Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

351
FXUS63 KLSX 020454
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1054 PM CST Sun Mar 1 2026

.KEY MESSAGES...

- Wintry precipitation, mainly accumulating snowfall, is expected
  tonight along/north of I-70 with a narrow swath of 2-4" leading
  to minor travel impacts somewhere within the Winter Weather
  Advisory.

- Multiple opportunities for rainfall are expected through the
  workweek.


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 255 PM CST Sun Mar 1 2026

Strong and somewhat gusty northeasterly flow behind last night`s
cold front has continued to reinforce more seasonable air into the
region today. However, even with continued cold air advection,
areawide temperatures have managed to reach the 40s this afternoon
with the aid of more robust solar insolation due to the higher sun
angle this late in the winter season. Analysis of the latest
satellite and radar imagery reveals the weather system that is set
to begin impacting the region this evening, as it continues to spin
up over the Central Plains.

For the most part, the forecast remains largely unchanged as newer
model guidance continues to maintain good consensus. Precipitation
is ongoing across western Missouri, with a portion of the leading
edge exhibiting a cellular convective appearance where numerous
lightning strikes have been observed within the last few hours. For
our area, precipitation will begin within the next hour or two for
central Missouri working its way to the Mississippi River by 00-02z.
Initially, precipitation may struggle to overcome the dry sfc-700mb
layer that is in place, especially where precipitation rates are
lighter in the beginning. Some hi-res guidance is keying in on a
potential heavier band of precip along the leading edge that would
work to quickly overcome the dry layer mentioned above. Given the
ongoing convection along the leading edge in western Missouri and
robust low/mid-level forcing expected to progress eastward, it is
certainly possible that the leading edge will have nebulous areas of
heavy precip.

The biggest forecasting challenge with this system continues to be
honing in on where exactly the transition zone between rain and snow
will be. Model guidance has been relatively consistent with the
transition zone that is still expected to occur near the I-70
corridor. Forecast model soundings show quick saturation of the low-
levels leading to wet-bulbing that will result in near freezing
surface temperatures (31-35F) for locations along and north of the
Missouri River. There are also indications of a subtle warm nose
leading to a near freezing isothermal layer from 750-900mb. A
difference of a degree or two within one or both of the layers
mentioned above will have significant implications on what type of
precipitation occurs. Within the transition zone, whenever
precipitation rates are heavier, greater dynamic cooling will allow
for a switchover to mostly snow. However, when precipitation rates
wane allowing near-surface temperatures to warm slightly, a rain or
rain/snow mix is certainly possible within this transition zone.
Confidence is high (80%) that locations south of the Missouri river
will remain predominately rain with very little wintry mix expected,
while snow will be the prevailing precipitation for locations 20+
miles north of the I-70 corridor.

Brief periods of sleet and/or freezing rain cannot be discounted for
areas within the transition zone, but is expected to remain
unimpactful due to the much smaller temporal and spatial extent than
compared to the forecasted accumulating snowfall. As precipitation
winds down early Monday morning, forecast model soundings show the
DGZ layer becoming unsaturated, indicating a loss of ice crystal
growth and a potential switchover to drizzle or freezing drizzle.
This will need to be monitored throughout the event, since impacts
from freezing drizzle are very sensitive to surface air and road
temperatures, both of which are troublesome to precisely forecast
with this lead time.

With a compact shortwave and robust vorticity maxima moving overhead
in the mid-levels, forcing will be strong with this system. A west-
east oriented area of 600-850mb frontogenesis will propagate across
the region overnight potentially leading to localized banding and
heavier rates of precipitation. The HREF has showed signs of
scattered 20-30% probabilities for snowfall rates >1", indicating
the potential for these locally heavier snowfall bands. With the
transient nature of the mid-level system and ample forcing, the
duration of accumulating precipitation will generally be limited to
a 6 hr window for most locations, while any banding potential would
last only 1-2 hours for a location. As a result, the greatest
accumulating snowfall of 2-4" is expected to be located within a
relatively narrow band (1-2 counties wide N-S), somewhere within the
Winter Weather Advisory and likely just north of where the
transition zone sets up. With road temperatures well above freezing
at the onset and near freezing surface temperatures during the
event, snow may have a difficult time sticking to surfaces and may
be limited to elevated and grassy areas where the snowfall rates
remain lighter. Under the locally heavier bands of snow, these
higher rates will be able to overcome the warmer road and surface
temperatures, leading to accumulating snowfall on roads.

