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478
FXUS63 KSGF 190900
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
400 AM CDT Thu Sep 19 2024

.KEY MESSAGES...

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- Slight (2 of 5) Risk for severe thunderstorms in extreme SE
  Kansas and portions of Vernon County. Marginal (1 of 5) Risk
  for much of west Missouri. Wind gusts up to 60 mph and hail up
  to the size of half dollars are the main hazards, especially
  along the Missouri-Kansas border.

- Becoming unseasonably warm through the rest of the work week
  with the hottest day on Friday. Some record highs may be
  challenged.

- More widespread rain chances over the weekend (30-75%) with
  the highest chances toward west-central Missouri...and
  additional chances through late next week (10-30%).
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&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
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Issued at 400 AM CDT Thu Sep 19 2024

A wacky upper-level pattern is currently in place across the
CONUS. Water vapor imagery depicts three upper-level lows. One
over the east coast, another over the west coast, and one along
the North Dakota/Canada border. In the middle of all these,
ridging continues to sit over the south-central CONUS, bringing
surface high pressure and fair (but warmer) weather to our
region. To our west, a cold front is stretching from north to
south along the Rocky Mountain front range.

With the ridge continuing to build into our region, lows tonight
into this morning are on track to be slightly warmer in the 60s
(lower 60s in the eastern Ozarks, upper 60s along the MO/KS
border).


Marginal(1 of 5) to Slight(2 of 5) Risk for severe thunderstorms:

Despite upper-level high pressure continuing to build into our
region, the aforementioned surface cold front will push east
through KS during the day. Attending the cold front will be a
weak surface low moving through central KS beneath weak height
falls aloft due to a very subtle mid-level shortwave. These
subtle forcing mechanisms should be enough to produce at least
isolated shower and thunderstorm activity across west MO and
extreme SE KS this afternoon into the late evening hours (15-40%
chance).

As the cold front and subtle surface low progress eastward,
moisture advection will commence, bringing upper 60s dewpoints
across the region. This will supply a corridor of 1000-2000 J/kg
MLCAPE west of Hwy 65 beneath marginal 25-35 kts of 0-6 km bulk
shear. The CAPE/Shear combo will bring the potential for some
severe thunderstorms this afternoon and evening, especially
along the MO/KS border where a Slight (2 of 5) Risk is in place.

While at least isolated showers and thunderstorms are expected
along the MO/KS border, the main uncertainty is storm mode and
evolution, which drives the uncertainty in severe hazard
potential. There are two main scenarios that could play out
today. Each are outlined below:

Scenario 1: The subtle forcing along with NNW`ly mean flow and
shear vectors perpendicular to the N-S cold front could trigger
isolated showers and thunderstorms this afternoon in east KS
that progress SE into west MO before dissipating in the evening
as they escape the favored CAPE/Shear corridor. If these storms
are surface-based, effective shear will be somewhat weaker at
25-35 kts, and hot temperatures will promote a deeper mixed
layer with HREF soundings depicting inverted-Vs in the low
levels. This will promote multicell storms with a primary wind
threat of gusts up to 60 mph. Some small hail up to the size of
quarters would also be possible. If these storms initiate and/or
live past sunset and become elevated, a 30-35 kt nocturnal LLJ
will elongate elevated straight hodographs to 40 kts of
effective shear. This would increase the hail threat to half
dollar size and marginally decrease the wind threat. The 12Z
HRRR, NAM, FV3, and ARW CAMs support this scenario.

Scenario 2: Stronger forcing and shear to the north force
initially discrete supercells around the Kansas City metro this
afternoon. With right-mover motion being to the SSE, the motion
will largely be along the N-S cold front orientation, favoring
cold pool conglomeration. This would produce a SSE propagating
MCS that moves through west MO along the MUCAPE gradient. As
normal with MCSs, the main hazard with this would be wind gusts
up to 60 mph and small sub-severe hail. The 12Z MPAS models
along with the NSSL and NAM favor this scenario. Since these
models generally handle cold pools better, and NW flow pattern
climatology generally favor cold pool driven systems, forecast
intuition points to this scenario being more plausible.
However, trends will need to continue to be monitored through
today to see which scenario becomes favored.

Additional sub-severe shower and thunderstorm redevelopment
looks possible Friday morning across the eastern Ozarks (15-30%
chance).


