Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

283
FXUS63 KLSX 021138
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
638 AM CDT Thu Apr 2 2026

.KEY MESSAGES...

- There is the potential for severe weather today and tomorrow.
Today, all hazards are possible with the severe threat focused in
northeast Missouri and west-central Illinois. Tomorrow, damaging
winds and brief tornadoes are possible in central Missouri
northeastward through west-central Illinois.

- A cold front on Saturday will usher in cooler and drier weather to
kick off next week.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 346 AM CDT Thu Apr 2 2026

As of 06z, a lingering quasi-stationary front extends from somewhere
between Columbia and Vichy, MO eastward through Mount Vernon, IL.
Continuous convection has kept the boundary much further south than
anticipated, as seen in our very cool high temperatures yesterday
afternoon. However, a surface cyclone currently swirling over
western Kansas is expected to quickly pull the front northward and
out of our CWA as it nears the region this morning. This will set
the forecast back on track and will open the Mid-Mississippi Valley
to very strong warm air and moisture advection transported by
sustained winds in excess of 20-25 mph and gusts of 45 mph+.
Confidence in these values has increased enough to support a Wind
Advisory for much of the area this afternoon.

Low, thick stratus will lift along with the now warm front, and
morning convection is expected to diminish as the low-level jet
weakens. Confidence is very high that the most clearing will occur
west of the Mississippi River and in west-central Illinois, and this
is where instability will be maximized during the afternoon. Latest
model soundings also remove the cap in the warm sector, opening up
the potential for buoyant CI as opposed to just CI initiated off the
cold front. HREF probabilities of >1000 J/kg of SBCAPE are 90-100%,
specifically from central Missouri through south-central Illinois.
Most of this is not collocated with the best bulk shear or SRH
spatially or temporally, which are modeled to be highest in Illinois
in the late afternoon and into the evening. Putting all of this
together, we do have an afternoon threat of severe thunderstorms,
but the exact strength of them depends on how much destabilization
we see by then. Bulk shear vectors will initially be mostly parallel
to the front, suggesting congealing thunderstorms during the
afternoon. Vectors become orthogonal during the late afternoon as
the cold front associated with a second surface low enters the
middle of Missouri, supporting a brief period of supercells and
providing our best severe threat in northeast Missouri and west-
central Illinois. The front then tilts zonally, forcibly making the
shear vectors parallel and causing ongoing convection to merge into
a loose line. During the first two phases, all hazards will be
possible, and straight hodographs suggest we`ll see splits. As
discrete convection exits Missouri and enters south-central
Illinois, it will be entering a lower CAPE  - higher shear and SRH
environment characterized by a 90-100% probability of both >30 kts
of bulk shear and >300 m2/s2 of 0-3 SRH. This will serve as a local
maximum for tornado potential before the front tilts and decreasing
instability kills off the leftovers.

There is another potential for severe weather Friday afternoon. The
cold front that is expected to initiate convection today will tilt
tonight and lift northward as a warm front during the day on Friday.
Meanwhile, another cold front will approach Missouri from the
central Plains. This leaves us in the warm sector yet again.
However, latest model soundings still show a pronounced cap above
the PBL, which should serve as a deterrent to CI for most of the
region during the afternoon. The exception to this is along the warm
front. Here, we may see thunderstorms with a localized, brief
tornado threat if discrete cells cross the warm front and surface
winds become backed. This is most likely to occur along or north
of our northern CWA border. The real severe threat will arrive
with the cold front. This system will be stronger than today`s and
the severe threat will be more robust and less uncertain. The
biggest uncertainty regarding the severe threat on Friday is
timing. CAMs are seeming to come into alignment regarding that,
with about half showing an arrival time of about 02z. If this
pushes later, our severe threat will lessen. If it trends earlier,
our severe threat will strengthen. Bulk shear vectors are
forecast to be much more supportive of a QLCS moving into central
Missouri, with 0-3 shear vectors of 20 - 30kts pointed northeast
according to the RAP. These aren`t prime conditions for a
weakening south-southwest to north- northeast QLCS to produce
mesovortices, but weak tornadoes are possible nonetheless.
Damaging winds are a more substantial threat. With the QLCS
weakening with time, confidence in severe weather is highest from
central Missouri northeastward into west-central Illinois. How
quickly thunderstorms weaken is still uncertain due in part to
timing as well as the speed at which a supportive environment
diminishes. If it weakens more slowly than anticipated, the severe
weather potential will exist farther to the east.


Jaja

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 346 AM CDT Thu Apr 2 2026

Anafrontal showers and perhaps weak thunderstorms will develop
behind the cold front and will linger into the day Saturday. More
notably, our warm weather will be scoured out and replaced by a
cooler, drier airmass that is expected to linger through at least
early next week.

Jaja

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 632 AM CDT Thu Apr 2 2026

A warm front is currently pushing northward this morning, and IFR
stratus is moving with it. By this afternoon, most if not all of
the CWA will be VFR, and conditions will have dried out to some
extent. This morning`s stratiform rain will be replaced by
scattered, discrete thunderstorms this afternoon some of which
may become severe. Exact timing and impacts to terminals are
uncertain, but the TAFs have been updated to reflect the current
best estimate. Spotty showers and thunderstorms are expected to
continue tonight along another east-west oriented front.

A Wind Advisory is in effect from noon until 7pm. South winds are
expected to become very elevated, with sustained winds of 25+ mph
gusting up to 45 mph. Winds will diminish quickly after sunset.

Jaja

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Wind Advisory from noon today to 7 PM CDT this evening for
     Audrain MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Marion
     MO-Monroe MO-Pike MO-Ralls MO-Saint Charles MO-Saint Louis
     City MO-Saint Louis MO-Sainte Genevieve MO-Shelby MO.

     Flood Watch until 1 PM CDT this afternoon for Audrain MO-Boone
     MO-Callaway MO-Cole MO-Gasconade MO-Knox MO-Lewis MO-Marion
     MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Ralls MO-
     Shelby MO.

IL...Wind Advisory from noon today to 7 PM CDT this evening for Adams
     IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene
     IL-Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
     Montgomery IL-Pike IL-Randolph IL-Saint Clair IL-Washington
     IL.

&&

$$

WFO LSX