546
FXUS63 KSGF 022030
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
330 PM CDT Tue Sep 2 2025

.KEY MESSAGES...

- There`s a 20-40% chance for rain to occur again this afternoon
  mainly for areas along/south of I-44 and along/west of I-49.
  Rainfall amounts remain light <0.25".

- Higher chance for thunderstorms (50-70%) along and north of
  Interstate 44 Wednesday afternoon and into the night. Some of
  these storms may be strong to severe as a Slight/Marginal
  risk for severe weather has been issued for that area.

- Strong cold front moves through Wednesday night bringing
  cooler than normal temperatures for Thursday. Another front
  moves through on Friday bringing another round of rain (30-60%)
  throughout the day and cooler temperatures in the 70s for the
  weekend and next week.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 330 PM CDT Tue Sep 2 2025

Current water vapor imagery depicts the stubborn longwave bowl
trough over the east CONUS, with many different smaller swirlies
progressing through the flow. One of these swirlies is evident
on imagery, diving south through the corners of NE/MO/KS. Ahead
of the wave, a very weak surface low pressure is positioned over
NE OK, bringing light and variable winds to our area. Surface
temperatures heating up into the upper 70s to lower 80s have
allowed for a puffy cumulus field to develop, generally along
and south of I-44, then west of I-49 where a moisture gradient
pivots northward along that interstate. Some very small isolated
showers have already developed in this region.


20-40% chance of showers and maybe some thunder this afternoon:

The semi-warm temperatures along with an axis of greater
moisture along and west of I-49 has generated some weak 250-750
J/kg MLCAPE west of Hwy 65. Based on RAP/HRRR forecast
soundings, these CAPE profiles are quite skinny. A warm nose
capping inversion is also noted at around 500 mb. As the wave to
our north continues to dive into our area, enough forcing will
be available for the CAPE to manifest in the form of isolated to
scattered showers. Indeed, a few showers are already noted south
of I-44 and west of I-49. Lightning chances are lower (the REFS
gives a 5-15% chance), likely due to the mid-level capping
inversion which could keep showers shallower below -10 C.
Though, any cell that can take advantage of the whole profile
could produce some lightning and heavier rain. All in all,
severe weather is not expected, and rainfall amounts will be
isolated and rather light less than 0.25-0.5". These are then
expected to dissipate after sunset. Temperatures tonight will
then be in the upper 50s to lower 60s.


Marginal (1 of 5) Risk for severe storms Wednesday into the night:

Within the larger longwave pattern, a very potent and dynamic
jet streak/shortwave for August`s standards (>99.5th percentile
jet speeds) is progged to surge southward into the Midwest
states Wednesday. The strong dynamics will bring with it a
strong cold front that will plow through some residual moisture
across the Midwest states. The residual moisture will be enough
to generate 1000-2000 J/kg MUCAPE across northern MO into
central KS, diminishing to 500-1000 J/kg across our area.
Nevertheless, this will be enough for thunderstorms to develop
along the front Wednesday afternoon, which are progged to dive
south into our area, mainly north of I-44, during the late
afternoon into the early overnight hours (50-70% chance).

With the wind speeds within the trough, wind shear will also
increase along and ahead of the front, with 0-6 km bulk shear
at 25-30 kts during the afternoon, increasing to 30-40 kts
overnight. The introduction of shear will allow for for the
chance for isolated severe thunderstorms with a Marginal (1 of
5) Risk for much of our area, and a Slight (2 of 5) Risk
clipping the corners of Bourbon, Vernon, St. Clair, and Benton
Counties.

