Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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384 FXUS64 KMRX 121134 AFDMRX AREA FORECAST DISCUSSION National Weather Service Morristown TN 734 AM EDT Sat Jun 12 2021 .UPDATE... FOR 12Z AVIATION. && .SHORT TERM (Today and Tonight)... Key Messages: 1) Isolated showers and thunderstorms may linger around the area today, with greatest storm chances along the higher terrain 2) Can`t rule out a rogue strong to severe storm, but most places should remain dry today. Discussion: Generally much quieter weather is expected today compared to the last several days. Trough axis that brought wide spread showers and storms has moved east of the forecast area. We are still within the broad trough over the eastern U.S. so there will still be enough synoptic forcing to see more isolated storms today. Greatest chances for showers and storms will be along the higher terrain of the southern Appalachian Mountains today as storms can tap into the orographic lift as they move southeastward. Expect coverage to once again increase with the heating later in the day, but still expect the coverage of storms today to be pretty spotty, and most people should remain dry throughout the day. Forecast soundings indicate that there will still be enough instability under this drier air that we could see an isolated strong to severe storm later in the day...Especially if they tap into the mid-level air we could see a strong wind gust, or hail. Most of the CAMs are fairly unimpressed with convective initiation later in the day today as they seem to keep most convection in our area suppressed under the drier air with more robust storm development further to our south across GA/SC. Think the threat for widespread severe weather is low, but can`t completely rule out a rouge severe storm. Storm chances really diminish after the sun sets as the trough continues to move eastward and storms lose the solar radiation, and tonight should be fairly quiet across the forecast area. ABM .LONG TERM...(Sunday through Friday night)... Key Messages: 1. Frontal passage on Sunday supporting isolated to scattered showers and thunderstorms. A few of these storms may become strong. 2. Temperatures will continue to be warm through early next week. Cooler and drier conditions will be found behind the mid-week front. Discussion: The extended period continues to be consistent with no significant changes to the forecast. With ridging centered across the Central CONUS and upper trough axis shifting eastward across the Carolinas, subsidence will become more pronounced with drier air and lower PW values. This will lower the overall flash flood risk with convection on Sunday. The increased ridging from the west on Sunday will result in some convective inhibition, and make any severe risk conditional. With MLCAPE of around 2000 J/Kg and DCAPE in excess of 1200 J/Kg, a conditional severe risk will exist with isolated to scattered convection that does develop along the approaching cold front and across the eastern mountain zones. The main risk will be damaging winds. Behind the front, drier air arrives across the forecast area on Monday and Tuesday, but temperatures remain above normal with upper ridging building in from the west. On Wednesday, an upper shortwave will amplify troughing across the Northeast CONUS and bring a stronger cold front across our area dropping temperatures below normal late in the period. JB && .AVIATION... 12Z TAF DISCUSSION. Spotty showers and thunderstorms will be the biggest weather story for today. Expect coverage to be highest along the southern Appalachian Mountains and decrease as you get further away from the higher terrain. KTRI has the highest chance of seeing storms today, but can`t rule it out at KTYS/KCHA either, but chances of storms are much lower at those airports. Guidance is suggesting some widespread dense fog to form tomorrow morning at the end of these TAFs, so have hinted at this but didn`t go into much detail to keep TAFs to a reasonable length. ABM && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 91 70 92 71 92 / 20 20 30 0 0 Knoxville McGhee Tyson Airport, TN 86 68 89 69 90 / 30 20 30 10 0 Oak Ridge, TN 87 68 90 68 90 / 20 10 30 10 0 Tri Cities Airport, TN 82 64 87 66 87 / 30 30 40 20 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$

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