Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

325
FXUS63 KLSX 191919
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
219 PM CDT Fri Jun 19 2026

.KEY MESSAGES...

- Widespread showers and thunderstorms are forecast late Saturday
  night through early Monday. A few of these storms may be strong to
  severe with damaging winds and locally heavy rainfall.

- Seasonably cool temperatures are forecast next work week.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 218 PM CDT Fri Jun 19 2026

A weak cold front is currently situated across eastern Iowa into
the Great Lakes early this afternoon. This feature is expected to
move into parts of northeast Missouri and west-central Illinois
late this evening into the overnight hours. Weak convergence near
this feature along with modest low-level moisture advection may be
just enough to produce some scattered light rain showers in these
aforementioned locations. With time, the boundary is forecast to
wash out as it attempts to move southeast. The moisture
convergence also abates after 0900 UTC, so activity should become
more isolated and eventually dissipate completely by mid morning
on Saturday. Dry weather is then favored for the remainder of the
day with temperatures climbing back into the low to mid 80s, or a
degree or two below normal for the date.


Gosselin

&&

.LONG TERM...  (Saturday Night through Next Friday)
Issued at 218 PM CDT Fri Jun 19 2026

(Saturday Night - Monday)

All eyes will be to our west Saturday night as an MCS is expected to
develop somewhere across KS/NE. This complex should move eastward
close to the forward-propagating Corfidi vectors. The low-level jet
also veers with time, which could help initiate storms on the
western flank and help push the southern edge more equatorward.
Speaking of the low-level jet, it also does not weaken during the
day on Sunday. This portends to convection continuing with the
morning MCS and not dissipating. There may be some weakening with
eastward extend due to the timing and weaker instability, but I do
believe thunderstorms will continue through Sunday morning. The key
questions then will be where exactly is the MCS focused Sunday
morning and how fast it is. The ECMWF is a bit further north with
the track compared to other deterministic guidance, but the focus at
this time seems to be honed in on parts of northeast Missouri and
west-central Illinois. Marginally severe winds and locally heavy
rainfall are the main threats late Saturday night through Sunday
morning. Rainfall totals in the 1-2+" range are expected in these
locations, aided by very anomalous precipitable water values (>1.8";
~99th percentile of climatology) and the possibility of some
training. The complex/MCS itself however should move at a pretty
decent clip from west to east. This factor may help limit the
duration enough to reduce the short-fused hydrological threat.

Uncertainty increases further for Sunday afternoon/evening. There is
at least a chance that ongoing activity becomes reinvigorated by
early afternoon as diurnal instability increases out ahead of the
remnant MCS. However, the current timing may tend to favor our far
eastern counties or areas just outside of our CWA for that threat.
The big caveat is if the MCS is a bit slower, then that severe
threat may expand westward into east-central Missouri as well.
Damaging winds are the main severe threat for the afternoon/early
evening, but an area of increased tornado threat may be located
near/just ahead of the track of a weak surface low. Guidance varies
on whether or not this feature will exist, but if it does, the low-
level shear/helicity would be enhanced. In terms of area(s) with the
best chance of this tornado potential, our early best guess would be
west-central Illinois.

Further southwest, convective initiation along the trailing cold
front seems likely, but I do have concerns on the coverage and
severity. Similar now to several events the past two weeks, there
are factors working against widespread organized convection in our
CWA. For one, the surface convergence along the front in our CWA
looks modest, with stronger ascent centered across southeast KS and
far southwest MO. Midlevel temperatures are also warm (> +10C), with
neutral to slightly rising heights behind the departing morning MCS.
This points to possible subsidence in mid/upper levels of the
atmosphere, which isn`t exactly conducive to strong/severe
convection. Additionally, the amount of instability in our area is
also highly questionable due to the possible impacts of the morning
MCS detailed above. Probabilities for >1000 J/kg of SBCAPE on the
GEFS/GEPS reach 60% only in central/southeast Missouri though the
IQR spread is pretty high (1000-1500 J/kg). However, if greater
instability is realized, there is sufficient (>30 knots) effective
shear that we may see a bowing segment or two or event some
transient supercells capable of producing damaging winds and/or
large hail respectively. At this juncture, this activity would be
more likely to impact central/southeast Missouri and points
southwest.


(Monday Night - Next Friday)

A period of dry weather is expected for the middle of next week
along with a more prolonged stretch of below normal temperatures,
which should last through at least next Friday. Broad northwest flow
aloft is expected to continue, with mean 850-hPa temperature
anomalies on both the GEFS/EPS in the -2 to -4C range. High
temperatures are most likely to range from the upper 70s to low 80s
each afternoon, with overnight lows in the mid 50s to low 60s. The
spread in the NBM inter-quartile range for both highs and lows
remains low next week, generally on the order of 3-5F. This
increases confidence in the temperatures mentioned above.


Gosselin

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1154 AM CDT Fri Jun 19 2026

Dry/VFR conditions with light/variable winds are forecast the
rest of this afternoon and into the early evening hours. Some
scattered showers may impact northeast Missouri/west central
Illinois late this evening/early overnight hours so added a PROB30
group. Farther south, this activity should weaken and eventually
dissipate. Cannot rule out a stray shower impacting the central
Missouri or metro St. Louis terminals, but visibilities are very
likely to stay VFR even if any site does observe -RA.

Gosselin

&&

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

$$

WFO LSX