Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 010638 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 235 AM EDT WED OCT 01 2014 .SYNOPSIS...WEAK HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH TODAY THROUGH THURSDAY. A COLD FRONT WILL APPROACH FROM THE WEST LATE FRIDAY... AND SWEEP EAST THROUGH THE AREA FRIDAY NIGHT INTO SATURDAY MORNING. COOL HIGH PRESSURE WILL PUSH IN FROM THE WEST SATURDAY AFTERNOON THROUGH SUNDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 235 AM WEDNESDAY... FOR TODAY: AS WAS THE CASE LAST NIGHT... THE MOST IMMEDIATE CONCERN IS THE DEVELOPMENT OF DENSE FOG EARLY THIS MORNING... FOSTERED BY CLEAR SKIES AND CALM WINDS. THUS FAR THE LOWEST VSBYS HAVE BEEN OVER NORTHERN SECTIONS OF THE FORECAST AREA. RECENT HRRR MODEL RUNS SHOW THIS FOG/STRATUS SPREADING OVER NEARLY THE ENTIRE FORECAST AREA OVER THE NEXT COUPLE OF HOURS... AND NOT IMPROVING UNTIL THE 14Z-16Z TIME FRAME... REASONABLE CONSIDERING THE SLOW DISPERSION SEEN YESTERDAY. A DENSE FOG ADVISORY WILL LIKELY BE NEEDED FOR A LARGE CHUNK OF CENTRAL NC THROUGH MID MORNING. WE SHOULD ALSO SEE POCKETS OF VERY LIGHT MIST WITHIN THE MORE DENSE FOG. THE DISSOLUTION OF THE FOG/STRATUS WILL POST THE NEXT CHALLENGE... GIVEN YESTERDAY`S SLOW IMPROVEMENT... AND WILL FOLLOW PERSISTENCE AS WELL AS THE HRRR TRENDS AND SHOW SLOWLY INCREASING SUNSHINE DURING THE LATE MORNING AND EARLY AFTERNOON... WITH THE SUN BREAKING THROUGH LAST OVER THE NORTHERN TIER. EXPECT A FEW HIGH THIN CLOUDS TO SPREAD OVER THE AREA LATE THIS AFTERNOON. THESE CLOUDS... NOTED ON IR AND WATER VAPOR IMAGERY... NOW EXTEND OVER TN INTO THE LOWER MISS VALLEY AND ARE ASSOCIATED WITH A WEAK WAVE UNDERCUTTING THE WEAK MID LEVEL RIDGE BUILDING IN FROM THE WEST. OVERALL... THIS EQUATES TO A TREND FROM DAYBREAK FOG/STRATUS TO PARTLY THEN MOSTLY SUNNY SKIES. THICKNESSES ARE 5-10 M HIGHER THAN NORMAL... SO EXPECT HIGHS FROM THE UPPER 70S TO NEAR 80 OVER PIEDMONT (WHERE CLOUDS SHOULD LINGER THE LONGEST) TO THE LOWER 80S ELSEWHERE. FOR TONIGHT: MOSTLY CLEAR SKIES IN THE EVENING SHOULD GIVE WAY TO ANOTHER ROUND OF PATCHY FOG/STRATUS... LIKELY LESS WIDESPREAD AND LESS DENSE THAN THIS MORNING OR YESTERDAY. IN ADDITION TO THE FEW HIGH CLOUDS PASSING OVERHEAD... NAM/GFS BUFR SOUNDINGS INDICATE A SHOT OF MOISTURE IN THE 925-700 MB LAYER ASSOCIATED WITH SUBTLE MASS CONVERGENCE ALONG A WEAK LOW-MID LEVEL RETREATING WARM FRONT. THE NAM IS MUCH MORE BULLISH WITH SUCH CLOUDS THAN THE GFS... SO SOME UNCERTAINTY REGARDING EXTENT AND COVERAGE REMAINS. BUT IF THESE CLOUDS COME TO PASS... THEY WOULD MITIGATE FOG DEVELOPMENT TONIGHT. WILL REFRAIN FROM INCLUDING FOG IN THE FORECAST FOR NOW... AS IT COULD SIMPLY BE LIGHT FOG. WILL SHOW A TREND TO PARTLY CLOUDY SKIES TONIGHT ESPECIALLY ACROSS THE NORTH AND NE. MILD LOWS OF 58-62. -GIH