+Becoming unseasonably warm through the rest of the work week:

With the ridge continuing to build, highs today will be hot in
the middle 90s along the MO/KS border and in the middle 80s
within the eastern Ozarks. After the storms tonight, the
surface cold front will still not fully make it into our region.
This paired with continued large-scale height rises will allow
Friday to be even hotter with highs in the middle 90s around the
Springfield and Branson areas, and in the upper 70s around the
Joplin area. These will be within 2 degrees or so of record
highs.

Additionally, with the highs being well above the 10th percentile
for this time of year and Heat Index values reaching around 100
F, there is a Moderate Heat Risk for around the Joplin area.
Those without effective cooling and adequate hydration,
especially if working outside, are encouraged to be aware and
practice proper heat safety. This is especially true as near
record high nighttime temperatures will provide little heat
relief. Lows Thursday and Friday night will be in the lower 70s.
See the Climate Section below for additional information on
potential challenged records.
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&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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Issued at 400 AM CDT Thu Sep 19 2024

+More widespread rain chances over the weekend (30-75% chance):

The aforementioned cold front will stall out as an E-W oriented
stationary boundary somewhere just north of our CWA Saturday.
With a potent mid- and upper-level shortwave moving through the
Four Corners region, wave amplification across the southern
Plains will keep a consistent flow of moisture northward into
the stationary boundary. This will bring shower and thunderstorm
chances across our region Saturday (20-50%) with higher chances
in our northern counties, closer to the stationary boundary.

The approaching shortwave will also begin to cool off
temperatures with highs Saturday in the middle 80s to middle 90s
and in the lower to middle 80s Sunday. Lows will be go from the
upper 60s Saturday night to the middle 50s to lower 60s Sunday
night.

The shortwave will propagate through the central Plains Sunday
through Monday. Surface cyclogenesis paired with a deepening
surface high pressure to the north will provide ample forcing to
squeeze out precipitation along a lifting warm front. This will
increase rain chances across our area Sunday (35-75%). Once
again, the higher chances will be in our northern counties,
close to the warm front. Much of the higher amounts should stay
north of our CWA, however, early QPF amounts suggest 1-2+ inches
in our far northern counties. Trends will have to continue to be
monitored for exact placement of the warm front and its
associated precipitation and subsequent amounts.

The system will exit the area through Monday, bringing 20-30%
shower and thunderstorm chances east of Highway 65.


+Additional rain chances through late next week (10-30%):

After the system exits, ensembles become widely variable, even
in the upper-level pattern as noted in cluster analysis. The
stark differences in the forecasted pattern next week manifest
as widespread 10-30% chances for rain everyday. This is largely
manifest to timing/location differences in precipitation of each
ensemble. As such, as time draws near, chances for rain will
likely increase for some days, while decreasing for others.
Additional rainfall will likely be seen sometime next week, but
the exact day and location is not yet revealed. Check back for
further updates in later forecasts.


Of additional note, forecasts are trending cooler next week
with highs in the lower to middle 70s and lows in the middle
50s. Though uncertainty in the exact pattern may still change
these forecasts.
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&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1240 AM CDT Thu Sep 19 2024

VFR conditions will prevail through the entire TAF period with
mostly clear skies, save for FEW high clouds and a 6 kft cumulus
field between 18-02Z. S`ly winds will pick up after 15Z to 8-12
kts, with JLN gusting to 20 kts at times.

There is a 30% chance for isolated showers and thunderstorms to
impact JLN after 02Z. Confidence is currently medium-high on
isolated shower and thunderstorm development, but low on timing
and location. Any thunderstorm that is in the vicinity of the
TAF site could produce wind gusts up to 40-50 kts and small
hail.

&&

.CLIMATE...
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Issued at 330 AM CDT Wed Sep 18 2024

Record High Temperatures (Joplin):

September 19:
98 (1954) Forecast: 95

September 20:
99 (1954)       Forecast: 97



Record Highest Minimum Temperatures (Springfield):

September 20:
74 (2018) Forecast: 70

September 21:
73 (1931) Forecast: 71

September 22:
70 (2017) Forecast: 70



Record Lowest Precipitation for Month of September:

Springfield: 0.05" (1928)
September 2024 Thusfar: 0.04"

Joplin: 0.2" (2013)
September 2024 Thusfar: 0.00"
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&&

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

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Price
CLIMATE...Camden