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

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000 FXUS64 KMRX 181855 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 255 PM EDT Mon Sep 18 2017 .SHORT TERM (Today into tomorrow)...
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Once again we can expect to see similar conditions today to what we saw yesterday with mostly sunny skies and slight above normal temperatures. Light winds and mostly clear skies will allow for some more fog to develop overnight in the sheltered locations. Fog should not be too widespread, partially, because we will begin to see increasing cloud coverage moving into tomorrow. A trough moving to our north will help bring in more clouds and keep temperatures a few degrees cooler. With the trough moving in we could see a few isolated showers/thunderstorms tomorrow, but am currently not expecting widespread precipitation with this weak system for tomorrow. .Long Term (Tuesday night through Monday)...High pressure over the coastal states will be present through the beginning of the work week...keeping moisture available...especially in areas south of I40. A weak boundary will move through the area on Wednesday...with scattered showers and thunderstorms possible in the afternoon. Lift will be weak...but enough instability will be present that can`t count out convection developing. PW values are around the 90th percentile in far southern plateau...southern valley...and southwest would expect the greatest chance for development in these areas. Behind the front...low level high pressure sets up over the Gulf Coast states...while an upper level trough and associated low pressure develop. Wednesday night...winds behind the frontal boundary will allow for northerly flow to briefly set up over the area through Thursday night with PW values decreasing to between the median average and 75th percentile. With instability also lowered...would expect only scattered showers and isolated thunderstorms to develop. By Friday morning...low level flow will transition to out of the east due to the flow around the low level high pressure. This will allow for greater warm air and moisture advection to areas south of I40 through Saturday. Upper level forcing will be weak Friday and Saturday...but enough moisture and instability will be present for weak diurnal showers and isolated thunderstorms to develop each afternoon. The greatest chance for this convection will be in areas south of I40 where the greatest advection is located. Sunday and Monday...the upper level trough will be east of the Appalachians...and moving towards Hurricane Maria which is expected to be off the FL coast. High pressure behind this trough will allow for mostly clear skies and dry weather to remain through the weekend.
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Chattanooga Airport, TN 67 87 67 85 / 0 10 10 20 Knoxville McGhee Tyson Airport, TN 63 85 64 84 / 10 10 10 10 Oak Ridge, TN 64 84 65 84 / 10 20 10 20 Tri Cities Airport, TN 59 81 60 83 / 0 10 10 10
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