469
FXUS64 KMRX 222313
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
713 PM EDT TUE JUL 22 2025
..NEW AVIATION
SHORT TERM AND LONG TERM
(THIS EVENING THROUGH NEXT TUESDAY)
ISSUED AT 130 PM EDT TUE JUL 22 2025
KEY MESSAGES:
1. A DRIER SURFACE AIR MASS AND RIDGING ALOFT WILL BRING LOWER
CHANCES OF SHOWERS AND STORMS THROUGH FRIDAY, WITH THE RAIN CHANCES
MAINLY IN THE MOUNTAINS.
2. RAIN CHANCES RISE OVER THE WEEKEND AS THE UPPER RIDGE WEAKENS AND
LOW LEVEL MOISTURE INCREASES.
DISCUSSION:
A BACKDOOR FRONT IS NEAR OUR NORTHERN BORDER THIS AFTERNOON,
EVIDENCED BY A WIND SHIFT TO N-NE, A DROP IN DEWPOINTS TO MID/UPPER
60S IN VA/WV/KY, AND A GRADIENT IN CUMULUS DEVELOPMENT. SOME
SCATTERED SHOWERS HAVE DEVELOPED JUST SOUTH OF THE FRONT IN SW VA
AND NE TN, BUT CONVECTION IS HAVING A HARD TIME DEVELOPING
VERTICALLY WHERE DRY AIR ALOFT IS PRESENT. AS THE FRONT PUSHES
SOUTHWARD THROUGH THE EVENING, A FEW SHOWERS MAY POP UP IN THE
CENTRAL AND SOUTHERN TN VALLEY, BUT COVERAGE SHOULD REMAIN ISOLATED
TO SCATTERED. THE FRONT APPEARS TO BE NEAR OUR SOUTHERN BORDER
OVERNIGHT, BASED ON MODEL STABILITY GRADIENTS, AND THE CAMS SHOW
SOME SHOWERS PERSISTING IN SW NC NEAR THE FRONT. TOMORROW LOOKS
QUITE STABLE IN MODEL SOUNDINGS, ESPECIALLY IN NORTHERN SECTIONS
WHERE SURFACE DEWPOINTS WILL BE IN THE 60S, PLUS THE FLOW FROM THE
SURFACE TO AROUND 700 MB TURNS EASTERLY AND DOWNSLOPE OFF THE
MOUNTAINS. SO CONVECTION WILL BE LIMITED TO SOUTHERN SECTIONS AND
THE HIGHER TERRAIN, AND COVERAGE SHOULD ONLY BE ISOLATED TO
SCATTERED. THE NBM POPS WERE TRIMMED BACK SLIGHTLY.
THE SURFACE HIGH OFF THE NEW ENGLAND COAST WILL EXTEND SW INTO THE
SOUTHERN APPALACHIANS THROUGH THURSDAY, WHILE A MID/UPPER LEVEL
RIDGE WILL BE CENTERED OVER THE MID MS AND TN VALLEYS. THE NET
EFFECT OF THIS PATTERN WILL BE TO SUPPRESS CONVECTION AND DRY THE
SURFACE AIR MASS. SURFACE DEWPOINTS WILL BE QUITE TOLERABLE FOR THIS
TIME OF YEAR (UPPER 60S TO LOWER 70S), WHICH WILL KEEP THE HEAT
INDEX WELL UNDER ADVISORY CRITERIA DESPITE HIGHS IN THE 90S THROUGH
FRIDAY. AGAIN, THE NBM POPS APPEAR TOO HIGH FOR THIS PATTERN, AND
WILL BE CUT BACK. NBM 10TH PERCENTILE DEWPOINTS WILL ALSO BE USED.
THE SURFACE HIGH OVER THE ATLANTIC SHIFTS SOUTHWARD THROUGH THE
WEEKEND, PRODUCING A MORE SOUTHERLY LOW LEVEL FLOW FROM THE GULF.
MEANWHILE, THE RIDGE ALOFT STARTS TO LOOSEN ITS GRIP ON THE REGION,
SHIFTING WEST OF THE MS RIVER. THIS WILL INCREASE THE CHANCE OF RAIN
OVER THE WEEKEND AND EARLY NEXT WEEK.
AVIATION
(18Z TAFS)
ISSUED AT 130 PM EDT TUE JUL 22 2025
DRIER AIR WORKING INTO THE AREA FROM THE NORTH SHOULD LOWER
DEWPOINTS ENOUGH TONIGHT TO KEEP THE CHANCE OF FOG LOW AT ALL TAF
SITES. STILL, SOME GUIDANCE SHOWS FOG AT TRI, ADDING SOME
UNCERTAINTY. WILL LEAVE FOG OUT FOR THIS SET AS THAT SEEMS LIKE THE
MOST LIKELY OCCURRENCE. VFR CONDITIONS ARE FORECAST FOR ALL
SITES, WITH LIGHT NE WINDS.
LONG TERM
AVIATION
(00Z TAFS)
ISSUED AT 711 PM EDT TUE JUL 22 2025
VFR CONDITIONS EXPECTED TO PERSIST THROUGH THE PERIOD. A VERY LOW
CHANCE FOG MAY FORM OVERNIGHT AT KTRI, BUT ADVANCING LOWER
DEWPOINTS IS FORECAST TO HOLD FOG AT BAY. OTHERWISE LIGHT WINDS
THROUGH THE PERIOD, WITH A LOW CHANCE OF SMALL SHOWERS SOUTH OF
KNOXVILLE TOMORROW AFTERNOON, SIMILAR IN INTENSITY TO TODAY'S WEAK
SHOWERS.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 73 92 72 93 / 20 30 0 30
KNOXVILLE MCGHEE TYSON AIRPORT, TN 71 93 71 94 / 20 20 0 20
OAK RIDGE, TN 71 92 72 93 / 20 10 0 20
TRI CITIES AIRPORT, TN 67 89 65 91 / 20 10 0 10
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
SHORT TERM...DGS
LONG TERM....DGS
AVIATION...WELLINGTON
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