485
FXUS64 KMRX 191754
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
1254 PM EST THU DEC 19 2024
..NEW AVIATION
UPDATE
ISSUED AT 1029 AM EST THU DEC 19 2024
FORECAST WAS UPDATED TO ACCOUNT FOR ISOLATED DRIZZLE/VERY LIGHT
RAIN BEING OBSERVED THIS MORNING. A COUPLE FORECASTERS NOTICED
THIS ON THEIR DRIVE'S IN TODAY. HISTORICAL OBS FOR THE PAST 6
HOURS OR SO, DEPICT SOME RAWS AND HADS SITES, ESPECIALLY IN THE
MOUNTAINS, RECORDING AT LEAST A HUNDREDTH OF AN INCH TO A COUPLE
HUNDREDTHS OF AN INCH OF RAIN. WE DON'T EXPECT THIS TO LAST ALL
DAY THOUGH. TODAY'S CHALLENGE WILL BE TIMING THE EXIT OF CLOUD
COVER ACROSS THE REGION. NEARLY ALL SITES ARE OVERCAST. WHAT'S
CAUSING THE DRIZZLE IS THOUGHT TO BE EITHER WEAK OROGRAPHIC LIFT
AND/OR CAA MOISTURE EXPULSION AS THERE'S NO REAL SIGNAL FOR UPPER
OR LOWER LEVEL MESOSCALE FEATURES.
KS
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 314 AM EST THU DEC 19 2024
KEY MESSAGES:
1. DRY DAY TODAY WITH COOLER TEMPERATURES.
DISCUSSION:
TODAY IS A TRANSITION DAY OF SORTS. WE WILL BE TRANSITIONING FROM
THE SMALL TROUGH THAT GAVE US YESTERDAY'S WEATHER TO THE LARGER
TROUGH SYSTEM WHOSE CENTER AXIS WILL BE DIRECTLY OVER TENNESSEE
BY FRIDAY MORNING. WE'LL BE TRANSITIONING FROM THE MILD 60S AND
RAIN SHOWERS THE LAST SEVERAL DAYS TO A DRIER AND COOLER PATTERN
TO COME. WE'LL BE TRANSITIONING FROM HEAVY CLOUD COVER AND
WIDESPREAD FOG TO SUNLIGHT SHINING DOWN THIS AFTERNOON.
TODAY AND TONIGHT ARE SEASONABLE DECEMBER WEATHER, TEMPERATURES REAL
CLOSE TO THE LONG TERM NORMALS. FLOW IS PRETTY WEAK OVERALL UNTIL
THE MORNING HOURS WHEN THE UPPER JET STREAK DIPS INTO THE REGION,
BUT DOWN HERE AT THE SURFACE WE WON'T KNOW. EXPECTATION IS FOR THE
LOW CLOUDS TO SCATTER OUT AROUND NOON TIME GIVING US A BIT OF
SUNSHINE BEFORE SUNSET. HREF AND SOUNDINGS INDICATE THAT LOW CLOUDS
ARE LIKELY TO BUILD BACK IN OVERNIGHT, ESPECIALLY IN NORTHEAST TN
INTO SOUTHWEST VA, AHEAD OF THE NEXT WEATHER SYSTEM.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 314 AM EST THU DEC 19 2024
KEY MESSAGES:
1. COLD FRIDAY THROUGH THE WEEKEND.
2. RAIN AND SNOW SHOWERS EXPECTED FRIDAY AFTERNOON AND THEN ALL SNOW
SHOWERS FRIDAY NIGHT MAINLY NORTHERN HALF. LIGHT SNOW ACCUMULATIONS
LIKELY MAINLY OVER THE MOUNTAINS, WITH GUSTY WINDS OVER THE HIGHER
ELEVATIONS AS WELL LATE FRIDAY INTO FRIDAY NIGHT.
3. MOSTLY DRY SUNDAY THROUGH TUESDAY, WITH A GRADUAL WARMING TREND
FOR MONDAY AND TUESDAY.
