269
FXUS63 KLSX 200849
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
349 AM CDT Thu Jun 20 2024

.KEY MESSAGES...

- Above normal temperatures through Saturday will continue with
  dry weather other than an isolated chance (20%) for a shower/thunderstorm
  across far northeast Missouri and west-central Illinois this
  afternoon.

- The next significant chance (up to 70%) of showers and thunderstorms
  will be late Saturday through Sunday.

- Much above normal temperatures are becoming increasingly likely through
  the first half of next week, with potential for excessive heat.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 348 AM CDT Thu Jun 20 2024

The mid-level ridge/high dominating the eastern CONUS will slowly
advance westward today and result in the anticipated continuous warm-
up and largely dry weather across the region. A mid-level
disturbance traversing across southern Iowa along with an area of
moisture convergence near the surface will result in a chance (20%)
for isolated showers and thunderstorms across far northeast Missouri
and west-central Illinois this afternoon. Height rises associated
with the deep high pressure and the region`s proximity to the center
of the mid-level high and substance aloft will suppress
precipitation chances and favor increasing temperatures.

Temperatures today will be warmer than yesterday with highs in the
upper 80s to mid-90s with the region being on the western periphery
of the mid-level high. As the mid-level high inches closer to the
region, southwesterly low-level flow on Friday will support hotter
temperatures than today with highs in the low to mid 90s.

MMG/Glass

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 348 AM CDT Thu Jun 20 2024

Little relief of these above normal temperatures is expected through
next week. Saturday is forecast to be the hottest day of the weekend
as the mid-level ridge remains centered across the Mid-Mississippi
River Valley. A shortwave trough will traverse the region late
Saturday into Sunday morning and sending a cold front into the area.
This cold front will provide the next chance (up to 70%) of showers
and thunderstorms. Confidence continues to increase that the
greatest precipitation chances will be overnight Saturday into
Sunday morning. However, there is uncertainty in the southern
penetration of the cold front into the CWA which could affect highs.
Should remnant cloud cover persist through the day Sunday, highs
could be suppressed. However, with an increase of low level
moisture, heat index values could be above 100 degrees Saturday
through Sunday. Despite above normal high temperatures into the 90s
and peak heat index values between 100-103 degrees in places, these
values remain below advisory criteria.

Next week, ensemble guidance is in consensus that the mid-level high
will be anchored over the western CONUS with the Mid-Mississippi
River Valley being in the eastern periphery. The accompanying low-
level southwesterly flow will favor hot, and potentially impactful
temperatures, and possibly dangerous heat levels. Current ensemble
850 mb temperatures range from 21-24 degrees C on Tuesday,
supporting potential highs of 100+ in some places. Further
increasing confidence in these extreme temperatures, the upper
quartile of the NBM high temperatures is 100+.

MMG/Glass

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1025 PM CDT Wed Jun 19 2024

Mainly dry and VFR conditions are expected through the period.
Only exception will be the potential for some brief fog between
08-12Z at SUS with MVFR or low VFR visibilities. Otherwise, just
light winds are expected.

Britt

&&

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

$$

WFO LSX