Sunrise 6:27 AM   Sunset 8:38 PM Moonrise 2:15 PM   Moonset 2:31 AM

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FXUS64 KMRX 170727 AFDMRX

Area Forecast Discussion National Weather Service Morristown TN 327 AM EDT Fri May 17 2024

New SHORT TERM, LONG TERM

SHORT TERM
(Today and tonight)
Issued at 259 AM EDT Fri May 17 2024

Key Messages:

1. Showers will overspread the area today and continue into tonight, and there may be a few thunderstorms as well.

Discussion:

We start the period under SW flow aloft with upper level short wave energy approaching from our southwest, and a surface frontal boundary well to our south. The better jet forcing looks to stay to our south today, and the stronger convection is expected to stay to our south as well and will likely help to inhibit much significant instability from making it into our area. Right now, most model sources suggest limited instability over our area, with the HRRR showing mean MUCAPES staying below 500 J/kg, and probabilities of reaching 500 J/kg of SBCAPE generally well below 50%. Showers will spread across the area generally from SW to NE today and continue into tonight, and some rumbles of thunder will be possible as well.
The main threat with any storms will be localized heavy rainfall, and localized flooding will be possible mainly if training of cells were to occur. With the clouds and precipitation today, high temperatures will generally be a bit below seasonal normals.

LONG TERM
(Saturday through Thursday)
Issued at 259 AM EDT Fri May 17 2024

Key Messages:

1. Scattered afternoon thunderstorms on Saturday, Sunday to be less wet.

2. Drier and warmer Monday and Tuesday as ridging builds.

3. Cold front to bring additional showers into the area mid to late week.

Discussion:

Weak upper trough gradually will move through the wider region this weekend, helping to fire more showers and thunderstorms. Saturday morning looks to be on a drying trend, with any lingering convection to dissipate. Looking at CAM soundings, enough instability is in place Saturday afternoon to fire showers and thunderstorms. Severe wise not likely to see any organized convection, with weak 0-6 km shear, but 1200 to 1500 J of CAPE should help fuel thunderstorms. As with any convection, lightning will be the big risk for Saturday outdoor activities along with gusty winds and small hail during the storms' brief individual lifespans.

A few lingering showers or storms are possible on Sunday, but the bulk of the rainy period will be moving on with the trough to the Carolinas. Meanwhile upper level ridging will begin to build in to fill the void, allowing for warmer temperatures and drier weather the first half of the workweek next week. Wednesday afternoon temperatures have increased since yesterday's afternoon forecast, with the next trough and cold front combo appearing slower in the latest guidance. If that holds, Chattanooga could flirt with 90F at midweek. At some point on the back half of the week the front will slide through, and along with associated rain showers Thursday will be cooler than Wednesday. Not too enthused on severe chances, especially with the parent low (regardless of model timing) ejecting quickly to the Great Lakes with questions on front orientation and strength as it approaches East Tennessee, but we can work out those details as we get closer.

AVIATION
(06Z TAFS)
Issued at 115 AM EDT Fri May 17 2024

Still uncertainty about cloud impact on fog development early in the period, but for now will go with MVFR/IFR conditions at TRI.
Otherwise, showers and perhaps some rumbles of thunder will spread across the area from SW to NE today and will continue into tonight. Given lower probability and timing uncertainty will leave thunder out of the forecast for now. Will likely see conditions lower to MVFR/IFR at CHA, with conditions likely lowering to MVFR at TYS and at least briefly to MVFR at TRI.

PRELIMINARY POINT TEMPS/POPS
Chattanooga Airport, TN 74 64 81 64 / 80 60 70 40 Knoxville McGhee Tyson Airport, TN 74 63 77 62 / 80 70 80 60 Oak Ridge, TN 74 63 77 62 / 80 70 60 50 Tri Cities Airport, TN 75 60 75 60 / 80 60 60 60

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

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