Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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095 FXUS64 KMRX 141514 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 1114 AM EDT Tue May 14 2024 ...New UPDATE... .UPDATE... Issued at 1110 AM EDT Tue May 14 2024 An upper low was located over Missouri late this morning with a surface low over the lower Ohio Valley. Showers were beginning to develop to the south of the area late this morning. Temperatures were in the mid to upper 60s. This convection should increase rapidly by early afternoon as temperatures warm to the lower 70s with some heating with a risk for some strong winds and marginally severe hail with instability increasing. This afternoon convection should decrease early this evening. Farther west over middle Tennessee ahead of the upper low where instability will be higher an area of showers and thunderstorms will approach the plateau around 00Z with a better risk for strong to severe thunderstorms across the central and southern areas through the evening along and south of I-40. Marginally severe hail around 1 inch diameter and wind gusts over 50 mph are possible and a very low risk for tornadoes. The upper low will move into northern KY and southern IN by around 06Z tonight. Updated zones to increase rain chances some this afternoon. Skies should stay mostly cloudy all areas with highs in the 70s. Updated forecast sent. && .SHORT TERM... (Today and tonight) Issued at 316 AM EDT Tue May 14 2024 Key Messages: 1. First round of showers and possibly embedded thunderstorms, will arrive later this morning with best chances along the Appalachians. Late morning and early afternoon clearing in some areas may allow the atmosphere to destabilize. 1. Strong to possibly severe storms from the next round arrive late this afternoon and evening for the Plateau and southeast Tennessee. Marginal severe hail up to 1 inch and strong gusty winds to 50 mph are possible. Low-end threat of tornadoes across southeast Tennessee late in the day. Discussion: A nearly vertically stacked upper low and sfc low pressure center will slowly edge eastward from west of the Mississippi to the Tennessee Valley by late tonight. A warm front is expected to lift north and then the occluded front will lift northeast later tonight. Generally, two rounds will occur today with a very short window between them. The early day showers and thunderstorms are not expected to be anywhere near severe thresholds as CAPE values will generally be under 500 J/kg with this first round. The best chances for this activity will be along the Appalachians. Breaks in the clouds and daytime heating will allow the atmosphere to destabilize in time for the next round late this afternoon and early evening. CAPE values will generally exceed 1000 J/kg. Shear will be strong enough to support organized multi- cluster storms with effective shear of 35 m2/s2 and up. Mid-level lapse rates near 6.5 deg C supports at least severe sized hail. Overall, marginal severe hail and damaging winds are the main threat. Which the SPC has placed us under for today. Also cannot rule out a low-end threat for tornadoes as well. The Wind Advisory for the mountains will also expire a 4 AM EDT this morning as winds have decreased. Winds elsewhere will generally be pretty light today, but of course can be gusty with any thunderstorms. && .LONG TERM... (Wednesday through Monday) Issued at 316 AM EDT Tue May 14 2024 Key Messages: 1. Showers and thunderstorms continue on Wednesday, though likely not severe in nature. 2. A short break is expected on Thursday before another round of storms begins heading into the weekend. Discussion: A slow moving upper low will traverse the southern Appalachian region on Wednesday, with center passing over general vicinity of the Kentucky, Virginia, and West Virginia border during the early to mid afternoon time frame. Models currently depict another vort lobe associated with this feature swinging through our CWA during the same general time of day. Model soundings show, understandably, weak shear in place, but the increased lapse rates aloft associated with the passing upper low will promote surface based instability of around 1,000 J/kg over the central and northern parts of the CWA Wed afternoon. Perhaps there`s an outside chance for a stray damaging wind gust, but overall I would expect just some stronger cellular convection. Much of Wednesday night and Thursday should be dry as the upper low pushes and we sit between systems. Expect temperatures to climb back up to near or above normal to end the week. The next system approaches on Friday, ejecting out of the plains towards the Ohio valley as we head into the weekend. Have pretty high confidence in increasing rain chances during the day Friday, and into Saturday, but less so about whether there will be any severe storms in our area. Some models are showing more vigorous thunderstorm activity to our south near the Gulf Coast which typically inhibits convection in the southern Appalachian. But if the boundary and storms develop further to the north we`ll likely see more widespread thunderstorms in our region. && .AVIATION... (12Z TAFS) Issued at 740 AM EDT Tue May 14 2024 Expecting a couple rounds of showers and thunderstorms today, with the first approaching the area later morning and the second and probably much stronger activity, arriving from the west sometime in the late afternoon and evening. CHA appears will remain mostly MVFR for the day. TYS and TRI appear will remain VFR to low VFR with CIGS dropping from a shower or thunderstorm through the period. Winds no more than 10 KT, but could very well gust with a thunderstorm. Depending how much clearing occurs overnight, if at all, there may be a chance for fog. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 77 62 78 61 / 80 70 60 0 Knoxville McGhee Tyson Airport, TN 78 61 74 61 / 80 80 80 20 Oak Ridge, TN 77 60 75 60 / 80 100 80 20 Tri Cities Airport, TN 76 58 72 59 / 60 80 80 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...TD LONG TERM....CD AVIATION...KS