4. MILD CONDITIONS AND RAIN CHANCES ARRIVE BY CHRISTMAS.
DISCUSSION:
A QUICK MOVING SHORTWAVE TROUGH AND CLIPPER LOW PRESSURE SYSTEM WILL
DIVE SOUTHEAST ACROSS THE OHIO VALLEY AND CENTRAL APPALACHIANS ON
FRIDAY WITH NORTHWEST FLOW AND COLD ADVECTION BEHIND THE FRONT.
WHILE MOISTURE WILL BE LIMITED WITH THE INITIAL SYSTEM AND
PRECIPITATION WILL BE LIGHT, THE PERIOD OF OROGRAPHIC LIFT ON THE
BACKSIDE OF THE SYSTEM WILL KEEP SNOW SHOWERS AND FLURRIES AROUND
ESPECIALLY NORTH AND MOUNTAINS FRIDAY NIGHT INTO SATURDAY MORNING.
THE PRECIPITATION AS IT MOVES IN FRIDAY AFTERNOON WILL LIKELY
BRIEFLY START AS A MIXTURE OF RAIN AND SNOW IN THE VALLEYS BEFORE
TRENDING TO ALL SNOW SHOWERS/FLURRIES, BUT OVER THE HIGHER TERRAIN
IT SHOULD BE ALL SNOW. RIGHT NOW, IT APPEARS 1 TO 3 INCHES OF SNOW
ACCUMULATION WILL BE POSSIBLE OVER THE HIGHER ELEVATIONS OF SW VA
AND THE E TN MOUNTAINS (AND LOCALLY HIGHER AMOUNTS MAY OCCUR OVER
THE HIGHEST PEAKS. IF THIS TREND CONTINUES A WINTER WEATHER ADVISORY
WILL LIKELY BE NEEDED IN SUBSEQUENT FORECAST UPDATES. WINDS WILL
ALSO BE QUITE GUSTY OVER THE HIGHER ELEVATIONS OF THE MOUNTAINS LATE
FRIDAY INTO FRIDAY NIGHT WITH GUSTS OF 30 TO 40 MPH POSSIBLE, AND
WIND CHILL VALUES WILL DIP INTO THE SINGLE DIGITS OVER THESE HIGHER
ELEVATIONS AS WELL.
SURFACE HIGH PRESSURE TO OUR NORTH SATURDAY NIGHT WILL MOVE EAST AND
WILL EXTEND INTO OUR AREA THROUGH MONDAY, AND A LOW AMPLITUDE UPPER
RIDGE WILL BUILD EAST OVER THE AREA AND THEN SHIFT OFF TO OUR EAST.
THE SUNDAY THROUGH TUESDAY TIME FRAME LOOK DRY OVERALL. SUNDAY WILL
CONTINUE TO BE COLD WITH WELL BELOW NORMAL TEMPERATURES, THEN A
GRADUAL WARMING TREND WILL START MONDAY AND TEMPERATURES BY TUESDAY
WILL BE BACK TO NEAR SEASONAL NORMALS. THE NEXT SYSTEM WILL BE
APPROACHING BY THE END OF THE LONG TERM PERIOD, WITH MODELS
GENERALLY TRENDING TOWARD A MILD BUT POTENTIALLY WET CHRISTMAS.
AVIATION
(18Z TAFS)
ISSUED AT 1243 PM EST THU DEC 19 2024
MVFR CIG MAY ACTUALLY PERSIST THROUGH THE NEXT TAF CYCLE AT TYS
AND TRI. CHA MAY BREAK TO VFR LATER TODAY, BUT FALL BACK TO MVFR
FRIDAY MORNING AHEAD OF A TROUGH. WINDS WILL EITHER BE LIGHT AND
NORTHERLY OR CALM, BUT WILL INCREASE OUT OF THE SW ONCE WE MIX
OUT AT THE SFC FRIDAY MORNING. PRECIP ENTERS THE REGION SOMETIME
FRIDAY AFTERNOON, BUT ISN'T REFLECTED IN THIS TAF ISSUANCE.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 52 35 47 31 / 0 0 10 10
KNOXVILLE MCGHEE TYSON AIRPORT, TN 50 35 43 29 / 10 0 20 20
OAK RIDGE, TN 49 33 42 29 / 10 0 20 10
TRI CITIES AIRPORT, TN 48 34 42 28 / 10 0 60 40
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
SHORT TERM...WELLINGTON
AVIATION...KS
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