Severe Thunderstorm Warning 166, NWS Morristown, TN

Area Forecast Discussion
National Weather Service Morristown TN
337 PM EDT Tue Jul 25 2023

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This evening through Wednesday)
Issued at 302 PM EDT Tue Jul 25 2023

Key Messages:

1. Isolated to widely scattered severe storms possible through
this evening. Damaging winds, hail up to quarter size, and
localized flash flooding are possible.

2. Heat indices of 100 to 105 degrees expected across the central
and southern Tennessee valley and Sequatchie county through early
this evening and again Wednesday afternoon.

Discussion:

Isolated strong to severe storms have developed across the region.
SPC meso-analysis depicts MLCAPES of 2000-3000. Greatest concern
with these storms will be damaging winds due to DCAPEs of
1100-1200, high low-level lapse rates of 8-8.5 degrees, and
melting of hail with Hail CAPES of 700-900.

Even though freezing level is high, the high Hail CAPES is
producing reports of dime to penny size hail.

Since these storms have locked into some of the terrain features
and training across the same locations, localized flash flooding
is also a concern.

Given limited to no upper forcing, these storms will quickly
diminish by around sunset.

For tonight, sky cover will clear with radiational cooling
allowing for patchy fog development, especially areas that receive
rain and along/near area streams and lakes. Some of the fog could
be locally dense.

For Wednesday, airmass will instability being less, per HREF.
Isolated storms are possible across the terrain features,
otherwise a hot and muggy day is in store. Heat indices will climb
to 100 to 105 degrees across much of the central and southern
Tennessee valley and Sequatchie valley during the afternoon.

&&

.LONG TERM...
(Wednesday night through next Tuesday)
Issued at 302 PM EDT Tue Jul 25 2023

Key Messages:

1. Scaattered to isolated afternoon convection along the mountains
Thu-Fri, expanding into the TN Valley Sat-Sun as a front approaches.

2. Heat Index values peaking in the 100-105 range in the central and
southern TN Valley through Saturday.

Discussion:

The main weather impact at the start of this period will be the
heat. It won't be record-breaking, but it will be above normal and
uncomfortable in some areas. While NBM dewpoints continue to appear
too high, in the mid 70s, even lower 70s dewpoints will give heat
index values between 100-105 in the central and southern portions of
the TN Valley, as highs will reach the mid/upper 90s.

For Thursday and Friday, a lack of forcing and low level moisture
should keep most convective development confined to the mountains
along thw NC border, and possibly parts of SW VA. A front pushes
into the OH Valley on Thursday, and stalls as it becomes parallel to
the low/midlevel flow. The NAM depicts a pre-frontal surface trough
and midlevel shortwave trough crossing WV/VA on Thursday, and some
convection with this trough may track into our SW VA counties.

The pattern becomes slightly more amplified on Saturday as a trough
deepens over eastern Canada and New England. This allows the stalled
front to our north to start a southward push. Moisture remains
limited but with some better QG forcing nearby, convective coverage
is expected to increase a bit, with chance PoPs forecast in the
northern sections Saturday and Sunday.

Models differ on whether the front will make it south of our area on
Sunday, but temps and dewpoints should drop slightly and take the
edge off the heat for a couple days. Another hot pattern may set up
for the middle of next week as a large ridge will be positioned over
the lower MS region and the Deep South.

&&

.AVIATION...
(18Z TAFS)
Issued at 133 PM EDT Tue Jul 25 2023

Overall, VFR conditions throughout the forecast. However,
isolated afternoon/early evening storms are expected across east
Tennessee. Confidence of a storm near the terminal is too low to
include. MVFR conditions due to fog/low clouds are possible at TRI
between 10-12Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             71  95  72  96 /   0  10   0  10
Knoxville McGhee Tyson Airport, TN  70  92  72  94 /  10  10   0  10
Oak Ridge, TN                       68  92  71  93 /  10  10   0  10
Tri Cities Airport, TN              65  90  68  92 /  10  10   0  10

&&

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

SHORT TERM...DH
LONG TERM....DGS
AVIATION...DH

Hazardous Weather Outlook
National Weather Service Morristown TN
307 PM EDT Tue Jul 25 2023

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-261915-
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-
307 PM EDT Tue Jul 25 2023 /207 PM CDT Tue Jul 25 2023/

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

.DAY ONE...This Afternoon and Tonight

Isolated severe storms through this evening. Damaging winds and
localized flash flooding are possible. The greatest coverage of
thunderstorms will be across the higher terrain.

.DAYS TWO THROUGH SEVEN...Wednesday through Tuesday

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this evening.

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