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Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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743 FXUS64 KMRX 141919 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 319 PM EDT Wed Aug 14 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Thursday) Issued at 155 PM EDT Wed Aug 14 2024 Key Message: 1. Patchy fog possible in spots tonight. Thursday will almost repeat today, with mostly sunny skies and an outside chance of a shower or storm over the higher terrain. Except temperatures and humidity a bit higher. Discussion: In the upper levels through tomorrow, troughing will continue to shift east with ridging following close behind. NWly flow will switch out of the south meaning, more humid air and warmer temperatures will be headed our way. Overall, Thursday will be a lot like this afternoon except temperatures a couple of degrees warmer with increased humidity. Isolated showers and storms, if they occur, will again be confined to only the higher terrain Thursday afternoon and evening. Overnight lows will be on the incline as well as the sticky conditions. Like this morning, low stratus/fog will be possible in spots again before sunrise. && .LONG TERM... (Thursday night through next Wednesday) Issued at 155 PM EDT Wed Aug 14 2024 Key Messages: 1. Scattered to numerous showers and storms Friday into Saturday, with some strong to severe storms possible Friday into Friday night. 2. Showers linger, at least in the mountains, Sunday into Monday. 3. Drier for the remainder of the period. Discussion: Shortwave ridging continues over our region Thursday night into Friday morning, but will be gradually shifting east in advance of a synoptic scale trough/upper low moving into the Great Lakes region. Shortwave energy will precede this trough, moving over our forecast area during the day Friday. A few showers and thunderstorms may make it into our northwest counties by midday Friday, then scattered to numerous showers and storms can be expected Friday afternoon into Friday night as additional energy moves through aloft. Models are in decent agreement overall in showing effective bulk shear values in the 20 to 30 kt range on Friday and Friday night. Agreement on instability is not quite as high, but even the more conservative guidance shows surface or mixed layer CAPE values in the 1000 to 1500 J/kg range. Still, this combo of shear and instability would be supportive of some strong to severe storms. Damaging winds and very heavy rainfall with the possibility of localized flooding currently look like the main threats for Friday into Friday night. The SPC has us in a marginal outlook area and this seems reasonable to me. The cold front associated with the aforementioned trough/upper low is forecast to move through Saturday with additional showers/storms expected. Late Saturday through the remainder of the weekend the Great Lakes low transitions into a deep trough across the eastern CONUS as upper ridging builds over the southwest. Current trends in model guidance indicate that Saturday night through Monday likely will remain active, with at least some chances for showers in the mountains in persistent northwest upslope flow. Temperatures should remain around or perhaps slightly below normal, but more importantly we`ll continue to have an influx of drier air from the northwest to keep things comfortable. && .AVIATION... (18Z TAFS) Issued at 133 PM EDT Wed Aug 14 2024 VFR to prevail with light and variable winds. Calm overnight. Low chance of some patchy fog around TRI in the morning, so have added a low end VFR VSBY TEMPO for a couple of hours. Not entirely confident if this will occur, but obs this morning did have some <10SM reported. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 91 72 91 / 0 10 10 40 Knoxville McGhee Tyson Airport, TN 67 90 70 89 / 0 10 10 50 Oak Ridge, TN 66 89 70 88 / 0 0 10 50 Tri Cities Airport, TN 63 86 66 85 / 0 10 10 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...KS LONG TERM....CD AVIATION...KS