341
FXUS63 KLSX 160856
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
356 AM CDT Sun Jun 16 2024

.KEY MESSAGES...

- Above average temperatures will persist through the upcoming
  week with today and Monday expected to be the warmest days
  including peak afternoon heat index values in the upper 90s to
  105 F.

- Isolated to scattered showers and thunderstorms are forecast at
  times through the upcoming week as well, with the greatest
  chances (20 to 40 percent) on Monday and Tuesday during the
  afternoon.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 355 AM CDT Sun Jun 16 2024

An upper-level ridge centered over the southern Appalachian
Mountains and Ohio Valley will begin amplifying and expanding today
increasing low-level southerly flow in the Mid-Mississippi River
Valley at the ridge`s western periphery. After a much milder night
tonight (5 to 15 F warmer than 24 hours ago), ingredients will come
together for the warmest day of the year thus far today, including
850-hPa temperatures warming above the 90th climatological
percentile, a slight southwesterly component of low-level flow
downsloped off the Ozark Mountains, and strong insolation. The
result will be widespread high temperatures in the low to upper 90s
F. Additionally, moisture/dewpoints will be increasing, but
compensated to some degree by deep mixing and slight downsloping,
contributing to peak heat index values reaching the upper 90s to 105
F this afternoon. These values fall just short of conventional
hazardous thresholds; however, care should be taken by individuals
spending time outdoors today. Lastly, recent CAMs are advertising
that a remnant MCV from an MCS currently tracking in eastern KS will
have the potential to produce a few showers and thunderstorms in
northeastern MO and west-central IL this afternoon. Otherwise, dry
conditions are anticipated.

On Monday, the first of a series of mid-level perturbations rotating
northward around the upper-level ridge will arrive to the Mid-
Mississippi River Valley, acting to enhance development of diurnal
isolated to scattered showers and thunderstorms during the afternoon
and evening as instability peaks and convective inhibition is at a
minimum. The presence of these showers/thunderstorms and greater
cloud cover along with a slight cooling of 850-hPa temperatures will
lead to slightly cooler temperatures on Monday mainly along and
south of I-70, but greater moisture/higher dewpoints will again
promote peak afternoon heat index values reaching the upper 90s to
105 F across most of the CWA.

Pfahler

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 355 AM CDT Sun Jun 16 2024

The center of the upper-level ridge will shift more northeastward
into the Mid-Atlantic and Northeast on Tuesday and Wednesday,
allowing low-level flow to back slightly with a brief cooling of 850-
hPa temperatures. Additional opportunities for diurnal isolated to
scattered showers and thunderstorms are also expected Tuesday and
Wednesday with the help of additional passing mid-level
perturbations, leading to some uncertainty in exact temperatures
each day. As a result, NBM temperature interquartile ranges still
span 5 to 8 F but remain largely above average. After Wednesday,
global models are in agreement that there will be a period of time
that the upper-level ridge retrogrades westward slightly, which is
indicated by ensemble models to support another increase in
temperatures further above average and lower chances of showers and
thunderstorms.

Pfahler

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1059 PM CDT Sat Jun 15 2024

Dry and VFR flight conditions are expected throughout the TAF period
with southeasterly winds becoming southerly and strengthening on
Sunday.

Pfahler

&&

.CLIMATE...
Issued at 328 AM CDT Sat Jun 15 2024

Daily High Temperature Records:
                 |=== June 16 ==|=== June 17 ==|
St. Louis (KSTL) | 100 F (1952) |  99 F (1944) |
Columbia  (KCOU) |  99 F (2006) | 100 F (1936) |
Quincy    (KUIN) | 102 F (1936) | 103 F (1918) |


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX