Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

240
FXUS63 KLSX 180322
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1022 PM CDT Tue Mar 17 2026

.KEY MESSAGES...

- Light snow is expected this evening, mainly across northeast
  Missouri and west central Illinois. Some intermittent light snow
  or flurries is also possible farther south. Expected
  accumulations are still under an inch.

- Well above normal temperatures remain in the forecast for
  Wednesday into the weekend.


&&

.SHORT TERM...  (Through Late Tonight)
Issued at 228 PM CDT Tue Mar 17 2026

A weak wave of low pressure will move across the Mississippi Vally
tonight.  Low level flow will turn to the southwest and increase
this evening ahead of the wave to produce a broad low level jet over
Missouri and Illinois.  Short range guidance is showing strong warm
advection with weak to moderate moisture convergence ahead of the
wave forced by the low level jet tonight.  However, forecast
soundings continue to show a layer of very dry air below around
850mb tonight which will limit how much precipitation will reach the
ground.  With that in mind, soundings also show the column should be
cold enough to support snow, at least through the evening, although
any lingering precip over night may turn to light rain or sprinkles.
The most likely areas to receive any accumulating precip will be
northeast Missouri and west central Illinois where the low level dry
layer is forecast to be shallowest.  QPF has been reduced to only
0.01 to 0.05 so snow amounts are expected to be less than 1 inch.
Temperatures are expected to drop a few degrees early this evening,
but will likely steady out and then rise slowly overnight.  Most of
the area is expected to be above freezing before sunrise on
Wednesday.

Carney

&&

.LONG TERM...  (Wednesday through Next Tuesday)
Issued at 228 PM CDT Tue Mar 17 2026

Still expecting a dramatic warm up this week.  The long wave pattern
over the U.S. begins shifting east on Wednesday allowing warmer air
to build across the Mid Mississippi Valley. This continues through
the week until the long wave trough moves off the East Coast late
Friday.  The most dramatic warm up will be over the next 24 hours as
highs are expected to be as much as 25 degrees warmer from this
afternoon to Wednesday afternoon.  Temperatures continue to warm
through the week with the NBM ultimately advertising the mid 70s to
low 80s on Saturday and Sunday.  Confidence remains relatively high
in the warm up through Saturday as ensemble guidance shows tight
temperature IQRs of only around 3 degrees, at least through Friday.
Saturday`s range increases to around 5 degrees, which is still
fairly tight for the medium range.

Deterministic guidance shows a short wave moving across the northern
U.S. Saturday night into Sunday .  the surface low then drags a cold
front through the Midwest at some point on Sunday.  The ECMWF is
about 12 hours faster than the GFS on today`s runs, and the NBM
seems to be leaning on this slower solution with highs on Sunday in
the mid 70s to low 80s.  Uncertainty in the position of the front on
Sunday is also apparent in the ensemble guidance as the IQR widens
t0 20-25 degrees.  Needless to say confidence in Sunday`s forecast
is low due to these model differences.  Confidence actually
increases slightly for Monday and Tuesday after the frontal passage
as high pressure builds into the Great Lakes.  This produces cool
east to northeast flow for the Mid Mississippi Valley which pushes
temperatures back to near seasonal normals.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1020 PM CDT Tue Mar 17 2026

Light snow is currently moving east of the Mississippi River and
should leave the terminals dry over the next 24-30 hours.
Southeast winds will be gusty overnight near 20 knots but should
weaken toward daybreak Wednesday as winds veer with time. A weak
cold front will come through later Wednesday, with winds turning
to the northwest.

Gosselin

&&

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

$$

WFO LSX