Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

992
FXUS63 KLSX 060607
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1207 AM CST Fri Mar 6 2026

.KEY MESSAGES...

- Severe weather is possible Friday night into very early Saturday morning.
  Damaging winds and a tornado or two will be the primary threats
  if anything does become severe.

- A dry and warm weekend is in store. The chance of showers and thunderstorms
  increases again early next week.


&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 155 PM CST Thu Mar 5 2026

A quasi-stationary front continues to wobble around the Mid-
Mississippi Valley, bringing with it ample stratus, fog, and on-and-
off showers and thunderstorms. As of 17z, the boundary extends from
about Fort Leonard Wood, MO northeastward to Vandalia, IL and
beyond. The bulk of showers have remained within the warm sector to
the south of this line, creating a relatively dry day today.
Tonight, however, the front is expected to buckle northward as
cyclogenesis ramps up near the Front Range of the Rockies. This will
open the CWA up to warm sector convection yet again. A strong 40-50
kt low-level jet developing in the evening will promote the
development of scattered showers and thunderstorms overnight. These
thunderstorms will be elevated and unlikely to produce anything more
than small hail and beneficial rainfall for our northern CWA who
missed out on the previous rain this week.

The real focus of the late week is the potential for severe weather
Friday evening through night. The daytime hours on Friday are
expected to be quite spring-like as the full CWA is encapsulated by
the warm sector. Temperatures are expected to rise into the 75 - 80
degree range despite broken cloud cover. Dewpoints will rocket as
well, with the HREF probabilities of 60+ degrees being 50-100% for
the vast majority of the CWA. If KSTL is able to achieve a 61 degree
dewpoint, which it is currently forecast to do, this will be a new
record high dewpoint for March 6th. Needless to say, with this
amount of warmth and moisture instability will be easy to come by.
However, a lack of forcing and lift will render this instability
useless during the afternoon.

To our west, this instability will be utilized during the late
afternoon and evening as thunderstorms fire up along and ahead of a
cold front. Bulk shear fairly perpendicular to the cold front will
result in supercells with all hazards possible before thunderstorms
congeal into a QLCS. Latest high-res guidance is converging on the
QLCS being nearly if not fully formed by the time it reaches central
and northeast Missouri at around 07-08z. If this holds true,
damaging winds and a brief tornado will be the primary hazards
initially before the QLCS weakens below severe limits for good.

How quickly this occurs is still uncertain. HREF, GFS, and RAP
guidance both show SBCAPE/MUCAPE maximums of ~1000 to ~1500 J/kg
occurring around 21z and dropping off after. By the time the QLCS
makes it into the CWA, these values are expected to drop
substantially to maybe 500 J/kg of SBCAPE and under 1000 J/kg of
MUCAPE. The highest values are also expected to be along the line
and not ahead of it, so the ongoing convection will be continually
entering a less favorable environment. This is amplified given the
potential for pre-frontal convection moving into southeastern
Missouri from the southwest at around 05z. These thunderstorms are
expected to be elevated and likely non-severe given the time of day
and that they`ll also be moving into a less favorable environment.
Being that these thunderstorms will be ahead of the QLCS, it`s
entirely possible that they scour out the environment of any
remaining instability and cause the QLCS to degrade at a faster
rate. It`s also possible that the two complexes merge and weaken
each other, and it`s possible again that the pre-frontal complex
feeds on the remaining instability and ends up being favored for
severe weather. All of this to say, although confidence is
increasing on timing, there is still plenty of variability
concerning how the situation evolves Friday night. Given the trends
we`ve been watching over the past several days, we`re leaning toward
the faster decay scenario.

Jaja

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 155 PM CST Thu Mar 5 2026

The cold front will be slow moving, not clearing the area completely
until late Saturday morning/early Saturday afternoon. Despite being
a cold front, most areas won`t notice any appreciable cooldown.
Temperatures Saturday through early next week will only increase,
with highs near if not achieving 80 degrees by Monday. This warmth
will be paired with dry and breezy weather each day, making this a
wonderful weekend for outdoor activities. The peace won`t last,
however. The chance of showers and possibly severe thunderstorms re-
enters the forecast Tuesday into Wednesday as a cutoff low over the
southwest CONUS ejects vorticity lobes into the Mid-Mississippi
Valley. However, there is still ample uncertainty regarding the
evolution and timing of the feature to extrapolate much further than
that.

Jaja

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1144 PM CST Thu Mar 5 2026

MVFR (possible IFR) ceilings and visibilites are expected at UIN
and CPS through 14Z. These conditions may move into STL and SUS
through 12Z, but confidence is too low to include in the TAF at
this time. Showers and thunderstorms seen over north central
Missouri is moving northeast and may affect UIN between 07-09Z
reducing ceilings and visibilities to IFR. There will be a chance
(20-30%) of showers and thunderstorms through the day at
UIN/COU/JEF, but have not included it in the TAF at this point as
I do not have enough confidence in timing. There is more
confidence that showers and thunderstorms will occur at COU/JEF
after 00Z and at UIN and the St. Louis area terminals after 06Z.


Britt

&&

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

$$

WFO LSX