Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

620
FXUS63 KLSX 270001
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
701 PM CDT Tue May 26 2026

.KEY MESSAGES...

- Tropical moisture brings showers and a few thunderstorms to
  parts of the area through Wednesday, but the rest of the week is
  looking drier.

- This weekend is looking drier with seasonably warm days and
  seasonably cool nights.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 218 PM CDT Tue May 26 2026

Moisture continues streaming very slowly northward today in
association with a weakening tropical wave to our south. The
associated surface low is lifting through West Tennessee this
afternoon with moist advection aloft bringing some showers into
southern portions of our forecast area. Dry air in place ahead of
this system being reinforced by ENE winds is counteracting some of
the arriving moisture aloft, leading to a rather sharp gradient
in rainfall. This is likely to continue as this moisture
continues lifting slowly northward tonight into Wednesday. Locally
heavy downpours and occasional lightning are the primary expected
impacts.

Farther to the west, a more pronounced shortwave trough is moving
through the southern Rockies, rotating around a larger, deeper
trough digging into the Great Basin. To the east of that, a high
amplitude ridge is building across the Northern Plains into the
Canadian Arctic, with another downstream trough over eastern
Canada. Our area is near the periphery of all of these features
giving us some impacts, or potential impacts, from each over the
coming days.

The most direct impact locally will be from the decaying tropical
wave lifting north along the Mississippi River. The moist
advection ahead of this spread a large area of rain from Arkansas
to West Virginia today while also greatly increasing the humidity
(dewpoints locally have risen 15 degrees or so from yesterday).
This wave is expected to continue weakening as it heads north, and
thus the more widespread rain associated with it is expected to
decrease in coverage and intensity overnight into the day on
Wednesday. However, some areas of embedded vorticity and moist
advection may lead to locally more persistent rain with embedded
thunder into the day on Wednesday, though the general trend is
toward drying. With the potential for less cloud cover on
Wednesday, high temperature forecasts are a few degrees higher
than today, especially in areas that saw persistent clouds and
rain today.

Kimble

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 218 PM CDT Tue May 26 2026

The eastern Canada trough drops south into New England on
Thursday, with a renewed push of cool, dry air behind it.
Meanwhile, the shortwave trough over the southern Rockies lifts
slowly northeastward. So on the one hand, we`ll have drier air
headed our way from the northeast, but on the other hand we`ll
have moisture being pulled toward us from the southwest. Latest
trends in guidance have been favoring the drier side of things for
most of our area, as that will increasingly become the dominant
feature through the end of the week. However, we`ll still have to
watch that trough to our west and how far east the moisture
associated with it can get. Rain chances through the weekend have
continued to tick downward as another reinforcing shot of dry air
comes on Saturday, but some lower chances persist in western and
southern portions of the forecast area where the influence of the
nearby moisture is stronger.

Regarding temperatures, the core of the heat building in the ridge
remains to our north, and we get multiple shots of modified
Arctic air around surface high pressure near the Great Lakes.
Forecast temperatures aloft support highs within a couple of
degrees of 80 most days when fully mixed. NBM and our official
forecast remain on the higher side of guidance most days, but are
within a reasonable range. Nighttime lows will trend toward the
50s as drier air becomes more dominant this weekend, a few
degrees below normal for this time of year.

As we go into next week, the high amplitude ridge over Canada
gradually breaks down while the western trough fills and becomes
hard to find in most deterministic guidance. The implications for
us locally depend on how those features evolve. Some scenarios
have a weak cut off low drifting toward us, which would spell
cooler conditions with potential for showers. Others have the
Canadian ridge becoming more dominant over our area as it shifts
southward, which would spell drier and warmer conditions. The NBM
interquartile range (IQR) for highs rise to 6-8F next week which
is about double the IQR for this week. The difference is highs in
the 70s, a bit below normal, or highs in the mid to upper 80s, a
bit above normal.

Kimble

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 626 PM CDT Tue May 26 2026

VFR flight conditions are expected to prevail through the evening
for most of the area. Areas of showers are diminishing, and should
continue to weaken through the evening. MVFR and IFR ceilings are
expected to build slowly into southeast Missouri and south
west/south central Illinois after 03Z. These low ceilings will
continue to spread northeast across the eastern Ozarks and east
central Missouri to generally along a line from KVIH to KFYG to
KTAZ. Ceilings will be lowest across the Ozarks and southern
Illinois where bases could be below 500 ft AGL. Low clouds will
lift from west to east through the morning and should be VFR
across the entire area by 18-20Z. Additional shower development is
possible overnight into Wednesday, primarily across southeast and
east central Missouri into south central Illinois however there
is little consistency in timing/location in the forecast guidance.

Carney

&&

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

$$

WFO LSX