Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261529 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1025 AM EST THU FEB 26 2015 .SYNOPSIS...
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LOW PRESSURE WILL MOVE AWAY FROM THE NORTH CAROLINA COAST THIS MORNING. COLD CANADIAN HIGH PRESSURE WILL FOLLOW THE STORM FRIDAY INTO SATURDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1025 AM THURSDAY... ...ACCUMULATING PRECIPITATION HAS ENDED BUT THREAT OF FALLING LIMBS AND TREES CONTINUES FROM HEAVY WET SNOW AND A WINTRY MIX... WE WILL CONTINUE THE WINTER STORM WARNING FOR A LARGE PART OF CENTRAL NC EARLY THIS MORNING TO COVER THE THREAT FROM FALLING TREES AND BRANCHES AS WELL AS DIFFICULT TRAVEL CONDITIONS MAINLY FROM ASHEBORO...RALEIGH AND ROCKY MOUNT NORTH. THE WARNING WILL BE ALLOWED TO EXPIRE AT NOON. WE WILL CANCEL THE WINTER ADVISORY FOR OUR FAR SOUTHERN TIER AS TEMPERATURES HAVE WARMED INTO THE MID 30S. EXPECT ONLY SOME AREAS OF LINGERING DRIZZLE AND FREEZING DRIZZLE FOR THE NEXT FEW HOURS ACROSS THE EASTERN PIEDMONT AND COASTAL PLAIN WITH DRY WEATHER BUT A LOW OVERCAST FOR MOST OF THE AFTERNOON. TEMPERATURES WILL CLIMB A FEW DEGREES INTO THE MID TO UPPER 30S BY LATE AFTERNOON. FORECAST FOR TONIGHT IS COMPLICATED BY THE DEGREE OF CLEARING WHICH WILL HAVE A BIG IMPACT ON LOW TEMPERATURES. IF SKIES CLEAR...LOW TEMPERATURES TONIGHT COULD FALL A CATEGORY OR TWO BELOW THE CURRENT FORECAST OF THE LOWER TO MID 20S. WILL EVALUATE THIS ISSUE FOR THIS AFTERNOONS PACKAGE. REGARDLESS OF HOW COLD IT GETS... MOISTURE... SLUSH AN SNOW WILL LIKELY RE-FREEZE LATE TONIGHT LEADING TO WIDESPREAD BLACK ICE CONDITIONS. FOR THE AFTERNOON PACKAGE WE PLAN ON ISSUING A WINTER WEATHER ADVISORY FOR BLACK ICE FOR LATE TONIGHT- EARLY FRI MORNING. -BLAES
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY/... AS OF 325 AM THURSDAY... FRIDAY AND FRIDAY NIGHT: ANOTHER WEAK S/W DISTURBANCE IS EXPECTED TO MOVE ACROSS THE REGION IN THE WEST-SOUTHWESTERLY MID LEVEL FLOW. HOWEVER... WITH PW`S LESS THAN THREE TENTHS OF AN INCH OR SO EXPECT WE WILL SEE LITTLE IF ANY PRECIP. WILL KEEP MENTION OF FLURRIES IN THE FORECAST FOR LATE FRIDAY AFTERNOON INTO THE EVENING ACROSS THE PIEDMONT... AS THE LATEST GFS BUFR SOUNDINGS CONTINUE TO SHOW SOME SATURATION UP CLOSE TO -10C ACROSS WESTERN AND NORTHERN PORTIONS OF CENTRAL NC... WITH STEEP LOW LEVEL LAPSE RATES. CANT RULE OUT A VERY BRIEF LIGHT SNOW SHOWER OR TWO, BUT FEEL NOTHING WILL BE MEASURABLE. EXPECT HIGH TEMPS FRIDAY WILL BE IN THE MID TO UPPER 30S NORTH TO NEAR 40 SOUTH. SURFACE HIGH PRESSURE OVER THE MID MS RIVER VALLEY AND OHIO VALLEY ON FRIDAY EVENING WILL BUILD EAST AND SOUTHWARD OVERNIGHT INTO CENTRAL NC. THIS YIELD LOW TEMPS BY SATURDAY MORNING IN THE TEENS