Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281134 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 635 AM EST FRI NOV 28 2014 .SYNOPSIS...HIGH PRESSURE WILL BUILD OVER THE REGION FROM THE WEST TODAY...AND SETTLE OVERHEAD TONIGHT AND SATURDAY. THE HIGH WILL DRIFT OFFSHORE BY SUNDAY RESULTING IN A WARM SOUTHWEST FLOW OVER OUR AREA. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 AM FRIDAY... TODAY...LOW LEVEL CAA AS HIGH PRESSURE CENTERED OVER THE LOWER OH VALLEY/LOWER GREAT LAKES SLOWLY DRIFTS SEWD. 850MB THERMAL TROUGH OVER THE REGION EVENTUALLY LIFTS NORTH-NE AWAY FROM OUR REGION LATE IN THE DAY. LOW LEVEL THICKNESSES SUGGEST MAX TEMPS A SOLID 10-15 DEGREES BELOW NORMAL. THIS YIELDS MAX TEMPS IN THE LOW-MID 40S...FAIRLY COMPARABLE TO MOS GUIDANCE NUMBERS. NW FLOW ALOFT HAS SUFFICIENT STRENGTH/PROPER ORIENTATION TO SUPPORT THE FORMATION OF OROGRAPHICALLY INDUCED CLOUDINESS. WATER VAPOR IMAGERY DOES DEPICT ADEQUATE MOISTURE UPSTREAM. HOWEVER MODEL RH CROSS SECTIONS DO NOT SUGGEST MUCH IN THE MANNER OF CLOUDS IN THE MID-UPPER LEVELS LATER THIS MORNING THROUGH THE AFTERNOON. FOR NOW...WILL ADJUST SKY COVERAGE TO GO MORE PESSIMISTIC (PARTLY CLOUDY VERSUS SUNNY). IF VEIL OF CLOUDS THICKER THAN CURRENTLY ANTICIPATED...THIS MAY LIMIT SUNSHINE ENOUGH TO CAUSE MAX TEMPS TO BE 3-4 DEGREES COLDER THAN CURRENTLY FORECAST. TONIGHT...LOW LEVELS WILL REMAIN DRY AND COOL AS SURFACE HIGH WILL BE OVERHEAD. ALOFT...PATCHY CLOUDINESS MAY DRIFT OVERHEAD AS A SERIES OF WEAK PERTURBATIONS CROSS THE REGION. GFS MORE AGGRESSIVE WITH THE CLOUDINESS VERSUS THE NAM/CANADIAN/ECMWF. WILL TREND SKY COVERAGE TO PARTLY CLOUDY. CHILLY WITH MIN TEMPS IN THE MID-UPPER 20S. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 300 AM FRIDAY... SATURDAY AND SATURDAY NIGHT...AIR MASS MODIFICATION GETS UNDERWAY AS SURFACE HIGH DRIFTS EAST AND 850MB FLOW BECOMES SWLY. THICKNESSES RESPOND BY RECOVERING INTO THE 1330-1334M RANGE...SLIGHTLY BELOW NORMAL. ASIDE FROM BRIEF PERIODS OF MID-LEVEL CLOUDINESS...EXPECT MOSTLY SUNNY SKIES SATURDAY AND CLEAR SKIES SATURDAY NIGHT. HIGH TEMPS LOW-MID 50S WHILE MIN TEMPS SATURDAY NIGHT IN THE LOW-MID 30S. && .LONG TERM /SUNDAY THROUGH THURSDAY/...
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AS OF 315 AM FRIDAY... SUNDAY THROUGH MONDAY: SEASONABLY WARM AND DRY CONDITIONS ARE EXPECTED FOR SUNDAY INTO MONDAY... WITH SURFACE HIGH PRESSURE OFF THE SOUTHEAST U.S. COAST AND A MID LEVEL RIDGE CENTERED TO THE SOUTH OF THE AREA... NEAR FL/OFF THE SOUTHEAST U.S. COAST. MOSTLY SUNNY/MOSTLY CLEAR CONDITIONS ARE EXPECTED DURING THIS TIME FRAME... OUTSIDE OF POSSIBLY SOME PRE-DAWN FOG AND/OR MORNING STRATUS ON MONDAY MORNING. A COLD FRONT WILL APPROACH THE AREA LATE IN THE DAY ON MONDAY FROM THE NORTH-NORTHWEST. HOWEVER... ANY CLOUD COVER ASSOCIATED WITH THE APPROACHING FRONT WILL GENERALLY HOLD OFF UNTIL VERY LATE IN THE DAY/EVENING... AS THERE WILL BE VERY LITTLE MOISTURE RETURN IN ADVANCE OF THE FRONT... WITH GENERALLY WESTERLY FLOW PRECEDING THE FRONT. TEMPS ON SUNDAY WILL CONTINUE THE WARMING TREND... WITH HIGHS EXPECTED TO BE IN THE 60S. A SIMILAR TREND WILL FOLLOW ON MONDAY. HOWEVER... GFS BUFR SOUNDINGS CONTINUE TO INDICATE A RATHER SHALLOW MIXED LAYER. THUS... POSSIBLY NOT REALIZING FULL SUN HIGHS WITH THE LOCAL THICKNESS SCHEME (ALSO THE CASE FOR SUNDAY`S HIGHS). NONETHELESS... WE STILL EXPECT TO SEE TEMPS CLIMB INTO THE MID TO UPPER 60S... WITH SOME LOW 70S SOUTH. LOW TEMPS ON MONDAY MORNING ARE EXPECTED TO BE IN