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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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497 FXUS64 KMRX 131731 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 131 PM EDT Tue Aug 13 2024 ...New AVIATION... .UPDATE... Issued at 909 AM EDT Tue Aug 13 2024 Forecast on track this morning with only minor tweaks to hourly temps and dewpoints to match up with latest obs. && .SHORT TERM... (Today and tonight) Issued at 256 AM EDT Tue Aug 13 2024 Key Messages: 1. Mix of clouds and sun, can`t rule out a shower in higher elevations, but otherwise dry and warm again today. Discussion: Northwesterly flow aloft caused by troughing to our northeast persists for another day today. Down closer to the surface, winds will remain generally northerly, helping keep our mild mannered airmass in place for a bit longer. There`s been some light returns early this morning across Kentucky, however observations indicate the rain is either not reaching the ground or its not measurable. It is conceivable though that some locations across southwest Virginia might see a sprinkle or two before activity dissipates around sunrise today. For this afternoon, HREF guidance really is not indicating much in the way of convection, with the subsidence aloft helping to cap the atmosphere. Expecting today to be another dry summer day, with a slight chance of a shower in the East Tennessee mountains along the North Carolina border. Tonight should then be another calm, quiet night much like the last few nights. Guidance indicates some potential for patchy fog early Wednesday morning, though left it out of the forecast for now. && .LONG TERM... (Wednesday through Monday) Issued at 256 AM EDT Tue Aug 13 2024 Key Messages: 1. Mostly dry weather for Wednesday into Thursday. 2. Chances for showers and storms will increase in the Friday/Saturday time frame, then decrease again for the latter periods. Discussion: We start the period with an upper ridge to our west and a trough over the East Coast, along with surface high pressure extending into our area from the north. The upper ridge will edge east into our area Wednesday into Thursday, but will be flattening out as an upper trough digs into the western Great Lakes region and Mississippi Valley. Models differ on how quickly the upper ridge over our area will break down with short wave energy moving out ahead of the main trough, but overall the Wednesday and Thursday time frame look to be mostly precipitation free as moisture, especially in the lower levels, will be slow to increase. Will carry slight chance PoPs in some of the higher terrain Thursday, but the better chance for precipitation will occur in the Friday/Saturday time frame as the main upper trough moves into our area and a cold front moves through. Models suggest an uptick in effective shear as the trough moves in although right now mean GEFS SBCAPES are limited with values generally around 1250 J/kg or less. We will continue to keep an eye on the potential for a few stronger/severe storms Friday and/or Saturday given the uptick in shear, especially if available convective energy trends higher. Right now the highest chances for showers and storms looks to be Friday, with most models suggesting drier air starting to filter in on Saturday. However, the timing of how quickly the front moves through and the drying commences is still uncertain. The upper trough is forecast to persist over the eastern CONUS Sunday and Monday. We will remain in northwest flow aloft and there may be some weak short wave energy moving through the flow during these latter periods, but available moisture/convective energy looks limited so will have lower chances for convection both days. && .AVIATION... (18Z TAFS) Issued at 121 PM EDT Tue Aug 13 2024 VFR conditions through the period at all sites with light northerly winds at CHA and TYS with VRB at TRI. A few data sources showing fog at TRI tonight but low confidence so will not include in this TAF set. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 69 91 70 91 / 0 0 0 10 Knoxville McGhee Tyson Airport, TN 64 89 66 89 / 0 0 0 10 Oak Ridge, TN 64 88 66 88 / 0 0 0 10 Tri Cities Airport, TN 61 85 61 86 / 0 10 0 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... AVIATION...