Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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005 FXUS64 KMRX 100235 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 1035 PM EDT Tue Jul 9 2024 ...New UPDATE... .UPDATE... Issued at 1030 PM EDT Tue Jul 9 2024 The isolated showers and storms that developed across parts of the forecast area late this afternoon and early evening have ended with daytime heating. The cold front that is trailing the remnants of Beryl was over middle Tennessee at this time with a narrow line of showers and a few thunderstorms. Over the next few hours this line will move into the plateau counties and then is expected to weaken and slowly dissipate as it moves into the Tennessee Valley counties around 6 to 8Z. Expect breezy winds in the mountains tonight as a tight pressure gradient will be across the higher elevations. Winds may gust into the 30s in the mountains. Updated forecast to change rain chances and update temperatures, dewpoints and sky conditions. && .SHORT TERM... (This evening through Wednesday) Issued at 240 PM EDT Tue Jul 9 2024 Key Messages: 1. Scattered to isolated showers/storms through this evening ahead of an approaching cold front. 2. Breezy conditions in the mountains tonight and Wednesday morning. 2. A cooler and drier air mass will build into the area behind the front tomorrow. Discussion: Through the rest of the afternoon, isolated to scattered showers and thunderstorms will affect portions of the area. The best coverage through the afternoon/evening will likely be in the NE TN areas, where convective development in the mountains will track north into the Tri-Cities area, and outflow boundaries may initiate Valley convection. As the remnants of Beryl track across the lower OH Valley and Great Lakes region, a trailing cold front will push across TN through tonight. Models show a line of showers/storms in the Plateau around 03-06Z, but dissipating as it moves into our area. Will have some chance PoPs west of I-75 for this feature, but dropping quickly to no PoPs after 08Z. The pressure gradient overnight and Wednesday morning will create some breezy conditions in the area, mainly the mountains where gusts up to 40 mph will be possible. Expect that winds will stay just under the criteria for a Wind Advisory for most mountain locations, as the SW direction will not be favorable for mountain wave enhancement. Behind this front, low level moisture will still be present, and will likely result in some broken to overcast low clouds through the morning hours. Some downslope effect off the Plateau may lead to gradual scattering/lifting of clouds late in the morning, followed by mostly clear skies by the afternoon. With deep boundary layer mixing, dewpoints should drop to a pleasant 60-65 range in most spots, and with cooler highs in the mid to upper 80s with a 8-12 mph wind, it will be a welcome change from the recent heat and humidity. && .LONG TERM... (Wednesday night through next Tuesday) Issued at 240 PM EDT Tue Jul 9 2024 Key Messages: 1. Normal humidity through the rest of the week, heat to return for the weekend. Temperatures early next week to be near record highs. 2. Low afternoon chance of showers or thunderstorms, likely isolated to the mountains. Dry weather likely to persist for most. Discussion: The long term period will be characterized by a potent upper ridge anchored over the Rockies out west, which at first allows for better troughing here in the Eastern US. The upper trough that Beryl`s remnants will be pivoting through will provide weak northerly to eventually variable 850 flow across the region. The result is we don`t see southerly return flow, so no strong low level moisture advection, and thus surface dewpoints stay reasonable from a July standpoint. Additionally, precipitable water profiles appear to run near normal through the extended. The bad news is though the humidity looks to cooperate, temperatures will not. Despite the upper ridge pattern being anchored by strong ridging in the Rockies and strong ridging in the western Atlantic, upper heights over the Mid South gradually increase on the backside of the week heading into the weekend. Heading into next week, modeled 850 temperatures look to approach near record values when compared against SPC sounding climatology. The NBM reflects this by painting a swath of upper 90s across the central and southern valleys, peaking into the end of the period early next week. A quick check of daily climate stats reveals these values to be a couple degrees below the records for the date, so quite hot. Afternoon dewpoints will beginning to increment upward, but with temperatures so high, a heat advisory will not be too hard to reach, should these values hold. As of now, there`s no solid signal for widespread rainfall, outside of a low chance in the mountains on most afternoons. Dry weather looks to persist for most locations. && .AVIATION... (00Z TAFS) Issued at 730 PM EDT Tue Jul 9 2024 Scattered showers/isolated storms moving NE towards TYS early this evening. Included VCTS there for 1 hour. A cold front then moves across the area later tonight, between about 06-10Z, with winds shifting to a more W/NW direction at 10-12 kt. Behind the front low level moisture lingers. MVFR cigs expected at CHA and TYS through Wednesday AM. TRI may also see MVFR cigs for a few hours Wednesday morning but confidence too low to include in current TAF. VFR conditions by afternoon all sites. A few gusts up to 20 kt possible at TRI and TYS Wednesday morning and afternoon behind cold front. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 72 89 69 93 / 20 10 0 0 Knoxville McGhee Tyson Airport, TN 75 87 67 90 / 20 10 0 0 Oak Ridge, TN 72 86 66 90 / 20 10 0 0 Tri Cities Airport, TN 73 86 63 88 / 30 10 10 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...TD LONG TERM....Wellington AVIATION...TD