Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

959
FXUS63 KLSX 010338
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1038 PM CDT Tue Mar 31 2026

.KEY MESSAGES...

- Showers and thunderstorms will become numerous tonight
  along/north of I-70. A few thunderstorms could be capable of
  small to marginally severe hail along with a threat of locally
  heavy rainfall.

- Additional rounds of showers and thunderstorms are expected at
  times through Saturday, but a multitude of factors preclude
  messaging additional strong to severe thunderstorms at this
  time.

- Cooler and drier conditions will return on Sunday.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 327 PM CDT Tue Mar 31 2026

An area of persistent showers and weak thunderstorms has gradually
waned along the Missouri River in central to east-central MO, which
has limited temperatures across those areas and the northern extent
of Elevated Fire Danger concerns beyond southeastern MO into the
evening. Showers and thunderstorms will eventually increase in
coverage tonight as a cold front reaches the area and there is some
increase in the strength of a modest LLJ. The earliest development
could be near the I-70 corridor this evening (5 to 7 pm) with a
subtle convectively reinforced boundary, but showers and
thunderstorms will generally expand northward in coverage through
the night toward northeastern MO and west-central IL.

A few thunderstorms could produce small to marginally severe hail
this evening, given marginal (~500 J/kg) in the hail growth zone.
However, it would be difficult to get larger hail since effective
wind shear is not favorable for sustained, rotating updrafts (only
20 to 30 kt), and aggregation of convection is favored with time.
The threat of damaging winds is low due to any thunderstorms likely
being elevated or high-based above a lower level capping inversion.
Another, relatively greater threat is locally heavy rainfall tonight
with anomalous PW, deep warm cloud depths, and wind profiles
favorable for training and backbuilding of thunderstorms. The latest
HREF depicts an axis of 2 to 4" QPF from central MO to just north of
St. Louis, but dry antecedent soil conditions and uncertainty in the
modest LLJ`s ability to focus convection long enough in one area to
get long-lived intense rainfall rates lowers confidence in flash
flooding being achieved. However, if such a heavy rainfall axis were
to occur across the urban footprint of the St. Louis metro, flash
flooding would seem more attainable, bearing that there is low
confidence in this scenario playing out.

As the LLJ weakens gradually Wednesday morning, showers and
thunderstorms will decrease in coverage, but the front will stall
near I-70 which could provide as the focus of showers and
thunderstorms during the afternoon and evening. A strong
thunderstorm or two with small hail and gusty winds cannot be ruled
out near the front where instability will be greatest, but most
indications are that wind shear will be even weaker than today.
However, large-scale forcing will be limited, which casts doubt in
the coverage of showers and thunderstorms, captured by disparities
across CAM output. It is uncertain how much northward advancement
this front will make during the afternoon, resulting in a large
spread of temperatures in the NBM near the I-70 corridor,
considering the very warm airmass residing to its south with 80+ F
high temperatures and to the north a cloud-shrowded cool airmass
with temperatures in the 50s F. It may not be until Wednesday
evening that the front makes much northward progress, since that
is the favored time period of surface cyclogenesis in the Central
Plains and when the LLJ restrengthens.

Pfahler

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 327 PM CDT Tue Mar 31 2026

On Thursday, the front will be to the north, leaving the CWA firmly
in the warm sector of an approaching surface cyclone tracking
generally across IA. A remnant line of showers and thunderstorms
will track eastward across the CWA during the morning into early
afternoon, followed by potential redevelopment of showers and
thunderstorms during the late afternoon and evening as instability
attempts to recover and a weak cold front approaches. There is some
uncertainty in how quickly this initial round of showers and
thunderstorms departs and breaks in cloud cover permit
destabilization during the afternoon with global ensemble model
guidance depicting 1000+ J/kg SBCAPE probabilities of 10 to 20
percent along/west of the Mississippi River. That being said, REFS
probabilities are much higher at 50 to 80 percent in those same
areas. Deep-layer wind shear will also be stronger, around 30 to 40
kt, along with some low-level wind shear. These factors lead to a
higher severe weather ceiling which would include all hazards.
However, another complicating factor is that the passage of an upper-
level shortwave trough may be out of phase with the greatest
instability and cold front arrival, with unfavorable mid-level
height rises expected to ensue behind the front sometime during the
evening. This factor could result in the greater severe threat being
northeast of the CWA on Thursday.

On Friday, the CWA will be back in the warm sector with another
developing surface cyclone to the west and attendant upper-level
trough ejecting across the Central Plains into Upper Midwest.
Regionally speaking, the ingredients of strong to severe
thunderstorms will again be present, but with at least a weak
capping inversion across the warm sector and weak forcing it is
uncertain if thunderstorms will develop across the open warm sector
in the CWA when instability is greatest. Instead, the more likely
initiation of thunderstorms Friday afternoon and evening is across
eastern KS/western MO. The general consensus in numerical and
machine-learning guidance is that these areas will also most
favorable for strong to severe thunderstorms where instability,
stronger wind shear, and more vigorous large-scale forcing meet.
Given the current timing, showers and thunderstorms should be
weakening as these enter the CWA Friday night with instability
decreasing, but trends will need to be monitored for any earlier
timing that could increase the severe threat locally. There will be
at least a low threat of locally heavy rainfall again, but the
generally progressive nature of showers and thunderstorms limits
confidence in flash flooding. The front and associated showers and
thunderstorm are not expected to fully exit the CWA until Saturday
afternoon or evening.

Behind the front, a much cooler airmass will arrive with seasonably
cool temperatures ahead of a warming trend back to near average
early next week. The majority of ensemble membership is also dry
during this time with moisture having little opportunity to return
and no signs at this point of significant large-scale forcing.

Pfahler

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1038 PM CDT Tue Mar 31 2026

Latest surface observations show a cold front extending roughly
from KCOU to K3LF. Radar trends have become more active along the
boundary with scattered showers and thunderstorms. This trend is
expected to continue overnight, expanding in coverage through at
least mid-morning Wednesday. While it is difficult to pinpoint
exact locations/timing with convective activity, highest
probabilities for embedded thunderstorms extend from KCOU through
KUIN. KJEF/KSUS/KSTL all sit at the edge of more active weather to
the north and merely isolated showers/thunderstorms south of the
boundary. There are some indications that KCPS is the latest
affected with the very slow southward sag in the front, which
eventually returns north Wednesday afternoon.

MVFR is favored at all sites Wednesday morning through early
afternoon. IFR/LIFR will be dependent on direct impacts from
thunderstorms, including locally heavy rainfall potential.
Fortunately, trends look less favorable for severe thunderstorms,
though a brief gust is possible. There may be periods of dry time
between scattered showers/thunderstorms Wednesday late morning
through early afternoon, pending location. Thunderstorms are
possible once again Wednesday afternoon, but specifics will rely
on how activity evolves tonight in Wednesday morning. In general,
MVFR is expected to lift back to VFR as the front shift northward
late in the day.

Maples

&&

.CLIMATE...
Issued at 238 AM CDT Sun Mar 29 2026

Records at Regional Long-Term Climate Sites - March 31st

             Record Highs | Record Warm Lows

St. Louis:   87F (1981)   | 63F (1917)
Columbia:    86F (1940)   | 59F (1967)
Quincy:      81F (2010)   | 58F (2010)


&&

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

$$

WFO LSX