Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

806
FXUS63 KLSX 091728
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
1228 PM CDT Thu Jul 9 2026

.KEY MESSAGES...

- Severe thunderstorms capable of producing damaging winds, large
  hail and a few brief tornadoes are possible this afternoon and
  evening. Locally heavy rainfall is also possible with these
  storms through tonight.

- Another round of severe thunderstorms is possible on Friday
  afternoon and evening, and locally heavy rainfall will also be
  possible with these storms.

- Generally dry weather is expected Sunday into next week with
  warmer than average temperatures.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 1226 PM CDT Thu Jul 9 2026

Severe thunderstorms and locally heavy rain remain the primary
forecast concerns today and Friday. An MCS over northeast Kansas
looks like it`s spinning up an MCV at this time. Short range
guidance moves this MCV east through the day at varying speeds.
The RAP may be the slowest, only pushing the vortmax as far as the
Mississippi River by 00Z. Various CAMs, the GFS and short range
ensembles such as the HREF and REFS move the wave more quickly
eastward, crossing the Mississippi river into Illinois around 18Z
today. The timing and track of the MCV will be part of what
determines convective trends this afternoon. The faster solution
would limit afternoon convection mainly to areas along and east of
I- 44 in Missouri and along and south of I-70 in Illinois.
However the slower solution puts the entire area under threat of
thunderstorms this afternoon. Since the model consensus is faster,
am leaning in that direction with highest PoPs over east central
and southeast Missouri into southern Illinois. Kept low chance
PoPs over most of the remainder of the area keeping the slower RAP
in mind. Models are showing 3000+ J/Kg CAPE with 30-35kts of deep
layer shear which is good enough for storms to become organized
into severe multicell clusters or even a severe MCS. Primary
threat remains damaging winds in excess of 50kts. Boundary
interactions along with a bit of extra directional shear
associated with the MCV may be enough for a brief tornado as well.
Additionally, there`s enough CAPE in the hail-growth zone to
support hail up to around 1 inch in diameter.

The severe threat should diminish with weakening instability during
the evening. The low level jet increases to 30-40kts tonight which
will produce moderate to strong moisture convergence along any low
level boundary laid down by earlier convection.  This should result
in more thunderstorms tonight, though precisely where the storms
will develop will depend on where the low level boundary settles.
Some guidance keeps it farther north closer to the I-70 corridor,
while others are more across the Ozarks.  Regardless, the low level
jet veers overnight which should make the storms progressive along
the boundary, but there will probably be more than one wave of
thunderstorms that track along it.  There is therefore a locally
heavy rain threat, though widespread flooding doesn`t look likely at
this time as flash flood guidance is pretty universally well in
excess of 2"/hr.  Convective trends for Friday and Friday night are
very dependent upon where the effective boundary ends up Friday
morning, and on another convectively enhanced wave moving across
Missouri into Illinois.  There`s a question of how unstable the
atmosphere will get Friday afternoon into Friday evening depending
on where the effective surface boundary is.  However, severe wind
gusts and hail will be possible again.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 1226 PM CDT Thu Jul 9 2026

Models vary in how strong the aforementioned convectively enhanced
short wave is as it moves from Missouri into Illinois late Friday
night into Saturday morning.  Some solutions show a strong wave
which develops a closed low at the surface that drives a composite
weak cold front and lingering convective boundary through Missouri
Saturday morning. This would dry out the low levels and likely end
the chance for thunderstorms.  Others are weaker and allow the
boundary to linger over the area through Saturday which would keep a
chance for precip going longer.  There`s no particular reason to
favor either solution at this point as it will depend on convective
trends upstream over the Great Plains.

Guidance continues to show a strong upper level ridge developing over
the western U.S. late Saturday into Sunday which spreads east across
the Plains and Midwest by early next week.  Models continue to show
some differences in the speed with which it builds east, and the
ultimate strength of the ridge. However, the consensus continues to
put the thermal ridge north of our area across the Upper Midwest.
The NBM temperature forecast therefore looks pretty good with
dry and warm, but not excessively warm weather next week.

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1226 PM CDT Thu Jul 9 2026

Thunderstorms are likely to develop by mid-late afternoon, mainly
in southeast Missouri and south-central Illinois. Additional
storms are forecast this evening into the early overnight hours
from central to southeast Missouri. That leaves the central
Missouri and the metro St. Louis terminals on the northern edge,
so maintained PROB30 groups. Any storm that does manage to
directly impact a terminal could produce some gusty winds and
lower visibility below 3SM in a downpour.

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch from 4 PM CDT this afternoon through Saturday
     morning for MOZ072>075-084-085-099.
IL...Flood Watch from 4 PM CDT this afternoon through Saturday
     morning for ILZ079.

&&

$$

SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Gosselin