Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

498
FXUS63 KLSX 051127
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
527 AM CST Thu Mar 5 2026

.KEY MESSAGES...

- Most showers and thunderstorms will exit by mid-morning, but
  isolated to scattered showers and thunderstorms will remain
  possible at times through Friday morning

- Showers and thunderstorms are forecast again Friday evening
  into Saturday morning with a passing cold front. Central and
  northeastern MO have the highest threat of severe thunderstorm
  relative to the rest of the CWA.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 316 AM CST Thu Mar 5 2026

A broad area of showers and embedded thunderstorms are ongoing early
this morning within low to mid-level isentropic ascent ahead of an
approaching upper-level trough and within a 30 to 40 kt LLJ
overrunning a wavering front. Some training of thunderstorms has
occurred across southeastern MO where heavier rain fell earlier on
Wednesday, resulting in isolated flash flooding where 2 to 4" is
estimated to have fallen overnight. Showers and thunderstorms will
gradually shift east of I-44 (MO) and I-55 (IL) through daybreak,
largely exiting the CWA by mid-morning as the shortwave trough axis
passes and shunts forcing and deeper moisture to the east.
Additionally, areas of dense fog have developed, but have become at
least temporarily confined to northeastern MO/west-central IL, mixed
out by showers and thunderstorms elsewhere. However, as
precipitation ends, we will have to watch for dense fog expanding
back southeastward through the morning.

Aside from a few isolated showers or thunderstorms in far
southeastern MO/southwestern IL this afternoon and evening near the
stalled front, largely dry conditions are expected after mid-morning
with mid-level height rises/subsidence becoming dominant. Fog will
also dissipate by mid-morning, but it is uncertain how much clouds
will break and scatter through the afternoon. With less
precipitation, high temperatures are forecast to at least be warmer
than previous days, but exact values will be dependent on cloud
cover. As such, high temperatures in the 60s F are forecast with
values closer to 70 F if/where clouds scatter.

Tonight into Friday morning, the front will lift northward as a weak
warm front accompanied by isolated to scattered showers and
thunderstorms, mainly after midnight along/north of I-70, as well as
perhaps some patchy drizzle and fog. Many CAMs and short-term models
also depict an MCV emanating from earlier Southern Plains
thunderstorms quickly lifting northward through western MO, which
could pose a conditional opportunity for greater coverage of showers
and thunderstorms in central and northeastern MO Friday morning
depending on its exact track.

After mid-morning, the daytime Friday should be mainly dry with a
capping inversion present and a lack of appreciable forcing. With
the CWA entrenched in a warm sector with 850-hPa temperatures around
the 99th climatological percentile and even some downslope warming
off the Ozark Plateau, the ingredients are all on the table for a
very warm (and breezy) day with high temperatures in the 70s to near
80 F. NBM probabilities of 80+ F high temperatures are 50 to 80
percent around the Missouri River, indicating the potential for
warmer temperatures if less cloud cover and deeper mixing occurs.


Pfahler

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 316 AM CST Thu Mar 5 2026

Friday evening, showers and thunderstorms are anticipated to
initiate across eastern KS/western MO along/ahead of a cold front in
an environment favorable for severe thunderstorms. Model guidance
still varies on the timing of the front with a slight convergence
toward an arrival in northeastern and central MO around 06z Friday
night and then the I-44 (MO) and I-55 (IL) corridors around 12z
Saturday. This late timing of the front suggest that a weakening
QLCS will likely move through the area ahead/along of the cold
front, although exactly how quickly thunderstorms weaken is not
quite certain. Global ensemble model probabilities of 500+ J/kg
SBCAPE are 50 to 70 percent through 06z, which has trended slightly
higher than previous runs, but these probabilities still fall below
10 percent by 12z. Therefore, the severe threat is higher in central
and northeastern MO relative to the rest of the CWA with damaging
winds and tornadoes being the main hazards. It is also worth noting
that a few CAMs do initiate scattered thunderstorms in the warm
sector and have them reaching central/northeastern MO around 00z,
which opens a potential earlier window of severe thunderstorms that
will need to be monitored.

Showers and thunderstorms will likely be ongoing Saturday morning,
eventually departing southeastern MO/southwestern IL by the
afternoon. Thereafter, dry conditions will prevail into Monday with
cooler, still above average temperatures on Saturday behind the
front, followed by a warming trend through Sunday and Monday as low-
level southwesterly flow and WAA prevails. The NBM interquartile
range is tightly clustered on high temperatures reaching the 70s to
around 80 F on Monday.

The next opportunity for showers and thunderstorms will be sometime
Monday night through Wednesday, but there is uncertainty regarding
the ejection of an upper-level cutoff low from the Desert Southwest
east/northeastward through the Mid or Lower Mississippi River
Valley. This uncertainty is mainly focused on the timing and track
of the cutoff low as it interacts with the northern stream, allowing
a cold front to also eventually advance southward. There are model
solutions of this evolution that would be supportive of severe
weather across Mid-Mississippi River Valley, which is captured by
machine-learning guidance. That being said, severe weather is not
being messaged due to the forecast uncertainty.

Pfahler

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 526 AM CST Thu Mar 5 2026

IFR flight conditions will persist through at least mid-morning
across the area as low stratus lingers along with areas of fog,
occasionally with visibilities to 1/4SM in central/northeastern MO
and west-central IL. Flight conditions will improve through late
morning and afternoon, but there is a large amount of uncertainty on
how much improvement will occur. Latest model guidance trends have
been more pessimistic, decreasing confidence in improvement to VFR
flight conditions today. Therefore, only MVFR flight conditions have
been included at this point with even the potential for a relapse
back to IFR flight conditions tonight. The highest chance of this
taking place is at KUIN. A warm front will lift northward tonight,
which may finally serve as the catalyst for improving flight
conditions. Additionally, isolated to scattered showers and
thunderstorms could accompany the front late tonight/Friday morning,
but confidence is not high that any of the terminals will be
directly impacted.

Pfahler

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Dense Fog Advisory until 6 AM CST early this morning for Audrain
     MO-Boone MO-Knox MO-Lewis MO-Marion MO-Monroe MO-Pike MO-
     Ralls MO-Shelby MO.

IL...Dense Fog Advisory until 6 AM CST early this morning for Adams
     IL-Brown IL-Greene IL-Macoupin IL-Pike IL.

&&

$$

WFO LSX