Severe Thunderstorm Warning 137, NWS Morristown, TN

AREA FORECAST DISCUSSION
National Weather Service Morristown TN
954 PM EDT Wed Jul 20 2022

.UPDATE...
EVENING UPDATE.

&&

.DISCUSSION...

Showers and thunderstorms are ongoing in central Kentucky ahead of
a weak front located near the Ohio River. These storms continue to
intensify as the environment consists of >3,000 J/kg of MLCAPE and
fairly weak overall shear. Based on the latest high-res model
guidance, a developing complex is forecast to move into the
region around midnight into the early morning hours. This will
continue the concern for damaging winds, in addition to localized
flooding, following heavy rainfall that occurred earlier. As
such, PoPs were updated to encompass these trends with a focus on
northern areas for the highest values. Also, dew points were
increased slightly to reflect the higher values that continued
into this evening. Otherwise, the forecast remains on track with
only minor adjustments made.

BW

&&

.AVIATION...
00Z TAF DISCUSSION.

A few pop up storms are anticipated this evening with one ongoing
near CHA. Otherwise, the main story will be the arrival of storms
from the northwest that are currently located near the Ohio River.
These storms will likely impact all of the terminals between 05Z
and 10Z with potential for strong winds and reduction to MVFR or
lower. Then after these storms, MVFR ceilings may linger at TYS
and TRI into the daytime hours with generally southerly to
southwesterly winds continuing. Additional storms are possible
later in the afternoon but will likely be more limited in
coverage.

BW

&&

.PREV DISCUSSION...
/ISSUED 312 PM EDT Wed Jul 20 2022/
SHORT TERM...(Tonight and Tomorrow)...

Key Messages:

1. Showers and thunderstorms are likely around and after midnight
tonight. Damaging wind gusts and heavy rainfall/localized
flooding will be the main threats.

2. Another round of showers and thunderstorms are expected
tomorrow with the best chance in the afternoon.

Discussion:

Multiple rounds of showers and thunderstorms will be possible this
forecast period as the wet pattern continues. In the upper levels,
a trough is moving through the Ohio Valley tonight. The Tennessee
Valley will be in northwesterly flow aloft with the possibility
of a minor shortwave or two moving through the region. Luckily,
with the overnight timing, instability will be low with CAPE
around 1000 J/kg. However, with dew points in the lower 70s if a
minor wave does move through, a few strong to severe storms will
be possible with the main threat of damaging winds. Some high res
ensemble guidance shows a line of storms weakening as it
approaches and moves through the region around or after midnight.
If storms are able to remain organized, high rain rates are
possible with PWat values around 1.8 to 2 inches across the
Valley. The official forecast calls for 1 inch of rain or less
tonight but if strong storms develop locally higher totals will be
likely and may lead to flooding issues in places prone to flooding
or places that have recently received a lot of rain.

Another round of showers and thunderstorms are likely tomorrow
afternoon as a cold front slowly sags southward. The I-75 to I-81
corridor and eastward will have the best chance for showers and
thunderstorms tomorrow afternoon. With high instability expected
tomorrow afternoon, a few strong to severe storms cannot be ruled
out. A wind shift indicating frontal passage is predicted tomorrow
afternoon for the northern and western parts of the region.
Despite the cloud cover, highs will be warm in the upper 80s and
near 90.

McD

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

Key Messages:

1. Hot and humid for the weekend and into next week. Heat indices of
100+ in the central/southern valley over the weekend and into next
week.

Discussion:

Some lingering showers and thunderstorms may remain in the mountains
and southern valley Thursday night and into the early morning hours
of Friday in wake of the frontal boundary. By mid morning on Friday
the boundary will be south of our area and mid/upper level ridging
will start to build, which leads us into a hot and humid pattern for
the weekend.

Heat indices will likely be in the triple digits in many places
throughout the central and southern Tennessee valley over the
weekend and into next week. Daily high temperatures are expected to
climb into the 90s, which will be exaggerated by dewpoints in the
mid 60s and 70s. It is advised to practice heat safety during the
afternoon and early evening hours when temperatures are expected to
be at their highest. Most areas are likely going to remain dry this
weekend, but a stray diurnal shower cannot be entirely ruled out.

More active weather is likely next week with shortwave energy and a
possible front drifting towards us from the Ohio Valley. This could
bring more significant chances for rain back into the forecast on
Tuesday and into the middle of next week, but there is still
uncertainty about the timing.

Williams

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             75  92  72  94  72 /  30  40  30  10   0
Knoxville McGhee Tyson Airport, TN  73  89  71  93  71 /  70  50  10  10   0
Oak Ridge, TN                       73  90  70  93  70 /  70  40   0   0   0
Tri Cities Airport, TN              70  87  67  91  66 /  60  40   0   0   0

&&

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

Hazardous Weather Outlook
National Weather Service Morristown TN
946 PM EDT Wed Jul 20 2022

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-220200-
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-
946 PM EDT Wed Jul 20 2022 /846 PM CDT Wed Jul 20 2022/

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

.DAY ONE...Tonight

Scattered showers and thunderstorms will continue tonight and into
the early morning hours. A few of these storms may be strong to
severe, with the primary threats being damaging wind gusts and
very heavy rainfall that could cause localized flooding.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Showers and thunderstorms will be possible Thursday along an
incoming frontal boundary. A few of these storms could be strong
to severe with gusty winds, and heavy rainfall being the main
threats, with the highest risk being in southeast Tennessee and
southwest North Carolina.

Over the weekend and into next week, temperatures in the central
and southern Tennessee valley will climb into the mid and upper
90s, with heat index values exceeding 100.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not needed at this time.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MORRISTOWN TN
1107 PM EDT WED JUL 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1030 PM     FLASH FLOOD      3 W POWELL              36.02N 84.09W
07/20/2022                   ANDERSON           TN   PUBLIC

            SOCIAL MEDIA PHOTO OF WATER FLOWING OVER
            ROADWAY BETWEEN CLAXTON AND POWELL.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MORRISTOWN TN
1221 AM EDT THU JUL 21 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1217 AM     FLASH FLOOD      1 N KNOXVILLE           35.99N 83.95W
07/21/2022                   KNOX               TN   LAW ENFORCEMENT

            KNOXVILLE PD REPORTING ROADS NEAR I275 AND
            HEISKELL AVENUE AS UNDER WATER.

&&

19

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