Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 282006 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 305 PM EST SUN DEC 28 2014 .SYNOPSIS...A COLD FRONT WILL MOVE INTO CENTRAL NC TONIGHT. A WAVE OF LOW PRESSURE WILL DEVELOP ALONG THE FRONT AND MOVE ACROSS THE EASTERN CAROLINAS ON MONDAY. THE FRONT WILL MOVE OFFSHORE MONDAY NIGHT BEFORE HIGH PRESSURE EXTENDS INTO THE REGION ON TUESDAY. && .NEAR TERM /THROUGH MONDAY/... AS OF 305 PM SUNDAY... LATEST SURFACE ANALYSIS SHOWS A COLD FRONT EXTENDING FROM NEAR WASHINGTON D.C. TO THE SOUTHERN APPALACHIANS TO NEAR ATLANTA. A BROAD UPPER LEVEL TROUGH AXIS STRETCHES FROM NEAR LAKE MICHIGAN TO EASTERN TEXAS. A SHEARING SHORT WAVE TROUGH EASILY SEEN IN THE WATER VAPOR IMAGERY ACROSS EASTERN TEXAS THIS AFTERNOON WILL LIFT NORTHEAST INTO THE TENNESSEE VALLEY TONIGHT AND THEN INTO THE WESTERN CAROLINAS TOWARD DAYBREAK MONDAY. THE COMBINATION OF THIS WEAKENING UPPER TROUGH WHICH INITIATES WEAK CYCLOGENESIS ALONG THE FRONT...MODEST ISENTROPIC LIFT AND A STRENGTHENING UPPER LEVEL JET SHOULD RESULT IN AN EXPANDING ARC OF RAIN ALONG AND BEHIND THE COLD FRONT WITH SCATTERED SHOWERS IN THE WARM SECTOR AHEAD OF THE FRONT. LOOK FOR PRECIPITATION TO STREAM NORTHEAST ACROSS THE SOUTHERN APPALACHIANS THIS EVENING WITH THE PRECIPITATION AXIS SLIDING SLOWLY EAST OVERNIGHT AND MONDAY AS INDIVIDUAL ELEMENTS TRACK NORTHEAST. THE COLD FRONT WILL DROP SOUTH ACROSS VIRGINIA THIS EVENING AND DROP INTO CENTRAL NC MONDAY MORNING AS THE SURFACE WAVE LIFTS NORTH WITH THE FRONT DROPPING SOUTH INTO THE COASTAL REGION LATE IN THE DAY. RAINFALL AMOUNTS WITH THIS SYSTEM HAVE BEEN TRENDING DOWN WITH RECENT MODEL RUNS BUT AMOUNTS SHOULD RANGE BETWEEN A THIRD AND A HALF INCH WITH THE GREATEST AMOUNTS EXTENDING SOUTHWEST TO NORTHEAST ACROSS THE WESTERN PIEDMONT. IN TERMS OF SENSIBLE WEATHER...SPOTTY LIGHT RAIN ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND SOUTHERN COASTAL PLAIN THIS AFTERNOON WILL MOVE NORTHEAST AND DEPART CENTRAL NC AROUND SUNSET. THIS WILL LEAVE MOSTLY CLOUDY AND GENERALLY DRY CONDITIONS ACROSS CENTRAL NC EARLY THIS EVENING WITH A FEW LINGERING PATCHES OF LIGHT RAIN AND SHOWERS. A NARROW AXIS OF RAIN EXTENDING NORTHEAST ACROSS THE MISSISSIPPI AND TENNESSEE VALLEY WILL BROADEN AND EXPAND THIS EVENING AS IT SHIFTS EAST ACROSS THE SOUTHERN APPALACHIANS. THE BROAD SHIELD OF PRECIPITATION SHOULD REACH THE TRIAD TOWARD MIDNIGHT AND THEN PUSH EAST OVERNIGHT REACHING THE COASTAL PLAIN IN THE PRE-DAWN HOURS. THE PRECIPITATION WILL WEAKEN DURING THE AFTERNOON AS IT SLIDES EAST WITH THE LARGE SHIELD OF RAIN BREAKING UP IN MORE SCATTERED PATCHES OF RIAN BY LATE IN THE DAY. AS THE FRONT DROPS SOUTH