434
FXUS64 KMRX 201052
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
652 AM EDT SUN SEP 20 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 648 AM EDT SUN SEP 20 2026
- WELL ABOVE NORMAL TEMPERATURES TO PERSIST INTO EARLY THIS WEEK. BUT
RELIEF IS ON THE WAY, WITH A PATTERN CHANGE EXPECTED MID-WEEK
AND MUCH COOLER TEMPERATURES TO FOLLOW.
- EXPECT ISOLATED TO SCATTERED SHOWERS TODAY, WITH INCREASING
COVERAGE MONDAY THROUGH WEDNESDAY.
- A FEW STRONG TO SEVERE STORM WITH DAMAGING WINDS COULD OCCUR
TODAY AND MONDAY, WITH DAMAGING WINDS BEING THE PRIMARY THREAT.
LOCALIZED FLOODING WILL BE POSSIBLE EACH DAY THROUGH WEDNESDAY
AS WELL.
DISCUSSION
ISSUED AT 112 AM EDT SUN SEP 20 2026
AN UPPER RIDGE, STILL CENTERED OVER THE ARKLATEX, WILL CONTINUE TO
WEAKEN ON SUNDAY. DESPITE LOWERING HEIGHTS, I WOULD EXPECT THERE TO
BE LESS SHOWER AND THUNDERSTORM COVERAGE TODAY VERSUS THE LAST
COUPLE OF DAYS THANKS TO A LACK OF FORCING MECHANISM AND SLIGHTLY
LOWER LOW LEVEL MOISTURE AND PWATS. THERE WILL BE CONVECTION, JUST
NOT AS MUCH. AN ISOLATED STRONG TO SEVERE STORM AND DAMAGING WIND
THREAT, OR SOME LOCALIZED HEAVY RAINS, CAN'T BE RULED OUT. BUT, THE
THREAT IS QUITE LOW AND I WOULD EXPECT THAT WE WILL REMAIN IN THE
GENERAL THUNDER AREA IN SPC'S DAY 1 CONVECTIVE OUTLOOK. FOR MONDAY,
EXPECT A MARKED INCREASE IN CONVECTIVE ACTIVITY AS A WEAK UPPER LOW
SHIFTS EAST FROM THE PLAINS INTO THE OHIO VALLEY. FORECAST SOUNDINGS
SUGGEST AFTERNOON MLCAPE VALUES WILL RANGE FROM AROUND 1,500 J/KG TO
OVER 2,000 J/KG AREA WIDE MONDAY AFTERNOON. PWATS WILL INCREASE A
BIT TOO, ALL OF WHICH WILL SUPPORT SOME ISOLATED DAMAGING WIND GUSTS
FROM COLLAPSING STORMS. STORM MOTIONS WILL BE SLOW TOO, SO LOCALIZED
HEAVY RAINS AND FLOODING COULD BE AN ISSUE TOO. TUESDAY SHOULD
FEATURE FAIRLY WIDESPREAD SHOWERS TOO, BUT INSTABILITY LOOKS FAR
LESS SO THE SEVERE POTENTIAL LOOKS NEGLIGIBLE.
LASTLY, DESPITE THE WANING INFLUENCE OF THE RIDGE, THERE'S NO AIR
MASS CHANGE UNTIL THE MID-WEEK TIME FRAME. SO TEMPERATURES WILL
REMAIN WELL ABOVE NORMAL SUNDAY THROUGH TUESDAY. HIGHS IN THE UPPER
80S TO MID 90S ARE ON TAP FOR SUN AND MON, WITH LOW 80S TO LOW 90S
FOR TUESDAY. BARRING ANY UNFORESEEN CIRCUMSTANCES, CHATTANOOGA LOOKS
TO CONTINUE IT'S RECORD SETTING STREAK OF 90 DEGREE DAYS AND SHOULD
TOP OUT AT 50. WEDNESDAY IS THE FIRST DAY OF SUB-90 FORECAST HIGHS.
SPEAKING OF WEDNESDAY, AND A BREAK IN THE HEAT...LATE TUESDAY INTO
WEDNESDAY A REX BLOCK PATTERN SETS UP, WITH THE UPPER RIDGE BUILDING
ON THE CANADIAN SIDE OF THE GREAT LAKES, AND THE UPPER LOW
RE-INTENSIFYING SOUTH OF THE RIDGE OVER THE OHIO VALLEY. THIS WILL
RESULT IN SURFACE HIGH PRESSURE WELL TO OUR NORTH, AND NORTHERLY LOW
LEVEL FLOW PUSHING A COLD FRONT THROUGH THE REGION SOMETIME ON
WEDNESDAY. WE'LL STILL BE WARM...MAYBE 1-3 DEGREES ABOVE NORMAL AS
OPPOSED TO +12-15 DEGREES...BUT RAIN AND CLOUDY CONDITIONS WILL BE A
WELCOME CHANGE. WE'LL WRAP THE WEEK WITH TEMPERATURES AROUND OR
SLIGHTLY BELOW NORMAL WITH HIGHS IN THE 70S TO 80S, AND LOWS IN THE
50S MAY EVEN MAKE AN APPEARANCE BY WEEK'S END.
AVIATION
(12Z TAFS)
ISSUED AT 648 AM EDT SUN SEP 20 2026
DENSE FOG AT TRI WILL BURN OFF SHORTLY AFTER TAF ISSUANCE AND
RETURN TO VFR. FOR TYS AND CHA, VFR CONDITIONS ARE FORECAST
THROUGHOUT THE PERIOD. THE SIGNAL FOR THUNDERSTORMS AND SHOWERS
THIS AFTERNOON ISN'T TOO IMPRESSIVE. HI-RES MODELS INDICATE
ISOLATED STORM COVERAGE AT BEST, WITH THE GREATEST CHANCE AT TRI.
I HAVE MAINTAINED THE PROB30 THERE AND KEPT THE OTHER TWO SITES
VFR AND DRY. WINDS REMAIN GENERALLY LIGHT AND VARIABLE. PATTERN
WOULD LIKELY SUPPORT THE REDEVELOPMENT OF FOG SUNDAY NIGHT/EARLY
MONDAY MORNING AT TRI, BUT I'VE LEFT IT OUT FOR NOW TO FOCUS ON
THE EARLIER TIME FRAME.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 95 72 95 70 / 20 10 40 50
KNOXVILLE MCGHEE TYSON AIRPORT, TN 93 70 93 69 / 10 10 40 60
OAK RIDGE, TN 92 70 92 68 / 10 10 40 50
TRI CITIES AIRPORT, TN 87 66 88 65 / 20 10 30 60
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...CD
AVIATION...BH
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