804
FXUS62 KRAH 151945
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
245 PM EST SUN DEC 15 2024
SYNOPSIS
HIGH PRESSURE AND ASSOCIATED COLD AIR DAMMING WILL EXTEND ACROSS THE
PIEDMONT OF THE CAROLINAS, WHILE GRADUALLY WEAKENING, THROUGH
TUESDAY. A SERIES OF COLD FRONTS WILL PROGRESS ACROSS THE REGION
WEDNESDAY NIGHT THROUGH SATURDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 205 PM SUNDAY...
* LIGHT RAIN WILL MOVE ACROSS THE NORTHERN PIEDMONT AND COASTAL
PLAIN THROUGH TONIGHT.
* AREAS OF FOG, POTENTIALLY DENSE DEVELOPING BY MON MORNING.
REGIONAL SATELLITE IMAGERY AND SURFACE OBSERVATIONS SHOW THE
EXPECTED CAD REGIME TACKING SHAPE OVER THE WESTERN PIEDMONT WHERE
LOW OVERCAST AND TEMPERATURES HAVE ONLY MANAGED TO REACH INTO THE
LOW 40S TO UPPER 30S THIS AFTERNOON. ELSEWHERE, MID/HIGH LEVEL
CLOUDS HAVE MOVED EAST AND HAVE RESULTING IN PARTLY CLOUDY SKIES
ACROSS THE EASTERN PIEDMONT AND COASTAL PLAIN. THIS HAS SUPPORTED
TEMPERATURES RISING INTO THE 50S TO LOW 60S, CREATING A 20 DEGREE
TEMPERATURE GRADIENT ACROSS CENTRAL NC.
REGIONAL RADAR IMAGERY HAS SHOWN WAVES OF LIGHT RAIN AND MOSTLY
DRIZZLE OVER THE NORTHWEST PIEDMONT, SUPPORTING THE CLASSICAL CAD
DEVELOPMENT. ONLY TRACE AMOUNTS TO A HUNDREDTH OR TWO HAVE BEEN
MEASURED SO FAR, BUT A MORE PERSISTENT AREA OF RAIN LOCATED OVER
UPSTATE SC AND SOUTHERN APPALACHIANS IS FORECAST TO MOVE ENE AND INTO
THE AREA LATER THIS AFTERNOON. ISENTROPIC ANALYSIS FROM THE RAP
SHOWS THAT IN THE ABSENCES OF MID/UPPER LEVEL FORCING, THIS AREA OF
RAIN WILL BE SUPPORTED BY MOIST ISENTROPIC UPGLIDE FROM THE 280 TO
295K SURFACE. THE ASCENT IS NOT PARTICULARLY STRONG, SO MOSTLY LIGHT
AMOUNTS ARE EXPECTED WITH UP TO 0.2 OF AN INCH IN THE TRIAD TO
SEVERAL HUNDREDTHS AROUND THE TRIANGLE. LOCATIONS SOUTH AND EAST OF
MAY SEE A FEW SPRINKLES, BUT WILL LARGELY REMAIN DRY.
A SOUTHEASTWARD EXPANSION IN THE CAD REGIME, FEATURING LOW OVERCAST
AND PATCHY FOG, IS EXPECTED THROUGHOUT THE NIGHT AS NOCTURNAL COOLING
BEGINS AFTER SUNSET AND BOUNDARY LAYER MOISTURE INCREASES. AHEAD OF
THE CAD BOUNDARY, CALM SURFACE CONDITIONS AND INCREASED BOUNDARY
LAYER MOISTURE WITH DEW POINTS IN THE MID/UPPER 40S MAY SUPPORT AN
AREA OF FOG, POTENTIALLY DENSE, WITH GREATEST RISK IN THE COASTAL
PLAIN INTO THE EASTERN SANDHILLS. OVERNIGHT LOWS WILL SETTLE INTO
THE UPPER 30S TO UPPER 40S, ONLY DROPPING 2-4 DEGREES IN THE NW
PIEDMONT FROM THEIR AFTERNOON HIGH.
SHORT TERM /MONDAY AND MONDAY NIGHT/
AS OF 200 PM PM SUNDAY...
UPPER LEVEL LOW OVER THE NORTHEAST EARLY MONDAY MORNING WILL SHIFT
OFFSHORE FOLLOWED BY UPPER LEVEL RIDGE BUILDING OVER THE EASTERN US
THROUGH THE DAY. MONDAY MORNING WILL START OUT WITH PATCHY FOG AND
SOME ISOLATED SHOWERS ACROSS THE NORTHERN PIEDMONT BEFORE THE CAD
ERODES THROUGH MID/LATE MORNING. WHILE MUCH OF THE DAY WILL BE DRY,
SKIES ARE EXPECTED TO BE MOSTLY CLOUDY AS AN APPROACHING COLD FRONT
MOVES IN FROM THE WEST. ANOTHER ROUND OF MOISTURE WILL MOVE THROUGH
PORTIONS OF THE NORTHERN PIEDMONT (ESPECIALLY THE NORTHWESTERN
AREAS) WITH SOME ISOLATED SHOWERS IN THE EVENING AND OVERNIGHT HOURS
AS A COLD FRONT MOVES THROUGH THE REGION. NOT MUCH MOISTURE WILL BE
AVAILABLE ON THE EAST SIDE OF THE MOUNTAINS SO LIMITED POPS TO LOW
END SLIGHT CHANCE. HIGH TEMPERATURES WILL RANGE FROM MID 50S NW TO
MID/UPPER 60S SE. AS THE COLD FRONT MOVES THROUGH MONDAY NIGHT, LOW
TEMPERATURES WILL RANGE FROM THE MID/UPPER 40S TO LOW 50S.