INTO CENTRAL NC...COOLER TEMPERATURES WILL PUSH INTO NORTHERN NC WITH TEMPERATURES FALLING INTO THE MID 40S NEAR THE VA BORDER BY LATE IN THE DAY. FURTHER SOUTH NEAR THE SC BORDER THE COLDER AIR WILL BE LATE IN ARRIVING AND HIGH TEMPERATURES WILL CLIMB TO NEAR 60. -BLAES && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 305 PM SUNDAY... MONDAY NIGHT INTO TUESDAY... ATMOSPHERE BELOW 700MB TO REMAIN NEARLY SATURATED AS 925-850MB TROUGH REMAINS WEST OF THE FORECAST AREA UNTIL TUESDAY AFTERNOON. LIFT TO GENERATE APPRECIABLE PRECIPITATION LACKING THOUGH 12Z/NAM DOES DEPICT WEAK UPGLIDE AT 290K LEVEL OVER OUR REGION LATE MONDAY NIGHT-TUESDAY MORNING (GFS DEPICTS NEUTRAL ADVECTION). MARGINAL UPSLOPE FLOW AT 925 MB MAY GENERATE SPOTS OF LIGHT RAIN OVER THE NW PIEDMONT OTHERWISE EXPECT AREAS OF DRIZZLE MONDAY NIGHT THROUGH TUESDAY MORNING. PASSAGE OF 925-850MB TROUGH A LITTLE SLOWER COMPARED TO MODEL GUIDANCE 24 HOURS AGO. WHILE PARTIAL CLEARING STILL EXPECTED ACROSS THE FAR WEST-NW PRIOR TO SUNSET...PARTIAL CLEARING MAY NOT MAKE IT TO THE TRIANGLE AREA OR TO THE SANDHILLS AND COASTAL PLAIN UNTIL AFTER SUNSET. MIN TEMPS MONDAY NIGHT MID-UPPER 30S NORTH TO THE LOWER 40S SOUTH. TEMPS TUESDAY WILL BE HELD DOWN BY EXTENSIVE CLOUDS AND PATCHY LIGHT RAIN/DRIZZLE. MAX TEMPS TUESDAY LOW-MID 40S NORTH TO THE UPPER 40S/AROUND 50 SOUTH. TUESDAY NIGHT...PASSAGE OF 925-850MB TROUGH LATE TUESDAY-TUESDAY NIGHT SHOULD INITIATE SOME PARTIAL CLEARING DUE TO SUBSIDENCE AND DOWNSLOPE COMPONENT OF LOW LEVEL WINDS. SOME GUIDANCE SUGGEST LOW CLOUDS HOLDING ON IN THE EAST UNTIL SHORTLY AFTER DAYBREAK WEDNESDAY. IF PARTIAL CLEARING OCCURS...MAY SEE PATCHY/AREAS OF FOG DEVELOP AFTER MIDNIGHT. MIN TEMPS UPPER 20S FAR NORTH-NW TO AROUND 30 FAR SOUTH. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 305 PM SUNDAY... WEDNESDAY AND THURSDAY...S/W IN THE NORTHERN STREAM WILL CROSS THE GREAT LAKES AND NORTHERN MID ATLANTIC LATE WEDNESDAY AND WEDNESDAY NIGHT. THIS FEATURE WILL PROPEL A DRY SURFACE COLD FRONT ACROSS CENTRAL NC WEDNESDAY NIGHT. THIS PASSAGE WILL OCCUR PRETTY UNEVENTFUL WITH JUST A DECK OF MID-HIGH LEVEL CLOUDS EXPECTED. THUS PARTIAL CLEARING EARLY WEDNESDAY EXPECTED TO BE SHORT-LIVED AS APPROACH OF S/W AND ASSOCIATED MID-HIGH LEVEL CLOUDINESS WILL CROSS CENTRAL NC LATE WEDNESDAY AND WEDNESDAY EVENING. NLY WINDS BEHIND THIS PASSAGE WILL REINFORCE THE COOL AIR MASS ALREADY IN PLACE BUT ADVECT A BATCH OF DRIER AIR AS DEWPOINTS WILL LOWER INTO THE TEENS/LOWER 20S. LOW LEVEL THICKNESSES BY EARLY THURSDAY ARE IN THE 1290-1295M RANGE. HISTORICALLY...THIS SUPPORTS MIN TEMPS IN THE MID-UPPER 20S. THE COOL DRY AIR MASS FOR THURSDAY WILL SUPPORT MOSTLY SUNNY