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

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000 FXUS64 KMRX 030748 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 248 AM EST Sat Dec 3 2016 .SHORT TERM (Today through Sunday morning)... The low pressure trough over the Rockies and Desert SW tonight will split into a southern stream closed low that will slowly track east into northern Mexico, and a more progressive northern stream trough that will move into the MS Valley on Sunday. The southern stream low will spread a deep flow of moisture across the Southeast today, with isentropic lift increasing in our southern sections this evening as the northern stream trough approaches. Lift continues to strengthen as the 850 mb low moves into West TN Sunday morning, with a convergence zone extending east across the southern TN border. Will have POPs in the categorical range from late tonight through noon Sunday. As the precip spreads in tonight, temperatures in the northern mountains and SW VA may support a little snow, mainly at or above 3000 ft. With initial QPF amounts in the northern half being light while temperatures are cold enough, there should be little accumulation before warm advection raises temperatures Sunday morning. .LONG TERM (Sunday through Friday)... Rain chances will continue through the day on Sunday as the atmosphere remains relatively moist. The better chances for precipitation on Sunday will be in our Southern counties closer to the boundary near the Gulf of Mexico. Models are in some disagreement with when/if the precipitation will end before our next round begins. GFS wants to move the precipitation south of us by Monday morning and slowly bring in the low pressure system from Mexico/Texas by Monday night. The ECMWF looks to hold on to rain chances a bit longer and keep the precipitation present in our southern counties through Monday. The European solution is also a bit faster in bringing in precipitation from the low Monday evening. Regardless of which solution you believe they both are producing decent widespread rain chances Monday night into Tuesday morning, and hopefully helping us erase some of the rainfall deficit we`ve seen this year. The majority of the rain leaves the area with the low pressure system by Wednesday morning. A cold front quickly moves in behind and will usher in some of the coldest temperatures we`ve seen this season. Highs will barely reach the 40`s in most places Thursday and many places won`t even get above freezing on Friday. Along with this front there will be some precipitation chances, but models vary largely with how much will be present. Will go with a blend between the GFS/ECMWF in this regard. If widespread precipitation does occur with this system and temperatures stay cold enough we could see some snow showers behind the front. However... due to past model performance and current disagreement with this latest run, confidence is very low on what might occur at the end of the work week. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 55 43 48 45 / 10 100 100 50 Knoxville McGhee Tyson Airport, TN 50 40 46 43 / 0 90 90 50 Oak Ridge, TN 51 40 47 43 / 0 80 80 50 Tri Cities Airport, TN 47 35 45 40 / 0 50 80 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ DGS/ABM

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