St. Joseph, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

175
FXUS63 KEAX 122305
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
605 PM CDT Mon May 12 2025

.KEY MESSAGES...

- Temperatures Continue to Warm

- Isolated Rain Chances Thursday Northern Missouri

- Rain/Storm Activity Saturday Into Sunday; Pattern Remains Uncertain

&&

.DISCUSSION...
Issued at 340 PM CDT Mon May 12 2025

Axis of deep H5 trough is moving inland in the western CONUS which
has provided increased flow to at least move the northern ridge axis
which had been a part of the Rex Block pattern over the past few
days. That ridge axis has now made it into the Northern Great Lakes
Region. The mid-level closed-low has shifted northward as a
secondary mid-level ridge axis expands across southern High Plains.
This mid-level low over the Gulf region though has moved a bit
further eastward than was progged in model guidance a couple of days
ago. As a result, the better lift associated with this has also
shifted east, keeping most of the light rain shower activity east of
Hwy. 63. Mid and upper-level moisture has worked around the low to
the back side, placing some cloud cover in our southeastern CWA.
Boundary layer destabilization today did help generate a few cumulus
clouds, but moisture return has still been slow to start across our
area. We did also see some mixing that has created wind gusts
between 15-20 MPH this afternoon. For the remainder of the evening,
weak dCVA will continue east of Interstate 35, with strongest lift
remaining well east of Hwy. 63. Will maintain slight chance (15 to
20 percent) for rain in our eastern counties along Hwy. 63, but the
better chances will push off into eastern Missouri. If the cloud
cover this afternoon breaks apart overnight and allows for stronger
radiational cooling, there may eventually be enough moisture
available in our eastern and southeastern counties where patchy fog
could develop. High resolution guidance has been spotty on
developing this, but under the right clearing conditions could
occur.

Tuesday, west coast trough continues to dig and propagate toward the
Intermountain West while area of stronger dCVA promotes lift and
surface cyclogenesis across the Front Range. This creates a southerly
response in flow below 850mb across much of the Plains, increasing
the WAA as far east as the lower Missouri River Valley. While the
stronger WAA axis remains over Central Kansas, there should be
enough to allow subtle H5 height rises to expand into our western
counties through the day on Tuesday, keeping conditions for the
western half our of area dry. The closed mid-level low slowly
continues to move eastward, but there is some weak vorticity capable
of promoting lift primarily along Hwy. 63 and eastward. Synoptic
scale models and ensembles have maintained low-end probabilities for
light rain shower activity Tuesday afternoon for our far eastern
counties. However, CAMs since 12z this morning have been dry, and
blended guidance solutions as a result have been decreasing rain
chances over their past few runs. With the mid-level low still in
place and promoting weak lift, will continue slight chance for rain
showers along Hwy. 63 on Tuesday afternoon. If rain showers do not
develop, still expecting cloud cover to increase for areas east of
Interstate 35, and may be able to expand westward. If there is
enough breaks in the cloud cover our western areas including the KC
metro, expecting temperatures in the mid 80s Tuesday afternoon,
while areas from central Missouri eastward should be cooler with
highs in the upper 70s. Along the Kansas-Missouri stateline,
temperature inner-quartile values are generally between 82F and 86F,
while in central Missouri spread is greater due to differences in
cloud cover projections, then further east where overcast skies are
highly confident, temperatures are clustered around 77F and 79F.
Wednesday western trough axis crosses through the Intermountain West
and deepens surface cyclone across the Plains. This should be the
final push to move the mid-level low well east of the Mississippi
River Valley. Stronger WAA axis pushes into our area and helps
amplify an H5 ridge axis. While theta-e advection may increase, the
subsidence associated with the AVA regime will keep conditions dry.
Clear conditions in our western counties should promote a decent
amount of mixing, achieving temperatures in the upper 80s, and
potential to cross above 90F. East of Interstate 35 for Wednesday,
temperatures stay in the mid to upper 80s. Thursday, trough crosses
through the Rockies, and closes off further north while a vort max
begins to lift northeastward across the Central Plains. This is
currently set to track the surface cyclone west and northwest of our
forecast area. We may see some weak convergence with surface
pressure falls, but better kinematics stretch from central Kansas to
eastern Nebraska and central Iowa. We may see some light activity in
far northern Missouri. GEFS and other ensemble suites generally hold
a less than 20 percent chance for measurable rain though, so far now
will keep slight chance POPs right along the Iowa border for
Wednesday.

Friday through the remainder of the weekend, the pattern evolution
remains uncertain. This appears to still be tied to how quickly the
trough begins to lift, along with secondary short-wave trough that
ejects out of the southern Plains. There will likely be a deeper
surface cyclone either in the Northern Plains or Midwest Region,
that could extend surface troughing or push a cold front through the
area Friday into Saturday. Some ensemble members develop a weak
surface cyclone across the southern Plains and into the Ozarks
region that could also bring active weather. At least for now
amongst deterministic solutions, the better instability and support
is either well north of the area or just southward on Friday through
most of Saturday. It is not until later Saturday into Sunday when a
stronger vort maxima ejects and better forcing brings more activity
to the area. 12z ensemble runs this morning have been painting
higher probabilities for rainfall late Saturday through most of
Sunday. If we see better forcing and strong theta-e advection, we
could see stronger to severe storms over the weekend. Looking beyond
the weekend into next week, ensemble probabilities are favoring
multiple waves moving across the area with fairly efficient QPF.
Therefore, anticipating an active pattern for next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 603 PM CDT Mon May 12 2025

Sub IFR conditions are possible overnight tonight as low lying
fog develops overnight. This fog is most likely east of highway
65, so no mention in the terminals at this time. Fog to lift mid
morning, with scattered cumulus ~3-4K feet agl developing
throughout the day. Southeast winds prevail through the period.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...None.
KS...None.

&&

$$

DISCUSSION...Krull
AVIATION...BT