Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

546
FXUS63 KLSX 181109
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
609 AM CDT Sat Apr 18 2026

.KEY MESSAGES...

- Dry conditions are expected through the remainder of the weekend
  with cooler (50s) air moderating back to the 60s Sunday.

- Many locations will cool into the 30s tonight with a low
  potential (<50%) for patchy frost Sunday morning. Any frost
  should be confined to vegetation and objects elevated off the
  surface.

- Warming continues through the remainder of week with another
  active period expected by late week into next weekend.


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 257 AM CDT Sat Apr 18 2026

A strong cold front continues to make its way southeastward this
morning with remnants of last night`s thunderstorms. Lightning has
become far less common through early this morning as cooler air has
undercut the precipitation, bringing an end to the severe threat.

Pockets of steady/moderate rainfall are embedded within the broader
field of stratiform rainfall behind the front. This all shifts
southeast of the CWA around 16z this morning with improvement expect
going forward. The airmass behind the front include dewpoints in the
teens and 20s over the northern Plains. While air will not be that
dry at all locations, it does make it into the northern reaches of
the forecast area with dewpoints in the 30s over southwest MO and
southwest IL. Cloud cover gradually clears from west to east with
increasing sunshine over central/NE MO through 12 p.m. Clearing
continues southeastward, but clouds linger through at least mid-
afternoon southeast of the metro area.

An upper level trough over Canada extends southward into the
Mississippi Valley today. The trough is below the 5th percentile of
climatological means with heights in the 10th-25th extending into
the local area. Cold air advection behind the front draws the 0C H8
isotherm into the region with mid-level temperatures ranging from
the low single digits below OC to the single digits above 0C on
northwesterly flow. Temperatures were in the 50s/60s with 40s not
far to the northwest as of 07z (2 a.m.) this morning. CAA will keep
temperatures fairly steady and where cloud cover lingers, it`ll feel
quite cool relative to recent warmth. Highs will range from the mid-
50s to near 60 degrees. Mixing deepens late this morning through the
afternoon with diurnally driven gusts of 20-25 mph.

Gusts subside this evening as mid-level ridging begins to shift from
near the TX Panhandle into the northern Gulf Region. Meanwhile, a
surface high begins to build southeast out of Canada into the Upper
Midwest. Clear skies and light winds will allow temperatures to drop
into the 30s/40s tonight. The coldest locations (mid-30s) may be
cool enough to support patchy frost. However, the strongest argument
against this potential is the warm surface with regional soil
temperatures showing 2 inch depths in the low-60s to near 70
degrees. Considering the recent rainfall, moisture content will keep
ground temperatures from cooling much and highly likely to stave off
frost at near-ground levels. Elevated, exposed objects may be the
most susceptible and even then 30s only lasts 3-4 hours (max) around
the coolest locations.

The tandem of ridges begin to slide east Sunday with modest warming
being driven in from the Plains. It`ll be the pick day of the
weekend with low dewpoints (30s) and rebounding temperatures. We
will tack on about 10 degrees to daytime highs under mostly clear
skies. Temperatures return to the 60s for most locations and
flirting with 70 degrees to the north/east of the Ozarks.


Maples

&&

.LONG TERM...  (Sunday Night through Friday)
Issued at 257 AM CDT Sat Apr 18 2026

Ridging that shifts east eventually consolidates into a broader
ridge over the eastern CONUS Sunday night into Monday. A weak cold
front extends well south of a low pressure system over Canada and
attempts to drop southward into the area in the later half of the
day Sunday. Guidance shows the front stalling or yielding to return
flow at the back side of the eastern ridge. The pattern carries over
into early next week with slightly warming over Sunday`s
temperautres. Highs range from the low/mid-60s (IL) to the low-70s
from the Ozarks through central and southeast MO.

NBM IQRs remain rather tightly clustered through Thursday with
increasing confidence in dry conditions and a more significant warm-
up Tuesday. This warm-up is driven by an increasing pressure
gradient between an upper low over the Hudson Bay and strong
mid-level ridging over the northern Gulf. 20-25C mid-level air is
sources from the lee side of the Colorado Rockies into the mid-
Mississippi Valley with mid-level air ranging from 10-15C locally.
This pattern persists through Thursday, where IQRs then begin to
spread late Thursday into Friday. Another period of above normal
warmth with highs in the mid-70s to low-80 Tuesday and Wednesday.
The warmest conditions arrive Thursday with low/mid-80s for highs.

The pattern that brought this weekend`s showers and thunderstorms
seems to repeat again next weekend. Global guidance varies on an
exact solution, but broader themes can be pulled from the synoptic
setup. The eastern ridge moves into the mid-Atlantic Region as an
upper trough leads to surface cyclogensis over the Plains. This is
where guidance deviates from one another with the timing, position,
and track of the surface low. A cold front trails the system and
supports convection over the central sections of the CONUS, but the
extent and placement of convective trends will depend on what plays
out between the more northern solution of the ECM and southern
solution of the GFS. Both show a version of showers and
thunderstorms along the cold front to our west Thursday night,
progressing eastward into the area by Friday. Timing will be key,
but as of now, this initial round comes during diurnal minimums and
may signal another round of weakening covection and widespread
showers/occasional thunderstorms.


Maples

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 605 AM CDT Sat Apr 18 2026

A strong cold front has moved southeast of all terminals this
morning with the back edge of rainfall pulling through the metro
terminals as of 11z. Rain is expected to linger through 12z and
taper off quickly thereafter.

Aside from a narrow ribbon of MVFR cigs immediately following the
front, conditions continue to improve to VFR further behind the
boundary. VFR conditions are expected to persist through the
period with occassional gusts of 20-25 knots today. Gusts subside
this evening with light and variable winds after 00z tonight.

Maples

&&

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

$$

WFO LSX