744
FXUS62 KCAE 150712
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
212 AM EST SUN DEC 15 2024
SYNOPSIS
WEAK COLD AIR DAMMING WILL DEVELOP TODAY, WITH BELOW AVERAGE
TEMPS EXPECTED. WELL ABOVE NORMAL TEMPS ARE EXPECTED MONDAY
THROUGH WEDNESDAY, WITH RAIN CHANCES INCREASING BY MID-WEEK AS
WELL. COLDER AIR RETURNS BY NEXT WEEKEND WITH A DEEP TROUGH
DIGGING INTO THE EASTERN US.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- COMPLEX SYNOPTIC SITUATION WITH A LARGE GRADIENT ACROSS THE
FORECAST AREA TODAY
RIDGE OF HIGH PRESSURE WILL BE ACROSS THE UPSTATE TODAY AS AN
UPPER LEVEL DISTURBANCE MOVES IN FROM THE WEST. THIS WILL
PRODUCE WEDGE CONDITIONS OVER THE WESTERN PORTIONS OF THE
FORECAST AREA WHILE THE CENTRAL AND EASTERN PORTIONS SEE MUCH
BETTER CONDITIONS. CURRENT REGIONAL WSR-88D IMAGERY SHOWS SOME
LIGHT RAIN DEVELOPING OVER THE UPSTATE HOWEVER THIS WILL BE
INTERACTING WITH THE SURFACE RIDGE AND MUCH OF THE RAIN PUSHING
NORTHEASTWARD. THROUGH DAYBREAK EXPECT A FEW SHOWERS TO DEVELOP
IN THE FAR WESTERN REACHES OF THE FORECAST AREA WHILE THE
REMAINDER OF THE AREA SEES MOSTLY CLOUDY SKIES.
SITUATION WILL BE SLOW TO CHANGE THROUGH THE DAY AS THE UPPER
LEVEL TROUGH SLIDES NORTHEASTWARD AND THE SURFACE RIDGE REMAINS
IN PLACE. WITH A BIT OF ISENTROPIC ASCENT OVER THE CENTRAL AND
WESTERN MIDLANDS EXPECT A FEW LIGHT SHOWERS MAINLY CONTAINED TO
THE WESTERN MIDLANDS AS DYNAMIC SUPPORT WILL REMAIN WELL
NORTHWEST OF THE AREA. THIS WILL KEEP THE WESTERN HALF OF THE
FORECAST AREA UNDER MOSTLY CLOUDY SKIES WITH DECREASING CLOUDS
IN THE EASTERN MIDLANDS AND SOUTHERN CSRA THROUGH THE AFTERNOON.
TEMPERATURES WILL FOLLOW A SIMILAR TREND WITH THE CLOUDS WITH A
SUBSTANTIAL GRADIENT FOR AFTERNOON HIGHS. EXPECT LOW 50S IN THE
WESTERN MIDLANDS AND NORTHERN CSRA WITH MID 50S ALONG THE I-20
CORRIDOR AND LOW 60S IN THE EASTERN MIDLANDS AND SOUTHERN CSRA.
CHANGE WILL BE SLOW THROUGH TONIGHT AS THE RIDGE OF HIGH
PRESSURE REMAINS ENTRENCHED OVER THE UPSTATE WHILE THE UPPER
LEVEL TROUGH PUSHES AWAY FROM THE REGION. THIS WILL KEEP MOSTLY
CLOUDY SKIES OVER THE WESTERN HALF OF THE FORECAST AREA WITH
DECREASING CLOUDS IN THE EAST. OVERNIGHT LOWS WILL BE IN THE LOW
TO MID 40S.
SHORT TERM /MONDAY THROUGH MONDAY NIGHT/
KEY MESSAGE(S):
- IMPROVING CONDITIONS FOR MONDAY
WEAK SURFACE RIDGING WILL RETURN AGAIN ON MONDAY. HEIGHTS WILL
QUICKLY RISE ALOFT THROUGHOUT THE DAY MONDAY AND WINDS ALOFT
WILL TURN OUT OF THE NORTHWEST AS THE SHORTWAVE RIDGE AXIS
APPROACHES. SOUTHERLY COMPONENT MOISTURE ADVECTION AT LOW LEVELS
HOWEVER WILL STRENGTHEN AS THE WEDGE IS ERODED AND DEW POINTS
WILL QUICKLY INCREASE BY MONDAY MORNING. PRECIP CHANCES ARE NEAR
ZERO HOWEVER WITH FAIRLY STRONG SUBSIDENCE ALOFT IN CONJUNCTION
WITH THE BUILDING HEIGHTS. TEMPS HOWEVER WILL CLIMB WELL ABOVE
AVERAGE, JUMPING INTO THE MID-60'S.
LONG TERM /TUESDAY THROUGH SATURDAY/
KEY MESSAGE(S):
- LITTLE CHANGE IN THE FORECAST THINKING FOR THE LONG TERM
PERIOD.
- AN ACTIVE WEATHER PATTERN IS EXPECTED WITH WARMER
TEMPERATURES THROUGH WEDNESDAY.