On the warmer side of the system, the heaviest precipitation (rain)
will be located south of the Missouri River, where robust moisture
transport overlaps with the greatest low/mid-level forcing. In fact,
across the Ozarks and near Farmington MO, there is a 40-50% chance
for more than 1" of rainfall from this system, resulting in a
beneficial and soaking rain for those locations.

Impacts from this weather system are expected to be short lived due
to the anticipated warm up on Monday and the borderline surface
temperatures during the event. Even with what will be an overcast
day with stubborn low-level clouds in place, temperatures will warm
into the mid 40s across the area, aiding in the melting of any
remaining snow on area roads. Dry conditions are expected to last
Monday late morning into early Monday night, before another system
rolls in bringing additional precipitation chances by Tuesday.

Peine/Elmore

&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 255 PM CST Sun Mar 1 2026

At the start of the extended period on Tuesday, guidance consensus
is that upper level flow will become increasingly southwesterly
ahead of a shortwave digging into the Intermountain West. Near the
surface, a west-to-east oriented warm front will be bisecting the
Midwest, roughly north of the CWA. This warm front will mark the
beginning of a period of well above normal temperatures through the
workweek. Associated isentropic lift amidst deepening southwesterly
flow will increase rain chances early in the morning and continue
them through the day, mainly focused along the front. Variability
among guidance in regards to the frontal positioning and phasing of
the shortwave leads to a low chance for changes in the focus for
rainfall, with confidence currently high (80-90%) in it occurring
along and north of I-70. The shortwave`s surface reflection develops
across the Southern Plains and moves northeastward along the warm
front Tuesday night into Wednesday, though guidance diverges on the
phasing of the shortwave and thusly, the timing and track of the
low. Despite this variability, confidence is high (80%) that rain
will continue across the CWA through Wednesday as the low moves
through the region.

The variability of the shortwave`s phasing and the low`s timing on
Wednesday has residual impacts into Thursday. The northeasterly
track of the low paired with flow remaining deeply southwesterly in
the wake of its attendant cold front supports the front being weak
and slowly departing the CWA. A minority of guidance has it clearing
the CWA enough that much of Thursday is dry. However, the majority
keeps it in the vicinity and close enough to continue rain chances
most favorably over southeastern MO and southwestern IL (60-70%
chance).

A deepening trough over the western CONUS Thursday into Friday will
send lobes of vorticity over the Plains and Midwest on Friday. As
the aforementioned cold front lifts back to the north as a warm
front, isentropic ascent and lift from the passing disturbances
aloft will keep rain and thunderstorm chances going across much of
the area on Friday ahead of a cold front set to pass through the
Middle Mississippi Valley late Friday or early Saturday. Per AI/ML-
based guidance, this is the most favorable portion of the period for
strong to severe thunderstorms. Confidence remains low in severe
weather, though, as guidance remains far away from a consensus on
frontal timing and pre-frontal instability. The threat of flooding
also remains low, as river levels are seasonably low, drought
conditions are area wide, and the signal for flash flooding is weak.

In the wake of the front Saturday, some portions of the area may see
a reprieve from rainfall (20-40% chance) depending on how much
eastward progress the cold front can make. At the very least,
ensemble-based IQRs favor temperatures cooling on Saturday compared
to their mid-week warmth, though still above seasonal normals.

Elmore

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1039 PM CST Sun Mar 1 2026


The snow is reducing visibilities at UIN will move out of the
terminal by 08Z. The rain and snow mix will also move out of
COU/JEF and the St. Louis area terminals between 08-10Z. Ceilings
will drop into the 1000-2000 foot range and not improve through
the period with possible IFR ceilings at times. Have also added
IFR ceilings and visibilities at STL after 06Z on Monday night.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory until 6 AM CST Monday for Audrain MO-
     Knox MO-Lewis MO-Lincoln MO-Marion MO-Monroe MO-Montgomery
     MO-Pike MO-Ralls MO-Saint Charles MO-Saint Louis City MO-
     Saint Louis MO-Shelby MO-Warren MO.

IL...Winter Weather Advisory until 6 AM CST Monday for Adams IL-
     Calhoun IL-Greene IL-Jersey IL-Macoupin IL-Madison IL-Pike
     IL.

&&

$$

WFO LSX