Severe Thunderstorm Warning 116, NWS Morristown, TN

AREA FORECAST DISCUSSION
National Weather Service Morristown TN
325 PM EDT Wed Jul 6 2022

.SHORT TERM...(Today through Tomorrow)

Key Messages:

1. Thunderstorms expected to continue this afternoon and evening
across the area. The strongest of these storms will be capable of
producing damaging winds, hail, and flooding.

2. Hot temperatures and high relative humidities will combine to
create heat index values of over 100 degrees this afternoon.

3. Strong storms and high heat index values will once again be
likely tomorrow.

Discussion:

Currently scattered to widespread storms are occurring across the
region. Very hot temperatures and ample moisture remaining trapped
under the flattening ridge have destabilized the atmosphere. With
the peak heating hours convection is firing off leading to pulse
thunderstorms. Mesoanalysis indices show MLCAPE around 2,000 J/kg
(possibly higher) across most of east TN and southwest VA, which
will provide ample instability for rapid growth of thunderstorms.
Shear continues to look weak with generally less than 10 knots of
deep layer shear. Main threat for these quickly developing storms
will be damaging straight line winds capable of knocking down trees,
very well indicated by DCAPE values of around 1,000 J/kg across the
area. Hail cannot be ruled out with these storms, but with the lack
of shear the residence time for hail stones should be fairly low
which should hopefully limit growth potential. Other factor to be
aware of today is the torrential rain under these thunderstorms.
PWAT values of 1.5-2.1" are present across the area, meaning storms
will be capable of producing lots of rain in a short period of time.
If any location gets hit with multiple rounds of thunderstorms it
could cause flooding of low lying and poor drainage areas this
afternoon/evening.

Outside of the thunderstorms the main concern today will once again
be the high heat index values, especially in the central and
southern valley, with heat index currently at triple digits, and
some locations approaching 110 degrees.

Once the sun begins to set and the temperatures start to cool down
these storms should begin to decrease in coverage and strength.
Patchy fog will likely form overnight once again, especially in
areas that received heavy rainfall this afternoon/evening.

Fairly similar atmospheric story expected tomorrow as we remain on
the northeast periphery of the ridge. Afternoon highs and dew points
will likely be similar to today, leading to another prime atmosphere
for strong to severe storms. With similar severe parameters expected
again tomorrow the same threats of strong winds, hail, and
torrential rain are also expected.. Have once again gone a degree or
two above guidance for temperatures tomorrow, as it's worked out
fairly well the past few days under these abnormally hot
temperatures. Heat index values are once again expected to rise
above triple digits in the central and southern valley tomorrow.

.LONG TERM (Thursday Night through Wednesday)...

Key Messages:

1. An active pattern will continue through the end of this week. The
main threat with any storms that develop will be damaging winds and
localized heavy rainfall. The possibility for high rainfall rates in
a short timeframe could lead to flash flooding later in the week.

2. Dangerously high temperatures Friday will likely warrant a heat
advisory. Temperatures are expected to reach the mid-90s in some
parts of the TN Valley with heat indices of in excess of 100
possible.

An upper level ridge will remain over our area for Thursday Night
and Friday. While the ridge is rather flat, a series of shortwaves
will ride along its edge, providing the opportunity for convective
clusters to form. Showers and thunderstorms, some of which could be
severe, are expected for East Tennessee and the southern
Appalachians, but the exact timing and locations of these storms is
still uncertain. The severe potential is evidenced by expected
MLCAPE values of 2,500+ J/kg. DCAPES around 700 J/kg, and high PW
values of 1.7-2.1 inches, will provide favorable conditions for
localized heavy rainfall and damaging downburst winds. High rainfall
totals could lead to flash flooding across the region, especially in
areas that already received heavy rainfall. In addition to the
aforementioned risks, Friday will likely need a heat advisory as
temperatures are expected to climb well into the 90s with heat
indices in excess of 100 degrees in some locations of the TN Valley.
It is advised to take measures to practice heat safety during this
time.

