-- Discussion containing changed information from previous version are highlighted. --
290
FXUS64 KMRX 291049
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
649 AM EDT Sat Jun 29 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 315 AM EDT Sat Jun 29 2024

Key Messages:

1. Some mainly scattered showers and thunderstorms around especially
this afternoon.

2. A hot afternoon.

Discussion:

We will remain under a broad and flat ridge aloft today. Low level
flow will be more southwesterly today with an uptick in moisture,
and forecast soundings show moderate instability and PWAT values
topping 2 inches across much of the area today. As the atmosphere
destabilizes today with heating, expect to see some scattered
showers and thunderstorms developing with the best coverage late
this afternoon. Shear is weak overall and DCAPES are not impressive,
so the threat of strong to severe storms looks to be on the low
side. However, deep layer shear does increase a bit north with
effective shear likely eclipsing 25kts, and the best chance for any
stronger/marginally severe storms is expected across these northern
areas. A cold front will begin to approach from the northwest later
tonight, so after an initial decrease in convection early this
evening with loss of heating, northern areas may see an slight
uptick in coverage later tonight as the front draws nearer.

It will be quite hot today, with temperatures in the lower 90s
across most valley locations. These temperatures will combine with
dew points in the lower 70s to produce heat index values near or
slightly above 100 degrees in many valley areas this afternoon.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 315 AM EDT Sat Jun 29 2024

Key Messages:

1. Widespread shower and thunderstorm activity expected Sunday
afternoon.

2. Drying out and warming up Monday through midweek.

3. Ridge breaks down toward the end of the week, giving us more
chances for showers and storms.

Discussion:

Front expected to pass through the Tennessee Valley region on
Sunday, helping to spark off widespread thunderstorms before
passage. A moist airmass coupled with the favorable front timing
should yield some efficient rainfall, but convection is expected to
be moving along so rainfall totals outside of stronger thunderstorms
may remain rather benign. FROPA is associated with an upper trough
passing through the northern US, and backside flow will allow for a
drier, slightly cooler airmass to come through. The good news is
Monday will be nice, the bad news is the upper ridge will build
right back in and return us to more of the weather we`ve been
experiencing the last couple weeks. Unfortunately the heat will
continue Tuesday through the remainder of the week.

Late week better moisture and less subsidence from the ridge should
allow for better diurnal chances of showers and thunderstorms,
ensembles indicate 40% to 70% chances for CAPE greater than 1000J,
which would be favorable for convection. How long convection sticks
around into the evening on the 4th may interfere with any outdoor
plans for fireworks, so something to keep an eye on.

Towards the end of the period, ensembles and the Euro continue to
persist the anomalous upper heights through the weekend. The GFS
attempts to bring a trough into the region on Friday and fully in by
the weekend, but it`s an outlier amongst the guidance, and it also
tends to have a speedy progressive bias so for now the next good
relief from the heat is outside of the period.

&&

.AVIATION...
-- Changed Discussion --
(12Z TAFS)
Issued at 528 AM EDT Sat Jun 29 2024

Will generally see scattered to broken clouds around for the
period, but cigs will be mainly VFR. Will likely see some brief
MVFR cigs again at CHA during the early morning hours, and will
include a tempo MVFR group there. In addition, we will see some
scattered showers/thunderstorms around mainly during the
afternoon, and will include a prob30 thunderstorm group at each
site. Additional convection may be around late mainly TRI, and
cigs may lower to near, or to, MVFR levels. Will just carry VCSH
and low VFR cigs at TRI late in the period for now.
-- End Changed Discussion --


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             92  75  94  71 /  40  20  60  20
Knoxville McGhee Tyson Airport, TN  92  75  92  68 /  40  30  70  30
Oak Ridge, TN                       91  74  91  65 /  40  20  70  20
Tri Cities Airport, TN              91  72  88  63 /  40  30  80  40

&&

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

$$

SHORT TERM...
LONG TERM....Wellington
AVIATION...