422
FXUS62 KCAE 191800
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
100 PM EST THU DEC 19 2024
SYNOPSIS
THE END OF THIS WEEK LOOKS MOSTLY CLOUDY AND COOLER. A SECOND
FRONT CLEARS SKIES OUT LATE FRIDAY INTO FRIDAY NIGHT, FOLLOWED
BY SEVERAL DAYS OF COLD WEATHER WITH SUBFREEZING TEMPERATURES AT
NIGHT. A WARMING TREND IS EXPECTED TOWARDS CHRISTMAS ALONG WITH
THE NEXT CHANCE OF RAIN.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE(S):
- CONSIDERABLE CLOUDS AND COOLER TONIGHT.
SURFACE COLD FRONT HAS MOVED OFFSHORE, WITH LINGERING TROUGH TO
THE NORTHWEST ALONG THE SAVANNAH RIVER AREA. SATELLITE IS
SHOWING CONSIDERABLE LOW CLOUDS ACROSS THE REGION AND TEMPS
RANGING FROM THE MID 50S IN THE CLOUDY AREAS TO THE MID 60S IN
THE BREAKS IN THE OVERCAST., MAINLY IN THE SOUTHEAST MIDLANDS.
THIS IS BEING CAUSED BY WEAK MOISTURE FLUX OFF THE ATLANTIC AND
RESULTING SHALLOW ISENTROPIC LIFT. ALTHOUGH THE DEEPER MOISTURE
IS MOVING OUT OF THE REGION AS THE AMPLIFIED UPPER TROUGH TO THE
EAST, THE LOW CLOUDINESS IS LIKELY TO PERSIST THROUGH THE
OVERNIGHT HOURS. A CLIPPER SYSTEM IN THE UPPER MIDWEST THIS
AFTERNOON WILL DIVE SOUTHEAST TOWARD THE OHIO VALLEY. AS THE
UPPER TROUGH AMPLIFIES INTO THE SOUTHEAST CONUS LATE TONIGHT, A
SHORT WAVE TROUGH WILL BE APPROACHING FROM THE WEST. MOISTURE IS
QUITE SHALLOW, AND PRECIPITABLE VERY LOW, LESS THAN 0.6 INCH.
SOME OF THE CAMS SUGGEST A FEW WIDELY SCATTERED LIGHT SHOWERS
TOWARD DAYBREAK. KEPT A DRY FORECAST THROUGH 12Z, ANY SHOWERS
SHOULD BE BRIEF AND QUITE LIGHT. TEMPERATURES SHOULD STILL BE
COOLER THAN PREVIOUS NIGHT DUE TO WEAK SHALLOW COLD ADVECTION
AND EXPECT LOW TEMPS IN THE 40S.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
KEY MESSAGE(S):
- DECREASING CLOUDINESS BEHIND A COLD FRONT ON FRIDAY WITH SIMILAR
DAYTIME TEMPERATURES TO THURSDAY.
DEEP UPPER TROUGH ACROSS THE GREAT LAKES AND OHIO VALLEY WILL DRIVE
OUR WEATHER FRIDAY INTO SATURDAY. TWO SHORTWAVES WILL ROTATE AROUND
THE BASE OF THE TROUGH ON FRIDAY, ALLOWING FOR CLOUDS MUCH OF THE
DAY. A FEW LIGHT SHOWERS ARE POSSIBLE, BUT CONFIDENCE IS LOW GIVEN
LIMITED MOISTURE AVAILABILITY AND PWATS AROUND 0.5". THE BEST
CHANCES WOULD BE NORTH ALONG THE SC/NC BORDER, WHERE SOME SLIGHT
CHANCE POPS WERE INTRODUCED. DAYTIME TEMPERATURES WILL CONTINUE
THEIR COOL DOWN, WITH FORECAST HIGHS IN THE UPPER-50S NORTH AND
WEST TO LOW-60S SOUTH AND EAST. STRONGER COLD ADVECTION WILL
SETTLE IN FRIDAY NIGHT WITH SURFACE WINDS TURNING OUT OF THE
NORTHWEST. HOWEVER, RADIATIONAL COOLING MAY BE LIMITED BY THE
PRESSURE GRADIENT KEEPING THE BOUNDARY LAYER MIXED, DESPITE
CLEARING SKIES AND A DRIER AIRMASS MOVING IN. CURRENT THINKING
IS THAT TEMPERATURES WILL FALL INTO THE UPPER 20S TO MID-30S BY
DAYBREAK SATURDAY.
