Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

240
FXUS63 KLSX 291141
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
641 AM CDT Sun Mar 29 2026

.KEY MESSAGES...

- Warm, dry air and southwesterly winds will combine to re-
  introduce elevated fire danger across much of the region this
  afternoon.

- Near-record warmth returns Monday and Tuesday, with a cold
  front Tuesday afternoon/night sending temperatures back to near-
  normal as we start April.

- The aforementioned cold front will bring our next threat for
  widespread showers and thunderstorms, kicking off a wetter
  pattern through the remainder of the week.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 238 AM CDT Sun Mar 29 2026

The remnants of today`s impressively-dry airmass remain evident
across the region, with regional surface observations still
reporting RH values in the 20-40% range at this hour. Some of that
can be attributed to stunted cooling from a mid-level stratus
deck over the bi-state region, but dew points are also stuck in
the teens to low/mid-20s areawide (below the 10th percentile of
local climatology). This type of poor RH recovery is exceptionally
rare for this part of the country.

With the surface ridge departing to our east and cyclogenesis
underway lee of the Rockies in the High Plains, the surface pressure
gradient is tightening overhead. The resultant southwesterly winds
today will promote stout warm-air advection and an areawide jump in
temperatures. While mid-level cloud cover will keep more dramatic
warming at bay, temperatures are likely (80-90%) to rise into the
mid-60s (south-central IL) to low 70s (central MO) today on the warm
southwesterly wind. Nearly all guidance suggests increased surface
moisture will accompany the warmth, but it almost certainly will lag
across most of our region due to blocking influences of the Ozark
Mountains. This lag combined with the poor RH recovery overnight
will send minimum RH values into the 20-35% range for most of the
forecast area. The only exception is across parts of northeast
Missouri where dewpoints are universally forecast to rise enough to
send RH values into the 40s at the worst. The combination of warm,
dry, and windy conditions will result in yet another day of elevated
fire danger for most of the region. Those planning to burn or engage
in activities that may spark a fire are strongly encouraged to alter
their plans, unless they are professionals with sufficient resources
to knock down a wildland fire if it starts.

Overnight lows will be balmy to say the least going into Monday
morning thanks to increased cloud cover limiting radiational cooling
and persistent overnight warm advection. The warming trend continues
through the day Monday, where nearly all of the forecast area jumps
back into the 80s. The ECMWF Extreme Forecast Index continues to
strongly suggest high temperatures above the 90th percentile of
model climatology, and NAEFS 850mb temperature percentiles range
from the 95th percentile to the maximum of model climatology. All to
say, we are in for yet another round of exceptional warmth for late
March. With records in the low to mid-80s at our climate sites (see
the Climate section of this AFD for more information), we may make a
little more climate history before the month is up. Exactly how warm
we get is fairly certain, with NBM IQRs for maximum temperatures
only 2-3F areawide, though high temperature records sit right within
that very narrow envelope. While broken records are not a guarantee
in St. Louis (40-45% chance per the NBM), we have a very good shot at it in
Columbia and Quincy (85-90% chance).

MRB

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 238 AM CDT Sun Mar 29 2026

A mid-level wave will track east across the northern CONUS through
the day on Tuesday, forcing a surface low and cold front as a result
that approaches the region through the day. Out ahead of this front,
continued strong southwesterly surface flow will promote another
very warm day, threatening records once again at our climate sites.
Due to uncertainty in cloud cover, precipitation, and timing of the
front itself, the chances of breaking these records is only 30-50%
at St. Louis, Columbia, and Quincy. The depiction of the front in
available deterministic and ensemble guidance continues to slow its
progression compared to previous runs. Nevertheless, it arrives
sometime late Tuesday afternoon into the evening. While a strong
capping inversion is depicted universally in the guidance that would
limit free convection ahead of the front, the boundary should be
able to overcome that to cause widespread showers and thunderstorms
along it. Given how poor the thermodynamic profiles look along the
front at this point (namely the copious warm air aloft and lack of
mid-level wave), there is nothing pointing to a threat for strong to
severe thunderstorms.

There is some concern the front may never cross completely through
the forecast area, as the wave aloft is fairly weak. That solution
was the outlier 24 hours ago, but a cluster analysis of the ensemble
members shows that scenario becoming more prevalent in the guidance.
If that occurs, the showers and thunderstorms Tuesday night into
Wednesday will linger over the region through Wednesday and result
in higher rainfall totals (1.00-2.00"). If the quicker, more
progressive solutions come to fruition, totals will be a bit lower
(up to 1.00") before the front exits. Either way, the rain will be
largely beneficial with drought conditions starting to worsen across
the region. Looking more closely at the thermodynamic details, model
soundings depict anomalous precipitable water values but fairly
shallow warm cloud depths. This combination doesn`t bode well for
efficient rainfall rates. While I can`t rule out rises on creeks and
streams, perhaps some minor nuisance flooding, there is nothing
concerning from an excessive rainfall perspective through Wednesday
either. Temperatures also hinge greatly on the front`s progress, and
while we will certainly cool down from the near-record warmth to end
March, exactly how cool we get varies greatly depending on where you
live and how far south the front gets.

The upper-level flow pattern begins to amplify by late Wednesday per
available guidance, with a trough-ridge pattern developing across
the CONUS. Amidst this flow, a shortwave is evident in deterministic
guidance (and some ensemble members) that represents another thrust
of showers and thunderstorms for the region late this week. If the
front remains stalled in the region, it will serve as the focus for
additional activity with this wave aloft. If not, the wave still has
the potential to bring additional rain. Details (timing, amounts,
potential threats) remain few and far-between regarding this
potential, with guidance diverging on its depiction of the threat
significantly. Regardless, all of the depictions show stronger
forcing amidst similar moisture which has some potential to cause
more efficient rainfall if it occurs.

The NBM envelope of solutions for temperatures does tick warmer
going into next weekend behind this late-week system, though IQRs
are still fairly high owing to uncertainty in how warm we get. The
pattern beyond the official forecast does largely favor continued
rounds of rain into early April, though the CIPS Extended Analog
Guidance from Saint Louis University does show a brief period of
cooler, dry conditions early next week (as does the NBM to a certain
extent).

MRB

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 638 AM CDT Sun Mar 29 2026

Dry and VFR conditions will persist through the valid TAF period
across the region. The only aviation concern is the increasing
threat for LLWS Sunday night through Monday morning. A strong LLJ
will develop around 2000-3000ft, and while an inversion will exist
that would promote wind shear near the ground, it`s still not
clear if true wind shear will develop vs turbulence. LLWS is not
yet included in the TAFs but may be added later as confidence
changes.

MRB

&&

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

Record Maximum Temperatures at Regional Long-Term Climate Sites

             March 30th   March 31st

St. Louis:   86F (1986)   87F (1981)
Columbia:    84F (1967)   86F (1940)
Quincy:      82F (1943)   81F (2010)

Record High Minimum Temperatures at Regional Long-Term Climate Sites

St. Louis:   67F (1998)   63F (1917)
Columbia:    65F (1967)   59F (1967)
Quincy:      61F (1998)   58F (2010)


&&

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

$$

WFO LSX