FXUS64 KMRX 071929 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 329 PM EDT Tue May 7 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Wednesday night) Issued at 326 PM EDT Tue May 7 2024 Key Messages: 1. Scattered to numerous showers and thunderstorms will be around this afternoon and tonight, some of which could be strong to severe with damaging winds and large hail as the main threats. A low-end tornado threat exists as well mainly across northern portions of the area. 2. A much higher severe weather risk exists from later Wednesday afternoon through Wednesday night. Damaging winds and hail are the main concerns, but there is also a fairly notable tornado risk in comparison to most events in our area, especially north and west of Knoxville. 3. Repeated showers and storms could lead to flash flooding anytime from this afternoon through Wednesday night. Discussion: We start the period in a broad warm sector with an upper level northern jet edging eastward across the Ohio Valley and a southern jet pushing east across the Gulf States. MLCAPE values are approaching or exceeding 1500 J/kg across most of the area and a strengthening and increasingly veered wind profile is bringing deep layer/effective shear values to around 40 kts. Thunderstorms that develop this afternoon into tonight may become severe, with damaging winds and hail the primary threats. There is also a very low risk of a tornado mainly across the north where the better shear will exist in the lower levels. For Wednesday into Wednesday night the complicated jet structure makes the upper forcing difficult to pin down at this time, and mutes confidence in the details of how the timing of the convection will play out. However, it appears we may see two periods of upper divergence moving across the area associated with the jet, one in the afternoon/early evening and another during the night. Any ongoing weaker convection in the morning may slow the destabilization early in the day, but MLCAPES look likely to approach or exceed 2000 J/kg by late afternoon and by late afternoon/early Wed night the veering wind profile shows effective shear approaching 50kts and 0-1km shear of 20 to 30kts across much of the area. Given the expected wind profile, instability, and very impressive mid-level lapse rates (7.0 C/km lapse rates and 700+ J/kg of -10 to -30 C CAPE), there is a threat for all severe weather hazards across the area with damaging winds, large hail, and tornados possible. The tornado threat looks highest over our northwestern areas, but does exist area wide. While the CAMS are still are not in great agreement on how the convection plays out, they are coming into somewhat better alignment and it currently looks like there will be an earlier round of storms with the greatest threat across the Plateau and north during the late afternoon/early evening, then another round area wide overnight. Some of the guidance suggests there will be a weak surface boundary across portions of the northern Plateau and north which could help to focus the convection during the late afternoon/early evening and also may be a focus for the tornado threat at least early on. In addition to the other threats, repeated rounds of rainfall will continue the concern for the possibility of flash flooding, especially given the recent rains the past few days. && .LONG TERM... (Thursday through next Tuesday) Issued at 326 PM EDT Tue May 7 2024 Key Message: 1. Several chances for showers, mostly light, through the period with much cooler temperatures through Sunday. No severe weather anticipated beyond Thursday morning. Discussion. We begin the long term period with showers and storms still ongoing across the area. The severe threat should be greatly diminished compared to the Wednesday night period. However, a few storms may still be strong to severe as the Thursday period begins. Showers and storms then exit to our east from late morning through mid afternoon as drier air begins to move into the region. The main threat with these lingering showers and storms still appears to be centered around flash flooding. Friday through Sunday, pops are back in the forecast as several shortwaves swing through the longwave trough that will be in place across our area. Temperatures will be much cooler as we will be in a northwest flow pattern, with temps 5 to 10 degrees below normal. Monday and Tuesday, we return to a more zonal pattern and temperatures begin to climb back into the upper 70s and low 80s. Pops remain in the forecast as a few disturbances are progged to zip through the zonal flow. && .AVIATION... (18Z TAFS) Issued at 123 PM EDT Tue May 7 2024 Will see convection around at times although location/timing uncertainties are still significant. Will try to indicate periods of higher probability with tempo and prob30 groups. Will likely see conditions dip to MVFR or lower with any stronger showers/thunderstorms, and may see a period of more persistent MVFR cigs late in the period with the highest chance for that looking to be at TRI. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 69 86 69 84 / 60 70 70 90 Knoxville McGhee Tyson Airport, TN 67 83 67 80 / 70 70 80 90 Oak Ridge, TN 67 82 66 82 / 60 70 70 90 Tri Cities Airport, TN 64 81 63 76 / 60 60 60 90 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... AVIATION...