TO LOWER 20S ACROSS THE AREA. SATURDAY: SURFACE HIGH PRESSURE WILL EXTEND INTO OUR REGION FROM THE NORTH ON SATURDAY... WITH POSSIBLY SOME HIGH CLOUDS INCREASING LATE IN THE DAY IN THE WEST TO WEST-SOUTHWESTERLY MID LEVEL FLOW IN ADVANCE OF THE NEXT SYSTEM. THIS WILL YIELD HIGH TEMPS AGAIN WELL BELOW NORMAL... WITH AFTERNOON LOW LEVEL THICKNESS VALUES SOME 50+ METERS BELOW NORMAL. EXPECT HIGH TEMPS TO BE IN THE 30S. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 1200 PM WEDNESDAY... THE LONG-TERM SATURDAY NIGHT THROUGH WEDNESDAY IS CATEGORIZED BY SOME UNCERTAINTY IN PRECIPITATION TIMING AND TYPE...WITH AT LEAST MODEST CONFIDENCE IN MUCH WARMER TEMPERATURES DEVELOPING BY THE END OF THIS PERIOD THAN WHAT HAS BEEN OCCURRING RECENTLY. DRYING IS FORECAST FOR SATURDAY NIGHT...WITH A MID-LEVEL SHORTWAVE MOVING INTO THE CAROLINAS BY SUNDAY NIGHT. AS HEIGHTS ALOFT RISE LATE IN THE WEEKEND AND EARLY NEXT WEEK...THE 06Z GFS IN PARTICULAR AND POSSIBLY EVEN THE 12Z GFS SEEMS TO HAVE ISSUES WITH FEEDBACK SUCH THAT THE ECMWF IS PREFERRED OVERALL. IT SHOULD BE COLD TO START SUNDAY MORNING AS CLOUDS INCREASE...BUT THE GFS AND ECMWF TREND OF A LATER ARRIVAL OF MID-LEVEL VORTICITY AND OVERALL MOISTURE INCREASE SHOULD RESULT IN PRECIPITATION BEING IN THE FORM OF LIQUID BY THE TIME ANY WOULD ARRIVE LATER IN THE DAY. PARTIAL THICKNESSES AND MODEL SOUNDINGS CURRENTLY SUPPORT THIS...AND WILL HAVE A CHANCE OF AFTERNOON RAIN SUNDAY PRIMARILY TOWARD THE YADKIN RIVER FOLLOWED BY CHANCES OF RAIN OVERNIGHT...WITH SURFACE TEMPERATURES REMAINING ABOVE FREEZING AND MODEL SOUNDINGS SHOWING WARMING ALOFT AS 1000- 850MB THICKNESSES RISE AROUND 20M DURING THE NIGHT...SUGGESTING THE POTENTIAL FOR LOW TEMPERATURES EARLY SUNDAY NIGHT FOLLOWED BY STEADY OR A SLOW RISE IN READINGS LATE. A BRIEF WARMUP OCCURS MONDAY AHEAD OF A COLD FRONT THAT MOVES THROUGH CENTRAL NORTH CAROLINA LATER IN THE DAY AND AT NIGHT. STRONG HIGH PRESSURE BUILDS IN BEHIND THE COLD FRONT...AND THE PATTERN WOULD SUGGEST PRETTY CHILLY TEMPERATURES ONCE AGAIN WITH THE 1000- 850MB THICKNESSES SUGGESTING LOWS A LITTLE BELOW FREEZING. MOS GUIDANCE LOWS ARE AT LEAST ONE IF NOT MORE CATEGORIES ABOVE THIS... SO FOR NOW WILL SIMPLY UNDERCUT GUIDANCE WITH OVERNIGHT LOWS AT OR SLIGHTLY ABOVE FREEZING. CONDITIONS SHOULD DRY BRIEFLY BEHIND THE FRONT AS HIGH PRESSURE BUILDS IN...THEN UNCERTAINTY INCREASES AS THE GFS AND THE ECMWF SUGGEST MOISTURE RETURNING TO CENTRAL NORTH CAROLINA AS THE GULF OPENS BY TUESDAY INTO TUESDAY NIGHT. IF PRECIPITATION WOULD RETURN TO CENTRAL NORTH CAROLINA QUICKLY ENOUGH ON TUESDAY...PRECIPITATION TYPE CONCERNS WOULD EXIST DUE TO CHILLY THICKNESSES TO START THE DAY. BY 00Z WEDNESDAY ON THE 12Z GFS...AND FOR THE MOST PART ON THE 00Z ECMWF...THICKNESSES ARE WARM ENOUGH FOR RAIN AND BASED ON THE WARM-AIR ADVECTION AT THE TIME WOULD ANTICIPATE ANOTHER POTENTIAL NON-DIURNAL TEMPERATURE SCENARIO AS ANY COLD-AIR DAMMING ERODES. BASED ON THE PATTERN WILL ONLY NOTE A SLIGHT CHANCE OF RAIN OR SNOW EARLY ON THE SIXTH DAY IN THE WESTERN PIEDMONT WITH A CHANCE OF JUST ALL RAIN THROUGHOUT CENTRAL NORTH CAROLINA BY TUESDAY AFTERNOON. 