438 
FXUS64 KMRX 172314 AAA
AFDMRX

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
714 PM EDT Sun Oct 17 2021

.UPDATE...
FOR 00Z AVIATION.

&&

.SHORT TERM...(Tonight and Monday)...

Key Message:

1. Cold. Patchy frost will be possible across parts of southwest VA 
and northeast TN

Surface high pressure centered over the ArkLaTex region has provided 
the southeast with abundant sunshine.  On the east side of the high 
where the surface pressure gradient is a little tighter, the winds 
are generally north to northwesterly with a few occasional gusts up 
to 20 mph. 

Clear conditions will persist overnight with the winds decoupling. 
Areas of frost will likely develop late tonight across parts of 
southwest Virginia and parts of northeast TN, perhaps for southwest 
NC. However, confidence is low for frost to develop across SW North 
Carolina.

Monday will be another stellar day as high pressure remains nearly 
stationary centered over Tennessee. Daytime highs will generally be 
in the 60s and 70s.

AC

.LONG TERM...(Monday Night through Sunday)...

Key Messages:

1. Dry weather with a warming trend through Wednesday is expected, 
followed by showers and isolated thunderstorms on Thursday.

2. Towards next weekend, the trend will be a return of dry and 
seasonally cooler weather, possibly like what has been seen lately. 

Monday Night through Thursday

To start off the period, mid/upper shortwave ridging will be 
centered over the Mississippi River Valley with surface high 
pressure dominating much of the eastern U.S. A closed low will also 
be in place over the Northern Rockies. This initial setup will 
continue with height rises promoting a warming trend back to near 
normal during the day on Tuesday. By Wednesday morning, the 
aforementioned closed low will have ejected into the High Plains 
with continued cyclogenesis leading to a developed surface low 
pressure system that will track towards the Great Lakes. During this 
time, the surface high will shift eastward with both of these 
features lending southerly flow and Gulf moisture advection, 
especially to our west. This will continue the warming trend through 
Wednesday with its associated cold frontal boundary being the main 
forcing mechanism for a return of rain chances before its passage on 
Thursday night. 

The recent trend in model runs has shown a more dynamic and possibly 
a sufficiently unstable setup for showers and isolated convection. 
There has also been a slower trend for the frontal passage with this 
recent model run as well. With the surface low and upper jet still 
far removed from the region to the north, these factors are fairly 
marginal at this point. Nevertheless, indications of the vertical 
wind profiles and instabilty of potentially >500 J/kg along and near 
the Cumberland Plateau will justify low probability HWO wording. 
This is also given the limited confidence, being that the event is 
still 5 days. Nevertheless, the main message to be gained will be a 
return of showers and isolated thunderstorms on Thursday before the 
front moves through, likely by Friday morning. 

Friday through Sunday

By Friday, the front will have moved through the region, shifting 
the pattern to a more northwesterly low-level flow pattern. With 
lingering moisture indicated near and below the 850mb level, a few 
sprinkles can't be ruled out in the mountains early in the day. 
Otherwise, drier and seasonally cool weather will prevail into the 
weekend with surface high pressure in place and near to below normal 
heights. With a lower sun angle and a similar setup to what we are 
currently seeing, another chance for frost exists by Sunday morning 
as the surface high will be in closer proximity to the area.

BW


&&

.AVIATION...
00Z TAF DISCUSSION.

Clear conditions will prevail through this TAF period at all
sites. Winds will be around 5 kts or less. While fog can't be
completely ruled out at TRI near sunrise, dewpoints have really
dropped today, making the chance of fog too low to mention at this
time.

DGS

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             44  70  46  73  49 /   0   0   0   0   0 
Knoxville McGhee Tyson Airport, TN  43  69  43  72  48 /   0   0   0   0   0 
Oak Ridge, TN                       42  69  44  71  47 /   0   0   0   0   0 
Tri Cities Airport, TN              37  66  40  71  43 /   0   0   0   0   0 

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Frost Advisory from 4 AM to 8 AM EDT Monday for Cherokee-Clay.

TN...Frost Advisory from 4 AM to 8 AM EDT Monday for Johnson-
     Southeast Carter-Sullivan.

VA...Frost Advisory from 4 AM to 8 AM EDT Monday for Russell-Scott-
     Washington.

&&

$$