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

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335 FXUS64 KMRX 261940 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 340 PM EDT Wed Apr 26 2017 .SHORT TERM (Tonight and Tomorrow)... A strengthening southerly flow and increasing clouds late tonight will keep temperatures about 10 degrees above seasonal averages. A shortwave trough to our west will initiate a line of showers and thunderstorms across the Mississippi River Valley this evening, but with lower instability across our area, these thunderstorms should weaken as they approach the Southern Appalachians late tonight and Thursday morning. More scattered showers and thunderstorms may develop along the cold front on Thursday afternoon, but coverage is highly dependent on the amount of forcing and instability. Overall, the severe threat looks low with only marginal instability of 500-1000 J/kg and modest mid-level lapse rates combined with relatively weak forcing. Drier mid- levels and strong deep layer shear may support some strong to marginally severe thunderstorms on Thursday afternoon with damaging winds being the primary threat. .LONG TERM (Thursday night through Wednesday)... Cold front will be over the mountains at the beginning of the period with a few lingering showers and thunderstorms over extreme northeast Tennessee and southwest Virginia and along the eastern Tennessee and southwest North Carolina mountains. Weak high pressure later Thursday night and Friday as Atlantic ridge retrogrades some. Friday looks to be mostly dry but lingering moisture along the mountains could trigger a few showers and storms over southwest North Carolina and southeast Tennessee mountains. With strong heating and highs in the 80s expect isolated showers and storms in the evening. Another low pressure area over the plains and front develops and moves into the Ohio Valley and Kentucky Friday night and early Saturday. Models are in disagreement of the placement of this feature if far enough south it would increase moisture across northern plateau and southwest Virginia and cause some showers and storms there. Other models have it farther north. So will have low pops in above mentioned area. Then Saturday as boundary shifts north and ridging shifts north from Atlantic there will be late chance showers and storms along northeast Tennessee mountains and southwest North Carolina. Sunday deep low pressure over Mississippi Valley and front moves into Tennessee Valley. Surge of moisture from south will bring in likely chance of showers and storms over the region by Sunday night and continue Monday. The front shifts east Monday with drying Monday night and Tuesday. Another front and chance of showers and storms approaches Wednesday. Temperatures will be very warm Friday through Sunday ahead of frontal system Sunday night. Northern and western sections of the forecast area could have some strong to possibly severe storms overnight Friday night. Also stronger storms possible Sunday night into Monday. Much cooler temperatures Monday and Tuesday with highs around 70 to the mid 70s then gradually rising through next week back to near 80 by Wednesday. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 64 76 55 85 / 50 70 10 10 Knoxville McGhee Tyson Airport, TN 62 76 55 85 / 20 50 10 10 Oak Ridge, TN 63 77 54 85 / 30 50 10 10 Tri Cities Airport, TN 54 77 53 85 / 0 40 20 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ JB/TD is the U.S. government's official web portal to all federal, state and local government web resources and services.