Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 252319 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 719 PM EDT SAT OCT 25 2014 .SYNOPSIS...A DRY NORTHWEST FLOW ALOFT WILL PREVAIL OVER THE CAROLINAS THROUGH THE WEEKEND AS AN UPPER LEVEL RIDGE PROGRESSES SLOWLY EASTWARD FROM THE ROCKIES TO THE MISSISSIPPI RIVER VALLEY. WARM AND DRY CONDITIONS ARE EXPECTED EARLY TO MID WEEK... BEFORE A TURN TO COLDER WEATHER BY THE END OF THE WEEK. && .NEAR TERM /THROUGH SUNDAY NIGHT/... AS OF 155 PM SATURDAY... THROUGH TONIGHT: SYNOPTIC SUBSIDENCE IN THE WAKE OF A RECENT SHORTWAVE PASSAGE HAS REINFORCED THE DRY/STABLE AIRMASS IN PLACE ACROSS THE CAROLINAS (AS EVIDENCED BY A COMPARISON OF 00/12Z RAOB DATA)... ENSURING A CONTINUATION OF CLEAR SKIES AND DRY CONDITIONS THROUGH TONIGHT. WESTERLY LOW-LEVEL FLOW WILL RESULT IN MODEST LOW- LEVEL WARM ADVECTION (H925 +2C TO +4C) ACROSS CENTRAL NC THIS AFTERNOON AS UPSTREAM HEIGHTS RISE IN ADVANCE OF AN UPPER LEVEL RIDGE PROGRESSING SLOWLY EAST FROM THE ROCKIES INTO THE MS RIVER VALLEY. AS A RESULT...ANTICIPATE HIGH TEMPS A FEW DEGREES WARMER THAN PRIOR DAYS...IN THE LOWER/MID 70S. THE MSLP/HEIGHT GRADIENT WILL TIGHTEN OVERNIGHT AS AN AMPLIFYING UPPER LEVEL LOW (IN ONTARIO AT 15Z) DIGS SOUTHEAST INTO NEW ENGLAND...MAINTAINING A LIGHT WESTERLY BREEZE OVER CENTRAL NC. NOCTURNAL MIXING ASSOCIATED WITH A LIGHT W/NW BREEZE IS EXPECTED TO PREVENT FULL RADIATIONAL COOLING...AND THIS WILL BE THE BASIS FOR INDICATING OVERNIGHT LOWS IN THE LOWER 50S. GIVEN OTHERWISE FAVORABLE CONDITIONS FOR RAD COOLING...IT SHOULD BE NOTED THAT A BRIEF (2-3 HR) PERIOD OF CALM WINDS WOULD PROBABLY BE SUFFICIENT FOR TEMPS TO QUICKLY FALL INTO THE UPPER 40S. SUN/SUN NIGHT: THE UPPER LEVEL LOW DIGGING INTO NEW ENGLAND LATE TONIGHT WILL LIFT NORTHEAST INTO THE CANADIAN MARITIMES SUN/SUN NIGHT. MEANWHILE...AN UPSTREAM RIDGE OVER THE CENTRAL CONUS WILL PROGRESS EASTWARD THROUGH THE TN/OH VALLEY TO THE WESTERN SLOPES OF THE APPALACHIANS BY 12Z MON. COLD ADVECTION IS EXPECTED ACROSS CENTRAL NC SUN MORNING IN THE WAKE OF A DRY COLD FRONT TRAILING THE POTENT UPPER LEVEL LOW DIGGING INTO NEW ENGLAND. COLD ADVECTION WILL BE SHORT-LIVED IN MOST LOCATIONS...HOWEVER...AS WARM ADVECTION ATTENDANT THE ADVANCING UPPER LEVEL RIDGE RETURNS BY EARLY AFTERNOON IN ALL AREAS EXCEPT THE NE COASTAL PLAIN. GIVEN THAT MOS GUIDANCE HAS BEEN CONSISTENTLY TOO WARM THE PAST SEVERAL DAYS...HAVE OPTED TO DECREASE HIGHS A FEW DEGREES FROM THE PRIOR FORECAST TO THE LOW/MID 70S...COOLEST IN THE NE COASTAL PLAIN...WITH A NORTHWEST BREEZE AT ~15 MPH GUSTING UP TO 25 MPH. HIGH PRESSURE WILL BUILD OVER CENTRAL NC/VA FROM THE WEST SUN NIGHT. GIVEN CLEAR SKIES/CALM WINDS AND A DRIER AIRMASS ADVECTING INTO THE AREA IN THE WAKE OF THE DRY FRONTAL PASSAGE EARLIER IN THE DAY...EXPECT GOOD RADIATIONAL COOLING WITH LOWS IN THE LOW/MID 40S. -VINCENT && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 315 PM SATURDAY... WARM AND DRY MONDAY INTO WEDNESDAY... THE SURFACE HIGH PRESSURE IS