683 FXUS64 KMRX 190022 AAA AFDMRX AREA FORECAST DISCUSSION...UPDATED National Weather Service Morristown TN 722 PM EST Wed Dec 18 2019 .UPDATE... UPDATED FOR THE 00Z AVIATION DISCUSSION BELOW. && .SHORT TERM...(Tonight and Thursday)... Mostly clear skies and cold temperatures today across the forecast area as cold air advection continues with higher pressure building southeast across the region. Mid afternoon temperatures are in the mid 30s to mid 40s. Dewpoints are in the mid teens to the mid 20s and winds are light in the south and 10 to 15 mph from the west and northwest. Low cloud deck across KY and northern middle TN has been eroding as it moved south today. The mostly clear skies and dry cold airmass continues tonight and Thursday and should contribute to good radiational cooling tonight. Lows down into the upper teens to mid 20s which are the coldest temperatures since last month. Friday the upper low and trough over the northeast will have moved off the coast and surface high pressure will be centered overhead. Temperatures will be only slightly warmer Friday then today. .LONG TERM...(Thursday night through Wednesday)... Thursday night through Saturday morning will be dry across the area as a large area of surface high pressure crosses the Central Appalachian and Mid-Atlantic region, with mid and upper level ridging across the eastern ConUS. The main system in the extended period continues to be one that could potentially bring rain from Saturday afternoon through Monday, associated with a closed low system that tracks east across the Gulf Coast region. The models continue to differ in their positions and strength of this system, which will impact how far northward precip can spread. The ECMWF continues to be farther north with the 500 mb low track compared to the GFS, taking it across the FL Panhandle vs. the GFS depiction of it staying offshore. Thus, the ECMWF spread precip farther north into our area, beginning on Saturday night and continuing through Monday as the closed low slowly moves east. Bottom line for the forecast - not much change will be made for now due to these model disparities, with chance PoPs favoring the southern sections to slight chances north. Temps appear to favor an all-rain scenario as well, although a little snow can't be ruled out in the higher elevations at onset Saturday night. There is good model agreement that a large high pressure ridge is expected to build east of the MS River for the first half of next week, providing a dry Christmas with above-normal temperatures in East TN. Highs on Christmas Day may reach well into the 60s. && .AVIATION... 00Z TAF DISCUSSION. Infrared satellite imagery shows MVFR deck moving from NW to SE across the Cumberland plateau this evening. It appears it will dissipate over the next 4 to 6 hours as the supporting air mass drops into the lower elevations of the Tennessee valley, which is supported by trends in satellite imagery. As such, will maintain VFR conditions at all terminals through the period. Otherwise, winds will be light through the period, gradually veering to a more northerly direction as high pressure moves in. CD && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 25 49 30 54 37 / 0 0 0 0 10 Knoxville McGhee Tyson Airport, TN 23 46 28 52 35 / 0 0 0 0 0 Oak Ridge, TN 22 47 27 52 33 / 0 0 0 0 0 Tri Cities Airport, TN 19 44 27 52 32 / 0 0 0 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$