####018005211#### FXUS64 KMRX 180208 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 1008 PM EDT Sat May 17 2025 ...New UPDATE... .UPDATE... Issued at 1005 PM EDT Sat May 17 2025 So far this evening, winds have remained across many of the observation sites with high-level clouds also moving in from the west. The combination of both trends has limited any radiational cooling and dept temperatures considerably warmer than expected. This has also done the opposite for dew points as they have remained lower than expected. Based on these recent and expected trends, temperatures have been increased with lesser change to dew points. The remaining aspects of the forecast were kept largely the same. && .SHORT TERM... (This evening through Sunday) Issued at 234 PM EDT Sat May 17 2025 Key Messages: 1. Dry and mild tonight. 2. A few showers or possibly a thunderstorm south Sunday, but most areas will be dry. Discussion: Gusty winds this afternoon will subside early this evening. Surface high pressure and dry air aloft will start our night out mostly clear and dry. Weak short wave energy moving through quasi-zonal flow aloft will bring an increase in high/mid clouds to the area mainly south tonight. Low temperatures will be just a bit above seasonal normals. As the weak impulse moves by Sunday, there may be enough weak forcing and moisture to squeeze out a few light showers or sprinkles early Sunday morning south, and models indicate modest instability developing by afternoon (HREF mean MUCAPE values generally reach 500- 1000 J/kg across much of the south), so a few more vigorous showers and perhaps even a few thunderstorms may develop south during the afternoon. However, most locations across our area will remain dry Sunday. && .LONG TERM... (Sunday night through next Saturday) Issued at 234 PM EDT Sat May 17 2025 Key Messages: 1. Marginal risk of strong to severe storms, particularly in the southern Valley and Cumberland Plateau, late Mon morning into afternoon. 2. Additional chances for strong to severe showers and storms Tuesday afternoon into early Wednesday morning, however, a fair amount of uncertainty exist at this time. 3. Cooler Wednesday into the late week. Discussion: An upper low will be positioned over the Mountain West as well as Nova Scotia as ridging builds in locally Sunday night into Monday. Additionally, a surface boundary extending from a surface low within the northern Plains will be draped across the region. Vort max translating through mean flow aloft will promote a potential ridge riding MCS late Monday morning or into the afternoon - timing discrepancies remain. LREF Joint probabilities of MUCAPE > 1500 J/kg and bulk shear > 30kts are around 60 to 80% in the southern Plateau and Valley, thus, we will continue to monitor for marginal severe potential with winds and hail the main threats. Uncertainty continues into Tuesday afternoon with whether there will be enough forcing to initiate convection. Latest NAM suggest a drier pattern while more coarse, long-range models suggest upper divergence and isentropic ascent well ahead of frontal forcing will prove potent enough. In this event, much of the area along and south of the TN/KY border will remain in the warm sector with MLCAPE between 1000-1500J/kg and effective shear near 40kts per latest GFS soundings. The cold front will then swing eastward maintaining showers and storms with the potential for severe weather late Tuesday night into early Wednesday. Hail and winds will be the primary threats. However, confidence still remains rather low as timing and mode of convective activity will play a crucial role on severe potential and associated hazards. We trend cooler post frontal passage Wednesday into the end of the work week, though the potential for showers will linger with wrap around moisture in a northwest flow pattern as an upper low churns over the Great Lakes region. && .AVIATION... (00Z TAFS) Issued at 726 PM EDT Sat May 17 2025 Breezy winds will decrease overnight, generally around 10 kts or less at all of the sites. By the early morning hours, showers may move into southern portions of the area with VCSH included at CHA. At this time, reductions are not likely but may be included in future issuances. Some additional activity is possible during the day further north, but this was left out for the time being. A persistent westerly wind can be expected later on. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 66 85 66 86 / 10 30 20 60 Knoxville McGhee Tyson Airport, TN 62 82 61 81 / 0 10 10 70 Oak Ridge, TN 61 83 60 80 / 0 10 10 70 Tri Cities Airport, TN 57 80 55 79 / 0 10 0 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... LONG TERM....KRS AVIATION...BW