182
FXUS63 KLSX 270738
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
238 AM CDT Mon May 27 2024

.KEY MESSAGES...

-Memorial Day will be largely dry, though a stray shower or
thunderstorm cannot be ruled out across far NE Missouri and west-
central Illinois late this afternoon.

-Dry weather with near normal temperatures will persist through
 the work week.

&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 224 AM CDT Mon May 27 2024

With the abundance of surface moisture and a mostly clear sky
there is a risk for patchy fog this morning, particularly in the
river valleys and hollows where winds will be sheltered. Any fog
that develops will mix out shortly after sunrise. In the wake of
Sunday`s severe weather a cold front is stretched across the mid-
Mississippi Valley. The front will continue to sink southward
through the morning as the mid-level trough lifts eastward out of
the forecast area and the surface low follows in lockstep. Behind
this system, northwesterly mid-level flow will establish as a mid-
level trough becomes rooted over the eastern CONUS, and a mid-
level ridge sets up over the Mountain West.

A shortwave disturbance will propagate down the northwesterly
flow this afternoon/evening, while a 850 mb jet noses into the
northern forecast area. While moisture will be limited across the
area, I cannot rule out a quick shower or thunderstorm popping up
across far northeast Missouri and west-central Illinois during the
late afternoon and early evening. Limited moisture and
instability (around 300 J/kg of MUCAPE) keep the chance for strong
thunderstorms very low. Otherwise, rising heights will keep the
remainder of the forecast area dry today and Tuesday. Temperatures
will return to seasonal levels, with highs peaking in the upper
70s across northeast Missouri and west-central Illinois and just
around 80 along and south of the I-70 corridor Monday and Tuesday.

MRM

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 224 AM CDT Mon May 27 2024

The mid-Mississippi Valley will remain in northwest flow aloft as
the mid-level trough and ridge stay locked in across the eastern
CONUS and Mountain West, respectively. This will keep the work week
largely dry with seasonal temperatures. The interquartile spread for
high temperatures through the work week is very small, around 3
degrees. This increases confidence that temperatures will indeed
be near normal for late May. As the weekend approaches so does the
mid-level ridge, which will throw the region back into
southwesterly flow over the weekend. This will open the region
back up to shortwave disturbances as well as warm, moist
advection. While specifics vary on the location and timing of
shortwaves, confidence is increasing that chances for
precipitation will return to the region over the weekend.

MRM

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1218 AM CDT Mon May 27 2024

By and large convection has ended across the region, and the
remainder of the TAF period is expected to be dry. A largely sky
and recent rainfall increases the potential for patchy fog
tonight, particularly in the valleys and river bottoms where winds
will be more sheltered. However, given the lingering cloud cover
still around, I don`t yet have enough confidence to include a
mention of visibility reduction at any of the TAF sites just yet.
If fog does develop it will clear by 12-13Z with sunrise.

Winds will remain from the northwest through the period, becoming
strong (sustained winds above 10 kts) and gusty (near 20 kts)
during the afternoon hours tomorrow.

MRM

&&

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

$$

WFO LSX