LONG TERM /TUESDAY THROUGH SUNDAY/
AS OF 245 PM SUNDAY...
A SURFACE LOW IS EXPECTED TO MOVE ACROSS THE OHIO VALLEY ON TUESDAY
AND WEDNESDAY BEFORE EXITING THE MID-ATLANTIC COAST ON THURSDAY. THE
GFS MOVES THIS LOW FASTER WITH A MORE NORTHERLY TRACK, VERSUS THE
ECMWF WHICH KEEPS THE LOW FURTHER TO THE SOUTH. GENERALLY, MODELS
AGREE THAT THE ASSOCIATED COLD FRONT WILL MOVE THROUGH CENTRAL NC
LATE WEDNESDAY NIGHT/EARLY THURSDAY MORNING. THE FRONT WILL BRING A
CHANCE OF RAIN BEGINNING EARLY WEDNESDAY BEFORE CLEARING THE REGION
THURSDAY. AFTER THIS, HIGH PRESSURE WILL BUILD BACK IN LEAVING THE
REST OF THE FORECAST COOL AND DRY.
MAXIMUM TEMPERATURES ON TUESDAY AND WEDNESDAY SHOULD WARM INTO THE
MID-60S TO LOW-70S. AFTER THE COLD FRONT MOVES THROUGH EARLY
THURSDAY, HIGH TEMPERATURES WILL BE IN THE 50S THURSDAY AND FRIDAY.
WEEKEND TEMPERATURES WILL BE CHILLY WITH HIGHS IN THE MID TO UPPER
40S ON SATURDAY AND UPPER 30S TO LOW 40S ON SUNDAY. LOW TEMPERATURES
WILL COOL EACH NIGHT, GOING FROM LOW 50S TUESDAY NIGHT TO UPPER
TEENS BY SUNDAY NIGHT.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
AS OF 100 PM SUNDAY...
IFR CIGS IN THE NC FOOTHILLS HAVE BRIEFLY LEAKED INTO INT WITH MVFR
CIGS FROM GSO TO JUST WEST OF RDU AND VFR ELSEWHERE. CIGS IN THE
TRIAD MAY BOUNCE AROUND FROM THEIR STARTING 18Z OBS, BUT AS AN AREA
OF RAIN OVER UPSTATE SC MOVES NE THROUGH THE AFTERNOON, CIGS WILL
LOWER TO IFR. AFTER SUNSET, NOCTURNAL COOLING AND INCREASING
BOUNDARY LAYER HUMIDITY WILL SUPPORT IFR CIGS TO OOZE EASTWARD AND
LOWER TO LIFR IN MOST LOCATIONS. SOME AIRPORT MINIMUMS MAY BE
REACHED BY MON MORNING AS CIGS LOWER AND BEGIN TO REDUCE VSBY AT THE
SURFACE. GRADUAL IMPROVEMENT THROUGH MON MORNING TO VFR AT RWI/FAY
FIRST AND PERHAPS RDU, BUT THE TRIAD TERMINALS WILL LIKELY REMAIN
BELOW ALTERNATE MINIMUMS (< 600 FT) THROUGH THE TAF PERIOD.
OUTLOOK: FLIGHT RESTRICTIONS AT INT/GSO WILL LIKELY FLUCTUATE
BETWEEN IFR-MVFR BY DAY AND LIFR-IFR BY NIGHT THROUGH WEDNESDAY
MORNING, AS COLD AIR DAMMING HOLDS OVER THE NW NC PIEDMONT.
MEANWHILE TO THE EAST, FLIGHT RESTRICTIONS ARE LIKELY TO BE CONFINED
MAINLY TO THE LATE NIGHT-MORNING HOURS. LOW-LEVEL WIND SHEAR WILL
ALSO BE POSSIBLE OVER THE PIEDMONT MON NIGHT. THE NEXT EXTENDED
PERIOD OF VFR CONDITIONS THROUGHOUT CNTL NC LIKELY WILL NOT BEGIN
UNTIL ANOTHER FRONTAL SYSTEM MOVES ACROSS THE REGION, WITH FOLLOWING
DRY AIR, WED NIGHT-THU.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...MWS
NEAR TERM...SWIGGETT
SHORT TERM...CA
LONG TERM...HELOCK
AVIATION...SWIGGETT/MWS
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