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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AS OF 235 PM TUESDAY... THURSDAY AND THURSDAY NIGHT: SYNOPTIC SCALE SUBSIDENCE WILL PREVAIL ACROSS CENTRAL NC ON THURSDAY AS HEIGHTS INCREASE OVER THE AREA...DOWNSTREAM OF THE SOUTHERN STREAM TROUGH EJECTING EASTWARD OUT OF THE CENTRAL/SOUTHERN ROCKIES...PROGRESSING EASTWARD INTO THE SOUTHERN PLAINS/LOWER MS VALLEY THURSDAY NIGHT. IF CURRENT TIMING HOLDS UP...IT SHOULD REMAIN DRY THROUGH THURSDAY NIGHT AS GFS BUFR SOUNDINGS REMAIN STRONGLY CAPPED ALOFT...WITH STRENGTHENING SOUTHERLY RETURN FLOW LEADING TO AN INCREASE IN CLOUDS FROM WEST- EAST. HIGHS 80 TO 85. LOWS IN THE LOWER TO MID 60S. FRIDAY AND FRIDAY NIGHT: MODELS INDICATE PHASING NORTHERN STREAM AND SOUTHERN STREAM TROUGHS ACROSS THE UPPER MS VALLEY/UPR MIDWEST AND INTO THE GREAT LAKES FRIDAY AND FRIDAY NIGHT. MODELS ARE IN REALLY GOOD AGREEMENT WITH THE TIMING OF THE ACCOMPANYING COLD FRONT PASSAGE INTO THE AREA LATE FRIDAY AFTERNOON/FRIDAY EVENING...EXITING EASTERN PORTIONS OF THE FORECAST AREA BY DAYBREAK SATURDAY. THE LEAD SOUTHERN STREAM WAVE OVER THE LOWER MS VALLEY/TN VALLEY FRIDAY MORNING REALLY SHEARS OUT/DAMPENS AS IT LIFTS NORTHWARD INTO MID- ATLANTIC REGION FRIDAY EVENING/NIGHT...RESULTING IN WEAK UPPER LEVEL SUPPORT WITH EASTWARD ADVANCING 30-35KT SWLY LLJ FOCUSING STRONG MOISTURE TRANSPORT AND LOW-LEVEL CONVERGENCE WITHIN A BAND OF CONVECTION ALONG THE FRONT. LATE DIURNAL TIMING AND MODEST LAPSE RATES ALOFT WILL RESULT IN LIMITED/WEAK INSTABILITY(200-400 MUCAPE)...THWARTING ANY SEVERE THREAT. HAVE INCREASED POPS TO LIKELY ACROSS THE FORECAST AREA FRIDAY NIGHT...DECREASING WEST TO EAST DURING THE PREDAWN HOURS AS FRONT MOVES EASTWARD TOWARDS THE COAST. PROGRESSIVE NATURE OF SYSTEM WILL LIMIT RAINFALL AMOUNTS...WITH AVERAGE QPF AMOUNTS OF A 0.25-0.50". MAX TEMPS FRIDAY AFTERNOON WILL DEPEND ON ARRIVAL/ONSET OF SHOWERS/CONVECTION...ESPECIALLY IN THE WEST. UNDER THICKENING CLOUD COVER...A BIT COOLER THAN THURSDAY RANGING FROM MID 70S WEST TO LOWER 80S EAST. MIN TEMPS WILL DEPEND ON WEST-EAST TIMING OF FROPA FRIDAY NIGHT THROUGH THE AREA...RANGING FROM LOWER/MID 50S NORTHWEST TO LOWER/MID 60S SE.