRAL NC... A MODERATE AMPLITUDE EASTERN U.S. TROUGH AT 12Z FRIDAY DEEPENS SIGNIFICANTLY AS AN INTENSE JET AT 500 HPA DROPS INTO THE OH VALLEY AND STRENGTHENS TO ~105KTS ON 00 UTC SUNDAY AS IT REACHES THE BASE OF THE NOW CLOSED TROUGH OFF THE SC COAST. GUIDANCE FROM THE GFS/EC/NAM ARE ALL RATHER SIMILAR WITH THE UPPER AIR PATTERN PATTERN WITH 500 HPA ANOMALIES OF 4-5 SD FROM NORMAL LATE SATURDAY WITH CIPS ANALOG GUIDANCE SUGGESTING A SIMILAR OUTCOME. AT THE SURFACE WEAK HIGH PRESSURE SLIPS OFF THE COAST EARLY ON FRIDAY AS A COLD FRONT AND WEAK SURFACE LOW ASSOCIATED WITH THE UPPER TROUGH MOVES INTO CENTRAL NC AROUND 00 UTC ON SATURDAY. WHILE THE EXACT TRACK OF THE SURFACE LOW IS UNCLEAR...CONSENSUS SUGGESTS THAT THE SURFACE LOW WILL MOVE INTO THE COASTAL PLAIN TOWARD 12 UTC AND THEN MOVES OFFSHORE AND DEEPENS AGGRESSIVELY. LIGHT RAIN IS EXPECTED TO SPREAD INTO THE WESTERN PIEDMONT LATE FRIDAY EVENING...LIKELY AFTER MOST TRICK OR TREATING ACTIVITIES END...AND THEN SPREAD EAST OVERNIGHT. A CHILLY AND RAW SATURDAY SHOULD FEATURE A FAIRLY WIDESPREAD RAIN THAT TAPERS OFF FROM WEST TO EAST DURING THE AFTERNOON AND EVENING. CONSENSUS PRECIPITATION GUIDANCE PROVIDES AROUND A HALF INCH TO THREE QUARTERS OF AN INCH OF RAIN WITH AN ARC OF HEAVIER RAIN LIKELY TO EXTEND NORTHWEST TO SOUTHEAST JUST NORTH OF THE UPPER LOW TRACK. WHILE THICKNESS VALUES WILL CRASH EARLY SATURDAY...BOUNDARY LAYER TEMPERATURES WILL BE SUFFICIENTLY WARM AND DEEP TO PRECLUDE ANY WINTRY PRECIPITATION... EVEN ACROSS THE WESTERN PIEDMONT WHERE SURFACE TEMPERATURES MAY FALL INTO THE UPPER 30S. A STRENGTHENING GRADIENT WILL RESULT IN A COLD AND GUSTY NORTH TO NORTHWEST WIND SATURDAY AFTERNOON AT 10-20 MPH WITH GUSTS TO 25 MPH OR MORE. HIGHS ON SATURDAY WILL BE COMPLICATED BY PRECIPITATION AND COLD AIR WRAPPING AROUND THE DEEPENING LOW OFF THE COAST WITH DAYTIME HIGHS RANGING IN THE LOWER 40S IN THE TRIAD TO THE LOWER 50S IN THE EAST. THESE VALUES ARE 15 TO 25 DEGREES BELOW NORMAL AND COULD THREATEN RECORD LOW MAX TEMPERATURES IN THE PIEDMONT ON SATURDAY(SEE CLIMATE SECTION BELOW FOR RECORD VALUES). PRECIPITATION SHOULD WRAP UP EVERYWHERE BY SATURDAY EVENING WITH CLEARING SKIES AND A BRISK NORTHWEST WIND OVERNIGHT. A CHILLY AIRMASS WILL PERSIST OVERNIGHT WITH LOW LEVEL THICKNESS VALUES BY SUNDAY MORNING RANGING IN THE 1305-1315M RANGE. DESPITE THE CLEARING SKIES AND CHILLY THICKNESS VALUES...MIXING SHOULD KEEP TEMPERATURES FROM BOTTOMING OUT COMPLETELY. LOWS SHOULD RANGE IN THE LOWER TO MID 30S. MOSTLY SUNNY SKIES ARE EXPECTED ON SUNDAY WITH SOME HIGH CLOUDS AND DIMINISHING WINDS. HIGHS WILL RANGE ABOUT 15 DEGREES BELOW NORMAL...RANGING BETWEEN 50-55 DEGREES. HIGH PRESSURE BUILDS OVERHEAD SUNDAY NIGHT WHICH SHOULD RESULT IN THE COLDEST NIGHT OF THE PERIOD WITH LOWS TUESDAY MORNING IN THE LOWER 30S AND PERHAPS SOME UPPER 20S IN SPOTS. FAIR WEATHER WITH MODERATING TEMPERATURES ARE EXPECTED ON MONDAY AND TUESDAY AS HEIGHTS RISE AND AN UPPER LEVEL RIDGE BUILDS TOWARD THE EASTERN SEABOARD. SOME MORNING LOW CLOUDS OR FOG IS POSSIBLE ON MONDAY AND ESPECIALLY TUESDAY AS A RETURN FLOW OFF THE ATLANTIC DEVELOPS. A SHEARING UPPER TROUGH APPROACHES FROM THE WEST ON WEDNESDAY. THIS SYSTEM MAY BE ABLE TO PRODUCE SOME SHOWERS BUT GIVEN THE LATE ARRIVAL ON DAY 7...HAVE OPTED TO KEEP THE FORECAST DRY AND JUST INCREASE CLOUD COVER. HIGHS IN THE UPPER 50S TO NEAR 60 ON MONDAY WILL MODERATE TO THE MID 60S TO AROUND 70 BY WEDNESDAY. -BLAES .CLIMATE... RECORD LO-MAX TEMPERATURES FOR NOVEMBER 1ST" LO-MAX RDU 50/1925 GSO 45/1925 FAY 48/1988
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 155 PM WEDNESDAY... VFR CONDITIONS ARE EXPECTED UNTIL A COLD FRONT AND ASSOCIATED BROKEN BAND OF POST-FRONTAL SHOWERS MOVES EAST ACROSS CENTRAL NC....WITH TIMING IN THE NW PIEDMONT BETWEEN 20-22Z...THE TRIANGLE BETWEEN 22- 00Z...AND THE COASTAL PLAIN AND EASTERN SANDHILLS BETWEEN 00-03Z. A BRIEF PERIOD OF SUB-VFR CONDITIONS ARE POSSIBLE WITH THE HEAVIER SHOWERS. POST-FRONTAL DRY COLD AIR ADVECTION WILL RESULT IN WEST- EAST CLEARING BETWEEN 06 TO 15Z THURSDAY. OUTLOOK: VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH FRIDAY EVENING. A POTENT UPPER LEVEL LOW AND SUBSEQUENT DEVELOPMENT OF A STRONG COASTAL LOW WILL RESULT IN WIDESPREAD SUB-VFR CONDITIONS IN RAIN LATE FRIDAY NIGHT THROUGH SATURDAY...ALONG WITH BLUSTERY NW WINDS. VFR CONDITIONS WILL RETURN SATURDAY NIGHT AND WILL DOMINATE THROUGH EARLY NEXT WEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL/MWS SHORT TERM...CBL LONG TERM...BLAES CLIMATE...CBL AVIATION...CBL

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