Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261142 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 640 AM EST THU FEB 26 2015 .SYNOPSIS...LOW PRESSURE WILL TRACK OFF OF THE NORTH CAROLINA COAST THIS MORNING. COLD CANADIAN HIGH PRESSURE WILL FOLLOW THE STORM FRIDAY INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 325 AM THURSDAY... ...MAJOR WINTER STORM WINDING DOWN... PLAN TO MAINTAIN WINTER STORM WARNING FOR A LARGE PART OF CENTRAL NC EARLY THIS MORNING AS MAJOR WINTER STORM GRADUALLY PULLS AWAY FROM OUR REGION. WILL ALSO MAINTAIN THE ADVISORY FOR THE FAR SOUTH AND SE COUNTIES AS TEMPS THERE WILL REMAIN CLOSE TO FREEZING WITH A SMALL POTENTIAL FOR A LIGHT ICE ACCRUAL ON EXPOSED OBJECTS. MAIN AXIS OF HEAVY WET SNOW HAS FALLEN FROM THE WESTERN PIEDMONT INTO THE NORTHERN PIEDMONT WITH AMOUNTS IN THE 6-8 INCH RANGE COMMON FROM ASHEBORO TO NORTH RALEIGH TO ROXBORO. 06Z GSO SOUNDING DEPICTS A DEEP ISOTHERMAL LAYER. WITH THIS TEMP PROFILE...EXPECT SNOW DURING PERIODS OF HEAVIER PRECIP INTENSITY AND A MIX OF SNOW/SLEET/FREEZING RAIN DURING LIGHTER PRECIP INTENSITY. THE DUAL POL CORRELATION COEFFICIENT PRODUCT (CC)WAS HELPFUL OVERNIGHT DEPICTING THE SNOW/MIX PHASED REGIONS VERY WELL. LATEST WATER VAPOR IMAGERY DEPICTS DRIER AIR ALOFT ADVANCING NEWD INTO CENTRAL NC. WITH LOSS OF MOISTURE IN THE FAVORED ICE NUCLEATION GROWTH ZONE...EXPECT CHARACTER OF PRECIP TO BECOME MORE RAIN/FREEZING RAIN VERSUS SNOW FOR MOST LOCATIONS EXCEPT FOR THE VA BORDER COUNTIES WHERE SNOW/SLEET MAY OCCUR UP TO OR JUST PAST DAYBREAK. THUS CURRENT RADAR TREND OF PRECIP BECOMING LIGHTER/SPOTTIER WILL CONTINUE THROUGH 12Z. AFTER 12Z...SHOULD SEE PRECIP DIMINISH/END FROM THE SW. WHILE NOT EXPECTING ICE ACCRUAL AMOUNTS OF ANY SIGNIFICANCE...WHAT ICE THAT DOES ACCRUAL COUPLED WITH HEAVY WET SNOW WILL LIKELY LEAD TO MORE POWER OUTAGES (PER DUKE PROGRESS ENERGY ALREADY OVER 50000 WITHOUT POWER IN THE RALEIGH-DURHAM AREA). EXPECT BULK OF LIGHT PRECIP TO DIMINISH/END IN THE 14Z-17Z TIME FRAME WITH MOSTLY CLOUDY TO OVERCAST SKIES TO PERSIST THROUGH THE REST OF THE DAY. AFTERNOON TEMPS SHOULD RECOVER 3-4 DEGREES FROM CURRENT LEVELS...WHICH WILL ALLOW FOR SOME MELTING. THIS MELTING WILL LIKELY RE-FREEZE LATE TONIGHT LEADING TO WIDESPREAD BLACK ICE CONDITIONS. ONCE CURRENT SET OF ADVISORY/WARNING EXPIRES...ANOTHER ADVISORY FOR BLACK ICE MAY BE NECESSARY FOR LATE TONIGHT-EARLY FRI MORNING. MIN TEMPS OVERNIGHT 20- 25. && .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/...
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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
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&& .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...BADGETT NEAR TERM...WSS SHORT TERM...BSD LONG TERM...DJF AVIATION...HARTFIELD

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