642 FXUS64 KMRX 301132 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 732 AM EDT Fri Jun 30 2023 ...New AVIATION... .SHORT TERM... (Today and tonight) Issued at 301 AM EDT Fri Jun 30 2023 1. Low confidence in the timing of upstream MCS activity and the extent of the impacts on our area. 2. Forecast high temperatures for Friday range from the upper 80s to mid/upper 90s. Discussion: Unfortunately, a lot of uncertainty surrounds the forecast still. CAMS point to showers and storms entering northeast TN from storms that are currently developing upstream in central and northern KY. Without much instability in the area as these showers/storms make their way to us in the early morning hours, not expecting any of these to become severe, but will continue to monitor as they get closer. Kept chance PoPs in the area for most of the day, but best chance for any activity in the morning looks to be between 6AM and Noon EDT. Afternoon high temps will likely climb into the 90s in many places, with the warmest temps (mid and upper 90s) near Chattanooga. This will push heat indices into the 100-105 degree range, so going to continue to hold of on any Heat Advisories for the time being since forecast highs have come down a few degrees, and are still contingent on cloud cover from any rain and storms as well. But, upper 90s are still very hot--so remember to practice heat safety if you are having any outdoor activities. Another round of showers and storms is possible in the afternoon and evening hours. Possible that an MCS will move into the area from the Ohio Valley tomorrow afternoon/evening. Some of the Hi-res guidance depicts a more organized complex of storms while others still show more scattered activity. If storms are able to develop and enter the area tomorrow afternoon, they could become strong and severe--main threats will be damaging winds and hail. && .LONG TERM... (Saturday through Thursday) Issued at 301 AM EDT Fri Jun 30 2023 Key Messages: 1. Hot conditions likely Saturday and Sunday, with heat indices of 100 or higher possible mainly across portions of the southern and central valley. 2. Showers and thunderstorms will be around at times through the period, although details on timing are uncertain. 3. Temperatures closer to seasonal normals are expected for Monday through Thursday. Discussion: We start the period under the upper ridge, but the ridge will be breaking down Sunday as an upper trough moves through the Great Lakes Region followed by quasi-zonal flow across the area. Models continue to suggest MCS development to our northwest that then impacts our area during the weekend, although there is disagreement on how many rounds as well as timing both of which are much more uncertain. There remains the possibility of strong to severe storms with any MCS that moves through, with wind and hail the primary threats. This will continue to mentioned in the HWO. It will be hot both Saturday and Sunday, although timing of any convection as well as possible debris cloudiness may moderate temperatures at least across portions of the area. However, right now it looks like heat indices will likely reach or exceed 100 across portions of the southern and central valley both afternoons. This will continue to be mentioned in the HWO. With the transition in the flow aloft, a weak cold front is forecast to sag into our area Monday along with additional showers and thunderstorms. This front will likely stall over or near our area before gradually washing out. With no strong drying expected, we will continue to see convection around at times for the Tuesday through Thursday time frame with highest PoPs expected during the afternoons. Temperatures should generally run closer to seasonal normals. && .AVIATION... (12Z TAFS) Issued at 722 AM EDT Fri Jun 30 2023 Rain and storms are currently making their way through the area from the north. The line of the storms approaching TYS is stronger, with gusty winds and frequent lightning. This round of activity is expected to dissipate around noon today, but some VCSH may linger around. It is possible that another round of rain and thunderstorms enters the area this afternoon and evening, but confidence about this is still low. If these storms do develop and move into the area, they would more likely effect TRI and TYS. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 96 73 96 74 / 40 30 30 20 Knoxville McGhee Tyson Airport, TN 90 72 92 72 / 60 30 30 30 Oak Ridge, TN 90 71 93 72 / 60 30 40 30 Tri Cities Airport, TN 86 67 89 68 / 50 30 50 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... AVIATION...Williams