732
FXUS64 KMRX 202037
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
337 PM EST FRI DEC 20 2024
..NEW SHORT TERM, LONG TERM
SHORT TERM
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 330 PM EST FRI DEC 20 2024
A FAST MOVING CLIPPER SYSTEM WAS MOVING INTO THE EAST TENNESSEE
AND SOUTHWEST VIRGINIA AT MID AFTERNOON AND BEGINNING TO PRODUCE
RAIN AND SNOW ACROSS THE NORTHEAST PART OF THE FORECAST AREA. SOME
SLEET HAS BEEN REPORTED BRIEFLY AS WELL. WINDS HAVE INCREASED OUT
OF THE WEST WITH THIS SYSTEM AND SHOULD REMAIN GUSTY OVERNIGHT
TONIGHT BEFORE DECREASING SATURDAY. STILL LOOKS LIKE MOST OF THE
WESTERN AND SOUTHERN PARTS OF THE AREA WILL NOT SEE MUCH RAIN OR
SNOW. SNOWFALL ACCUMULATIONS WILL BE MOSTLY A TRACE TO 0.5 INCH OR
SO CENTRAL AND NORTHERN LOW ELEVATIONS BUT 1 TO 4 INCHES IN THE
ADVISORY AREA AND THE HIGHEST ELEVATIONS OF THE SMOKIES AND
FARTHER NORTH INTO VIRGINIA 5 OR 6 INCHES. ALL AREAS WILL SEE
MUCH COLDER TEMPERATURES TONIGHT AND SATURDAY WITH COLDER AIRMASS
MOVING IN. HIGHS TODAY WERE IN THE LOWER TO MID 40S WITH
TEMPERATURES EARLY THIS AFTERNOON DROPPING INTO THE 30S IN MOST
LOCATIONS BY LATE AFTERNOON. WIND CHILLS WILL BE IN THE 20S LOWER
ELEVATIONS AND TEEN OR SINGLE DIGITS HIGHER ELEVATIONS OVERNIGHT.
BY LATE TONIGHT AND EARLY SATURDAY THE MOISTURE WITH THIS SYSTEM
MOVES OUT WITH SOME SNOW FLURRIES LINGERING IN THE COLD AIRMASS.
THE HIGHER EASTERN MOUNTAINS MAY SEE ANOTHER INCH OR SO OF SNOW
BUT MOST HIGHER ELEVATIONS WILL SEE LESS ACCUMULATION SATURDAY
MORNING. HIGHS SATURDAY SHOULD ONLY RISE 5 TO 10 DEGREES ABOVE
THE NIGHT TIME LOWS. EXPECT WINDS TO LOWER TO 5 TO 10 MPH BUT
HIGHER GUSTS IN THE EASTERN MOUNTAINS TO 25 MPH OR SO UNTIL EARLY
AFTERNOON. CLOUDS WILL LINGER IN THE COLD AIRMASS SATURDAY BUT
SHOULD DECREASE FROM SOUTHWEST TO NORTHEAST IN THE AFTERNOON.
LONG TERM
(SATURDAY NIGHT THROUGH NEXT FRIDAY)
ISSUED AT 330 PM EST FRI DEC 20 2024
KEY MESSAGES:
1. COLD THROUGH MONDAY.
2. WARMING TREND NEXT WEEK WITH CHANCES FOR RAIN THE SECOND HALF OF
THE WEEK INCLUDING CHRISTMAS.
DISCUSSION:
WE WILL BEGIN BENEATH A COLD NORTHWEST FLOW THAT WILL REINFORCE THE
SLIGHTLY BELOW NORMAL TEMPS THROUGH SUNDAY AND MONDAY. MODELS SHOW
THE FLOW ALOFT BECOMES MORE WESTERLY-ZONAL DURING MONDAY, WHICH WILL
SIGNAL THE ONSET OF WARMING TO DEVELOP.
A SHORTWAVE TROUGH WILL DROP OUT OF THE ROCKIES AND INTO THE
SOUTHERN PLAINS TUESDAY, WHICH WILL AMPLIFY OUR PATTERN ALOFT INTO A
TEMPORARY RIDGE THAT WILL BRING MILD WEATHER WITH VALLEY HIGHS IN THE
50S FROM CHRISTMAS EVE THROUGH FRIDAY, AND MOISTENING DEWPOINTS
THAT WILL RESULT IN MILDER DAILY LOWS AS THE WEEK PROGRESSES.
ENERGY LOOKS TO CONTINUE TO FLOW INTO THE SOUTHERN ROCKIES THROUGH
THURSDAY, KEEPING THE STORM PATH IN THE MID SECTION OF THE COUNTRY,
WHICH WILL HELP PREVENT ORGANIZED WEATHER SYSTEMS FROM REACHING OUR
AREA. THUS, EXPECT SCATTERED SHOWERS AT BEST FOR CHRISTMAS THROUGH
FRIDAY.
BEYOND OUR TIMEFRAME, MODELS DO BECOME DISCREPANT, BUT THE GFS
REMAINS PERSISTENT WITH EASTERN U.S. RIDGING EVEN THROUGH NEXT
WEEKEND. THE ECMWF DISAGREES. WE WILL WAIT AND SEE IF WE CLOSE OUT
THE LAST WEEK OF DECEMBER WITH WELL ABOVE NORMAL WARMTH.
AVIATION
(18Z TAFS)
ISSUED AT 1235 PM EST FRI DEC 20 2024
MOSTLY MVFR CIGS EXPECTED AT TRI AND TYS THROUGH FORECAST PERIOD.
VFR CONDITIONS MAY OCCUR A FEW MORE HOURS AT CHA UNTIL MVFR CIGS
SET IN LATE THIS AFTERNOON/EARLY EVENING. WESTERLY WINDS ARE BREEZY
THIS AFTERNOON WITH GUSTS AROUND 20 KNOTS POSSIBLE THROUGH EARLY
EVENING. LIGHT RAIN SHOWERS POSSIBLE THIS AFTERNOON NEAR TYS AND
MORE LIKELY FOR A FEW HOURS AT TRI. RAIN WILL TURN TO LIGHT SNOW
FOR A FEW HOURS NEAR TRI THIS EVENING WITH LITTLE TO NO
ACCUMULATION EXPECTED. CLOUD CEILINGS STAY MVFR OVERNIGHT AFTER
PRECIPITATION ENDS BUT LIFT TO VFR BY AROUND 15 TO 18Z.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 33 42 27 46 / 10 0 0 0
KNOXVILLE MCGHEE TYSON AIRPORT, TN 32 39 23 42 / 20 10 0 0
OAK RIDGE, TN 32 39 23 41 / 20 0 0 0
TRI CITIES AIRPORT, TN 30 36 19 37 / 50 10 0 0
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...WINTER WEATHER ADVISORY UNTIL 1 PM EST SATURDAY FOR BLOUNT SMOKY
MOUNTAINS-COCKE SMOKY MOUNTAINS-JOHNSON-SEVIER SMOKY
MOUNTAINS-SOUTHEAST CARTER-SOUTHEAST GREENE-UNICOI.
VA...WINTER WEATHER ADVISORY UNTIL 1 PM EST SATURDAY FOR LEE-RUSSELL-
WASHINGTON VA-WISE.
SHORT TERM...TD
LONG TERM....GC
AVIATION...TD
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