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000
FXUS64 KMRX 180157 AAB
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
957 PM EDT Wed Apr 17 2024

...New UPDATE...

.UPDATE...
Issued at 929 PM EDT Wed Apr 17 2024

Rain has pushed well to the southeast of the CWA this evening,
leaving us dry with a steady low level moist return flow in
progress. Dewpoints are rising steadily, especially west of the
I-75 corridor, and some low clouds have already been noted from
Knoxville southward to the Chattanooga area. Most all guidance is
in agreement with advertising a mix of fog and low clouds across
the region tonight. This seems reasonable given the pattern, but
confidence in whether it`s predominantly fog or just low clouds
isn`t particularly high given the mix of cirrus and elevated winds
to contend with for several more hours to come. Didn`t make much
in the way of changes to the forecast for the overnight hours as
it seems to be in good shape. Did freshen up the weather grids
with some slight expansion of patchy fog wording though.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 300 PM EDT Wed Apr 17 2024

Key Messages:

1. Rain to come to an end late this afternoon into early evening.

2. Dry and warm daytime Thursday.

Discussion:

The band of rain showers that has primarily afflicted those south of
Knoxville will continue to thin out as it progresses eastward for
the remainder of the day. Only a few rumbles of thunder occurred
in the southern valley today, and outside of a rare rumble of
thunder, nothing much is expected for the remainder of the day
outside of the rain. A medium amount of clearing will occur
overnight, with patchy fog and low clouds possible in the
morning. The upper trough over the Midwest will move off to
southern Canada, and the jet stream helping power today`s rain
will move south of us tonight. The movement of these features
allows for a mid level ridge to build in over us for Thursday.
Clearing skies and building heights will allow for temperatures to
rebound tomorrow, with valley temperatures in the low 80s for
most of the region.

Records for April 18th: CHA  90/2002   TYS  90/1896   TRI  87/2002

Compared with the records for the day guidance has persisted in
remaining a few degrees below the daily records. The SREF & NBM
probabilities indicate some low thick clouds in the morning hours,
but those are expected to mix out and clear heading into peak
heating. Otherwise relative humidities will drop below 40% in
northern Tennessee into southwest Virginia tomorrow afternoon.

&&

.LONG TERM...
(Thursday night through next Wednesday)
Issued at 300 PM EDT Wed Apr 17 2024

Key Messages:

1. Showers and thunderstorms return for Thursday night and Friday.
There is a low chance of strong to severe storms with gusty winds
and hail.

2. Turning much cooler this weekend, with some showers around
especially Sunday.

3. Mostly dry with a warming trend Monday through Wednesday.

Discussion:

We start the period with a low pressure system moving out of the
Mississippi Valley and tracking northeast into the Great Lakes
region. This system will drag a cold front through our area
Friday. We will see showers and thunderstorms moving in Thursday
night out ahead of the front and continuing Friday as the front
moves through. Models generally indicate there will be modest
instability, perhaps as high as 500-1000 J/kg in the south early
Thursday night, and there is some shear although effective shear
looks quite low to start and then is forecast to increase to
around 30+ knots later in the night although after the period with
better convective energy. Right now the strong to severe threat
still looks limited, but a few storms with strong gusty winds and
hail are possible especially Thursday night with the highest
threat across our southern areas and along/near the Plateau.

There is significant model disagreement for Saturday, with the NAM
bringing additional showers to the area as the colder air pushes in
behind the front, but much of the other model data does not support
this idea so will go with the NBM solution and just carry slight
chance PoPs for the eastern mountains and far south Saturday closer
to the boundary. It will be cooler with high temperatures
expected to be near or a bit below seasonal normals. A weak system
to our south may brush the area with additional showers Sunday
especially across the south and east, and it will be quite cool
with high temperatures expected to be well below seasonal normals.

Monday through Wednesday look mostly dry with a gradual warming
trend, although a weak frontal boundary may drift into the area by
Wednesday with a few showers and/or thunderstorms.

&&

.AVIATION...
(00Z TAFS)
Issued at 756 PM EDT Wed Apr 17 2024

Guidance suggests widespread fog and low clouds will be an issue
across the region tonight. Though CIGS are bouncing in and out of
MVFR territory at KCHA at the moment, their presence gives
confidence to the lower flight categories forecast tonight. Most
confident in this occurring at KCHA where almost an inch of rain
fell, so LIFR categories seem ok there. Will limit categories to
MVFR at KTYS and KTRI where confidence is lower. Expect to see a
return to VFR levels between 14-16z tomorrow morning. Winds will remain
elevated for 2-3 hours at KTYS and KTRI, but afterwards expect
light winds at all terminals.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             62  86  64  80 /   0  10  60  60
Knoxville McGhee Tyson Airport, TN  61  84  62  76 /   0   0  60  80
Oak Ridge, TN                       61  84  61  77 /   0   0  60  80
Tri Cities Airport, TN              58  80  57  75 /   0   0  30  80

&&

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

$$

SHORT TERM...CD
AVIATION...CD