SKIES FOR THE FIRST DAY OF 2015 WITH AFTERNOON TEMPS WILL AVERAGE 5-6 DEGREES BELOW NORMAL. HIGH TEMPS THURSDAY MID 40S NORTH TO NEAR 50 SOUTH. FRIDAY THROUGH SUNDAY... WEATHER PATTERN OVER CENTRAL NC BECOMES UNSETTLED AS AN UPPER LEVEL LOW WILL SLUGGISHLY LIFT EAST-NE ACROSS THE MID MS AND OH VALLEYS. MODEL GUIDANCE OFFER DIFFERING SOLUTIONS WITH TEH GFS MORE PROGRESSIVE THAN THE ECMWF. USUALLY...BETTER TO LEAN TOWARD THE SLOWER SOLUTION THIS FAR OUT. EXPECT AIR MASS TO MODIFY FRIDAY AS AS FLOW ASSUMES A RETURN FLOW OFF THE ATLANTIC. PRECIP CHANCES WILL LIKELY BEGIN TO INCREASE LATE FRIDAY...AND MORE SO SATURDAY PERSISTING INTO SUNDAY. PRESENCE OF A MODIFIED ARCTIC AIR MASS IN PLACE OVER CENTRAL NC PRIOR TO PRECIP ARRIVAL SIGNAL POTENTIAL FOR HYBRID OR INSITU COLD AIR DAMMING SATURDAY INTO THIS SUNDAY. IF THIS MATERIALIZES...THIS WOULD CREATE A WIDE VARIANCE IN TEMPS ACROSS CENTRAL NC (CHILLY NW TO RELATIVELY MILD SE). FOR NOW...WILL KEEP MAX TEMPS CLOSE TO AVERAGE ACROSS THE PIEDMONT...AND A CATEGORY OR TWO ABOVE NORMAL IN THE SE. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 125 PM SUNDAY... MVFR CONDITIONS WITH LOW CEILINGS BUT GENERALLY GOOD VISIBILITIES PREDOMINATE ACROSS CENTRAL NC THIS AFTERNOON WITH THE EXCEPTION OF THE SOUTHERN COASTAL PLAIN AND SANDHILLS WHERE VFR CONDITIONS AND EVEN SOME BREAKS IN THE HIGH OVERCAST ARE OBSERVED. EXPECT SKY CONDITIONS TO IMPROVE LATER THIS AFTERNOON AND EARLY EVENING AS AN UPPER LEVEL DISTURBANCE MOVES OFF THE MID ATLANTIC COAST. THE IMPROVEMENT WILL BE SHORT LIVED AS AN APPROACHING COLD FRONT ALONG WITH A WAVE OF LOW PRESSURE SPREADS AN AREA OF RAIN WITH REDUCED CEILINGS AND VISIBILITIES INTO THE REGION LATE TONIGHT INTO EARLY MONDAY. CONDITIONS LARGELY DRIVEN BY LOW CIGS ARE EXPECTED TO DETERIORATE AS A COLD FRONT CROSSES THE REGION OVERNIGHT AND LIGHT RAIN BEGINS. AVIATION CONDITIONS WILL FALL INTO THE IFR RANGE AROUND 04Z AT KINT/KGSO...AROUND 06Z AT KRDU/KRWI AND AROUND 08Z AT KFAY AS A SEVERAL HOUR PERIOD OF LIGHT TO OCCASIONALLY MODERATE RAIN SPREADS INTO THE REGION. SOUTHWESTERLY WINDS AHEAD OF THE FRONT WILL BECOME NORTHERLY AT 5-10KTS BEHIND THE FRONT AND EVENTUALLY BECOME NORTHEASTERLY ON MONDAY. LOOKING AHEAD...LINGERING LOW CLOUDS ALONG WITH SOME LIGHT RAIN AND DRIZZLE WILL CONTINUE MONDAY NIGHT AND TUESDAY AND BEGIN TO IMPROVE LATE TUESDAY AND WEDNESDAY. FAIR WEATHER AND NO ADVERSE AVIATION CONDITIONS ARE EXPECTED WEDNESDAY THROUGH EARLY FRIDAY BEFORE THE NEXT STORM SYSTEM APPROACHES LATE FRIDAY. -BLAES && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES SHORT TERM....WSS LONG TERM...WSS AVIATION...BLAES

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