FORECAST TO SHIFT OFFSHORE MONDAY AFTERNOON AND NIGHT. THIS WILL GRADUALLY ALLOW A SW FLOW TO RETURN TO THE REGION BY LATE MONDAY AND ESPECIALLY BY TUESDAY. SINCE THE STRONGEST WAA IS EXPECTED TUESDAY... THAT WILL LIKELY BE THE WARMEST DAY THIS UPCOMING PERIOD. HIGHS MONDAY SHOULD REACH THE MID 70S WITH UPPER 70S TO NEAR 80 OVER THE SANDHILLS. LOWS WILL BE IN THE MID 40S TO LOWER 50S MONDAY... WARMING INTO THE LOWER TO MID 50S TUESDAY AND WEDNESDAY. HIGHS WEDNESDAY SHOULD BE TEMPERED BY SOME INCREASE IN CLOUDS (EXPECT MOSTLY MID TO UPPER 70S). && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 315 PM SATURDAY... ...INCREASING ODDS OF THE FIRST FREEZE BY NEXT WEEKEND... ...PATTERN CHANGE TO COLDER WEATHER FROM THE GREAT LAKES TO THE SE COAST LATE IN THE WEEK... WHILE OPERATIONAL MODELS CONTINUE TO SHOW LARGE SPREAD OF SOLUTIONS FOR OUR REGION MID TO LATE WEEK... THEY HAVE BEEN TRENDING TOWARD A DEEPER AND COLDER UPPER TROUGH DEVELOPMENT FROM THE GREAT LAKES TO THE TENNESSEE VALLEY TO THE EAST COAST BY FRIDAY AND SATURDAY. THIS WOULD ALLOW A GOOD PUSH OF CONTINENTAL POLAR AIR... DRIVEN BY A 1035+ SURFACE HIGH PRESSURE... TO DIVE INTO THE CENTRAL AND EASTERN STATES FRIDAY AND SATURDAY. WHILE A LOT IS YET TO BE DETERMINED LIKELY DRIVEN BY THE REMNANTS OF ANA AS IT DRIVES INTO THE ALASKA PANHANDLE. THE EUROPEAN AND ITS ENSEMBLES INDICATE A DEEPER AND MORE CUT OFF MID/UPPER TROUGH OVER OUR REGION BY SAT-SUN... WHILE THE GFS IS NOT AS STRONG. REGARDLESS... A BLEND OF THE ENSEMBLES AND TRENDS STRONGLY SUGGEST AT LEAST A ROBUST MID/UPPER TROUGH OVER THE EASTERN STATES. THE MORE EXTREME EUROPEAN MAY STILL DEVELOP... BUT IS STILL CONSIDERED A LOW PROBABILITY AT THIS TIME. THE BOTTOM LINE... THE PROBABILITY OF THE FIRST KILLING FROST OR FREEZE FOR OUR REGION IS INCREASING FOR NEXT WEEKEND. HIGHS MAY REMAIN IN THE 50S BY SATURDAY... WITH LOWS BY SATURDAY NIGHT POTENTIALLY ENDING THE GROWING SEASON FOR MOST OF OUR WESTERN AND NORTHERN ZONES IF NOT MORE OF THE REGION. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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AS OF 715 PM SATURDAY... 24-HOUR TAF PERIOD: HIGH CONFIDENCE THAT VFR CONDITIONS WILL DOMINATE THE TAF PERIOD. A WEAK WAVE IS EXPECTED TO MOVE ACROSS THE AREA TONIGHT...AND WHILE SKIES SHOULD REMAIN CLEAR...WINDS MAY REMAIN GENERALLY WESTERLY AT 3-6 KTS. THERE IS A CHANCE WINDS COULD BECOME LIGHT OVERNIGHT...HOWEVER CONFIDENCE IN THAT HAPPENING IS NOT HIGH AT THIS TIME. WITH THE HIGH APPROACHING FROM THE WEST AND THE LOW LINGERING OVER NEW ENGLAND SUNDAY...EXPECT WINDS TO BECOME NORTHWESTERLY AND INCREASE TO 10-12 KTS WITH GUSTS OF 18-25 KTS DURING THE DAY SUNDAY. GUSTS SHOULD ABATE AROUND SUNSET SUNDAY. -KC LOOKING AHEAD: VFR CONDITIONS WILL PERSIST THROUGH THE MIDDLE OF NEXT WEEK IN ASSOCIATION WITH A PERSISTENTLY BENIGN SYNOPTIC PATTERN. -VINCENT
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...PWB LONG TERM...PWB AVIATION...KC/VINCENT

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