Flash Flooding and Flood in Tennessee, July 20 to 21, 2022

AREA FORECAST DISCUSSION
National Weather Service Morristown TN
311 AM EDT Wed Jul 20 2022

.SHORT TERM...(Today and tonight)...

Key Messages:

1. Scattered showers and thunderstorms again today, with another
increase in showers storms later tonight. Damaging wind gusts and
heavy rainfall/localized flooding will be the main threats.

2. A hot and humid afternoon today, especially southern/central
valley.

Discussion:

A few showers over mainly northern half of the area at the moment.
These will continue to lift northeast, but models continue to show
additional showers and eventually thunderstorms developing in this
moist airmass later tonight into today. Instability will increase,
and HREF CAPE values exceed 2000 across much of the area this
afternoon. However, the lack of a significant forcing mechanism
should keep coverage mainly scattered today. There is enough DCAPE
available that a stronger storm may produce damaging wind gusts, and
torrential downpours leading to localized flooding will also
continue to be threat for the short term period.

There may be a lull in the activity early tonight, but as a weak
surface cold front and short wave energy aloft approaches later
tonight we will see additional showers and thunderstorms moving in.
Timing of this activity is still uncertain, but near or after
midnight seems most likely. Several of the hi-res CAMS suggest this
may include a line of showers/storms moving southeast out of
KY/Middle TN, and while decreased convective energy tonight should
lead to some weakening there is potential for some of these storms
to bring damaging wind gusts mainly to the areas across/near the
Plateau tonight.  The wind and heavy rain/localized flooding threat
for today/tonight will be included in the HWO.

It will be hot and humid today with near to slightly above normal
temperatures.  However, combined with the humidity some locations
mainly across the southern/central valley will see heat index values
in the high 90s to around 100 this afternoon.

.LONG TERM...(Thursday through Tuesday)...

Key Messages:

1. Showers and thunderstorms expected on Thursday.

2. Heat indices of 100+ in the central/southern valley over the
weekend and into next week.

Discussion:

By daybreak on Thursday the front will likely be pushing into
eastern KY on it's way towards the Appalachians. We'll be in a lull
in storm activity in the morning after the possible overnight
convection. Better chances for isolated to scattered convection will
come Thursday afternoon and evening, depending on where the front
is. If it moves through a bit quicker on Thursday the convective
activity will be more across the Carolina's into GA/AL. Will
continue with moderate PoP chances, with the best chances for storms
across southeast TN and southwest NC. Forecast soundings in
southwest NC indicate that the atmosphere could support storms
capable of winds that could knock down trees, and brief heavy
rainfall.

After the front moves through we'll unfortunately return to a hot,
muggy, and pretty rain free regime over the weekend and into next
week. Highs will surge into the 90's across most locations through
at least Tuesday. At the same time the surface high off of the
Atlantic will remain in place and help bring in humid air at the
surface, keeping dew points at or above 70 through the weekend. This
will likely result in another round of 90+ Heat Index values across
most of the area, and triple digits in the central and southern
valley over the weekend and into next week. There could be a few
isolated diurnal showers that bring a quick bit of relief at some
point, but for most people it will just be a hot weekend. For this
weekend, remember to practice heat safety during the afternoon and
early evening hours when temperatures are going to be at their
highest.

A frontal boundary may try and drop in from the Ohio Valley during
the middle of next week, but guidance has been backing off with how
far south the front makes it compared to previous runs. It's
possible the ridge may be a bit stronger than previously forecasted,
but it will be worth keeping an eye on as it will be the best chance
for relief from the heat next week.

&&

.AVIATION...
06Z TAF DISCUSSION.

There will be convection around again at times, and will include
vcsh and vcts all sites. Outside of any convection, mainly VFR
conditions are expected. The main exception is at TRI, where MVFR
cigs are expected to develop early in the period and continue into
the morning hours before lifting to VFR. Winds will increase from
the southwest to around 10kts with some higher gusts during the
day.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             92  75  94  72  95 /  40  40  40  30  20
Knoxville McGhee Tyson Airport, TN  90  74  92  71  93 /  50  40  40  20  10
Oak Ridge, TN                       90  73  92  70  92 /  40  40  30  10  10
Tri Cities Airport, TN              87  70  87  67  91 /  40  50  40  10  10

&&

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

Hazardous Weather Outlook
National Weather Service Morristown TN
311 AM EDT Wed Jul 20 2022

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-210715-
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-
311 AM EDT Wed Jul 20 2022 /211 AM CDT Wed Jul 20 2022/

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

.DAY ONE...Today and Tonight

Scattered showers and thunderstorms can be expected today and
tonight. A few of these storms may become strong to severe, with
damaging wind gusts and very heavy rainfall with the potential for
localized flooding the primary threats.

.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 of 100 to 105 degrees expected.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not needed at this time.