St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

029
FXUS63 KEAX 011726
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
1126 AM CST Mon Dec 1 2025

...18z Aviation Update...

.KEY MESSAGES...

- Accumulating Snowfall Today

- Widespread 1-2 Inches, Areas of 2-4 Inches

- Cold Airmass This Week

&&

.DISCUSSION...
Issued at 240 AM CST Mon Dec 1 2025

Happy first day of meteorological Winter! We`ve got snow in the
forecast for you!

Modest H5 ridge axis has passed through the area, and has
deamplified into a brisk zonal flow regime. Broad surface
anticyclone is still in place across the region, allowing a cold
airmass to settle as temperatures are hanging around in the teens
during the early morning hours. The surface high will actually stick
around while the approaching trough moves through the area. The calm
surface winds with this anticyclone will actually help snowfall
accumulations.

As of 08z positively tilted trough axis is moving across the
Rockies this morning, with H3 jet streak extending into Central
Kansas, while H5 jet streak currently sits just west of the TX/OK
Panhandle Region. There is a surface cyclone attempting to develop
in the lee of the Rockies with the stronger dCVA ahead of the trough
axis, but is still progged to become disconnected later this
morning, which is not unusual for troughs exhibiting a positive tilt
like this. The vort max will eject will eastward into the Central
Plains and become dislocated from the surface low. Ahead of this
trough, flow above 900mb has allowed moisture transport for the past
several hours. While the immediate boundary layer remains dry due
the polar airmass that moved in, the troposphere between 800mb to
500mb is starting to saturate. At far distances from WSR-88Ds across
the Plains, you see some returns. Not much is occurring at the
surface though. Some light snow has occurred in Concordia KS, and
then a few reports near Colby and Goodland KS. Between 10z-13z this
morning, main vorticity maxima moves across Central Kansas, and
modest mid-level height falls will start over eastern Kansas and
western Missouri. Some weak lift may begin to develop, allowing for
initial flurry development in northeast Kansas and northwest
Missouri early this morning. It will still take several hours for
the entire column to fully saturate. 00z HREF has slowed down the
initial timing of potential snow by a few hours. However, synoptic
scale models still indicate some potential for initial snowfall.
Accumulating snowfall though may hold off until after 12z for even
our western counties. Most model soundings show full saturation by
13z-14z. This is also when the 00z HREF 1-hr mean snowfall begins to
show a signal for accumulating snow, then slowly moves this eastward
through the afternoon and into the evening hours. Late morning
through early afternoon is when the primary mid-level vort maximum
will also move through. Strong 700-500mb Q-vector convergence is
still depicted along the leading edge of this, and this will be the
primary forcing for precipitation for this snowfall event. This is
also roughly where the DGZ will be located, and both synoptic scale
models and CAMs show an uptick in omega through the DGZ along this
feature, which explains the favorable timing for accumulating
precipitation as the afternoon and evening progresses. Most of the
forecast area is still looking at a widespread 1-2 inches of
snowfall, with a band of 2-4 inches primarily just north of the
Missouri River. Model consensus for the location of this heavier
band has become better over the past 12-18 hours, especially
compared to the model cycles last night that had a difference of
nearly 100 miles. The most notable change to the forecast this
morning, is increased snowfall to the south-southeast of the
heaviest snowfall axis. While the past few CAM cycles have slightly
decreased snowfall totals, there had been an upward trend from
yesterday afternoon`s model cycles. NBM, GEFS, and other ensemble
suites probabilities for at least 2" of snow along and south of
Interstate 70 east of the Kansas City Metro increased to around 50
percent. With a stronger signal for convergence along the short-wave
further south-southeast, the Winter Weather Advisory has been
expanded with this forecast update to now include Johnson [MO],
Pettis, Cooper, and Howard Counties from this afternoon through late
Monday night. This is mainly driven by the increased probabilities
for 2 inches of snow. The past few days, the probabilities for
exceeding 1 inch were fairly low, but confidence has increased
enough to warrant expansion of the Winter Weather Advisory. Further,
afternoon commute along I-70 may be impacted by hourly snowfall
rates of 0.50 to 0.75 inches.

