Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000 FXUS64 KMRX 190251 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 1051 PM EDT Mon Mar 18 2024 ...New UPDATE... .UPDATE...
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Issued at 1046 PM EDT Mon Mar 18 2024 Moisture continues to move into portions of the area tonight. Added a few hours of flurries to southwest Virginia where a few returns are showing up on radar. Most of this is probably evaporating but a few flurries seem possible over the next couple of hours. Otherwise, the rest of the forecast is in good shape.
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&& .SHORT TERM... (This evening through Tuesday) Issued at 308 PM EDT Mon Mar 18 2024 Key Messages: 1. Hard freeze expected tonight area wide. Winds may bring overnight and early morning wind chills into the teens in higher elevations or northeastern TN into southwest VA. 2. Dry weather continues through Tuesday, with temperatures rebounding slightly in the afternoon. Low relative humidities and breezy afternoon winds present fire danger. Discussion: The sharp upper trough that is driving our cold weather today and tonight will pass through the wider region overnight tonight. Additionally northwest winds aloft will increase to 20 to 30 knots. The advection of a significantly cold airmass will bring a strong hard freeze for nearly all of East Tennessee, southwest Virginia, and especially Cherokee and Clay counties in North Carolina. Best chances to remain above 28F will be in the urban heat islands of Chattanooga and Knoxville, and on the southeastern slopes of any ridge or terrain feature, due to downslope warming. Tacked on some flurries in the Smokies for tonight, HREF has been persistent in this possibility, zero snow accumulation expected. So far Jackson KY radar still shows possible flurries a couple hours out from the Kentucky border, not sure how much, if any, will fall in elevated portions of southwest Virginia thanks to the dry lower atmosphere. Tuesday surface winds will pivot to the southwest, with daytime high temperatures a few degrees warmer than today. The dry airmass associated with this system will yield another day of low relative humidities, and afternoon mixing will bring some breezy winds to the surface in the afternoon once more. For both those reasons, another afternoon of elevated fire danger will be present tomorrow afternoon. && .LONG TERM... (Tuesday night through next Monday) Issued at 308 PM EDT Mon Mar 18 2024 Key Messages: 1. Dry conditions will continue Wednesday and Thursday with Wednesday being breezier and Thursday being drier. 2. Light rain is expected Friday into Friday night. 3. Drier and slightly cooler conditions are expected on Saturday, followed by a warming trend. Tuesday Night through Friday At the start of the period, westerly to northwesterly flow will be in place aloft with surface high pressure centered over the northern Gulf. This pattern will continue a dry start to the period with low- level moisture advection from the northwest expected ahead of another weak frontal boundary. Based on the overall synoptic setup, this will result in increased cloud cover, which will limit mixing and drop in RH`s. However, a more persistent westerly breeze will be in place based on the MSLP gradient and 850mb flow approaching 25 kts. By the end of the day, winds will shift to a more northerly direction, keeping fairly cool temperatures overnight. By Thursday, focus will turn towards a developing system over the Southern Plains where a shortwave/closed low will be ejecting from the main flow. Locally, Thursday will ultimately be drier due to subsidence and passage of the recent frontal boundary. This will likely allow for better mixing and a further drop in RH`s, but thankfully the MSLP gradient and 850mb flow will be weaker than Wednesday. Thursday night into Friday, the aforementioned system will move into the area with the surface low itself tracking to our south. This will limit instability and overall moisture to the Gulf Coast towards Florida. The more easterly to southeasterly flow in the lower levels will also cause downsloping, which will limit rainfall totals even more. Nevertheless, this system will bring area- wide PoPs to the forecast late-week. 850mb flow could exceed 30 kts, which may lead to a low-end mountain wave event when combined with a decent MSLP gradient. However, any impacts would likely be pretty limited. Saturday through Monday By Saturday, the system will progress east of the area, which will shift the flow to a more northerly or northwesterly direction and increased CAA. Moisture will likely exit the area fairly quickly, keeping PoPs focused closer to the mountains. Most places will likely see exiting cloud cover and slightly cooler conditions. Saturday night into Sunday morning, high pressure will be centered to our north, promoting subsidence and a return of drier conditions. Also during this time and towards Monday, there are indications of a strong system developing in the central U.S. Currently, the potential impact is increasing southerly flow, combined with dry conditions. For now, messaging will be limited based on limited confidence. && .AVIATION... (00Z TAFS) Issued at 716 PM EDT Mon Mar 18 2024 Winds will remain elevated overnight between 5 to 10 knots. The current thinking is that skies will remain SCT to BKN tonight, with SKC at CHA. Not expecting any precipitation near the terminals tonight. Winds turn toward the southwest on Tuesday with gusts up to 25 knots by the afternoon. Otherwise, VFR conditions expected to prevail. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 29 57 37 69 / 0 0 0 0 Knoxville McGhee Tyson Airport, TN 27 54 37 66 / 0 0 0 0 Oak Ridge, TN 26 56 35 67 / 0 0 0 0 Tri Cities Airport, TN 26 51 34 61 / 0 0 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...Wellington LONG TERM....BW AVIATION...Diegan

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