308
FXUS64 KMRX 201158
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
758 AM EDT THU AUG 20 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 740 AM EDT THU AUG 20 2026
- WIDESPREAD FOG LESS LIKELY THIS MORNING, BUT ISOLATED PATCHY
FOG POSSIBLE FOR SOME.
- DECAYING BOW ECHO MAY BRING SOME GUSTY WINDS ACROSS THE NORTHERN
PLATEAU LATER THIS MORNING.
- ANOTHER ROUND OF SHOWERS/STORMS BECOMING MORE LIKELY FOR THIS AFTERNOON
AND EVENING. MAIN THREATS: DAMAGING WINDS AND SMALL HAIL.
- MOSTLY DRY CONDITIONS WITH NEAR NORMAL TEMPERATURES THROUGH THE
WEEKEND AND EARLY NEXT WEEK
DISCUSSION
ISSUED AT 247 AM EDT THU AUG 20 2026
MID/HIGH CLOUDS CURRENTLY STREAMING ACROSS THE AREA, WITH MORE TO
COME THROUGH THE NIGHT. THIS WILL LIKELY DETER FOG FOR MOST AREAS.
THOUGH ISOLATED INSTANCES OF PATCHY FOG ARE CERTAINLY POSSIBLE,
ESPECIALLY NEAR LOCAL WATERWAYS.
A CLUSTER OF STORMS IS CURRENTLY DEVELOPING BACK ACROSS SOUTHERN MO
AND IS FORECAST TO BECOME MORE ORGANIZED AS THEY TRACK ACROSS KY/TN
THROUGH THE NIGHT. MODEL CONSENSUS SHOWS THIS LINE OF STORMS
WEAKENING AS THEY MOVES INTO THE NORTHERN PLATEAU LATER THIS
MORNING. HOWEVER, THIS LINE OF STORMS MAY STILL PRODUCE SOME GUSTY
WINDS ACROSS THE CENTRAL/NORTHERN PLATEAU AS THEY ARRIVE. THE MOST
LIKELY ARRIVAL TIME WILL BE AROUND 7 TO 8 AM EDT. SPC HAS EXPANDED
THE MARGINAL RISK EASTWARD AND INCLUDED OUR NORTHERN PLATEAU
COUNTIES TO ACCOUNT FOR THIS ACTIVITY. THEREAFTER, SHOWERS AND
PERHAPS A FEW REMAINING STORMS WILL MAKE THEIR WAY ACROSS THE REST
OF THE AREA THROUGH THE LATE MORNING HOURS. AREAS ALONG AND NORTH OF
I-40 WILL HAVE THE BEST CHANCES TO SEE PRECIP WITH THIS DECAYING
LINE. AREAS SOUTH OF 40 MAY STAY COMPLETELY DRY.
THEN ALL EYES TURN TOWARD THE AFTERNOON/EVENING HOURS. BIGGEST
CHANGE FROM PREVIOUS FORECAST IS THAT THE 00Z NAM DOESN'T SHOW THE
MID-LEVEL STABLE LAYER AT 21Z THAT WAS PREVIOUSLY SHOWN. THIS
MEANS BETTER CHANCES FOR CONVECTIVE INITIATION. THIS IS SUPPORTED
BY THE RECENT RUNS OF THE HRRR AND RRFS AS THEY SHOW INITIATION AS
WELL, THOUGH TIMING VARIES. IT SEEMS LIKE THE EARLIEST INITIATION
WOULD BE AROUND 18 TO 21Z AND THE LATEST AROUND 23 TO 00Z. THE
ENVIRONMENT WILL BE FAVORABLE FOR A FEW STRONG TO SEVERE STORMS AS
MLCAPE VALUES WILL BE AROUND 2000 J/KG AND 0-6KM SHEAR AT AROUND
20 TO 30KTS. THE MAIN THREATS WILL BE DAMAGING STRAIGHT LINE
WINDS, AND PERHAPS A MICROBURST, ALONG WITH SMALL HAIL. SHEAR IN
THE LOWEST LEVELS DO NOT LOOK CONDUCIVE FOR TORNADIC DEVELOPMENT
WITH VALUES LESS THAN 10KTS. ALSO, LCL HEIGHTS WILL BE QUITE HIGH
THIS AFTEROON AROUND 1500 METERS, DUE TO DEEP MIXING, WHICH CAN BE
SEEN IN THE "INVERTED V SOUNDING PROFILES".
THE LATEST SPC OUTLOOK FOR DAY 1 (TODAY) COMPARED TO WHEN IT WAS
DAY 2, PULLS THE MARGINAL RISK A BIT MORE NORTH COVERING MORE OF
THE NORTHERN PLATEAU, VALLEY, AND SOUTHWEST VA.
SHOWER AND STORM CHANCES CONTINUE THURSDAY NIGHT INTO FRIDAY
MORNING. COVERAGE AND INTENSITY IS LOW CONFIDENCE DURING THIS
TIME. ADDITIONAL SHOWERS AND STORMS ARE EXPECTED ON FRIDAY
AFTERNOON, DUE TO THE FRONTAL BOUNDARY STILL IN THE VICINITY. A
FEW STRONG TO SEVERE STORMS ARE ONCE AGAIN POSSIBLE, THOUGH LOWER
CHANCES COMPARED TO THIS AFTERNOON/EVENING.
DRY CONDITIONS ARE EXPECTED ON SATURDAY AND SUNDAY DUE TO BUILDING
SURFACE HIGH PRESSURE AND THE MIDLEVEL INFLUX OF DRIER AIR FROM THE
NORTH. NEXT WEEK, THERE ARE SIGNS OF ANOTHER NORTHWEST FLOW PATTERN
REMAINING ACROSS THE AREA INTO NEXT WEEK. WHILE NBM POPS ARE LOW, WE
WILL HAVE TO KEEP AN EYE OUT FOR ANY UPSTREAM IMPULSES THAT MAY
AFFECT OUR AREA NEXT WEEK. TEMPERATURES SHOULD BE NEAR NORMAL
THROUGHOUT THIS TIME FRAME.
AVIATION
(12Z TAFS)
ISSUED AT 740 AM EDT THU AUG 20 2026
SHOWERS AND A FEW STORMS MOVING INTO THE CENTRAL VALLEY MAY
IMPACT TYS THIS MORNING. SHOWERS POSSIBLY MOVE INTO TRI NEXT.
THERE'S GREAT UNCERTAINTY AS TO HOW LATER ON COULD BE IMPACTED BY
THE ACTIVITY THIS MORNING. IT HASN'T DISSIPATED LIKE MODELS HAD
SHOWN. LEFT THE LATER IN THE TAF PERIOD PROB30S EXCEPT TRI, WHERE
IT LOOKS LIKE THEY POSE THE LEAST CHANCE OF PRECIPITATION TONIGHT.
MVFR CIG FORECAST THERE OVERNIGHT TONIGHT.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 96 73 93 70 / 30 50 30 10
KNOXVILLE MCGHEE TYSON AIRPORT, TN 92 71 89 69 / 30 50 40 10
OAK RIDGE, TN 90 70 89 67 / 30 50 30 0
TRI CITIES AIRPORT, TN 87 67 84 65 / 30 60 60 30
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...99
AVIATION...KS
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