Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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710 FXUS64 KMRX 150731 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 331 AM EDT Thu Aug 15 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today and tonight) Issued at 314 AM EDT Thu Aug 15 2024 Key Messages: 1. Dry weather to continue, humidity a little higher today. Discussion: Narrow upper ridge axis will be sliding overhead today, with sinking air over the wider region. 00z CAMs are quiet with most forming light returns over the mountains, whereas the most recent HREF had at least some activity dotting both the mountains and the rim of the Plateau. Left a slight chance for a shower in over the East Tennessee Mountains, where the better low level CAPE might allow for a brief shower during peak heating. Very unlikely for anyone in the valleys to see rainfall once again today. Otherwise low level winds will finally pivot to a more southerly to southwesterly flow, and while they`ll remain weak, it marks the beginning of low level moisture flowing northwards once more. Depending on cloud coverage tonight, it might also allow for another round of patchy fog, especially with guidance keeping rain at bay through sunrise on Friday. && .LONG TERM... (Friday through Wednesday) Issued at 314 AM EDT Thu Aug 15 2024 Key Messages: 1. Scattered to numerous showers and storms Friday and Saturday, with some strong to severe storms possible. 2. More scattered showers/storms possible Sunday and Monday, with better coverage across the north. 3. Dry Tuesday and Wednesday. Discussion: Models are in general agreement that an upper low over the western Great Lakes region early Friday will move east/southeast with multiple short waves dropping southeast around the back side, carving out a significant upper trough over the eastern CONUS by early in the week. However, the models differ significantly in the details and have been rather inconsistent. Timing and strength of the individual short waves is uncertain as is the timing of a cold front that will drop southeast across our area sometime in the Saturday/Saturday night time frame, which leads to uncertainties in how the convection will unfold. The overall environment continues to show significant effective bulk shear for this time of year although latest runs have generally trended a bit lower for Friday with values more in the 15 to 25 kt range, and show the higher values of 20 to 30+ kt for Saturday. Models vary widely on how much convective energy will be available as well, but perusing the HREF and SREF ensemble means would suggest SBCAPES will be in the 500-1500 J/kg range Friday and more like 1000-2000 J/kg Saturday. Overall the atmosphere looks supportive of more organized convection with some strong to severe storms possible both Friday into Friday evening and again Saturday. Damaging winds will be the primary severe threat with these storms. In addition, any areas that see repeated and/or prolonged rounds of heavy rainfall may experience localized flooding. Poor agreement in the CAMS does not lend high confidence to timing of convection Friday, but current thinking is it will be focused more late morning into the evening hours and this will likely be the case for Saturday as well. Additional upper short wave features are expected to be moving through the upper trough and are expected to bring additional showers/storms Sunday and to a lesser extent Monday with the better coverage across the north. Cooler air will also be moving in behind the front, with temperatures likely below normal both days. Surface high pressure will build in from the north Tuesday as the trough axis shifts further east, providing dry weather both Tuesday and Wednesday along with a slight warming trend. && .AVIATION... (06Z TAFS) Issued at 139 AM EDT Thu Aug 15 2024 VFR and dry weather conditions expected to persist through the TAF period. Patchy fog between 09z to 13z possible, maintained a VCFG at KTRI for river fog near the terminal. Calm winds will become southerly to southwesterly during the day along with a scattered to broken deck of high clouds and a lower scattered deck of cumulus clouds. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 91 72 93 73 / 10 10 40 50 Knoxville McGhee Tyson Airport, TN 90 71 90 71 / 10 10 50 70 Oak Ridge, TN 89 70 89 70 / 10 10 50 70 Tri Cities Airport, TN 86 66 85 69 / 10 10 50 70 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...Wellington AVIATION...Wellington