904 FXUS64 KMRX 200535 AFDMRXArea Forecast Discussion National Weather Service Morristown TN 135 AM EDT Sat Sep 20 2025
...New DISCUSSION, AVIATION...
.KEY MESSAGES... Updated at 129 AM EDT Sat Sep 20 2025
- Above normal temperatures will persist through early next week.
- A few afternoon showers and storms will be around today through Tuesday. Coverage will be more isolated in valley locations but could become more scattered across higher terrain.
- Chances for showers and storms will trend upward by the middle and latter portions of the work week.
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.DISCUSSION... Issued at 129 AM EDT Sat Sep 20 2025
A ridge over the forecast area will be pushed northeast by a shortwave trough today, leading to the potential of a few PM showers and storms. Greatest coverage is expected in the higher terrain, but some isolated convection cannot be ruled out in valley locations as well. MLCAPE near 1500J/kg and DCAPE near 1000J/kg suggest the strongest updrafts could lead to localized gusty winds up to 40mph. Will continue to keep low probability wording in the HWO.
The most notable change in the forecast from previous night comes with increased PoPs for Sunday and Monday. Models now show some additional impulses that may traverse mean flow aloft over the next few days, and some of the CAMs such as the HRRR and ARW have responded with an upward trend in convective coverage as a result. 20-40% PoPs are generally in place Sunday through Tuesday, though coverage will be some what reliant on how well any impulses and associated vort lobes align with diurnal heating. It can also be noted that temperatures will remain above normal through this time frame. Southwesterly surface flow will bring increasing dewpoints and it will be a tad more muggy feeling relative to the lower humidity afternoons we have seen the past few days.
Regarding the mid to late week system, models are showing signs of increasing agreement as the GFS has trended more towards Euro with a developing cutoff low. Still some discrepancies associated with the amplitude and exact position of the system, but Wednesday through Saturday PoPs have increased to around the 50-70% range per latest NBM. Mean ensemble suites from the GFS and Euro begin to paint probabilities of total rainfall 1" or greater around the 50-60% range by the end of the week. While details are still coarse it is worth mentioning that latest WPC days 3-7 hazards highlight portions of the southern Appalachians for heavy rain by Thursday.
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.AVIATION... (06Z TAFS) Issued at 129 AM EDT Sat Sep 20 2025
Scattered clouds around with VFR conditions expected to continue. Low confidence on any patchy fog appearing by morning with the continued dry weather. Isolated convective showers will be around during the late afternoon and evening hours, though coverage is too sparse to include in the TAFs.
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.PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 91 67 89 68 / 10 10 20 20 Knoxville McGhee Tyson Airport, TN 88 64 87 65 / 20 10 20 20 Oak Ridge, TN 87 63 86 64 / 20 10 30 20 Tri Cities Airport, TN 84 59 83 61 / 30 10 20 10
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.MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. &&
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DISCUSSION...KRS AVIATION...Wellington
NWS MRX Office Area Forecast Discussion