088
FXUS63 KLSX 010731
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
231 AM CDT Fri May 1 2026

.KEY MESSAGES...

- Seasonably cool and mostly dry weather will continue through
  Saturday.

- A return to warmer and wetter weather is expected to begin
  Sunday and last through at least early next week.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 229 AM CDT Fri May 1 2026

Surface observations show a cold front stretching through the CWA
from the southwest to the northeast. A loose band of showers
continues to weaken as they push southeast. By sunrise, these
showers and forecast to be long gone, and the only evidence of a
frontal passage will be the cool weather. Today will be nearly a
carbon copy of yesterday, albeit slightly cooler due to the front.
Highs in the low to mid-60s are forecast for most, though areas
north of I-70 may not even reach 60 degrees (0-40% chance east to
west). Another more diffuse front is expected to enter the CWA late
this afternoon and bring a slight chance (up to 20%) of showers
north of I-70 early in the evening. On Saturday, convection may try
and fire along the front in portions of southwest Illinois and
southeast Missouri, but limited convergence along the front and
MUCAPE of under 100 J/kg won`t be working in favor of upward
development. Continued weak cold air advection will drag down highs
a couple of degrees Saturday afternoon, with widespread upper 50s to
low-60s forecast. This will be the coolest day of the period.

Jaja

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 229 AM CDT Fri May 1 2026

An intense warm-up is in store on Sunday as the surface pressure
gradient compresses and warm air advection strengthens. Highs
Sunday will be 10 to 15 degrees warmer than Saturday, with most
locations forecast to reach the 70s. While we bask in the newfound
warmth, a surface cyclone will be developing and deepening lee of
the Rockies. This system is forecast to dive into the Southern
Plains, and intensify southwest flow in our region. For this
reason, there is high confidence that temperatures will boost yet
again, as denoted by the NBM 10th percentile for Monday being
nearly as warm as the 90th percentile for the previous day. The
trajectory of the surface cyclone will also open up the region to
modest moisture advection from the Gulf, which will arrive just in
time to meet an advancing cold front.

Model guidance remains spread given the timing, speed, and
trajectory of the aforementioned cold front. Models appear to center
the front`s arrival around Monday night into Tuesday morning.
Despite what sounds like a small difference in timing, this
discrepancy determines if and when the area will see its next round
of potentially strong to severe thunderstorms. Note: Any severe
weather that may culminate from this system will not be comparable
to earlier this week. This is a completely different setup. As of
now, the 90th percentile of SBCAPE from the LREF peak at 2000 J/kg
Monday night, which is less than the HREF minimum on April 27th. The
LREF`s SBCAPE values will change as its members converge on a
solution, but it`s very doubtful that we`ll see any robust severe
parameters given only modest moisture return and very little
directional shear.

Jaja

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1145 PM CDT Thu Apr 30 2026

VFR conditions will prevail through the TAF period. The only
exception to this is at river valley terminals where fog may
develop again tonight. JEF has the highest potential at seeing
fog, as winds will be lightest farther west. Have fog at SUS and
CPS despite a higher wind forecast given they`re settled in
valleys and experienced rain this evening. There is another
chance of light rain north of I-70 late this afternoon, but
confidence in direct impacts is too low to mention in the TAFs at
this time.

Jaja

&&

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

$$

WFO LSX