Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

732
FXUS63 KLSX 080359
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
959 PM CST Sat Mar 7 2026

.KEY MESSAGES...

- Dry weather with warming temperatures is expected through Monday.

- Another round of widespread showers and thunderstorms is
  expected late Tuesday - Wednesday.


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 211 PM CST Sat Mar 7 2026

The synoptic cold front is finally nearing far southeast
Missouri/south central Illinois and will push east of the area
early this evening. West/northwest winds will slacken off this
evening as a surface ridge of high pressure moves into southern
sections of the area overnight. We will have to keep a close eye
on cloud trends as current indications are that at least some
clearing will overspread the entire area from west to east. The
concern is that areas that see this clearing along with
light/variable winds will be susceptible to fog development. The
area of most concern is in east central and southeast Missouri
where winds should be lightest. In addition, most of this same
area has seen quite a bit of rain over the past 24 hours so there
will be an extra source of surface-level moisture. All that being
said, model guidance is not hitting widespread fog much at all.
Not sure if this is because there could be just enough midlevel
clouds to prevent cooling overnight or because winds may stay up
just enough. For now, did add some fog in sheltered valley areas
where winds tend to decouple easier.

A warming trend will begin on Sunday as low-level winds turn out of
the southwest behind the aforementioned surface ridge. Highs in the
mid to upper 60s are forecast for much of the area, or about 10-15
degrees above normal for the date.


Gosselin

&&

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 211 PM CST Sat Mar 7 2026

(Sunday Night - Monday Night)

The warming trend will continue into early next week as mid/upper
level heights rise and 850-hPa temperatures climb closer to +15C
(~99th percentile of climatology). Highs well into the 70s are
forecast Monday afternoon, with some locations potentially topping
out near the 80 degree mark. Surface winds also look to veer a bit
more to the southwest, which is favorable for downslope warming off
of the Ozark Plateau across parts of central, east central, and
southeast Missouri. Daily record highs may be threatened at KCOU and
KSTL. For more information on records early next week, please see the
CLIMATE section below.


(Tuesday - Wednesday)

Another unseasonably warm day is expected on Tuesday, with
potentially record-breaking temperatures once again. While the air
mass is similar on Tuesday compared to Monday, we may have more
cloud cover to deal with as model RH plots show increasing humidity
at mid/upper levels of the troposphere. However, even partial breaks
may be enough to see low 80s given the very warm start to the day
(lows near 60 degrees).

Attention will then turn to possible convective initiation within
the open warm sector Tuesday afternoon/evening. Deterministic
guidance shows a subtle midlevel shortwave trough moving out of the
south-central Plains, which may be enough for scattered thunderstorm
development at least by late afternoon. Given the warm, moist air
mass in place, there should be plenty of instability. Probabilities
for at least 1000 J/kg of SBCAPE from the GEFS/GEPS are over 70%
areawide, and peak closer to 50% for 1500+ J/kg. Deep-layer shear
also looks moderately high, with chances for 35+ of deep-layer shear
of 70-80%. If indeed convection develops, a mixed mode of supercells
and multicellular clusters would be capable of large hail and
damaging winds.

Similar to last night, the synoptic cold front really doesn`t make
it through much of the area until the overnight hours into Wednesday
morning. Instability should wane overnight, and may be mostly turned
over if there is any antecedent convection. Both low and deep layer
shear increase however, so if there is sufficiently instability, a
severe weather threat may persist.

What is more certain is for widespread rain Tuesday night into at
least Wednesday morning. The rain should linger longest across parts
of southeast Missouri/southwest Illinois as the rain may not shut of
until the passage of a southern stream midlevel shortwave trough.
Probabilities on the LREF for at least 1" of rain by Wednesday
afternoon are in the 30-70% range, with the best chances right now
across parts of northeast Missouri and west-central Illinois. The
threat for heavy rainfall may also need to be monitored if multiple
rounds of showers and thunderstorms impact the same regions or there
is training. The atmosphere looks to be very moist, with
precipitable water values running >1.25" or above the 99th
percentile of climatology.


(Wednesday Night - Next Saturday)

Behind the cold front, a brief period of much colder temperatures
look sin store Wednesday night through Thursday. Near to below
normal readings are expected during this time period.

Forecast uncertainty increases late this week into next weekend. The
mean flow on both the GEFS/EPS transitions to more zonal flow across
the mid-Mississippi Valley, with anomalous troughing across the
Upper Midwest. This should entail a warmup ahead of an approaching
cold front, but when this occurs and how much does it cool off
behind that front are highly uncertain at this time.


Gosselin

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 958 PM CST Sat Mar 7 2026

An MVFR stratus field continues to slowly push eastward this evening
and has cleared the central Missouri terminals and KUIN within the
last hour. This deck has been obscured on satellite imagery by an
overcast mid-level cloud field, which has made it tough to
accurately time the exit of the MVFR stratus for the STL metro
terminals. Regardless, based on upstream observations, an exit of
06z for the MVFR stratus and the mid-level clouds still appears to
be a good estimate. With clearing expected around 06z, the formation
of fog becomes a concern, particularly for the river valley
locations along and south of the I-70 corridor, where calmer surface
winds will be in place. As a result, a TEMPO group has been added at
KSUS, KJEF, and KCPS for MVFR visibilities later tonight between 10-
14z. Winds remain light overnight with southwesterly winds picking
up after sunrise gusting to 20kts across northern and central
Missouri before fading off and becoming more southerly Sunday
night.

Peine/Elmore

&&

.CLIMATE...
Issued at 211 PM CST Sat Mar 7 2026

Daily record high temperatures may be threatened both on Monday 3/9
and Tuesday 3/10. Below are the records for each day from our
official climate sites:

            Monday 3/9          Tuesday 3/10
KSTL        80F (1925)          86F (1955)
KCOU        80F (1986)          82F (1955)
KUIN        75F (1986)          79F (1955)


Gosselin


&&

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

$$

WFO LSX