1000-850MB THICKNESSES ON THE 12Z GFS AND 00Z ECMWF ARE QUITE WARM WEDNESDAY...APPROACHING 1380M ON THE LATEST GFS AND ONLY SLIGHTLY COOLER ON THE 00Z ECMWF...SUCH THAT... WITH SHOWERY CONDITIONS IN A MOIST AIR MASS AND A SOUTHWEST FLOW ALOFT...HIGH TEMPERATURES COULD POSSIBLY REACH THE 60S THROUGHOUT CENTRAL NORTH CAROLINA WITH SOME TEMPERATURES PUSHING 70F ESPECIALLY OVER PARTS OF THE SANDHILLS AND SOUTHERN COASTAL PLAIN. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... AS OF 640 AM THURSDAY... PRIMARY AVIATION CONCERNS NEXT 24 HRS: IFR CIGS TRENDING TO MVFR THIS MORNING... LASTING THROUGH 00Z-03Z THU (THIS EVENING)... AND MAINLY IFR VSBYS WITHIN WINTRY PRECIP THROUGH 13Z-15Z. POOR AVIATION CONDITIONS WILL PERSIST THROUGH MUCH OF THE DAY. PRESSURE SYSTEM NOW OFF THE SC COAST WILL TRACK NE THROUGH MID MORNING... REACHING JUST OFF CAPE HATTERAS AROUND 13Z... THEN CONTINUING NORTHEAST AWAY FROM THE NC COAST THROUGH THE AFTERNOON. BANDS OF MOSTLY WINTRY PRECIP (MAINLY SNOW AT INT/GSO/RDU/RWI AND MAINLY RAIN AT FAY) WILL TAPER DOWN TO FREEZING DRIZZLE BEFORE ENDING FROM SW TO NE THIS MORNING... 14Z-16Z AT INT/GSO TRENDING TO 16Z-18Z AT RWI. CIGS ARE EXPECTED TO BE MVFR AT ALL SITES UNTIL EARLY THIS EVENING... WHEN CIGS SHOULD RISE TO VFR. BUT UNCERTAINTY GROWS LATE TONIGHT AS WE KEEP VERY HIGH MOISTURE (HIGH RH VALUES) NEAR THE GROUND... SUGGESTING THAT AS WINDS GO LIGHT/VARIABLE WE`LL SEE DEVELOPMENT OF LOW STRATUS AND/OR SUB-VFR FOG OVERNIGHT. RUNWAYS ESPECIALLY AT INT/GSO/RDU/RWI ARE LIKELY TO REMAIN TREACHEROUS THROUGH AND BEYOND THE TAF VALID PERIOD. LOOKING BEYOND 12Z EARLY FRI MORNING: MVFR CIGS ARE EXPECTED THROUGH FRI... THEN CONDITIONS SHOULD TREND TO VFR FRI NIGHT... EXCEPT AT GSO/INT WHERE REDEVELOPMENT OF SUB-VFR CIGS IS EXPECTED WITH AN EASTERLY WIND AS CHILLY HIGH PRESSURE NOSES INTO CENTRAL NC FROM THE NORTH. OTHERWISE... VFR CONDITIONS SHOULD HOLD THROUGH SUNDAY... BUT ANOTHER STORM SYSTEM APPROACHING FROM THE WEST AND SOUTHWEST MAY BRING MORE IFR CONDITIONS AND PRECIP SUN NIGHT/MON. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL NOON EST TODAY FOR NCZ007>011- 021>028-038>043-073>078. WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ083>086- 088-089. && $$ SYNOPSIS...RAH NEAR TERM...BLAES SHORT TERM...BSD LONG TERM...DJF AVIATION...HARTFIELD

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