Despite being only a day out, there is some distinct differences
in CAMs on the evolution of thunderstorms and the attending
severe threat. A bimodal timing setup is in place. This means
there`s two (well, three) scenarios. The HRW models have
thunderstorms developing along the surface cold front Wednesday
afternoon, impacting counties north of I-44 Wednesday afternoon
into the early evening. This outcome is a little uncertain since
upper-level support is forecast to be well north of the front
for the afternoon, and with CAPE profiles rather skinny, deep
convection may struggle to develop. On the other hand, the
HRRR/NAM/RRFS models have elevated thunderstorms developing
along the 850 mb front when ascent aloft increases, impacting
counties north of I-44 during the Wednesday evening and early
overnight hours. The (kind of) third scenario is that some of
the HRW models depict both storms along the surface front in the
afternoon, and storms later in the evening along the 850 mb
front, so two rounds. The fact that most models depict storms
later in the evening owes credence to that scenario being most
likely, especially with upper-level support increasing
overnight. The overnight scenario, however, may decrease severe
threat potential in our area due to instability diminishing
rather quickly toward the late evening.

In terms of hazards, large hail up to nickels to quarters
appears to be the primary threat due to the somewhat elevated
nature of the storms, especially if the after sunset scenario
pans out. 30+ kts of bulk shear, and fast storm motions amid
weak inflow-layer CAPE could lead to some elevated large-hail
producing storms. Damaging wind gusts up to 60 mph become the
secondary threat, especially if the afternoon scenario pans out.
Strong mean-layer wind and shear would be enough for some strong
downbursts, especially if a complex evolves as some CAMs
suggest.


&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 330 PM CDT Tue Sep 2 2025

Series of cold fronts bring back cooler than normal temperatures:

Following the cold front Thursday night, temperatures will
slightly drop to the middle 70s to lower 80s (warmer to the
south). As the dynamic upper-level bowl trough continues to
settle in to the north, another cold front will drop through
Friday. Following this cold front, cooler than normal
temperatures will filter in and sit here for an extended period
of time as the longwave pattern struggles to fall apart. This
will bring highs in the lower to middle 70s and lows in the
50s through the beginning of next week.


Front Friday into Friday night bring 30-60% rain chances:

The aforementioned secondary front should also bring chances for
rain. The nature of the timing, intensity, and location of the
rain is still uncertain, though. This is due to quite a bit of
ensemble spread despite it being 3 days out. Ensemble cluster
analysis reveals two scenarios with two sub-scenarios, each with
an equal chance of occurring. Approximately 50% of the models
keep our area mostly dry save for some light sprinkles that move
through with the front. The other 50% of the models bring rain
to the area. Half of the rain-making models portray a quick
progression of the shortwave trough and surface cold front,
keeping the heavier rain either south of our area or just along
our southern CWA border. The other half portray a slower
trough/front progression, bringing decent rains to our area (QPF
clusters show a swath of 1-1.5 inches), particularly south of
I-44. Interestingly, there isn`t really any ensemble
differences here. All the differences are made up of equal
weight from the GEFS/ENS/GEPS.

So, in other words, there`s a 50% chance of sprinkles Friday
into Friday night, a 25% chance of sprinkles into some more
appreciable rain right along the southern MO border, and a 25%
chance of greater rain accumulation along and south of I-44.
We`ll have to wait and see which scenario becomes favored.


Additional rain chances amid cooler temperatures next week:

Differences in the details of the pattern increase as we go out
into the beginning of next week, however there are hints of
another shallow shortwave allowing for southerly flow and return
of moisture which may allow for some daily rain chances next
week. Currently, there is a 15-30% chance of precipitation,
mainly west of Hwy 65, early next week.


&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1240 PM CDT Tue Sep 2 2025

Light and variable winds are expected to continue through 14Z as
a weak low pressure system traverses the TAF sites. Within the
low pressure area, some isolated to scattered showers are
possible around the sites between 19-01Z, especially around SGF
and BBG. Current short-term guidance only gives a 10-20% chance
of lightning with any given convective shower, therefore have
precluded any thunder mention in the TAFs.

Otherwise, there is a low-end chance for lowered cigs/patchy fog
at BBG between 09-13Z, though confidence is currently too low
to include in the TAF at this time.

Winds will settle out of the west by 14Z, increasing to 5-10 kts
by the end of the period.


&&

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

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Price
CLIMATE...Burchfield