FXUS63 KLSX 222310
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
610 PM CDT Sat Aug 22 2026

.KEY MESSAGES...

- Pleasant and mostly dry conditions are expected through the
  upcoming week.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 230 PM CDT Sat Aug 22 2026

Northwest flow continues aloft across the region. A ridge is
bringing hot weather out west while a trough over the Great
Lakes is bringing considerably cooler weather in the east. At 
the surface, high pressure is pushing south into the Northern 
Plains, with winds out of the north across our region bringing 
in drier air. As this high nudges further south overnight we'll 
see winds die off and temperatures drop in the fresh dry air 
mass. Lows tonight will dip into the low to mid 60s, with some 
upper 50s possible in the cooler spots. Sunday will be one of 
the coolest days of this air mass with highs only reaching into 
the low 80s. Some mid and high level cloud cover will contribute
to those lower temperatures.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 230 PM CDT Sat Aug 22 2026

This week we continue in some flavor of western ridging and
eastern troughing, keeping our area in the northwest flow in
between. Showers and thunderstorms rotating around the ridge
stay largely west of our area, keeping us mainly dry through
Tuesday with temperatures eventually making a modest rebound
back into the mid to upper 80s.

The initial eastern trough weakens and lifts into the Canadian 
Maritimes by midweek, but it gets replaced by a new trough 
arriving from around the top of the ridge. It's this trough 
that's probably the most interesting feature for our weather 
this week. It initially arrives in the Pacific Northwest 
tomorrow but moves into the western Great Lakes on Wednesday. As
it does so, it will slide another cold front southward through 
the middle of the country, pushing through our area Wednesday or
Wednesday night. This represents our best chance of rain this
week, though those chances aren't particularly high at this
point. Most of the forcing from the trough passes by to our
north while the better moisture and instability remains further
south. NBM PoP remains quite low, generally 20 percent or less,
but if we look at the low resolution ensemble guidance we see 
that 50 to 60 percent of these members produce measurable rain
in the 24 hours ending Wednesday night. It's the timing and
location uncertainty that's holding PoP lower at this point, but
this does represent our best chance of rain locally this week.

Wednesday's front may knock temperatures back a few degrees, but
guidance is in general agreement that the western ridge weakens
and broadens later in the week, nudging its influence eastward.
This would nudge us back toward warmer temperatures, but not as
extreme as we've seen recently. We'll also have a few other
opportunities for rain as shortwave troughs round the edge of
the ridge even as it approaches our area. However, confidence 
in the timing and track of those waves is even lower than for
Wednesday's trough, so daily rain chances remain fairly minimal
in the current forecast until that confidence changes.

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 606 PM CDT Sat Aug 22 2026

Northerly post-frontal winds will continue to usher cooler,
drier air into the region though the TAF period, limiting
aviation concerns. That said, there is a narrow band of isolated
showers dropping SE through central IL that could bring a very
weak shower to UIN over the next few hours or the STL metro
terminals between 04Z and 06Z. Lightning is not expected with 
these showers. Otherwise, the only concern is the threat for 
some river valley fog at SUS, CPS, and JEF. I'm not confident 
that those conditions will materialize, so I've just included a 
mention of 6am BR at those sites.

&&

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

&&

$$

SHORT TERM...Kimble
LONG TERM...Kimble
AVIATION...Kimble