THE 40S. MONDAY NIGHT THROUGH THURSDAY: THE AFOREMENTIONED COLD FRONT WILL SINK SOUTHWARD THROUGH THE AREA... PROPELLED BY A 1040+ MB SURFACE HIGH TO THE NORTH/NORTHWEST. MODELS CONTINUE TO INDICATE THE POTENTIAL FOR SOME PRECIP TO DEVELOP BEHIND THE FRONT WITH A DAMMING AIRMASS DEVELOPING. THE GFS CONTINUE TO BE FURTHER SOUTH WITH ITS INITIAL PLACEMENT OF THE SURFACE HIGH TO THE NORTH OF THE AREA VS THE ECMWF (GFS... CENTERED OVER NEW ENGLAND BY TUESDAY). EITHER WAY THIS WILL BUT AN ABRUPT END TO THE WARMTH. IN FACT... TEMPS MAY STRUGGLE TO REACH 40 ON TUESDAY IN THE NORTHWEST PIEDMONT AFTER EARLY TUESDAY MORNING (COULD SEE AN EARLY MORNING HIGH TEMP ON TUESDAY... DEPENDING ON HOW FAST SOME LIGHT PRECIP DEVELOPS). FOR NOW WILL GO RATHER CONSERVATIVE AND JUST LOWER TEMPS TO THE COLD SIDE OF STATISTICAL GUIDANCE (TOWARDS THE GFS STATISTICAL GUIDANCE). WHILE IT DOESNT LOOK LIKE WE WILL SEE A LOT OF PRECIP WITH THIS SYSTEM... WE WILL NEED TO KEEP AND EYE ON THE PARTIAL THICKNESS VALUES... AS THE LATEST GFS IS INDICATING THE POTENTIAL FOR SOME FREEZING RAIN/FREEZING DRIZZLE ACROSS THE NORTHWEST PIEDMONT ON TUESDAY MORNING... WITH ANY LINGERING FREEZING RAIN THREAT ENDING BY AT LEAST TUESDAY AFTERNOON AS THE SURFACE HIGH BEGINS TO SHIFT OFFSHORE... ENDING/WEAKENING THE NEEDED SUPPLY OF COLD DRY AIR TO OFFSET THE LATENT HEAT RELEASE CREATED BY PHASE CHANGE. WE ARE STILL A WAYS OUT IN THE FORECAST THOUGH... SO WILL KEEP EVERYTHING LIQUID FOR NOW AND TEMPS ABOVE FREEZING (WHICH IS WHAT THE LATEST ECMWF HAS... A COLD RAIN). LOWS TUESDAY MORNING FOR NOW IN THE MID 30S N/NW TO LOWER 40S SE. HIGHS TUESDAY... *FOR NOW*... RANGING FROM THE LOWER 40S NW TO LOWER TO MID 50S SE. THE STRONG SURFACE HIGH WILL QUICKLY SHIFT EASTWARD OFF THE NORTHEAST U.S. COAST/SOUTHEAST CANADIAN COAST ON TUESDAY NIGHT/WEDNESDAY MORNING AS THE NEXT SYSTEM QUICKLY APPROACHES FROM THE WEST. NOT SURE HOW MUCH WE WILL SEE THE CAD AIRMASS ERODE BEFORE IT IS SCOURED OUT WITH THE PA1SSAGE OF A COLD FRONT ON WEDNESDAY NIGHT. FOR NOW WILL ONLY LOWER TEMPS SLIGHTLY AND SHOW HIGHS RANGING FROM AROUND 50 NW TO LOWER 60S SE ON WEDNESDAY. THE THREAT FOR ANY PRECIP WILL END WITH THE FRONTAL PASSAGE... WITH SURFACE HIGH PRESSURE BUILDING INTO THE AREA FROM THE NORTHWEST. LOWS WEDNESDAY MORNING WILL DRIVEN BY THE CAD... LOWS WILL LIKELY OCCUR EARLY ON IN THE OVERNIGHT PERIOD... WITH SLOWLY RISING OR NEAR STEADY TEMPS. FOR NOW WILL NOT SHOW THIS MUCH DETAIL IN THE FORECAST THIS FAR OUT THOUGH. WILL SHOW LOWS IN THE 30S TO LOWER 40S FOR NOW... WITH A USUAL DIURNAL TREND. LOWS THURSDAY MORNING BEHIND THE COLD FRONT ARE EXPECTED TO BE IN THE UPPER 30S TO LOWER 40S. WITH A RETURN TO AT LEAST PARTLY SUNNY SKIES FOR 1THURSDAY. EXPECT HIGHS WILL BE IN THE 50S.
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&& .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 635 AM FRIDAY... HIGH PRESSURE BUILDING INTO THEN SETTLING OVER THE CAROLINAS THROUGH SATURDAY WILL PROVIDE VFR CONDITIONS. THE HIGH WILL DRIFT OFFSHORE SATURDAY NIGHT INTO SUNDAY. THE RESULTANT SLY FLOW WILL ADVECT LOW LEVEL MOISTURE...INCREASING THE PROBABILITY FOR PATCHES OF MVFR/IFR FOG SUNDAY MORNING AND AGAIN MONDAY MORNING. A COLD FRONT WILL APPROACH FROM THE NORTHWEST MONDAY AND CROSS THE REGION MONDAY NIGHT. THIS WEATHER SYSTEM WILL INCREASE THE THREAT FOR MVFR CEILINGS AND AREAS OF RAIN MONDAY NIGHT INTO TUESDAY.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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