017 
FXUS64 KMRX 151944
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
244 PM EST Tue Jan 15 2019

.SHORT TERM...(Tonight and Wednesday)...
The upper pattern today is highlighted broad troughing over the 
eastern seaboard with ridging to the west atop the Rockies which is 
yielding deep nwly flow across the OH/TN valleys.  A weak shortwave 
impulse moving along the mean flow aloft on the tail end of a jet 
streak will sweep through the region today/tonight, however with 
little/no consequence.  The main story of the weather in the short 
term is the persistence of a llv inversion, and the modest llv 
moisture trapped beneath.  Given the inversion, said llv cannot 
escape as long as flow remains orthogonal to the mountains, or the 
inversion erodes. Am expecting H85/H925 flow to back swly with time, 
thus some scattering of low clouds is favored through the remainder 
of the afternoon/evening.  That said, per latest visb sat loop, 
there is an interesting region of downslope drying (in the lee of 
the Black Mountain range in KY) across portions of the northern TN
valley and southwest VA. Otherwise, a fairly quiet short term in 
store as sly high pressure prevails on Wednesday amidst rising 
heights aloft. Thus, am expecting temperatures to moderate nearly 
10 degrees from that of today. 

.LONG TERM...(Wednesday night through Tuesday)...
Shortwave trough will be moving towards the area Wednesday night 
into Thursday and a surface low will race along with it. These will 
combine to bring chances of precipitation with the highest 
likelihood of rain coming Thursday afternoon and night. Rain will 
begin to decrease as we move into Friday from southwest to 
northeast. When everything is said and done this first system will 
probably bring less than 0.25" of rain to most locations.

The second system of the forecast will move in quickly on the heels 
of the first, a southern stream shortwave will interact with a 
trough further to the north and combine over the Eastern United 
States. Strong surface low will move to the northeast on Saturday 
just north of the Tennessee Valley. This will bring in very warm and 
moist air on Saturday. There may be enough  dynamics with this 
system to produce a few rumbles of thunder on Saturday as well. 
Highs on Saturday are currently forecasted to be about 20-25 degrees 
above normal for this time of year. Moderate to heavy rain looks to 
be the main mode of precipitation on Saturday afternoon/night with 
widespread rainfall totals around 1-2" over the weekend looking 
possible.  After this system exits to the north we will see strong 
cold air advection from the northwest at the end of the weekend and 
into next week. 

High temperatures will drop about 25 or more degrees on Sunday 
compared to Saturday. Overnight lows look to drop well below 
freezing into the teens on Sunday night/Monday morning. With some 
lingering winds behind the system we could see wind chill values 
drop into the single digits as well. The final aspect to watch with 
this weekend system will be the potential for some snow showers as 
it exits the region on Sunday. A bit difficult to time the departure 
of the moisture with the drop in temperatures, but can't rule out 
some light snow showers in the Valley on Sunday at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             29  53  37  50 /   0   0  10  60 
Knoxville McGhee Tyson Airport, TN  29  48  34  48 /   0   0  10  70 
Oak Ridge, TN                       28  48  35  48 /  10   0  10  70 
Tri Cities Airport, TN              26  46  31  48 /  10  10   0  70 

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&

$$

CDG/ABM