WITH HIGH PRESSURE BUILDING IN FROM THE WEST, SATURDAY WILL FEATURE
MOSTLY CLEAR SKIES AND TEMPERATURES ABOUT 10 DEGREES COOLER COMPARED
TO FRIDAY, GENERALLY IN THE UPPER 40S TO LOW 50S. THE TIGHT GRADIENT
WILL ALSO LEAD TO SOME BREEZY NORTHERLY WINDS, MAKING IT FEEL EVEN
CHILLIER. THIS GRADIENT DOES RELAX A BIT MORE THAT THE PREVIOUS
NIGHT THOUGH, WITH LOWS GENERALLY IN THE 20S.
LONG TERM /SUNDAY THROUGH THURSDAY/
KEY MESSAGE(S):
- COLD AND DRY CONDITIONS LIKELY THROUGH MONDAY.
- SEVERAL NIGHTS OF SUBFREEZING TEMPERATURES EXPECTED.
- TEMPERATURES MODERATE TOWARDS THE END OF THE PERIOD.
SUNDAY AND MONDAY ARE THE COLDEST DAYS IN THE 7 DAY FORECAST WITH A
POLAR HIGH OVER MUCH OF THE EASTERN CONUS AND GENERALLY ZONAL FLOW
ALOFT. SKIES REMAIN MOSTLY CLEAR WITH PWATS DOWN BELOW 0.3". MAIN
FORECAST CHALLENGE WILL BE ASSESSING THE NEED FOR ANY COLD WEATHER
PRODUCTS GIVEN SEVERAL NIGHTS OF SUBFREEZING TEMPERATURES. WITH HIGH
PRESSURE TO OUR NORTH AND NOT DIRECTLY OVERHEAD, SURFACE WINDS MAY
REMAIN HIGH ENOUGH TO PREVENT IDEALIZED RADIATIONAL COOLING KEEPING
VALUES ABOVE ADVISORY CRITERIA. ON THE OTHER HAND, THE MOST LIKELY
PERIOD A HEADLINE MAY BE NEEDED IS SUNDAY NIGHT INTO MONDAY MORNING,
WHEN WIND CHILL VALUES ARE FORECAST TO BE IN THE TEENS. IT SHOULD
ALSO BE MENTIONED THAT OFFICIAL FORECAST TEMPS FEATURES A BLEND OF
NBM/NBM50, GIVEN MEAN VALUES ARE ABOVE THE 75TH PERCENTILE WHICH
SEEMS TOO WARM.
ON THE UPSIDE, DAYTIME TEMPERATURES ARE LIKELY TO MODERATE EARLY
NEXT WEEK THROUGH THE HOLIDAY WITH WEAK RIDGING ALOFT. WE'LL ALSO
KEEP AN EYE ON A FEW WEAK DISTURBANCES IN THE SOUTHERN STREAM WHICH
MAY BRING INCREASING CHANCES FOR PRECIP PERHAPS ON TUESDAY AND
WEDNESDAY, BUT THE DETAILS STILL NEED TO BE WORKED OUT.
AVIATION /18Z THURSDAY THROUGH TUESDAY/
MVFR CEILINGS EXPECTED THROUGH THE AFTERNOON INTO THE EVENING.
IFR CEILINGS LATE TONIGHT.
WIDESPREAD MVFR STRATO-CUMULUS WILL CONTINUE ACROSS THE REGION
AS SHALLOW MOISTURE ADVECTS INLAND FROM THE ATLANTIC. THE
GUIDANCE IS INDICATING THE CEILINGS MAY LOWER LATE TONIGHT TO
IFR. FOG IS POSSIBLE TONIGHT GIVEN DRY AIR ALOFT, BUT LOW CLOUDS
LIKELY TO BE IN PLACE THROUGH THE OVERNIGHT. SO THINK FOG THREAT
LOWER THAN PREVIOUS NIGHT AND KEPT VISIBILITY AT MVFR LEVELS.
LOW CLOUDS EXPECTED TO MIX OUT EARLIER IN THE AGS/DNL THAN
CAE/CUB TERMINAL AREA FRIDAY MORNING AROUND 12Z-14Z. WINDS WILL
BE NORTH TO NORTHEAST 5 TO 10 KNOTS, DIMINISHING TO LIGHT
NORTHEAST OVERNIGHT.
EXTENDED AVIATION OUTLOOK...NO SIGNIFICANT IMPACTS TO AVIATION.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
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