Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251756 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 156 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. && .NEAR TERM /THROUGH SUNDAY NIGHT/...
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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
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 AM SATURDAY... SURFACE HIGH AND ASSOCIATED LOW AMPLITUDE UPPER RIDGE AXIS MIGRATES EAST AND ACROSS THE AREA MONDAY. INITIALLY COOL MORNING TEMPS AND A WEAK SURGE OF COOL AIR...MAINLY IN THE NORTHEAST...WILL BE OFFSET BY DOWNSLOPE WARMING AND STRONG INSOLATION. HIGHS IN THE NORTHEAST MAY TOP OUT IN THE LOWER 70S...BUT MOST AREAS WILL REACH THE MID AND UPPER 70S. AS THE STACKED HIGH PRESSURE MOVES OFFSHORE LATE MONDAY...SOUTHWEST FLOW WILL MODERATE MINS MONDAY NIGHT AND MOST AREAS WILL SEE LOWER 50S TUESDAY MORNING. THE WARM START AND THERMAL RIDGE OVERHEAD...LOW LEVEL THICKNESSES AROUND 1390M...WILL ALLOW HIGHS UNDER STRONG SUN TO APPROACH 80 OVER MUCH OF THE AREA...WITH SOME LOWER 80S EXPECTED ACROSS THE SOUTHERN TIER. SOUTHWEST FLOW WILL AGAIN MODERATE MINS TUESDAY NIGHT...WITH MID 50S OVER MUCH OF THE AREA. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 302 AM SATURDAY... MODEL CONSENSUS IS GOOD IN REGARDS TO THE TIMING OF A COLD FRONT APPROACHING FROM THE WEST ON WEDNESDAY. THE FRONT WILL BE SLOWING AS IT ALIGNS PARALLEL TO THE DEEPER FLOW AND WILL BE CUT OFF FROM SIGNIFICANT MOISTURE ADVECTION. IN ADDITION...THE MID LEVEL REFLECTION OF THE FRONT WILL BE STRONGLY SHEARED AS THE INITIAL PUSH FROM A MID LEVEL VORT MAXIMA LIFTS NORTHEAST INTO NEW ENGLAND. AS A RESULT...POPS WILL BE ON THE ANEMIC SIDE INITIALLY...WITH SLIGHT CHANCE POPS BARELY WARRANTED WEDNESDAY NIGHT AND THURSDAY. HIGHS WEDNESDAY WILL BE SLIGHTLY HAMPERED BY CLOUDINESS...BUT SHOULD REACH THE MID 70S AFTER THE WARM MORNING AND WARM AIR ADVECTION AHEAD OF THE FRONT. LOWS WEDNESDAY NIGHT WILL BE MOSTLY IN THE LOWER 50S. WITH THE FRONT SLOWING AS IT PROGRESSES EAST...CLOUDINESS WILL BE THICKER WITH A FEW MORE SHOWERS AROUND ON THURSDAY...STILL SLIGHT CHANCE...BUT SHOWERS SHOULD BE A LITTLE MORE WIDESPREAD LATE IN THE DAY IN THE EAST WHERE THE FRONT WILL BE MORE LIKELY TO STALL OR SLOW SIGNIFICANTLY. HIGHS WILL RANGE FROM THE UPPER 60S NORTHWEST TO LOWER 70S IN THE EAST. THE FRONT WILL RECEIVE A STRONG NUDGE FROM A DIGGING UPPER SHORT WAVE ON THURSDAY NIGHT...WHICH WILL LIMIT LINGERING SHOWERS TO THE EAST FRIDAY MORNING...WITH CLEARING AND HIGHS SIMILAR TO THURSDAY...WITHIN A COUPLE OF DEGREES EITHER SIDE OF 70. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... AS OF 1200 PM SATURDAY... 24-HR TAF PERIOD: VFR CONDITIONS AND CLEAR SKIES WILL RULE THROUGH THE TAF PERIOD IN ASSOC/W A DRY NW FLOW ALOFT. LIGHT AND VARIABLE WINDS WILL BECOME WSW AT 5-10 KT THIS AFTERNOON AND PERSIST AT 4-8 KT OVERNIGHT. NW WINDS WILL INCREASE TO 10-15 KT WITH GUSTS TO 20-25 KT WITHIN A FEW HRS AFTER SUNRISE AND PERSIST INTO THE AFTERNOON... EVENTUALLY WEAKENING TO 5-10 KT BY SUNSET SUN EVENING. LOOKING AHEAD: VFR CONDITIONS WILL PERSIST THROUGH MID NEXT WEEK IN ASSOC/W A PERSISTENTLY BENIGN SYNOPTIC PATTERN. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...MLM AVIATION...VINCENT

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