Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

113
FXUS63 KLSX 031958
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
258 PM CDT Fri Apr 3 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms will become more numerous
  late this evening and tonight. A few may be severe. All hazards
  are possible this afternoon into early evening, transitioning
  primarily to damaging winds and an isolated tornado late this
  evening.

- Cooler temperatures (5-15 degrees below average) are forecast
  late Saturday lasting into Tuesday with a 30-50% for a freeze
  Monday night north of the I-70 corridor.

&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 223 PM CDT Fri Apr 3 2026

A closed upper low and longwave trough will progress almost due east
across South Dakota this afternoon. Upper diffluence ahead of the
longwave trough is expected to draw a surface low east-northeast out
of eastern Kansas/Nebraska into southern Iowa through late tonight.
In the process, a warm front that extended east along I-70 this
morning, has lifted into northern Missouri/west-central Illinois.

The warm front has shifted north of I-70 fairly quickly this morning
with slower progress this afternoon. Along as south of the front,
boundary layer moisture has deepened within strong south-
southwesterly flow. While CAMs have become excited about development
in the warm sector, forcing is largely focused along the warm front
to the north and the cold front to the west with limited support
south of the front. Therefore, initial concern will be development
along over far northeast Missouri and west-central Illinois, where
RAP guidance builds MUCAPE to 2500-3000 J/kg, winds are backed at
the surface with 0-6km shear of 40-45kts, and increasing SRH values
of 100-250 m2/s2. The caveat - Higher SRH is focused along and north
of the MO/IA border with marginal mid-level lapse rates of 6.5-7C.
RAP soundings has also narrow CAPE profiles through the hail growth
zone over the last few hours. Should an updraft become sustained, it
will be capable of producing marginally severe hail (1") and a brief
tornado, mainly over the northern two rows of counties of the CWA
(NE MO/WC IL) as early as 20Z through 22z. Further into the warm
sector, the lack of forcing, unidirectional flow, and recent height
rises limit potential, but an isolated thunderstorm cannot be
entirely ruled out. Hail is favored hazard within the warm sector
this afternoon, but chances are quite limited.

The main impacts will arrive this evening and overnight with the
approach a cold front from the central Plains. This remains the main
focus, but not without caveats here, too. As the surface low lifts
into Iowa, upper ascent and lift from the surface low remains rather
far departed from the region. Additionally, a pre-frontal trough
attempts to ignite scattered convection ahead of the boundary as
the primary severe threat remains well to the west. Strong to severe
thunderstorm development is largely concentrated over the east
Plains into western Missouri, then into central Missouri well after
peak diurnal heating. Timing with this front has been pretty
consistent, reaching western parts of the CWA around 04-05Z. One
question is how much development occurs with the pre-frontal trough,
helping to stabilize some areas ahead of the front. This doesn`t
bode well for a nocturnal front that is well departed from its
parent low. Additionally, instability and mid-lapse rates quickly
weaken with the eastern progression of what looks to be a broken
line of convection remnant from severe thunderstorms initiating in
Kansas. Considering the timing and various caveats, confidence in the
severe threat quickly drops off from west to east, as updrafts begin
to compete, and cooler air undercuts ongoing convection.

In the grand scheme, while severe potential is there, it`s largely
conditional on pre-frontal development and limited by nocturnal
timing. Thunderstorms may very well become more progressively cold
pool dominant as the cold front lags west of a majority of the
activity. Though severe gusts and a brief tornado cannot be ruled
out, threats will likely become limited with eastward movement
overnight.

Showers linger along the southeastern 1/3rd of the CWA Saturday
morning, but should clear the area by late morning/early afternoon.
Much of the day will be much cooler and drier with gradual clearing
through Saturday afternoon. Highs will range from the 50s northwest
of Washington/St. Louis, MO and Litchfield, IL, to the low to mid-
60s to the southeast.

