349  
FXUS64 KMRX 212306  
AFDMRX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MORRISTOWN TN  
606 PM EST SAT DEC 21 2024  
   
..NEW AVIATION  
 
   
SHORT TERM  
 
(THIS EVENING THROUGH SUNDAY)  
ISSUED AT 315 PM EST SAT DEC 21 2024  
 
KEY MESSAGES:  
 
1. COLD TONIGHT AND SUNDAY.  
 
2. WINDS DECREASING TONIGHT ALONG WITH CLOUDS.  
 
3. SLIGHTLY WARMER SUNDAY BUT STILL SEVERAL DEGREES BELOW NORMAL.  
LESS WIND CHILL EFFECT WITH LIGHT NORTH TO NORTHEAST WINDS.  
 
DISCUSSION:  
 
LOW CLOUDS WERE SLOWLY DECREASING ACROSS EAST CENTRAL AND  
NORTHEAST TENNESSEE AT MID AFTERNOON BUT HOLDING TIGHT ACROSS  
SOUTHWEST VIRGINIA AS LOW LEVEL MOISTURE IS SLOWLY ERODING.  
MID AFTERNOON TEMPERATURES WERE IN THE MID 30S TO LOWER 40S. FOR  
TONIGHT AND SUNDAY THE CLOUDS SHOULD KEEP DECREASING INTO THE  
EVENING AND THEN BECOME MOSTLY CLEAR AS HIGH PRESSURE BUILDS  
SOUTHEAST FROM THE UPPER MIDWEST AND WESTERN GREAT LAKES. WINDS  
HAVE BEEN GUSTY AT TIMES THIS AFTERNOON UP TO 20 MPH OR SO WITH  
WIND CHILLS IN THE 20S TO LOWER 30S. TONIGHT WINDS WILL BE LIGHT  
AND LOWS IN THE UPPER TEENS AND 20S. SUNDAY HIGHS WILL BE A FEW  
DEGREES WARMER AND WITH LIGHTER WINDS.  
 
 
   
LONG TERM  
 
(SUNDAY NIGHT THROUGH NEXT SATURDAY)  
ISSUED AT 252 PM EST SAT DEC 21 2024  
 
KEY MESSAGES:  
 
1. WARMING TREND NEXT WEEK WITH LOW CHANCES FOR LIGHT RAIN ON  
CHRISTMAS.  
 
2. DAILY PRECIPITATION CHANCES AND ABOVE NORMAL TEMPERATURES LINGER  
LATE WEEK AND INTO THE WEEKEND, HOWEVER, MUCH UNCERTAINTY EXISTS  
WITH ANY FINER DETAILS AT THIS TIME.  
 
DISCUSSION:  
 
PLENTY OF SUNSHINE AMONG A QUASI-ZONAL UPPER LEVEL PATTERN WILL  
ALLOW FOR A WARMING TREND INTO THE NEW WORK WEEK ALL WHILE SURFACE  
HIGH PRESSURE MAINTAINS A PRECIPITATION FREE FORECAST THROUGH  
CHRISTMAS EVE. A WEAK SHORTWAVE WILL PROPAGATE THROUGH MEAN FLOW  
ALOFT INTO CHRISTMAS DAY. WHILE LOW RAIN CHANCES MAKE A RETURN, THE  
DISTURBANCE IS EXPECTED TO WEAKEN AS IT TRANSLATES EASTWARD AND  
MINIMAL SYNOPTIC SUPPORT WILL REDUCE PRECIPITATION EFFICIENCY.  
ENSEMBLE PROBABILITIES OF 24-HR PRECIPITATION GTE 0.10" GENERALLY  
PEAK AROUND 25%. OTHERWISE, ABOVE NORMAL TEMPERATURES AND INCREASING  
CLOUDS WILL ACCOMPANY THE LIGHT RAIN CHANCES FOR CHRISTMAS DAY.  
 
AS WE APPROACH THE TAIL-END OF THE WEEK AND INTO THE WEEKEND,  
FORECAST UNCERTAINTY QUICKLY RAMPS UP. A SERIES OF SHORTWAVES WILL  
ENHANCE LONG-WAVE TROUGHING AND CYCLOGENESIS TO OUR WEST BUT THE  
EXACT LOCATION OF THESE FEATURES ARE HIGHLY VARIABLE AMONG OUR LONG-  
RANGE AND MORE COARSE WEATHER MODELS. SCENARIOS IN WHICH  
AFOREMENTIONED FEATURES ARE IN CLOSER PROXIMITY RESULT IN ENHANCED  
UPGLIDE AND LINGERING PRECIPITATION CHANCES, HOWEVER, MODELS THAT  
PLACE THE FEATURES FURTHER NORTHWEST SUGGEST A DRY PERIOD TO END THE  
WEEK. OVERALL, THE FINER DETAILS REMAIN UNCERTAIN BUT ANY LINGERING  
PRECIPITATION INTO THE LATE WEEK AND WEEKEND WILL FALL AS RAIN AMONG  
CONTINUED ABOVE NORMAL TEMPERATURES.  
 
 
   
AVIATION  
 
(00Z TAFS)  
ISSUED AT 604 PM EST SAT DEC 21 2024  
 
CURRENT CLOUD COVER OVER THE SITES WILL GRADUALLY DIMINISH THROUGH  
THE EVENING WITH MOST OF THE AREA EXPECTED BE CLEAR BY AROUND  
MIDNIGHT. WINDS WILL REMAIN FROM A NORTHERLY TO NORTHEASTERLY  
DIRECTION THROUGH THE TAF PERIOD. MOSTLY CLEAR CONDITIONS ARE ALSO  
EXPECTED.  
 
 
   
PRELIMINARY POINT TEMPS/POPS  
 
CHATTANOOGA AIRPORT, TN 26 46 29 50 / 0 0 0 0  
KNOXVILLE MCGHEE TYSON AIRPORT, TN 23 42 25 49 / 0 0 0 0  
OAK RIDGE, TN 22 42 25 47 / 0 0 0 0  
TRI CITIES AIRPORT, TN 17 37 22 47 / 0 0 0 0  
 
 
   
MRX WATCHES/WARNINGS/ADVISORIES  
 
NC...NONE.  
TN...NONE.  
VA...NONE.  
 
 
 
 
SHORT TERM...TD  
LONG TERM....KRS  
AVIATION...BW  
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