Excessive Heat and Heat in Missouri, June 29, 2024

Area Forecast Discussion...UPDATED
National Weather Service Paducah KY
1229 PM CDT Sat Jun 29 2024

.KEY MESSAGES...

- A Heat Advisory remains in effect today across portions of the
  region for heat index values peaking between 105 to 109
  degrees.

- Shower and storm chances will be on the increase today as a
  cold front slowly pushes south. The greatest risk peaks
  between 8PM to 1AM, especially across portions of southeast
  Missouri and far western Kentucky. A few isolated severe
  storms remain possible with damaging winds, small hail,
  torrential downpours, and lightning being the main concern.
  Localized flash flooding issues are also possible.

- Relief from the heat and humidity is in store Sunday into
  Monday before turning unpleasant again in time for the 4th of
  July. An unsettled pattern with daily chances for showers and
  storms also begins the middle of the week.

&&

.DISCUSSION...
Issued at 220 AM CDT Sat Jun 29 2024

GOES 16 satellite imagery shows clouds rapidly cooling this morning
upstream across central Missouri where a MCS has developed.
Downstream over the FA, conditions are quite uncomfortable and soupy
with dewpoints well into the 70s. The CAMs are in better
agreement that convection will be on the downward trend by 12z
before reaching southern IL. Otherwise, a Heat Advisory remains
in affect across portions of the CWA where heat index values
will peak between 105 to 109 degrees with diurnal heating.
However, portions of southern Illinois, southwest Indiana, and
western Kentucky will have enough residual cloud cover to keep
temps cooler.

Another complex may impact north of the Ohio River mid morning to
early afternoon, but any showers or storms looks to be fairly
disorganized and scattered. However, this will likely set off some
type of outflow boundary that will be the main focus for CI this
evening, especially across portions of southeast Missouri and far
western Kentucky. The greatest risk for storms will be between 8PM
to 1AM tonight when many of the CAMs show yet another MCS moving
southeast as a shortwave combined with a cold front sags south with
forcing for ascent. The 00z HRRR is a bit of an outlier with model
soundings showing a cap just above the sfc, but think there
will be enough forcing to overcome this given increasing 300 mb
divergence and 850 mb frontogenesis.

As for the severe weather potential, the risk remains marginal in
SPC's D1 outlook. MLCAPE between 3000 to 3500 J/kg, DCAPE over 1000
J/kg, and sfc-3km theta-e difference around 25-30K still remains
fairly supportive of an isolated damaging winds risk with
updrafts that are able to become organized. However, deep layer
shear remains modest at best around 25-30 kts favoring only
small hail given a high WBZ around 600 mb. PWATS near the 99th
percentile above 2.00 inches will also lead to torrential
downpours with storms. Given a slow storm motion with a mean
cloud layer westerly wind around 20 kts, isolated flash
flooding will also be possible, especially in low-lying
locations that are prone to poor drainage.

Any lingering showers or storm quickly diminish on Sunday as the
cold front pushes south of the FA. Sfc high pressure builds
into the Ohio Valley supporting more tranquil conditions into
Monday. It will certainly feel much cooler compared to today as
northerly winds advect in much lower dewpoints in the 50s and
possibly even a few 40s. This will set the stage for a very
refreshing Sunday night after a day with maxTs only in the mid
80s as minTs are progged to fall into the upper 50s to near 60
degrees.

High pressure then pushes east on Tuesday as southerly return flow
quickly advects in more humid and hotter conditions again. By the
middle of the week, conditions are progged by the NBM to be similar
to today with heat index values once again exceeding 105 degrees.
The other concern will be for a more unsettled pattern with daily
chances for showers and storms through the end of the week as a
series of 500 mb troughs dig down from the northern Plains. This may
eventually push a front through the FA by next weekend. Given better
shear, will need to monitor for a potential severe/wind risk if the
parameters are able to line up. At the moment, there is no strong
signal on any particular day, but something to watch for in the
coming days for the 4th of July.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1228 PM CDT Sat Jun 29 2024

Clouds should remain above VFR thresholds through the afternoon.
Convection is the primary flight concern today. Generally think
things will hold off til 21-22z but with abundant humidity/low
moisture in place can't completely rule out something popping up
through the afternoon. Best chances will be in the 00-06z
timeframe as a front moves in from the north.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory until 7 PM CDT this evening for ILZ084-085-
     088>090-092>094.
MO...Heat Advisory until 7 PM CDT this evening for MOZ076-086-087-
     100-107>112-114.
IN...None.
KY...Heat Advisory until 7 PM CDT this evening for KYZ001>013-017-
     022.

&&

DISCUSSION...DW
AVIATION...JGG

Hazardous Weather Outlook
National Weather Service Paducah KY
227 AM CDT Sat Jun 29 2024

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-301000-
Jefferson-Wayne IL-Edwards-Wabash-Perry IL-Franklin-Hamilton-
White-Jackson-Williamson-Saline-Gallatin-Union-Johnson-Pope-
Hardin-Alexander-Pulaski-Massac-Gibson-Pike-Posey-Vanderburgh-
Warrick-Spencer-Fulton-Hickman-Carlisle-Ballard-McCracken-Graves-
Livingston-Marshall-Calloway-Crittenden-Lyon-Trigg-Caldwell-
Union KY-Webster-Hopkins-Christian-Henderson-Daviess-McLean-
Muhlenberg-Todd-Perry MO-Bollinger-Cape Girardeau-Wayne MO-Carter-
Ripley-Butler-Stoddard-Scott-Mississippi-New Madrid-
227 AM CDT Sat Jun 29 2024 /327 AM EDT Sat Jun 29 2024/

This Hazardous Weather Outlook is for portions of southern
Illinois, southwest Indiana, western Kentucky, and southeast
Missouri.

.DAY ONE...Today and Tonight

Heat index values of 105 to 109 degrees are forecast for portions
of the area today and over 100 degrees for essentially the entire
area. See the Heat Advisory for additional details.

Isolated strong to severe storms are possible this evening into
tonight with damaging winds, small hail, torrential downpours,
and lightning being the main concern.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Heat index values around 100 to 105 degrees are forecast for
portions of the area on Wednesday and Thursday.

Daily chances of showers and thunderstorms begins on Wednesday and
continues through Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

DW