A more pronounced shortwave will move over our area on Saturday,
while an upper trough becomes more established over the Northeast
U.S. A frontal boundary pushes south of our area in this timeframe,
with more widespread showers and thunderstorms anticipated. Despite
this front being south of our area, the upper trough axis allows the
chance for some convection to linger on Sunday. High temperatures on
Saturday and Sunday are expected to be slightly milder in the mid
80s with some areas in the valley possible reaching the lower 90s.

Drier conditions are expected early next work week as surface
ridging builds into the southern Appalachians. A frontal boundary
moves into the area on Tuesday and will provide another opportunity
for scattered convection here in East TN while a well defined upper
level ridge builds over the Central Plains.

Williams

&&

.AVIATION...
18Z TAF DISCUSSION.

Isolated to scattered showers and thunderstorms will continue
across the area the rest of the afternoon and into the evening.
Several rounds of storms could impact a terminal today, with the
possibility of strong winds, and hail being the primary concern.
Around sunset the convection should really diminish and generally
VFR conditions are expected. Patchy fog is expected overnight, but
it will really depend on where heavy rain falls this afternoon.
Have included fog at KTRI where it's most likely, and will wait
for later TAF issuances before introducing it at KTYS or KCHA.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             77  95  75  95  75 /  30  40  20  50  50
Knoxville McGhee Tyson Airport, TN  75  95  75  94  74 /  30  50  30  60  60
Oak Ridge, TN                       74  93  74  93  72 /  30  50  30  60  60
Tri Cities Airport, TN              71  90  71  89  71 /  30  50  30  60  60

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     Anderson-Bledsoe-Bradley-Grainger-Hamblen-Hamilton-
     Jefferson-Knox-Loudon-Marion-McMinn-Meigs-North Sevier-
     Northwest Blount-Northwest Monroe-Rhea-Roane-Sequatchie-
     Union-West Polk.

VA...NONE.
&&

Hazardous Weather Outlook
National Weather Service Morristown TN
327 PM EDT Wed Jul 6 2022

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-071930-
Cherokee-Clay-Scott TN-Campbell-Claiborne-Hancock-Hawkins-
Sullivan-Johnson-Morgan-Anderson-Union-Grainger-Hamblen-
Northwest Cocke-Cocke Smoky Mountains-Northwest Greene-
Southeast Greene-Washington TN-Unicoi-Northwest Carter-
Southeast Carter-Roane-Loudon-Knox-Jefferson-Northwest Blount-
Blount Smoky Mountains-North Sevier-Sevier Smoky Mountains-
Sequatchie-Bledsoe-Rhea-Meigs-McMinn-Northwest Monroe-
Southeast Monroe-Marion-Hamilton-Bradley-West Polk-East Polk-Lee-
Wise-Scott VA-Russell-Washington VA-
327 PM EDT Wed Jul 6 2022 /227 PM CDT Wed Jul 6 2022/

This Hazardous Weather Outlook is for portions of southwest North
Carolina...east Tennessee and southwest Virginia.

.DAY ONE...This Afternoon and Tonight

Strong to severe storms will be possible this afternoon and
evening. The primary threat will be damaging wind gusts.
Additionally, localized flash flooding is possible, especially in
areas impacted by stronger storms the previous days. Flooding of
small streams, ponding of low lying areas, and street flooding are
all possible.

A heat advisory has been issued for this afternoon as well. See
product for additional details. If spending any time outside, take
frequent breaks in the shade and stay hydrated.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

...A risk of severe storms exists for Thursday and Friday with
increasing coverage of Thunderstorms through the week...

Thunderstorm complexes will continue to move across the area for
Thursday and Friday. Some of these storms will likely become
severe with the main concern being damaging winds. Timing of the
these storm complexes is uncertain but confidence is high that
some severe weather will occur.

Besides the damaging winds, these storms will also produce
torrential rains with localized flash flooding possible. Flooding
of small streams, ponding of low lying areas, and street flooding
are possible.

Heat advisories may be needed again for Thursday and possibly
Friday across the central and southern Tennessee valley. Heat
indices of 105 to 108 degrees are possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed for today through Friday, mainly
during the afternoon and evening hours.

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