959
FXUS63 KLSX 162022
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
222 PM CST Sun Nov 16 2025

.KEY MESSAGES...

- Scattered showers are expected (up to 90% chance) Monday evening
  mainly along and east of the Mississippi River. There is a low
  chance for isolated thunderstorms within these showers.

- More widespread rain is forecast for late Wednesday into early
  Friday, with up to a 60% chance for 1" or more of rainfall for
  portions of central and southeastern Missouri.


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 219 PM CST Sun Nov 16 2025

The Middle Mississippi Valley is beneath northwesterly flow aloft
thanks to an upper-level trough digging across the East Coast per
current water vapor imagery. Within this northwesterly flow, an area
of high pressure at the surface has dipped into region, bringing a
cool and dry air mass to the CWA. Clear skies have offset the weak
cold air advection, with afternoon highs topping out in the mid 50s
for most locations - just below climatological normals.

This surface high begins to edge eastward tonight in response to a
cut off low that is currently undercutting the western ridge moves
into the Plains. The high will be in place long enough to still
impact overnight temperatures thanks to clear skies and light winds.
This will be particularly the case over south-central Illinois in
closer proximity to the high, where overnight lows will drop into
the low 30s.

Through the day tomorrow, the high will continue eastward as a low
deepens across the Central High Plains. Mid-level ridging will warm
temperatures aloft enough to produce a boost to surface values by a
couple of degrees compared to Sunday, though increasing cloud cover
and strengthening winds will cause this relative warm up to go
unnoticed. The cloud cover will be in response to isentropic lift as
a warm front pivots toward the CWA through the day, with forcing
becoming enough to spawn convection during the evening. This
convection will be mainly scattered showers, though there is a low
chance for a thunderstorm or two as this activity moves east-
northeastward across Missouri. The chance for showers and isolated
thunderstorms will peak overnight as convection crosses into
Illinois thanks to the strengthening low-level jet.

Elmore

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 219 PM CST Sun Nov 16 2025

At the start of the extended period early Tuesday, the aforementioned
shortwave will be located roughly over the Middle Missouri Valley
with its attendant surface low just west of the CWA. There still
remains subtle variations of the phasing of the wave and
therefore, the surface low`s placement and track through the day
on Tuesday. Despite the variability, a majority of guidance has
rain departing the CWA to the east through Tuesday morning, though
temperatures are more uncertain. Given the the 25th percentile of
temperatures among ensemble guidance tops out in the mid-60s on
Tuesday, confidence is high that much of the CWA will at least be
within the warm sector of the surface low, but how far north the
warm front will reach is uncertain. Areas south of I-70 have the
highest probability of reaching or exceeding 70 degrees (up to 90%
per the NBM). Guidance consensus is that a weak cold front will
drop into the region late Tuesday and stall thanks to ridging
building aloft, leading to an approximately 10-degree spread
within the IQR of ensemble temperatures into Wednesday, with
highs varying by just as much from north to south across the CWA.

A majority of guidance continues to show a broad upper-level trough
with embedded shortwaves digging into the Southwest through the day
on Wednesday, with the effects of the leading waves being felt
locally as early as Wednesday night or early Thursday morning. Then,
a low-level jet will begin ramping up and nosing into the region,
interacting with the stalled front to spawn rainfall extending from
the Southern Plains into the Ohio Valley. Isentropic ascent will
continue to feed rain chances in this general region ahead of a
surface low that will form over the Central or Southern High Plains
and move northeastward through the Midwest from Thursday through
Saturday.

Despite the general consensus among guidance on the evolution of
this pattern, there still remain notable differences among ensemble
clusters and deterministic guidance on the phasing of the trough and
associated shortwaves, leading to track and timing variability of
the surface low. Solutions with a faster low have the relatively
heavier rainfall ending across the CWA as soon as mid-day Friday,
while slower guidance has the rainfall departing as late as Friday
night/Saturday morning. To what extent the axis of higher rainfall
totals stretch into the CWA also varies based on the track of the
low. Recent ensemble and NBM initializations have the probability of
totals reaching or exceeding 1" topping out at 50-60% across central
Missouri, with probabilities decreasing gradually eastward through
the rest of the CWA. These probabilities are in this range due to
the spread in placement of the main swath of rain. More
deterministically, anomalous PWATs of around 1.5" (above 90th
percentile) support individual solutions showing as much as 2" of
total rainfall for western and southern portions of the CWA.

Elmore

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1129 AM CST Sun Nov 16 2025

Confidence is high in VFR flight conditions through the forecast
period at all local terminals. A warm front sweeping through the
region will bring decreasing ceilings and a low chance for showers
just beyond this TAF period.

Elmore

&&

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

$$

WFO LSX