Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

342
FXUS63 KLSX 251143
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
543 AM CST Wed Feb 25 2026

.KEY MESSAGES...

- Widespread very light rain is likely (50-70%) tonight. In northeast
  Missouri and west-central Illinois, there is a chance (20- 40%)
  for a brief wintry mix. No significant impacts are expected.

- Warm weather will continue through at least Friday. A cold front will
  usher in much cooler weather and the potential for wintry
  precipitation to start the new month.


&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 336 AM CST Wed Feb 25 2026

As of 08z, a cold front is pushing through the southeastern CWA, and
rain associated with it has mostly exited. We`re only glanced by the
cooler airmass behind it, and as such the temperature forecast for
today won`t change much from yesterday. This morning`s lows will
land in the widespread 30s, with highs ranging from the 40s north of
I-70 (closer to the cooler air) and the 50s south of I-70.
Thursday`s highs and lows will be similar to today`s, but the high
temperature gradient will range from 50-60 from northeast to
southwest as the airmass pushes eastward.

The real focus is the potential for light precipitation tonight into
early Thursday morning. A mid-level shortwave will quickly pass
through the Mid-Mississippi Valley tonight and will interact with
our low moisture content to produce a quick hitting, light
precipitation event. For most, temperatures will remain above
freezing overnight and rain will be the p-type. Along our northern
border extending from Knox Co, MO southeastward to Fayette Co, IL,
however, the forecast becomes more varied. These locations have a
higher chance at falling below freezing tonight and thus
experiencing light snow. If any snow does fall, it will be light.
HREF probabilities of 24 hour QPF > 0.01" are about 80%, but the
probabilities of 0.05" drop to 10-20% at any given location. With
snow ratios under 10:1 from marginal air temperatures and warm
ground temperatures both before and after tonight, this light, wet
snow will not last long if it does fall. A possible exception to
this is if banded snowfall currently forecast just north of our
CWA boundary scoots south enough to impact us. Within the band,
higher rates, dynamic cooling, and higher SLRs will make it easier
for snow to accumulate. Even in this worst case scenario, the
aforementioned corridor would likely peak around 0.5" of snow
given probabilities in the band only peaking at a 60% chance of
this occurring. Even if this did occur, it would melt quickly and
produce no impacts beyond isolated slick spots.

The DGZ will desaturate behind the snow, resulting in the chance of
drizzle. Despite sub-freezing temperatures existing in the northern
CWA, freezing drizzle is not a concern. The window for the cold will
be short, likely not enough time for roads to drop to freezing given
the antecedent warmth.

Jaja

&&

.LONG TERM...  (Thursday Night through Tuesday)
Issued at 336 AM CST Wed Feb 25 2026

Warm air advection will ramp up ahead of our next cold front,
rocketing temperatures into the 60s and low 70s Friday afternoon.
The current IQR for KSTL is a tight 3 degrees with a forecast of 69.
However, the NBM usually underperforms in these regimes. Given that
we`ll have clear skies and potentially elevated due southwest winds
that afternoon, it`s reasonable to assume efficient mixing and
downsloping will place us closer to the 75th - 90th percentile for
highs, or 70-72 degrees. The temperature forecast for Saturday is
much more uncertain due to uncertainty in the timing of the
aforementioned cold front, with the IQR jumping from the 3 degrees
on Friday to 14 degrees Saturday ranging from 57 to 71 degrees.
Confidence is high that it will cool substantially after Saturday as
highs drop from 20-25 degrees above average on Friday to 10-15
degrees below average by Monday (avgs at KSTL: 50/31).

This weekend`s cold front will drop temperatures enough to
reintroduce snow into the forecast. A series of mid-level vort maxes
will traverse the central CONUS Sunday into Monday. In the meantime,
warm air and Gulf moisture will be advecting into the region,
ascending over the cold front and into the cold air stationed over
our region. The height of the warmer air will cause an inversion
aloft, putting all p-types on the table at this forecast issuance
including freezing rain and sleet. Of course at this point in time
there is an abundance of variability regarding the exact location of
the cold front, the strength of the warm and moist advection, and
thus the thermal profile as a whole. Ensembles do lean toward
measurable snow falling between Sunday and Monday, with the Grand
Ensemble showing 60-80% chance north of I-70. It also shows a
corridor of a 30% chance of freezing rain, heavily weighted by the
GEFS.

The front is forecast to exit the Mid-South very slowly next week.
Its presence may result in additional precipitation through the
early week until it finally shunts southward for good around
Wednesday.

Jaja

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 538 AM CST Wed Feb 25 2026

VFR conditions with generally light winds are forecast through
this evening. A quick hit of light rain will move through the area
tonight into early Thursday morning. In northeast MO southeastward
into south-central IL, a light wintry mix is possible. This
includes KUIN, where I have added prevailing rain but kept the
PROB30 for the mix. This site, as well as far southeast MO, will
see MVFR ceilings until around sunrise when the cloud deck is
forecast to scatter and exit. VFR conditions will prevail after
that.


Jaja

&&

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

$$

WFO LSX