269  
FXUS64 KMRX 222328  
AFDMRX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MORRISTOWN TN  
728 PM EDT FRI OCT 22 2021  
   
UPDATE
 
 
FOR 00Z AVIATION.  
 

 
   
SHORT TERM...(TONIGHT AND TOMORROW)
 
 
KEY MESSAGES:  
 
1. ISOLATED AREAS OF FOG/DENSE FOG ARE POSSIBLE OVERNIGHT BUT  
CONFIDENCE ON OCCURRENCE AND COVERAGE IS VERY LOW.  
 
DISCUSSION:  
 
PLENTY OF CLOUD COVER REMAINS THIS AFTERNOON BEHIND A COLD FRONTAL  
PASSAGE THAT BROUGHT RAIN AND STORMS YESTERDAY. GRADUAL CLEARING IS  
EXPECTED INTO THE OVERNIGHT HOURS BUT SOME CLOUD COVER WILL REMAIN.  
AREAS THAT SEE CLEARING WILL HAVE A BETTER CHANCE OF FOG DEVELOPING.  
ALTHOUGH ISOLATED, SOME OF THE FOG COULD BE LOCALLY DENSE.  
 
UPPER JET AND 500MB SHORTWAVE DIP BACK DOWN INTO OUR AREA OVERNIGHT  
BUT THE BEST LIFT REMAINS TO OUR NORTH. UPPER JET/SHORTWAVE  
COMBINED WITH LINGERING MOISTURE AND UPSLOPE FLOW MAY BE ENOUGH TO  
SQUEEZE OUT A FEW SPRINKLES ACROSS THE MOUNTAINS OF NORTHEAST TN AND  
SOUTHWEST VA. CONFIDENCE IS LOW THAT THIS OCCURS SO KEPT THE  
FORECAST DRY.  
 
THE FLOW BECOMES MORE ZONAL TOMORROW AS HIGH PRESSURE PUSHES IN FROM  
THE SOUTHWEST. WITHIN THIS ZONAL FLOW A WEAK DISTURBANCE MOVES  
ACROSS OUR AREA TOMORROW AFTERNOON. DON'T ANTICIPATE PRECIP BUT THIS  
FEATURE WILL INCREASE CLOUD COVER AS IT MOVES ACROSS DURING THE  
AFTERNOON HOURS. HOWEVER, MOST PLACES SHOULD SEE A GOOD AMOUNT OF  
SUNSHINE FOR THE FIRST HALF OF THE DAY.  
 
SR  
   
LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
 
 
KEY MESSAGES:  
 
1. ACTIVE LONG TERM PERIOD WITH A SYSTEM ON MONDAY, AND ANOTHER ONE  
MID TO LATE NEXT WEEK.  
 
2. HOWEVER, CONFIDENCE IN THE FORECAST IS PRETTY LOW BEYOND TUESDAY  
NIGHT.  
 
DISCUSSION:  
 
SATURDAY NIGHT THROUGH SUNDAY LOOKS TO BE DRY. SURFACE LOW PRESSURE  
DEVELOPS IN THE CENTRAL PLAINS LATE SAT NIGHT INTO SUN MORNING AS A  
SHORTWAVE EJECTS EAST FROM THE COLORADO ROCKIES. EAST TN SHOULD BE  
FIRMLY IN THE WARM SECTOR OF THIS DEVELOPING SYSTEM, WITH ANY  
PRECIPITATION ASSOCIATED WITH ISENTROPIC ASCENT LOCATED TO OUR WEST  
AND NORTHWEST WHERE BETTER FORCING WILL BE. EXPECT A FAIRLY WARM DAY  
ON SUNDAY AS A RESULT, WITH HIGHS WELL INTO THE 70S, POSSIBLY  
APPROACHING 80 DEGREES IN THE TN VALLEY (AS SOME MOS GUIDANCE IS  
SUGGESTING).  
 
MATURING MID-LATITUDE CYCLONE SHIFTS TO NORTHERN IL/IN BY MONDAY  
MORNING, WITH TRAILING COLD FRONT SHIFTING EAST THROUGH TN DURING  
THE DAY. RAINFALL LOOKS TO REACH THE TN VALLEY BY LATE MORNING OR  
MIDDAY TIME FRAME. TRENDED TOWARDS THE OPERATIONAL MODELS WITH  
RESPECT TO ONSET OF RAINFALL ON MONDAY; NBM WAS A LITTLE TO QUICK I  
THOUGHT. HAVE MOSTLY SHOWERS MENTIONED, WITH A SLIGHT CHANCE OF  
THUNDER DUE TO WEAK INSTABILITY ALOFT. THE COLD FRONT CLEARS THE  
AREA TO THE EAST MONDAY EVENING, BUT THE UPPER SHORTWAVE RESPONSIBLE  
FOR THIS SYSTEM PHASES WITH ANOTHER WAVE TO FORM A DEEP UPPER LOW  
OVER THE EASTERN GREAT LAKES BY TUESDAY MORNING. RESULTING LOW LEVEL  
NW FLOW REGIME LOCALLY WILL LIKELY PRODUCE SOME SHOWERS IN THE  
MOUNTAINS THROUGH THE DAY TUESDAY BUT EXPECT RAINFALL TO WIND DOWN  
BY LATE TUESDAY.  
 
TO OUR WEST, STRONG UPPER RIDGING TRAVERSES THE MISSISSIPPI RIVER  
VALLEY DURING THE DAY TUESDAY AHEAD OF ANOTHER DEEP UPPER TROUGH  
MOVING OFF THE ROCKIES. MODELS ARE NOT IN GOOD AGREEMENT WITH THE  
DETAILS ON HOW THE PATTERN UNFOLDS FOR WEDNESDAY ONWARD. ONE THING  
THAT APPEARS CERTAIN IS THAT RAIN CHANCES WILL INCREASE  
SIGNIFICANTLY LATE WEDNESDAY AFTERNOON THROUGH THE END OF THE PERIOD  
AS A STRONGLY, NEGATIVELY TILTED UPPER TROUGH MOVES EAST THROUGH THE  
CONUS. DEPENDING ON HOW THIS EVOLVES WE MAY NEED TO WATCH FOR SEVERE  
POTENTIAL LATE WEDNESDAY. HOWEVER, THAT IS HIGHLY DEPENDENT ON THE  
DETAILS WHICH ARE BY NO MEANS CLEAR AT THIS TIME.  
 
CD  
 

 
   
AVIATION
 
 
00Z TAF DISCUSSION.  
 
MAIN CONCERN FOR THE TAF PERIOD IS POTENTIAL OF FOG DEVELOPMENT AT  
CHA WITH THE POSSIBILITY OF MVFR CONDITIONS BETWEEN 09-12Z. LOW  
PROBABILITY OF MARGINAL MVFR AT TYS. CLOUD COVER WILL INHIBIT FOG  
DEVELOPMENT AT TRI.  
 
OTHERWISE, CEILING AROUND 3500-4500FT CAN BE EXPECTED AT THE TAF  
SITES WITH A SLOW DIMINISHING THROUGH THE NIGHT AND EARLY SATURDAY  
MORNING FROM CHA-TYS-TRI.  
 
WINDS WILL GENERALLY BE BELOW 10KTS THROUGH THE FORECAST PERIOD.  
 

 
   
MRX WATCHES/WARNINGS/ADVISORIES
 
 
NC...NONE.  
TN...NONE.  
VA...NONE.  

 
 

 
 
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