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

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777 FXUS64 KMRX 170858 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 358 AM EST Fri Nov 17 2017 .SHORT TERM...(Today and Tonight)... Surface high pressure will drift from the Ohio Valley this morning to the NC coast by tonight, while a 850-700 mb ridge will also be crossing our area today. Cloud cover along our northern broder should retreat as this ridge progresses east and the flow in that layer turns to a SW direction with warm advection in the afternoon. Cirrus in advance of the jet stream will be over the area today, with highs in the lower to mid 60s expected. Tonight, a strengthening SW flow as low pressure tracks into the Great Lakes region and its resulting positive theta-e advection/isentropic lift should bring increasing cloud cover, but moisture depth and lift will not be adequate for precip yet. Higher elevations could be breezy tonight as the LLJ increases to around 40 kts, but the SW direction of flow does not favor a mountain wave event. .LONG TERM...(Saturday through Thursday)... At the beginning of this period, we will be in a fast WSW flow aloft, that will be in the process of backing, as an upper trough and frontal system approach the area. At the surface, as mentioned a front will be to our west, ridging in the Carolinas, and a return flow intensifying over us. The front is expected to move quickly through our area generally Saturday evening. The weather from Saturday through Saturday night will be quite active with increasing winds Saturday and into Saturday evening ahead and behind the front. The angle of the winds is not set up for a classic mountain wave pattern, but the winds are favorable for stronger winds up the valley, even flirting with advisory criteria for parts of the valley. Showers and possible embedded storms will bring even faster winds from aloft, down to the surface, as the precip moves in from the west late Saturday afternoon and into the evening. Late Saturday night as the colder air moves in the rain showers will be changing over to snow showers in the higher mountains, and lingering into Sunday morning. Sunday will be much colder, and with an inversion above the cold air, moisture will likely be trapped making for stubborn stratocumulus clouds for a good part of the day, especially in upper east TN and SW VA. This will help prevent the temps from rising much on Sunday as well, so went a few degrees below guidance at most locations. For the rest of the forecast, it turns very quiet overall, with temperatures rebounding as we get into the work week. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 65 50 65 40 / 0 0 60 70 Knoxville McGhee Tyson Airport, TN 62 47 66 39 / 0 0 50 80 Oak Ridge, TN 62 47 63 39 / 0 0 60 80 Tri Cities Airport, TN 62 39 63 37 / 0 0 30 70 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ DGS/GM is the U.S. government's official web portal to all federal, state and local government web resources and services.