597
FXUS63 KLSX 260745
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
245 AM CDT Wed Jun 26 2024

.KEY MESSAGES...

- Thunderstorms this morning will exit off to the southeast early
  in the day, giving way to a much nicer day with cooler
  temperatures than we`ve seen in a while.

- The heat returns this weekend, but not as intense. Heat index
  values around 100 are expected on Saturday. We`ll also have more
  opportunities for thunderstorms Friday and Saturday ahead of the
  next front.

&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 245 AM CDT Wed Jun 26 2024

Multiple convective complexes pushing south this morning have made
it pretty hard to identify where the surface cold front is, but we
will be seeing a change in air mass today as cooler and drier air
moves in. The morning thunderstorms should exit to the southeast
fairly early in the day, although some of the CAMS do keep some
showers lingering into the afternoon. This just reinforces the
idea that it will be significantly cooler today, especially if the
clouds and showers linger into the afternoon. Temperatures tonight
drop well into the 60s as the surface high pressure axis
approaches. We`ll see the temperature warm a few degrees on
Thursday with more sun, but still at or a little below normal for
this time of year, mostly in the mid 80s.

Kimble

&&

.LONG TERM...  (Thursday Night through Tuesday)
Issued at 245 AM CDT Wed Jun 26 2024

Ridging over the western US moves east and flattens as it does so.
So while we will see another warm up, it shouldn`t be as intense
as our last heat episode. Friday and Saturday warm back into the
90s with increasing humidity as well. Heat index values over 100
are most likely on Saturday.

Troughing moving onshore in the Pacific Northwest today will
continue to push slowly eastward near the US/Canada border through
the weekend. We`ll see a surface front developing out in the
Plains and pushing southeast through our area as the upper trough
axis moves into the Great Lakes on Saturday. Ahead of the front,
multiple rounds of thunderstorms are possible beginning on Friday.
Much of the lift stays north of our area on Friday, but the
northern part of Missouri into western Illinois may be close
enough to get in on some thunderstorms. The better lift moves
through on Saturday ahead of the cold front with more widespread
thunderstorms possible. With a southerly low level flow and a
modest westerly flow aloft, there`s just enough shear available
for some storm organization, so we`ll have to keep an eye on the
potential for strong to severe storms both days, especially as
heat and humidity peak leading to a peak in instability as well.

A progressive upper pattern continues with a shift toward cooler
temperatures behind Saturday`s trough, but warming back up again
next week as ridging moves in to replace it. How hot we get will
depend on how well established the ridge becomes over our area and
whether we are affected by daily thunderstorms on the northern
periphery of the ridge.

Kimble

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1221 AM CDT Wed Jun 26 2024

Main concern for the TAF forecast is timing of thunderstorms at
each location. Confidence has grown relative to prior forecasts
that the final round of storms will be moving through overnight.
The best instability, and most confidence for thunderstorms, is in
central Missouri, but most of the area will see rain and some
embedded thunder. Winds are variable as downdrafts are coming from
many directions with all the convection around, but the general
trend will be toward northerly winds by morning. There`s a low
chance we could develop some MVFR ceilings behind the main line of
convection, but so far this has not materialized and confidence
has decreased in it occurring. We should see a trend toward VFR
clearing during the day Wednesday.

Kimble

&&

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

$$

WFO LSX