Maples

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 256 PM CDT Fri Apr 3 2026

For the first half of the extended, the large scale pattern will be
mid/upper-level ridging across the Intermountain West with a
persistent longwave trough centered near the Great Lakes Region,
placing our region under deep northwesterly flow for the first time
in a while. Our early weekend system will be departing to the
northeast around the base of the trough leaving us in post-frontal
flow with a surface high dropping southeast across the Plains that
will help to reinforce the cooler conditions. The result for us will
be temperatures generally 5-15 degrees below average this weekend
into early Wednesday.

On Monday, an anomalously strong (99th percentile) surface high
slides southeast out of Canada into the Northern Plains. Out ahead
of the approaching high, a low/mid-level cold front will drop
southward into the area, bringing with it a shot of reinforcing cold
air. With remnant weak bands of low/mid-level frontogenesis possibly
lingering across northern Missouri, chances for precipitation creep
in late Monday into Tuesday. Current LREF probabilities for QPF
>0.01" max out around 30-40% across central/northern MO, where the
better mid-level forcing is expected to be. The anomalously strong
surface high is forecasted to be just north of the region Monday
night, reinforcing much colder air as LREF mean 850mb temperatures
will be near 20th percentiles across northern MO/west-central IL.
Long-range deterministic guidance reveals that mid/level saturation
may be collocated with the strongest forcing, with the most likely
limiting factor for precipitation reaching the ground being a lack
of low-level moisture and a dry near surface layer. Forecast model
soundings indicate a sub-freezing atmospheric profile across
northern MO/west-central IL late Monday into early Tuesday,
suggesting that there is some potential for some light snow. A
freeze is possible for some of the area Tuesday morning, but is
highly dependent on sky cover and surface winds overnight, where
calm and clearer conditions would allow for efficient radiational
cooling, increasing the potential for a freeze. Regardless, as it
stands now, the best chance for a freeze is north of I-70, with the
best chance across northern MO/west-central IL, where probabilities
are up to 50% for lows <32F Monday night.

As the surface high departs eastward by Wednesday, low/mid-level
flow turns southerly allowing temperatures to rebound quickly on
Wednesday with highs 10-20 degrees warmer than Tuesday areawide.
LREF temperature consensus is fairly good mid to late next week with
IQR`s remaining around 6-10F centered near highs and lows that are
about 10 degrees above climatology. A mid-level shortwave trough
moves east along the US-Canadian border Thursday into Friday with
its surface reflection dropping a cold front near the area sometime
Thursday. With a potential boundary within close proximity to the
area once again, precipitation chances increase Thursday into next
weekend and is represented well by LREF probabilities for QPF >0.01"
slowly increasing to 40-50% by next Friday.

Peine/Maples

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1246 PM CDT Fri Apr 3 2026

Low pressure will lift northeast out of the eastern Plains into
the Upper Midwest this afternoon into tonight. A warm front is
lifting through northern Missouri, where a few thunderstorms are
possible, including KUIN (PROB30) through around sunset. Central
Missouri and metro terminals are into the warm sector, where winds
have shifted out of the south. Within the warm sector, an isolated
to widely scattered thunderstorm is possible. This potential was
not included at the metro terminals with better support remaining
to the west.

The greatest impacts will hold off until late this evening as the
cold front approaches central Missouri, then progresses east
through the metro terminals. Numerous to widespread showers and
thunderstorms are expected along the front with the potential for
a few strong to sever thunderstorms containing hail, gusty winds,
and a brief tornado. This potential is greatest over central
Missouri with waning intensity as thunderstorms move east. VFR
conditions sink to MVFR/IFR along and just behind the cold front
tonight. LIFR is likely to accompany the strongest thunderstorms
with heavy rain, low cigs, and restricted vsbys. Behind the front,
showers trail off with improving conditions through Saturday
morning. VFR is expect through much of Saturday.

Maples

&&

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

$$

WFO LSX