Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

243
FXUS63 KLSX 071831
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
131 PM CDT Tue Apr 7 2026

.KEY MESSAGES...

-Warm temperatures and low humidity values result in elevated fire
conditions Wednesday across portions of the area.

-Temperatures will warm above normal starting Wednesday, lasting
through the end of the period.

-Widespread chances for showers and thunderstorms return to the
 region Friday and continue into early next week.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 131 PM CDT Tue Apr 7 2026

This morning`s mix of snow, sleet, and rain has dissipated over
northeast Missouri and west-central Illinois, though cloud cover has
lingered along and north of I-70. This has resulted in a wide range
of temperatures across our forecast area with temperatures north of
I-70 at 1PM in the 40s and areas south of I-70 in the 50s. Before
the mid-level moisture lifts to the northeast overnight, a subtle
mid-level disturbance will push through the region and produce a
brief period of sprinkles across portions of far northeast Missouri
and west-central Illinois. Deep southwesterly flow will begin to
establish overnight, helping to eject moisture from the region and
kick start warm air advection across the area.

At the same time a surface low will slide across the upper
Mississippi Valley, in step with a mid-level low. This system will
drag a cold front into the upper/mid-Mississippi Valley Wednesday.
Deep mixing ahead of the front during the day will allow the surface
access to the 8-10C 850 mb temperatures. This, combined with
increased sunshine and some Ozark downsloping influence will push
surface temperatures into the low to mid 70s areawide. Deep mixing
near a decaying low-level jet and a tight surface pressure gradient
will result in a breezy day with the highest speeds across northeast
Missouri and west-central Illinois, closest to the decaying low-
level jet. These strong winds will overlap low RH values less than
35% during the afternoon tomorrow to produce elevated fire danger
mainly across southeast, central, and east-central Missouri, as well
as portions of west-central Illinois. Confidence is lowest in
reaching elevated fire danger criteria in the hollows of southeast
Missouri where winds are generally lower.

By Wednesday evening the surface low will be lifting northeast out
of the Great Lakes region, reorienting the cold front with a more
west to east component and stalling its southern progression. The
result is that at most the cold front is expected to skim the far
northern portions of the forecast area. Moisture convergence along
the portion of the front closest to our area is rather weak, but I
cannot rule out a brief shower or thunderstorm across portions of
northeast Missouri and west-central Illinois as the cold front
brushes the northern forecast area.

Delia

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 131 PM CDT Tue Apr 7 2026

The mid-level shortwave low will continue to push northeastward
Thursday, with another, weaker shortwave progressing through the
northern stream flow just behind it. This disturbance will pass
across the upper Mississippi Valley overnight Thursday into Friday,
renewing lift and moisture convergence along the cold front
stretched just north of the forecast area. The cold front will begin
to make southward progress into the forecast area Friday, aided by
mid-level height falls. How far south it extends remains uncertain
but most guidance is showing it stalling generally around the I-70
corridor. Showers and a few thunderstorms are expected along and
behind the front during the morning, as far south as I-70 where
there is a 50-80% chance of exceeding 0.25" of rain. Rising mid-
level heights during the afternoon will limit persistent
precipitation and halt the southward progress of the front much
beyond the I-70 corridor. Temperatures on Friday will vary depending
on the final resting place of the front with areas north of the
front remaining in the 60s (near normal for this time of year!) and
areas south of the front pushing into the upper 70s. Both KUIN and
KSTL have high temperature interquartile spreads around 7-8 degrees,
while KFAM, which is well south of where the front is expected to
be, has a spread of 4 degrees. This further highlights the
uncertainty in the local of the front, specifically along and north
of I-70.

Through the remainder of the day Friday and into the weekend mid-
level heights will continue to rise as a mid-level ridge builds in
across the southern US. Southwesterly flow in the lower-levels
through the weekend will promote additional warming, resulting in
high temperatures increasing over the weekend to around 80 by
Sunday. By Monday the ridge will be shifting eastward as a mid-level
trough comes onshore over the West Coast and broadens through the
first half of next week. The broadening and eastern progress of the
trough into the western CONUS will bring southwesterly flow and
embedded shortwaves across the mid-Mississippi River Valley. The
result will be increasing temperatures well above normal and a more
active pattern with chances for showers and thunderstorms during the
beginning of next week.

Despite machine learning guidance highlighting the central US for an
increased risk for severe weather during this period, uncertainty
remains in how favorable the broader environment will be. Joint
probabilities for surface based instability greater than 500 J/kg
and bulk wind shear greater than 30 kts is still around 50% across
the forecast area Monday afternoon/evening, which is largely
unchanged from the last 12 hours. The joint probabilities for the
same parameters are even lower on Tuesday. The timing of finer
synoptic and mesoscale level features Monday and Tuesday remain
uncertain and we will need to keep an eye on severe chances moving
forward.

Delia

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1202 PM CDT Tue Apr 7 2026

The rain/snow from this morning across northeast Missouri and
west-central Illinois has dried up, leaving mid to upper level
cloud cover with a scattered MVFR/fuel alternate deck underneath.
Through the day this MVFR deck is expected to lift and scatter
even further, and confidence is high that conditions will remain
VFR at KUIN.

Elsewhere the cloud deck is scattered and is expected to stay
this way through the end of the TAF period. Winds Easterly winds
will become southerly by tomorrow morning, with increasing gusts
during the morning. Winds will gust into the 20s across the
terminals, with KUIN seeing the strongest winds. These winds will
diminish with sunset tomorrow evening.

Delia

&&

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

$$

WFO LSX