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

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000 FXUS64 KMRX 040800 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 300 AM EST Sun Dec 4 2016 .SHORT TERM (Today and tonight)...
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A surface low will track east along the Gulf coast today, while a strengthening S-SW flow spreads deep moisture across the area in response to an approaching northern stream shortwave trough. Isentropic lift and divergence aloft in the right entrance of the jetstream will produce catergorical pops all day. Temperatures in higher elevations, mainly at or above 4000 ft, will support some snow this morning through 15z, but accumulations should be less than 1 inch. Highest QPF amounts will be in southern sections where 850 mb convergence and theta-e advection will be strongest, and 1 to 1.5 inches are expected through today. Based on the 850 mb winds shown by the NAM, winds in the mountains will likely be near advisory levels with gusts of 40-50 mph, and the Wind Advisory will be continued. Dry air aloft begins to move into the area from the west late this afternoon, and most of the significant lift will be to our east by 00z. Forecast soundings after 06z tonight show saturation up to 800 mb, with very dry air above, suggesting just clouds and drizzle with little measureable rain. ZCZC MEMWRKAFD 040748 TTAA00 KMEM DDHHMM .LONG TERM (Monday through Saturday)... We will get a break from rain on Monday, but the big question is how long will this break be? If you believe the NAM/ECMWF it will be relatively brief with rain ahead of the low in Texas expected to move into our southwest counties Monday morning/early afternoon. However, if the GFS is correct rain will stay to our south and west longer and not move into our southwest counties until Monday night. All the models agree that there will be enough moisture to produce rain, but the GFS keeps all of the lift well to our south. The GFS is much slower and further south with respect to a the surface low as it moves out of TX/LA early next week. So confidence is somewhat low for this part of the forecast even though it`s less than 48 hours away. Rain will definitely be present by Tuesday morning as the low moves through Tennessee. If the timing/track of the system lines up well enough we could even see some thunderstorms Monday evening into Tuesday morning. Rain will linger through Tuesday evening and in some locations even into Wednesday morning. On the backside of this system much colder air will funnel in from the north and bring the coldest temperatures we`ve seen this season for the end of the work week and into the weekend. Temperatures will bottom out on Friday/Saturday morning with lows in the teens to 20`s across the area. Daytime won`t help warm us up that much with Friday`s high temperatures expected to be below or barely above freezing across much of the forecast area. Along with these colder temperatures might see another round of precipitation (depending on which model you believe) on Thursday. ECMWF shows a system zip across the area and bring us precipitation while the GFS keeps most of the moisture to our north and any system that moves through dry. Both agree that colder temperatures will stick around and we could see some light snow over the area on the back side of this. However at this time any accumulations would be light and the forecast is likely to change as this is still 5+ days out with low confidence in the models due to their disagreement.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 47 42 56 53 / 100 40 60 100 Knoxville McGhee Tyson Airport, TN 45 41 57 49 / 100 60 50 90 Oak Ridge, TN 45 40 56 49 / 100 40 50 90 Tri Cities Airport, TN 45 38 53 46 / 90 60 40 90
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...Wind Advisory from 10 AM this morning to 10 PM EST this evening for Cherokee-Clay. TN...Wind Advisory from 10 AM this morning to 10 PM EST this evening for Blount Smoky Mountains-Cocke Smoky Mountains-East Polk- Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. VA...None. && $$ DGS/ABM

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