Area Forecast Discussion
041
FXUS63 KLSX 180421
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1021 PM CST Wed Dec 17 2025
.KEY MESSAGES...
- Widespread rain showers are forecast on Thursday associated with
a cold frontal passage. Gusty (30-40 mph) northwest winds are
forecast behind the front Thursday late afternoon/evening.
- After a brief return to seasonably cold temperatures on Friday,
milder weather returns this weekend through the holiday week.
&&
.SHORT TERM... (Through Late Thursday Night)
Issued at 228 PM CST Wed Dec 17 2025
Broad, weak low-level moisture convergence is expected to begin
this evening in southeast Missouri and move north/northeast with
time. Isolated to widely scattered showers are possible, mainly
before midnight across southeast Missouri and southwest Illinois.
By late tonight into early Thursday morning, the first of two cold
fronts will begin to approach central/northeast Missouri near
daybreak. More widespread rain shower activity is expected along
this frontal boundary, aided by strong surface convergence along
with mid/upper level diffluence. This area of showers should sweep
from west to east with the front. An isolated rumble or two of
thunder is also possible, mainly across southwest Illinois between
1500 and 1800 UTC as the boundary exits the CWA. Rain chances
really drop behind this initial cold front, but a few isolated
showers may be possible along the second of the double-barreled
cold front during the late afternoon across northeast Missouri and
west-central Illinois. Behind this front, some snow showers are
possible in northeast Missouri and west-central Illinois Thursday
evening.
In terms of rainfall totals, most locations are forecast to see
between 0.20-0.40". HREF probabilities for at least 0.25" of rain
range from 30-80% from west to east. Given the limited coverage of
shower activity ahead of the front, limited duration of the more
widespread rain along the initial cold front, and lack of true
convection expected, more substantial rainfall amounts are very
unlikely. The LPMM of the HREF is below 0.50" areawide.
Winds are another concern on Thursday. More specifically, the
strongest winds should be behind the second cold front late
afternoon/early evening on Thursday. Gusts of 35-40+ mph are
expected, especially in northeast Missouri and west-central
Illinois. A brief, isolated gust to 45+ may is possible given almost
50 knots of flow at the top of the mixed layer. However, the signal
is very brief over a very small area. Therefore, did not issue a
wind advisory at this time. HREF probabilities for 45+ mph gusts are
also very small (
NWS LSX Office Area Forecast Discussion