Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

193
FXUS63 KLSX 070801
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
301 AM CDT Thu May 7 2026

.KEY MESSAGES...

- Today will begin a warming trend that will take us into the
  upper 70s and low 80s by Saturday.

- There will be multiple chances for showers and thunderstorms between
  Friday and Sunday.

- A cold frontal passage late this weekend will bring cooler weather
  back to the forecast Sunday into early next week.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 300 AM CDT Thu May 7 2026

After a chilly morning, abundant sunshine and renewed warm air
advection along gusty southwest winds will allow temperatures to
climb into the 60s areawide this afternoon. This warming trend will
continue through Friday as well, but with varying degrees depending
on location. In southeast Missouri, highs are forecast to jump
nearly 10 degrees from today and tomorrow. However, much of the area
north of I-70 is expected to rise only a couple of degrees due to
increased cloud cover and morning showers.

A weak cold front is forecast to drop south into the forecast area
Friday morning. Concurrently, lift aloft will increase with the
passing of energy lobes ahead of a shortwave, and moisture will be
advecting into the region from the southwest. These ingredients will
allow showers to develop south of the boundary during the morning
hours, though a dry sub-cloud layer will likely limit how much rain
actually reaches the ground. Rain and thunderstorm chances will
increase in the afternoon as more abundant moisture pools along the
boundary and instability increases. The HREF shows SBCAPE values of
up to 1000 - 1250 J/kg and effective bulk shear values of 40 to 45
kts. Though humble values compared to weeks past, these parameters
paired with the arrival of the mid-level shortwave and forcing along
the boundary will allow for convective initiation during the
afternoon. Atmospheric profiles show tall, very skinny CAPE that
quickly becomes elevated with time and unidirectional shear vectors
with height, suggesting that convective development will not be
robust nor will it be favorable for sustained strong updrafts. If
any thunderstorm does manage to become strong to severe, hail will
be the primary threat and central/southeast Missouri, having the
greatest instability, will have the highest potential of receiving
it. Again, the severe parameter space is not particularly favorable
for severe weather. Because of this, we have decided not to message
the potential further. Showers and thunderstorms will push southeast
before exiting the area entirely by midnight.

Jaja

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 300 AM CDT Thu May 7 2026

Friday`s cold front will have no real cold air behind it. In fact,
warm air advection into the region will have a little, if any, break
as the front passes. The continued warm air advection and abundant
insolation on Saturday will allow temperatures to climb into the
upper 70s and low 80s. The warmth will be short-lived, though,
considering our next cold front is forecast to reach us that night.
This cold front will be much more robust than Friday`s, and it will
sweep the warmth away as it passes. Although the NBM IQR high
temperature percentiles range from 70 to 79 degrees at KSTL on
Sunday, this may still be too warm. The spread accounts for
differences in the timing of the front and strength and timing of
the cold air behind the front. However, with most guidance having
the front still in the CWA in the afternoon, the potential for all
day overcast skies and cold air advection may result in highs cooler
than the NBM 25th percentile in the vicinity of the front. In fact,
despite the NBM showing an 80% chance of KSTL reaching 70 degrees on
Sunday, the LREF shows a 15% chance. That is to say, there is still
plenty of wiggle room for Sunday`s high temperature forecast.

The timing of the frontal passage will not be favorable for strong
thunderstorms. Ensembles depict only a few hundred J/kg of MUCAPE
ahead of the front early Sunday morning, and not much more Sunday
afternoon. Showers with a few thunderstorms will likely push through
the forecast area along the front with very little redevelopment
during the afternoon due to a stout capping inversion atop the
boundary layer.

There are a few more chances for rain next week associated with
passing shortwaves, but there is too much variability among guidance
to expound on these just yet. A warming trend is also expected next
week after a seasonably cool Sunday and Monday. The NBM IQR spread
is 10 - 15 degrees each day beginning Tuesday due to the
aforementioned variability, so exact temperatures are still
uncertain. However, it does show a pronounced warming trend, which
increases confidence that each day will be warmer than the last
despite the uncertainty in values.


Jaja

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1033 PM CDT Wed May 6 2026

Dry and VFR conditions are expected through the period. Light and
variable winds are expected to increase out of the southwest
around 13Z on Thursday morning and increase into the the 10-12
knot range with higher gusts during the afternoon.

Britt

&&

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

$$

WFO LSX