839 
FXUS63 KLSX 031718
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1218 PM CDT Fri Oct 3 2025

.KEY MESSAGES...

- Unseasonably warm temperatures are expected to continue through early
  next week. Temperatures will fall back to near normal behind a 
  cold front by the middle of next week.

- The is a slight chance (20%) of showers and thunderstorms over
  parts of the area this afternoon. There is a better chance
  (30-40%) with the cold front on Monday night and Tuesday.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 321 AM CDT Fri Oct 3 2025

The latest water vapor imagery was showing an upper trough extending 
from the Great Lakes through Illinois into the Lower Mississippi 
Valley with a ridge just off to the west.  Conditions are dry across 
the area early this morning despite the trough as there is little 
instability or low level forcing for it to act on. The RAP and 
NAM is showing that the trough will supply some weak lift in the 
into this afternoon across far eastern MO into south central 
Illinois as it slowly weakens with time. This is the same area 
that will become weakly capped by this afternoon with MUCAPES of 
500-1000 J/kg, so have included slight chances (10-20%) for 
showers and thunderstorms. Any convection will rapidly dissipate 
early this evening with the loss of daytime heating.

Temperatures early this morning are all in the 60s across the area, 
so with warm start and similar conditions to yesterday, went with
highs in the upper 80s to near 90 today. Lows tonight will be in 
the lower 60s, with a few upper 50s in river valleys and over 
southeast Missouri.

Britt

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 321 AM CDT Fri Oct 3 2025

It still looks the weekend will be mainly dry as the upper ridge 
moves back over Missouri and Illinois.  Rain chances show up as 
early as Monday as both the global models and their ensembles are 
begin to increase (20%) over the northern CWA associated with a 
trough/front and in the south with increased moisture transport from 
the Gulf. The chances will increase (Monday night through Tuesday) 
when the aforementioned trough will pass through the Great Lakes and 
bring a cold front across Missouri and Illinois.  The LREF is 
showing 30-40% of its members producing precipitation during this
timeframe before dry weather returns Wednesday into Thursday as 
another ridge will move into the Midwest. As mentioned in previous
discussions, significant rainfall does not seem likely as the 
LREF chances for seeing >0.5" over the CWA by next Thursday is 
<25%. Likewise, severe weather chances look low through the end of
next week.

Highs are expected to stay well into the 80s through Monday ahead of 
the front before dropping back into the 70s on Wednesday and 
Thursday which is near normal for early-mid October.   The NBM IQR 
at STL is only 1-3 degrees through Monday, but then increases to 6-
10 degrees by mid-late next week showing that there is a spread in 
the models and increasing uncertainty in the forecast.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1215 PM CDT Fri Oct 3 2025

Isolated pop-up showers and thunderstorms are forecast mostly
north of I-70 this afternoon. The chances of these impacting any
given terminal are low, so left mention from the TAFs. If a shower
or storm does impact a terminal, expect brief moderate to heavy
rain and reduced visibilities. For all not impacted, dry and VFR
conditions will prevail through the TAF period.

Jaja

&&

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

$$

WFO LSX