- RAIN CHANCES INCREASE ON WED/THUR, WITH COOLER TEMPS ARRIVING
FRI/SAT
COMPLEX AND ACTIVE FORECAST PERIOD ON TAP, WITH RAIN CHANCES
INCREASING ON WED/THUR FOLLOWED BY MUCH COOLER TEMPERATURES. HIGH
CONFIDENCE IN THE FORECAST THROUGH WEDNESDAY AS ENSEMBLE GUIDANCE IS
IN GOOD AGREEMENT. CLUSTER ANALYSIS SHOWS SIMILAR PROGRESSION OF
FEATURES AMONGST ALL CLUSTERS, WITH ABOVE NORMAL TEMPERATURES
FAVORED UNDER INCREASED RIDGING AND SOUTHWESTERLY FLOW AS OUR NEXT
WEATHER MAKER ORGANIZES ACROSS THE CENTRAL US. A WEAK FRONT IS
LIKELY TO APPROACH ON TUESDAY AS ANOTHER SHORTWAVE RACES INTO THE
NORTHEASTERN CONUS BUT PRECIP AGAIN REMAINS UNLIKELY WITH THIS
FEATURE. RIDGING IS EXPECTED TO CONTINUE HOLDING ON INTO WEDNESDAY,
WITH HIGHS BOTH DAYS IN THE 60S AND 70S BOTH DAYS. FROM THERE,
CONFIDENCE IN THE FORECAST DECREASES PRETTY SIGNIFICANTLY.
OPERATIONAL MODELS DIFFER PRETTY DRAMATICALLY IN TERMS OF SYNOPTIC
SCALE EVOLUTION, WITH ENSEMBLE CLUSTERS VERY DIFFERENT FROM ONE
ANOTHER AS WELL. THE PATTERN IS LIKELY TO BE MODULATED BY UPSTREAM
CHANGES FORCED BY AN INTENSE UPPER-LEVEL JET STREAK (180-200 KNOTS!)
OVER THE NORTH PACIFIC DURING THIS TIMEFRAME. THE MINOR CHANGES THAT
THIS INTRODUCES TO RIDGE/TROUGH PAIRINGS DOWNSTREAM WILL HAVE
IMPORTANT IMPACTS ON HOW THE PATTERN IMPACTS OUR SENSIBLE WEATHER.
THE GRANULAR PICTURE REVEALS AN ACTIVE PERIOD IN THE WED-FRI
TIMEFRAME, WITH RAIN LIKELY ONE OF WEDNESDAY OR THURSDAY. GUIDANCE
IS IN GOOD AGREEMENT THAT A PLUME OF ABOVE NORMAL PWS SHOULD REMAIN
ACCESSIBLE FOR THE DEVELOP LOW & FRONT TO INTERACT WITH AS THEY
APPROACH THE REGION IN THIS TIMEFRAME. SO RAIN IS PROBABLE IN THIS
TIMEFRAME, BUT TIMING, AMOUNTS, AND DURATION ARE HARD TO PIN DOWN AT
THIS POINT. THE EC DETERMINISTIC AND ENSEMBLE DOES SUGGEST
WEDNESDAY AS THE PRIMARY FRONTAL PASSAGE, AND CONSEQUENTLY,
DEVELOPS SIGNIFICANTLY MORE INSTABILITY. SO THE EC WOULD YIELD
A SMALL THUNDERSTORM THREAT WEDNESDAY AFTERNOON, BUT IT DOES
REMAIN A PRIMARY OUTLIER AT THIS TIME.
BEHIND THIS, COLDER TEMPERATURES ARE EXPECTED BY THE END
OF NEXT WEEK BUT MAY NOT BE AS COLD AS SOME GUIDANCE HAS SUGGESTED
THE PREVIOUS FEW DAYS. ENSEMBLE TELECONNECTIONS FORECAST A STRONGLY
POSITIVE PNA, NEUTRAL/POSITIVE NAO, AND NEUTRAL AAO WHICH DOES
SUGGEST A PROGRESSIVE PATTERN THAT MAY LEND TOWARDS SHOTS OF COLD
AIR BUT NOTHING COMPLETELY OUT OF THE ORDINARY. SO FOR NOW, WE WAIT
FOR GUIDANCE TO COME INTO BETTER AGREEMENT ON THE MID-LATE WEEK
WEATHER WHILE ALSO ACKNOWLEDGING THAT IT LOOKS PRETTY ACTIVE.
AVIATION /07Z SUNDAY THROUGH THURSDAY/
RESTRICTIONS EXPECTED THROUGH MIDDAY THEN IMPROVING.
RIDGE OF HIGH PRESSURE REMAINS CENTERED ACROSS THE UPSTATE WITH
NORTHEAST FLOW PERSISTING OVER THE TERMINALS. WITH MOIST LOW
LEVELS CIGS HAVE CONTINUE TO SLOWLY LOWER WITH ALL TAF SITES
CURRENTLY MVFR AND EXPECTED TO REMAIN SO THROUGH THE FIRST HALF
OF THE PERIOD. A MID LEVEL DISTURBANCE WILL BE MOVING NORTHWEST
OF THE AREA THROUGH THIS AFTERNOON AND AS IT MOVES AWAY THIS
AFTERNOON EXPECT IMPROVING CONDITIONS. BY 18Z EXPECT ALL SITES
TO BE VFR HOWEVER SCATTERED LOWER CLOUDS WILL LIKELY PERSIST
INTO THE LATE AFTERNOON HOURS. WINDS WILL BE NORTHEASTERLY AT 10
KNOTS OR LESS THROUGH THE DAY THEN DIMINISH TO LIGHT AND
VARIABLE WITH SUNSET.
EXTENDED AVIATION OUTLOOK...INCREASING POTENTIAL FOR SHOWERS,
POSSIBLE THUNDERSTORMS, AND ASSOCIATED RESTRICTIONS ON WEDNESDAY.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
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