Hidden Valley

000
FXUS63 KLSX 301653
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
1153 AM CDT Fri Oct 30 2026

.KEY MESSAGES...

- Temperatures remain abnormally-warm through early next week.

- Showers and a few thunderstorms are expected at times through
  the weekend, mainly this morning and late Saturday into 
  Sunday morning with plenty of dry time otherwise.

- Widespread, beneficial rainfall arrives next week.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 329 AM CDT Fri Oct 30 2026

Convection continues to percolate at this hour across northern 
Missouri into west-central Illinois along a weak, stalled front 
impinged by an equally-weak low-level jet centered in the 
Plains. The thunderstorms are stalling where they form, leading 
to locally- heavy rainfall. A few weaker showers extend south to
near the eastern I-70 corridor, but are more isolated and 
further removed from any forcing. Aloft, weak ridging persists 
but a longwave evident in mid-level water vapor imagery is 
crawling north from Mexico into the southern Plains. The 
presence of the front and resultant cloud cover and intermittent
convection will keep temperatures in check across northern 
Missouri and west-central Illinois today. Further south, another
unseasonably-warm and largely dry day is in store. Short-range 
guidance is in pretty fair agreement that sometime today, likely
in the afternoon, flow aloft gradually amplifies and becomes 
more southwesterly ahead of the slow- moving trough from the 
southern Plains. This change will result in increased rain 
chances, mainly west of our forecast area, this afternoon and 
evening. A few stray showers can't be ruled out across central 
and northeast Missouri associated with the diffluent flow aloft,
but most will stay dry into early Saturday.

By the morning hours of Halloween, weak, broad troughing aloft will 
be overhead in the Mid-Mississippi Valley, promoting abundant cloud 
cover that will inhibit temperatures noticeably compared to 
previous days. Model soundings are quite stable and struggle to 
saturate the low-levels, keeping a threat for any stronger 
showers or thunderstorms at bay. Weak, nebulous isentropic 
ascent is evident in most guidance, suggesting light rain 
remains a threat for outdoor activities. That said, most 
solutions suggest that what little ascent exists will maximize 
late in the evening Saturday. While a completely-dry day is not 
a guarantee, trick-or-treating won't be a washout by any 
standards and most areas will be largely dry until the ghosts 
and goblins are inside for the night.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 329 AM CDT Fri Oct 30 2026

As the clocks roll back and the calendar turns forward to November, 
the light rain associated with this initial weak wave tracks east 
and exits the region early Sunday afternoon. Meanwhile, a deeply-
amplified trough comes onshore across the western CONUS. In between 
these two waves, weak ridging aloft will promote a dry start to the 
work week on Monday. The western wave makes quick eastward progress 
and arrives in the Mid-Mississippi Valley by late Monday night, 
according to a growing consensus of ensemble guidance. As it tracks 
east, it will occlude, slow down, and draw copious Gulf moisture 
poleward. As a result, precipitable water values are forecast above 
the 99th climatological percentile across much of the region, 
potentially setting records for early November. The strong forcing 
and abundant moisture will all but certainly result in widespread, 
beneficial rain for the region from very late Monday through at 
least early Thursday. In this timeframe, there is an areawide 20-30% 
chance for at least 1.00 inches of rain according to the NBM. The 
highest totals (perhaps as high as 3.00 inches locally) appear to be 
most likely across western Missouri where forcing and moisture 
overlap is maximized in ensemble guidance. 

Despite these favorable synoptic parameters, model soundings show 
very limited instability and only marginal warm cloud depths for 
more efficient rainfall. While I cannot rule out some instances of 
heavier rain where multiple rounds impact the same place, that 
should be the exception and not the rule in this event. As for a 
severe thunderstorm risk, while shear parameters are understandably 
more impressive with the strong wave, instability remains very 
limited and jet-level dynamics are very unfavorable for large-scale 
ascent. These factors greatly limit any strong convection, however 
if more instability can be made available to this impressive shear 
and forcing, we would have a much higher severe weather threat. That 
scenario is currently highly unlikely. 

Depending on the speed and structure of this trough, we may see 
intermittent rain linger through most of the week. By Friday, most 
depictions of the wave show it east of the region. Unfortunately for 
those looking for another decided taste of Fall, near to slightly-
above normal temperatures stick around in its wake. The airmass that 
follows our widespread rain, while cooler, is not really Arctic in 
nature by any stretch. The polar jet remains locked across southern 
Canada for the foreseeable future, keeping shots of cold air from 
making any intrusions south. By the end of the week, above-normal 
temperatures and drier conditions appear favored yet again going 
into mid-November.

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1152 AM CDT Fri Oct 30 2026

Predominantly dry and VFR flight conditions will persist through the 
TAF period. Isolated showers are expected in northeastern MO/west-
central IL through early afternoon and then sprinkles or light 
showers areawide on Saturday, but impacts are unlikely. Light, 
mainly easterly winds will continue.

&&

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

&&

$$

SHORT TERM...MRB
LONG TERM...MRB
AVIATION...Pfahler