Let`s take a deeper dive into this 2-4 inch band we are seeing a
signal for north of the Missouri River. As mentioned before, HREF
and GEFS both show this area between the Missouri River to just
south of Hwy. 36 for a few runs now. Looking at cross section
analysis of the RAP, GFS and NAM, this is where the greatest
magnitude of omega is showing lift through a large portion of the
DGZ, allowing for healthy dendritic growth that will push snow
ratios in this cold column upwards of 14:1. Yesterday`s model cycles
were showing the potential for stronger FGEN processes, which is
usually a positive enhancement of snow to liquid ratios resulting in
higher snowfall accumulation. However, those FGEN signals have
actually gone down. Within this same region, EPV values show a few
pockets that dip down to zero or just slightly below it, but
generally speaking are not screaming strong conditional symmetric
instability (CSI) release, with may limit the ability for a robust
mesoscale band to develop. The heavier snowfall is largely being
driven by the healthy lift through the DGZ. Will point out that the
probability matched mean field in the 00z HREF, does depict and area
of 4-6 to inches north of the Missouri River to around Hwy. 36.
These PMM values are likely showing a reasonable outcome for very
localized pockets of heavier snow within the area we are
anticipating 2-4 inches for. If there was a clearer signal for a
strong FGEN band or some kind of CSI release, would have more
confidence to call for 4-6 inches in the forecast. However, with the
current data analyzed, this is not the case. As this event unfolds,
this will probably be the mesoscale analysis challenge of the day,
tracking to see if a localized FGEN band is able to develop or some
kind CSI release. That is likely the condition needed to get that 4-
6 inch measurement somewhere. Some CAM guidance attempt to place
this elevated snowfall range in northern Platte and Clay Counties,
while another takes that pocket but places it in Ray and Carroll
Counties. Therefore, due the lack of a clear FGEN or CSI signal,
along with inconsistent placement amongst high resolution guidance,
have kept the Winter Weather Advisory as is for the area of likely 2-
4 inches. At this time, there is not enough confidence to warrant a
need for a winter storm warning.

The main trough axis and vorticity maxima exits the forecast area
between 00z-01z this evening, and moves east of the Mississippi
River after 03z. Accumulating snowfall should end for our eastern
counties in central Missouri between 02z-03z. A few flurries may
still be ongoing.

Very modest mid-level ridge moves across the area on Tuesday, and
surface anticyclone gradually shifts eastward toward the Ohio River
Valley. While low-level flow will attempt to turn southerly, the
appreciable WAA will stay far south in the southern Plains. We may
see temperatures Tuesday and Wednesday climb back above 30F. Another
trough moves across the western CONUS Wednesday into Thursday which
will provide northwesterly flow across the northern Plains. Stronger
cyclone attempts to develop in the southern Plains. Across the
northern Plains strong anticyclone reinforces an Arctic Airmass
toward the area. Depending on where forcing sets up, we may see some
convergence toward the end of the week that brings additional
precipitation potential. Ensemble suites are showing low-end
probabilities for detectable precipitation late Thursday into
Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1123 AM CST Mon Dec 1 2025

Poor overall conditions remain blanketed across the TAF sites,
with visibilities often less than 1 mile due to falling snow and
ceilings often around 1kft at the moment. Conditions will
gradually improve over the next few hours, but too will remain
well below VFR until around 00z as back edge of snowfall drifts
eastward. Winds, fortunately, light to variable throughout. VFR
conditions attempt to return overnight, but depending on how the
cloud deck behaves, there is some uncertainty on that exact
time overnight into Tuesday morning.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory until 6 PM CST this evening for
     MOZ001>005-011>014-020>022-028>030-037-043-053.
     Winter Weather Advisory until 9 PM CST this evening for
     MOZ006>008-015>017-023>025-031>033-038>040-044>046-054.
KS...Winter Weather Advisory until 6 PM CST this evening for KSZ025-
     057-060-102>105.

&&

$$

DISCUSSION...Krull
AVIATION...Curtis