304 
FXUS64 KMRX 211850
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
250 PM EDT Sat Mar 21 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 224 PM EDT Sat Mar 21 2026

- Scattered showers and storms are possible late this afternoon
  and evening. The main threat with these storms will be hail and
  strong/gusty winds. 

- Unseasonably warm and breezy Sunday with a low chance of rain
  returning Sunday night/Monday morning, mainly north of
  interstate 40.
 
- Dry and seasonally cooler conditions are expected Monday until a
  warming trend and returning rain chances late in the week.

&&

.DISCUSSION...
Issued at 224 PM EDT Sat Mar 21 2026

Currently Smoke is not as widespread as yesterday but HRRR Smoke
Product shows another area moving into the region late today into
the evening hours. Will maintain smoke/haze in the forecast. One 
of the main problems will be poor air quality.

Satellite shows a wave within northwest flow aloft moving across
the Ohio valley toward the region late this afternoon and 
evening. Boundary layer has moisten some from this morning with
dewpoints mainly in the 50s. SPC meso-analysis shows MLCAPE
increasing to near 1000 J/Kg with weak effective shear of 25-28
knots. 

HREF CAMs and deterministic models show widely scattered to
scattered showers and thunderstorms developing late today into
this evening. Given mid-level lapse rates near 7 degree/C
producing Hail CAPEs of 400+ and low Wet Bulb Zero heights,
isolated hail is possible up to quarter inch.

Dry air aloft and boundary layer will also produce strong/gusty
downbursts possibly up to 50-60 mph.

Convection is expected to continue until around midnight or
thereafter.  

Otherwise main weather story will be strong upper ridge over the
Great Basin and troughing in the east producing northwest flow
aloft. 

For Sunday, after some early morning clouds rise heights, plenty
of sunshine, and southwest boundary layer flow will produce an
unseasonably warm day. Highs 15 to 20 degrees above normal. Here
are the record highs:

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge          
03-22   89(1907)       87(1907)       81(1938)       83(2011) 

For Sunday night and Monday morning, a stronger short-wave will
move across the Great Lakes into the northeast United States/mid-
Atlantic area. Associated frontal boundary will move across the
area but dynamics with upper trough will be mainly north and east
of the area. A line of weakening showers and possibly a
thunderstorm will move into southwest Virginia and northeast
Tennessee. Main chances of rain will be north of interstate 40.

For the latter half of Monday through Wednesday, mostly dry 
northwest flow and surface ridging will produce dry and near 
seasonable cool temperatures. Main concern is the low afternoon 
relative humidity behind the front. 

For Thursday through next Saturday, boundary layer moisture and
instability will increase with a chance of showers each day.

&&

.AVIATION...
(18Z TAFS)
Issued at 131 PM EDT Sat Mar 21 2026

Main question...will we break the boundary layer cap for more
robust convection this evening at TRI and TYS. Latest meso-
analysis shows MLCAPEs increasing to 500-1000 J/Kg with a capping
inversion near 800-850mb. If the environment does break the cap,
there is a threat of hail and strong/gusty winds. Mid-level lapse
rates near 7 degrees/C and relative good CAPE in the Hail growth
region to produce up to quarter size hail. Also, mid-level and
boundary layer dry air to support localized strong downbursts. 

This activity will end by around midnight or thereafter. 

Besides the widely scattered to scattered convection, HREF and
latest deterministic models show potential of low-cloud
development producing IFR/LIFR conditions at TRI early Sunday
morning. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             58  85  63  75 /  10   0   0   0 
Knoxville McGhee Tyson Airport, TN  59  83  60  69 /  40   0  10  10 
Oak Ridge, TN                       58  83  58  69 /  30   0  20   0 
Tri Cities Airport, TN              55  82  55  63 /  40   0  40  10 

&&

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

$$

DISCUSSION...DH
AVIATION...DH


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