Excessive Heat and Heat in Missouri, August 20 to 26, 2023

Name: Excessive Heat and Heat in Missouri, August 20 to 26, 2023
Start: 2023-08-20T11:00
End: 2023-08-26T17:00
Location: Missouri

August 20 to 26, 2023 · NWS MEG · 6 events in 2 counties and zones

The strong upper ridge of high pressure that dominated the weather across the southwest US during the summer of 2023 bulged east into the Mid-South at times during the month of August. High temperatures combined with high humidity produced heat index values over 105 degrees and in some cases over 110 degrees.

Where it happened

Every event with a place to put it; 6 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 6

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS MEG wrote it up.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Memphis, TN wrote its last area forecast discussion before the first event at Aug 20, 10:35 AM CST, 25 minutes earlier.

Area forecast discussion, Aug 20, 10:35 AM CST, 25 minutes before

Area Forecast Discussion
National Weather Service Memphis TN
1135 AM CDT Sun Aug 20 2023

...New UPDATE...

.UPDATE...
Issued at 1135 AM CDT Sun Aug 20 2023

12Z upper air analysis places the center of an upper-level ridge
over east Kansas and west central Missouri. This is producing
mostly sunny skies across the Mid-South late this morning with
temperatures as of 10 AM CDT in the 80s.

METAR observations across the Lower Mississippi Valley show
surface dewpoints rising somewhat across areas mostly west of the
Mississippi River. Latest short-term trends are indicating some
of the guidance may be a bit too high with the afternoon surface
dewpoints while taking into account known AWOS observational
biases at sites such as 4M9. Will make some adjustments to the
dewpoints for the remainder of today. Otherwise, the remainder of
the forecast is in good shape.

CJC

&&

.SYNOPSIS...
Issued at 420 AM CDT Sun Aug 20 2023

Heat continues to be the main concern through Friday. As the
strong upper-level ridge continues to build east, our surface
temperatures and dewpoint temperatures will continue to increase.
No precipitation is expected for the next six days as we continue
in this stationary weather pattern. The pattern will shift next
weekend as models suggest a cold front will move across the Mid-
South and bring decreased temperatures and the chance of
precipitation back into the forecast.

&&

.DISCUSSION...
(Today through Saturday)
Issued at 420 AM CDT Sun Aug 20 2023

A 600 dam ridge, centered over the Plains, continues to build
east allowing the dry airmass associated with it to bring warmer
temperatures across the Mid-South. There is an upper-level low
currently centered over the New England states and an upper-level
trough along the west coast associated with Hilary. Hilary's
trough is working to strengthen the ridge to create southwest
flow across the lower Mississippi Valley. Some patchy fog is
possible overnight and each successive night as winds go calm.

The pre-existing Heat Advisory has been expanded to include
portions of west TN and northwest MS. Dewpoint temperature values
have climbed allowing heat indices to reach up to 109F in these
counties. A few counties in northeast AR were upgraded to an
Excessive Heat Warning today with heat indices reaching up to
113F. For the Heat Advisory expect heat indices up to 109F.

Moving into the remainder of the week, we will continue to see
heat indices in the triple digits across the Mid-South likely
requiring an expansion and an extension of Heat Headlines through
week's end. A frontal boundary looks to move into the Mid-South
next weekend which will allow our temperatures to decrease and
could bring precipitation back into the forecast.

AEH

&&

.AVIATION...
(12Z TAFS)
Issued at 617 AM CDT Sun Aug 20 2023

VFR conditions with light southeasterly winds are expected through
the period due to a strong upper level ridge over the central
Plains.

CAD

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Excessive Heat Warning until 7 PM CDT this evening for ARZ009-
     018-026.

     Heat Advisory until 7 PM CDT this evening for ARZ027-028-035-036-
     048-049-058.

MO...Heat Advisory until 7 PM CDT this evening for MOZ113-115.

MS...Heat Advisory until 7 PM CDT this evening for MSZ001-007-008-
     010>012-020.

TN...Heat Advisory until 7 PM CDT this evening for TNZ001-002-019-048-
     049-088.

&&

PUBLIC FORECAST...AEH
AVIATION...CAD

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

4 heat, 2 excessive heat. Local standard time, as filed.

Heat, Dunklin

When: August 20, 11:00 AM CST to 7:00 PM CST
Where: Dunklin forecast zone
Reported by: AWOS
Coordinates: 36.106, -90.166 (the zone’s center; the record gives no point)

Heat indices in excess of 105 degrees.

Heat, Pemiscot

When: August 20, 11:00 AM CST to 7:00 PM CST
Where: Pemiscot forecast zone
Reported by: AWOS
Coordinates: 36.211, -89.785 (the zone’s center; the record gives no point)

Heat indices in excess of 105 degrees.

Heat, Dunklin

When: August 21, 11:00 AM CST to August 22, 11:00 AM CST
Where: Dunklin forecast zone
Reported by: AWOS
Coordinates: 36.106, -90.166 (the zone’s center; the record gives no point)

Heat indices in excess of 105 degrees.

Heat, Pemiscot

When: August 21, 11:00 AM CST to August 22, 11:00 AM CST
Where: Pemiscot forecast zone
Reported by: AWOS
Coordinates: 36.211, -89.785 (the zone’s center; the record gives no point)

Heat indices in excess of 105 degrees.

Excessive Heat, Dunklin

When: August 22, 11:00 AM CST to August 26, 5:00 PM CST
Where: Dunklin forecast zone
Reported by: AWOS
Coordinates: 36.106, -90.166 (the zone’s center; the record gives no point)

Heat indices in excess of 110 degrees.

Excessive Heat, Pemiscot

When: August 22, 11:00 AM CST to August 26, 5:00 PM CST
Where: Pemiscot forecast zone
Reported by: AWOS
Coordinates: 36.211, -89.785 (the zone’s center; the record gives no point)

Heat indices in excess of 110 degrees.

What these are

Heat: Heat below excessive heat criteria that still caused deaths, injuries or significant impacts.
Excessive Heat: Heat at or above the local excessive heat warning criteria, or heat that caused deaths.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Missouri in 2023 Every state in 2023 This day in weather history Warnings in Missouri, August 2023

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1134069, 1134070, 1134538, 1134539, 1134540, 1134541.