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 235 PM TUESDAY... IN THE WAKE OF THE FRONTAL PASSAGE SATURDAY MORNING...DRY CONDITIONS WILL PREVAIL THROUGH EARLY NEXT WEEK AS SFC HIGH PRESSURE OVER THE SOUTHERN PLAINS/LOWER MS VALLEY BUILDS EAST THROUGH THE PERIOD...SHIFTING EAST OFF THE SOUTHEAST COAST ON MONDAY. AFTER A CHILLY SATURDAY NIGHT/SUNDAY MORNING IN WHICH FAVORABLE RADIATIONAL CONDITIONS WILL HELP SUPPORT MIN TEMPS IN THE MID TO UPPER 40S ACROSS A LARGE PORTION OF THE FORECAST AREA...TEMPERATURES WILL MODERATE TO NEAR NORMAL BY MONDAY. TIMING/MAGNITUDE OF THE NEXT SYSTEM STILL IN QUESTION AS NORTHERN STREAM ENERGY ROTATING SOUTHEASTWARD THROUGH THE BASE OF THE AMPLIFIED TROUGH LOOKS TO IMPACT THE REGION LATE MONDAY-TUESDAY TIME FRAME. UNTIL MODEL DISCREPANCIES CAN BE IRONED OUT WITH THIS CLIPPER- LIKE TROUGH...WILL INDICATE CONSERVATIVE/SLIGHT CHANCE POPS...ESPECIALLY GIVEN POTENTIAL FOR LIMITED MOISTURE AVAILABILITY. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 125 AM WEDNESDAY... CHANCES ARE GOOD FOR IFR/LIFR CONDITIONS AT RDU/RWI/FAY UNTIL MID MORNING. THE COMBINATION OF MOSTLY CLEAR SKIES AND CALM WINDS HAS PROMPTED FORMATION OF AREAS OF FOG... DENSE IN SPOTS. THIS FOG IS EXPECTED TO FILL IN ACROSS MUCH OF CENTRAL AND ERN NC OVER THE NEXT FEW HOURS... HOLDING THROUGH 14Z OR 15Z BEFORE SLOWLY DISPERSING. THERE IS MUCH MORE UNCERTAINTY AT INT/GSO... WHERE FOG IS CURRENTLY LIGHT/PATCHY... AND HIGH-RES MODEL OUTPUT PLACES THE WESTERN EDGE OF THE FOG/STRATUS JUST EAST OF THE TRIAD AREA. WILL HAVE SCTD LOW STRATUS AND LIGHTER FOG AT INT/GSO... WHILE AT RDU/RWI/FAY... WILL INDICATE LIFR CIGS/VSBYS UNTIL 14Z/15Z. AFTER THIS TIME... EXPECT A TREND TO VFR CONDITIONS AT ALL CENTRAL NC TAF SITES THROUGH THE REST OF TODAY... AS WEAK HIGH PRESSURE EXTENDS OVER THE REGION. RENEWED FOG DEVELOPMENT IS EXPECTED TOWARD THE END OF THE TAF VALID PERIOD (06Z THU). SURFACE WINDS WILL STAY LIGHT/VARIABLE. LOOKING BEYOND 06Z EARLY THU MORNING... MVFR OR IFR VSBYS IN FOG MAY DEVELOP ONCE AGAIN AND AFFECT CENTRAL NC TERMINALS FROM 08Z-13Z THU MORNING. OTHERWISE... EXPECT VFR CONDITIONS THU. A FEW SPRINKLES OR SHOWERS ARE POSSIBLE MAINLY AT RWI/FAY THU AFTERNOON/EVENING... BUT SUB-VFR CONDITIONS ARE NOT EXPECTED. PATCHY FOG MAY AGAIN DEVELOP EARLY FRI MORNING. A STRONG FRONTAL SYSTEM WILL BRING INCREASING SURFACE WINDS FROM THE SW AND A GOOD CHANCE OF SUB-VFR CONDITIONS IN SHOWERS AND STORMS LATE FRI AFTERNOON THROUGH FRI NIGHT/EARLY SAT MORNING. VFR CONDITIONS SHOULD THEN RESUME SAT AFTERNOON... LASTING THROUGH SUNDAY. -GIH && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...CBL LONG TERM...CBL AVIATION...HARTFIELD

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