FXUS64 KMRX 092319 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 719 PM EDT Fri May 9 2025 ...New AVIATION... .SHORT TERM... (This evening through Saturday) Issued at 155 PM EDT Fri May 9 2025 Key Messages: 1. Drier and cooler tonight with lows in the 40s and 50s. 2. Rain chances will creep into the region from the south by Saturday afternoon. Discussion: Tonight, the upper level cut-off low will be moving away from the region into the Northeast. At the surface, a cold front will be just south of the region. A cooler, drier air mass is in place behind the front. Therefore, POPs will be near zero overnight and fog will not be an issue like it was this morning. Lows will be in the 40s for Northeast Tennessee and Southwest Virginia. Lows will be in the lower to mid 50s from generally Knoxville southward as clouds move into the region from the south. Tomorrow, rain chances will start to creep into the region from the south by afternoon as an upper level cut-off low sits over LA/MS. The surface low will be near the AL/MS coast with a warm front over Central or Northern AL/GA. Shower activity will likely weaken as it moves in from the south tomorrow afternoon. Some rain may not reach the ground with a fairly dry air mass near the surface. Any rain amounts will be low and generally confined to south of I-40. With increasing cloud cover tomorrow, highs will be slightly below normal in the lower to mid 70s. && .LONG TERM... (Saturday night through next Friday) Issued at 155 PM EDT Fri May 9 2025 Key messages: 1. Active and frequently rainy Saturday night through the middle of next week. Discussion: The long term forecast period revolves around the evolution of a blocking pattern across the central/eastern US. An upper low forms over southern Louisiana tonight into Saturday, then cuts off and gets stuck south of a western ridge that shifts east to the upper Mississippi valley Saturday night into Sunday. Late in the weekend another trough/upper low digs south into the Pac NW which should displace the ridge and allow the Louisiana low to open up and lift northward towards the TN valley, but this feature and associated rainfall may not clear our area to the northeast until mid/late next week. While Saturday evening or even into the overnight hours could remain dry, Sunday through mid week looks fairly wet. The upper low remains over Louisiana during the day Sunday but then shifts north to the Missouri bootheel by Monday night, resulting in numerous impulses ejecting north around the eastern periphery of this low into our forecast area. All of this points to numerous rounds of rainfall Sunday into the first part of next week. I'm quite sure there will be dry periods in there, but the heavy handed and widespread rain chances most all guidance has Sunday night through Tuesday night is hard to go against. For instances, increasing southeast H85 flow Sun afternoon through Mon would promote mountain wave activity and downslope drying, but will it be enough to lower PoPs significantly in any place...I'm just not sure at this point. Otherwise, the upper low opens up and ejects northeast of our forecast area Wednesday night into Thursday next week. If that timing holds up, then ridging will build in from the west to finish out next week and it could get fairly warm, with current NBM guidance pointing to highs in the mid and even upper 80s by week's end. Timing on these blocking patterns is oftentimes poorly handled though , so time will tell. && .AVIATION... (00Z TAFS) Issued at 640 PM EDT Fri May 9 2025 Some patches of light rain or sprinkles will be around CHA late in the period, but vsby/cigs should stay at VFR levels. VFR conditions are expected for the period all sites. Winds will generally be light from the north and northeast. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 56 70 57 74 / 10 50 50 50 Knoxville McGhee Tyson Airport, TN 51 73 55 77 / 0 10 40 40 Oak Ridge, TN 50 73 55 77 / 0 10 30 30 Tri Cities Airport, TN 43 74 51 73 / 0 0 20 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...McD LONG TERM....CD AVIATION...