420 FXUS64 KMRX 011407 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 1007 AM EDT Sat Apr 1 2023 ...New UPDATE... .UPDATE... Issued at 1001 AM EDT Sat Apr 1 2023 The precipitation has exited on schedule, and the forecast generally looks to be on track. Still will see strong gusty winds this afternoon after the brief lull this morning, so will leave afternoon winds and the high wind warning/wind advisories as they are and only tweak the winds down a bit during the next few hours. Otherwise, just some minor adjustments to sky, temps and dew points with this update. && .SHORT TERM... (Today and tonight) Issued at 110 AM EDT Sat Apr 1 2023 Key Messages: 1. A line of showers and thunderstorms will cross the area this morning, mainly between 3 and 7 am. Main threat will be damaging winds, with the highest risk along and near the Cumberland Plateau. An isolated tornado cannot be ruled out in the southern Plateau and southern TN Valley area. 2. Strong pressure gradient winds across the entire area today, especially across the far East Tennessee mountains and foothills. Wind Advisories and High Wind Warnings remain in effect. Discussion: A warm front is currently located across the area, approximately along I-75 from the KY border to Knoxville, then eastward along I-40, evidenced by a sharp temperature gradient and gusty winds south of the front. Over the next few hours, this front should slowly move northward. Areas south of this front will have surface-based instability, and thus the greater risk of seeing strong to severe storms as the linear convection moves through. Shear parameters remain very high across the region, with low instability. But the HRRR does show some 0-1 km CAPE values that may support a tornado threat in southern parts of the area, and the HREF shows some updraft helicity tracks in our southern counties. Current convection in Middle TN is expected to have a weakening trend as it approaches as it encounters a less favorable environment, but frontogenetic forcing will still remain quite strong, and thus a severe threat will be present in our area overnight. The other concern in the short term will be strong pressure gradient winds through this afternoon. Gusts in the TN Valley will be between 40-50 mph, potentially higher in isolated spots (like TYS, which tends to be the windiest obs site). We are seeing winds in the mountains well into High Wind Warning range, with 75 mph at Cove Mountain. These gradient winds will likely peak this afternoon with mixing of 40-50 kt 850 mb winds down to the surface. Some locations in the foothills and Plateau are already gusting above 40 mph. The current Advisories and High Wind Warnings appear to capture the situation well, so no changes will be made to them. Winds will diminish this evening as high pressure builds over the area. Temperatures will drop into the mid and upper 30s in most spots, with some lower 30s in western and northern sections, and 20s in the mountains. This may result in some areas of frost developing. Will defer any front/freeze products to the day shift due to the higher priority of severe and high wind concerns on this shift. && .LONG TERM... (Sunday through Friday) Issued at 110 AM EDT Sat Apr 1 2023 With the focus on the short term period, no major changes will be made to the long term grids. The previous discussion remains valid. Key Messages: 1. Below normal temperatures Saturday night/Sunday morning with patchy frost possible on the Plateau and Appalachian Mountains. 2. Shower and thunderstorm chances return beginning Tuesday as a cold front tries to move through the area. Discussion: Surface high pressure and weak mid level ridging will begin to build in late in the weekend, which kick start a quick warm up into next week. Temperatures are expected to climb into the lower 80's by Tuesday. A weak shortwave is expected to push through the southeast to start off the work week. Still some discrepancies with the exact location of this shortwave, but areas near or south of the TN/GA state line have the highest chance to get a shower from this system. A strengthening system will develop across the plains and try to drag a cold front through the eastern US. With our area being in the warm sector expect to see scattered showers and thunderstorms develop on Tuesday and Wednesday. Some of the deterministic models are indicating that the mid week could stall out somewhere along the Tennessee Valley into the Mid Atlantic. Should this happen it would likely act as a focusing mechanism for continuous rain chances for the second half of the week and into the weekend, before finally moving out late in the weekend. Still lots of uncertainty with the location of the front this far out, but it will be worth keeping an eye on as showers and storms are expected along the front for several days next week. && .AVIATION... (12Z TAFS) Issued at 704 AM EDT Sat Apr 1 2023 Gusty winds will be the main aviation impact today. Gusts of 35 to 45 kt are expected at all sites from late morning into the evening. Direction will be predominantly SW, with a gradual shift to W and NW tonight as winds diminish. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 77 42 69 50 / 10 0 0 20 Knoxville McGhee Tyson Airport, TN 74 38 65 45 / 20 0 0 10 Oak Ridge, TN 75 37 65 45 / 10 0 0 10 Tri Cities Airport, TN 72 37 60 40 / 40 10 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Wind Advisory until 8 PM EDT this evening for Cherokee-Clay. TN...Wind Advisory until 8 PM EDT /7 PM CDT/ this evening for Anderson-Bledsoe-Bradley-Campbell-Claiborne-East Polk- Grainger-Hamblen-Hamilton-Hancock-Hawkins-Jefferson-Knox- Loudon-Marion-McMinn-Meigs-Morgan-North Sevier-Northwest Blount-Northwest Carter-Northwest Cocke-Northwest Greene- Northwest Monroe-Rhea-Roane-Scott TN-Sequatchie-Sullivan- Union-Washington TN-West Polk. High Wind Warning until 11 PM EDT this evening for Blount Smoky Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. VA...Wind Advisory until 8 PM EDT this evening for Lee-Russell-Scott VA-Washington VA-Wise. && $$ SHORT TERM...DGS LONG TERM....DGS AVIATION...DGS