Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

991
FXUS63 KLSX 170856
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
256 AM CST Tue Feb 17 2026

.KEY MESSAGES...

- Warm temperatures continue, peaking Wednesday and Thursday near
  record levels for mid February.

- A front on Thursday brings the potential for a few severe
  thunderstorms and a shift back toward cooler temperatures
  through the weekend.

&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 255 AM CST Tue Feb 17 2026

The upper air pattern this morning features a ridge across the
center of North America with a large trough over the West Coast. At
the surface, high pressure over the Carolinas is moving out into the
Atlantic while surface low pressure is developing in the lee of the
Northern Rockies setting up a southerly flow across our region. Over
the coming days, the western trough will push east in pieces, with
each wave bringing varying impacts to our region. Today we see our
warmest temperatures aloft, with 850MB temperatures near 15C, near
the climatological max for this time of year. But we`re not going to
be mixing to 850MB, so much of this warmth remains just out of reach
today. In fact, with a good deal of high cloud cover, we may top out
a couple of degrees cooler today than yesterday. Low pressure
strengthening and pushing east into the Northern Plains will
increase the pressure gradient across our area leading to a stiff
southerly breeze developing this afternoon and continuing into the
evening. NBM probability of max wind gust over 40 mph reaches 50 to
70 percent.

The first in a series of troughs pushes east across the Northern
Midwest tonight helping to push back on the ridge over the central
US. While the surface low pressure tracks through Minnesota, a
"Pacific" style cold front moves west to east through our area
overnight into early Wednesday morning. Despite a significant surge
of low level moisture ahead of the front, the previously mentioned
warm 850MB temperatures serve as an effective cap on that moisture.
Among low resolution guidance, 40 to 60 percent produce some very
light rain, but less than 20 percent of high resolution guidance
agrees.

Kimble

&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 255 AM CST Tue Feb 17 2026

Despite the early morning frontal passage and cooling temperatures
aloft on Wednesday, we`ll actually see a substantial uptick in
temperatures here at ground level. The air mass behind this front is
a warm, dry one downlsoped from the Rockies into the Plains.
Significantly deeper mixed layer depth allows greater access to the
warm air aloft, even if it`s not quite as warm as the day before. In
this well mixed environment, temperatures warm some 10 to 15
degrees, nearing record values for the date in the 70s, while
dewpoints drop some 20 degrees. The combination will lead to lower
relative humidity values during the afternoon. A significant
relaxation of the pressure gradient will lead to weakening winds
helping to prevent a more significant fire weather threat.

The next wave emanating out of the western US trough tracks
eastward further south than the prior one. This time the track is
through the Central Plains, with the surface low tracking out of
central Kansas on Thursday toward the southern Great Lakes with our
region in the warm sector. After significant drying on Wednesday,
we`ll see an attempted return of moisture across the area on
Thursday ahead of the next "Pacific" style cold front. With much less
of a cap in place this time, if we can get enough moisture return
then we will see a threat for showers and thunderstorms ahead of the
Pacific front. The environment ahead of the front will be strongly
sheared, so any storms will be capable of developing into supercells
with damaging winds and perhaps a tornado the primary severe weather
threat. Guidance has been fairly consistent in showing this moisture
return more likely across Illinois and Indiana with our area on the
western fringes where thunderstorm development initially becomes
possible Thursday afternoon. As a result, POPs on Thursday have a
strong west to east gradient reflecting that greater likelihood of
showers and thunderstorms developing over Illinois than Missouri.

As the low pushes east, another front, this time more polar in
nature, pushes south across the region Thursday night. This time we
see a significant temperature drop behind it with a return to cooler
weather more typical of February. In fact, this weekend we`re
increasingly likely to see temperatures dip back below normal for
the first time in about 10 days.

There`s one more trough to traverse the area this weekend. This time
it`s the remnants of the more potent primary trough tracking even
further south than the prior waves. We`ll be solidly in the cold air
by the time it moves through our region Saturday into Saturday
night, so if this wave produces precipitation in our area it has a
greater potential to fall as snow. The uncertainty at this point is
in how dynamic this wave will be, how much lift it will be able to
produce, and how much moisture will be available to produce
precipitation. Among the 00Z low resolution ensemble guidance, 40 to
50 percent of members produce precipitation, including 30 to 40
percent which produce snowfall. Thus our confidence is higher that
if precipitation occurs it will be snowfall. Surface temperatures
may be marginal for accumulations, but if the stronger wave
scenarios develop, then an accumulating snowfall will be possible.
Up to about 20 percent of ensemble guidance produces 1+ inch of
snowfall.

After this weekend`s trough moves east we see the return of ridging
and warmer weather for next week.

Kimble

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 941 PM CST Mon Feb 16 2026

Dry and VFR conditions will continue through the TAF period at
all terminals. There remains a limited fog threat, but as of now
the areal extent is limited and will not impact any of the
terminals directly. Winds will gradually strengthen out of the
south tomorrow and turn southwesterly tomorrow evening, with gusts
approaching 30kts. A surface boundary is poised to track through
the region, which has a low (10-25%) chance of sparking very light
showers overnight Tuesday into Wednesday morning. That said, any
direct terminal impact is very unlikely.

MRB

&&

.CLIMATE...
Issued at 232 AM CST Sat Feb 14 2026

Daily record high temperatures may be threatened this week. Here
are records between Tuesday 2/17 and Thursday 2/19 at our three
official climate stations:

        Wednesday 2/18      Thursday 2/19
KSTL       74/1971             77/2016
KCOU       71/2017             77/2017
KUIN       68/2017             72/2017

&&

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

$$

WFO LSX