Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

483
FXUS63 KLSX 052305
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
605 PM CDT Sun Jul 5 2026

.KEY MESSAGES...

- Isolated to scattered showers and thunderstorms are expected
  through this evening. A few of which could be capable of gusty
  winds.

- At least patchy fog is possible overnight into Monday morning,
  especially in locations that receive rainfall today. Dense fog
  cannot be ruled out.

- Seasonable temperatures are forecast through the first half of
  the week.


&&

.SHORT TERM...  (Through Tuesday)
Issued at 245 PM CDT Sun Jul 5 2026

Within an overhead upper-level longwave trough, an MCV is
propagating slowly eastward across southeastern MO/far southwestern
IL early this afternoon with lingering showers. However, another
MCV/low is departing IA and progged to track southward through MO
through this evening, which will support isolated to scattered
showers and thunderstorms this afternoon and evening, focused in
confluent surface flow axes and a differential heating zone
along/north of I-70. With weak (10 to 20 kt) deep-layer wind shear,
instability lower than Saturday, and not as much dry air in
soundings; it is less likely that any thunderstorms will be able to
produce damaging winds, but "inverted-V" sounding signatures still
suggest they could still contain gusty winds. Following sunset and
the loss of daytime heating, showers and thunderstorms will wane.

Predominantly dry conditions are expected overnight through Monday
morning, but light surface winds, residual PBL moisture, and
locations of rainfall today point to a threat of at least patchy
fog. Fog would be most likely in locations that have moistened soils
from rainfall today and typical river valleys with the potential for
dense fog needing to be monitored.

On Monday, model guidance, although varied, indicates that the
MCV/low will continue to meander and potentially become cut off near
southern MO or AR, assisting isolated to scattered diurnal showers
and thunderstorms mainly south of I-44 (MO) and I-70 (IL). These
locations will have the greatest instability and lingering moisture
as weak low-level northerly flow along a building surface pressure
ridge attempts to filter a slightly cooler and drier airmass into
the CWA. Accordingly, high temperatures will be another degree or
two cooler with lower dewpoints as well. Tuesday will be similar to
Monday, but rising heights behind the cutoff low as an upper-level
ridge arrives and even lower instability/moisture will lead to
minimal diurnal showers/thunderstorms.

Pfahler

&&

.LONG TERM...  (Wednesday through Next Sunday)
Issued at 245 PM CDT Sun Jul 5 2026

The influence of the aforementioned upper-level ridge will only
persist through Wednesday before it flattens and gives way to quasi-
zonal flow across the Mid-Mississippi River Valley through Thursday
and Friday. Multiple shortwave troughs within this flow will force a
weak, slow-moving/wavering front into the CWA sometime during the
Thursday-Friday time period leading to one or more opportunities for
showers and thunderstorms along with pre-frontal, low-level
southerly flow warming temperatures back to above average at least
briefly on Thursday. With humidity/dewpoints also increasing, global
model ensemble probabilities of 100+ F heat index values are 15 to
20 percent on Thursday.

Over next weekend, global model guidance signals that upper-level
flow will veer to northerly ahead of a much more substantial
upstream ridge favoring southward movement of the front with a
slightly cooler airmass arriving in its wake. The longevity of this
airmass is uncertain with model solutions varying on how long
northwesterly flow holds before the ridge extends eastward, which
would favor warming temperatures. During this time, NBM
interquartile temperature ranges span 5 F between below average and
average.

Pfahler

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 601 PM CDT Sun Jul 5 2026

Thunderstorms will continue to percolate nearby Jefferson City and
Columbia near the start of the TAF period, but are expected to
diminish before sunset. Occasional visibility reductions and
erratic wind gusts/direction changes will be possible, but shortly
thereafter winds should become nearly calm.

Overnight through tomorrow morning, the main concern will be fog
due to clearing skies, light winds, and lingering humidity and
surface moisture from this evening`s rain. This will be most
likely at central MO terminals and river valley locations
(JEF/SUS/CPS/SUS), but will be possible in most areas. Fog should
diminish shortly after sunrise. MVFR cumulus will be briefly
possible late morning/early afternoon before ceilings lift, and
there is a low (20%) chance of showers/weak thunderstorms tomorrow
afternoon at St. Louis area terminals. Chances are too low to
include in the TAF at this time.

BRC

&&

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

$$

WFO LSX