126
FXUS63 KSGF 151040
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
540 AM CDT Sat Jun 15 2024

.KEY MESSAGES...

-  Low-end thunderstorm chances today (15-30%).

-  Heat and humidity will continue through much of next week.

-  Daily chances for isolated showers and thunderstorms (15-30%)
   thanks to the hot and humid air mass.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 400 AM CDT Sat Jun 15 2024

Current water vapor imagery depicts large-scale clockwise flow
over the Plains states with an MCS in KS/Ne ahead of a shortwave
trough ejecting out of CO/NM. The longwave ridge axis creating
the clockwise flow is currently entering MO. At the surface, a
weak boundary is progged just south of the MO/AR border with
E`ly winds north of it across our region. Temperatures are on
track to remain mild into this morning with lows only reaching
into the lower 70s near the MO/AR and MO/KS border and in the
middle to upper 60s toward central MO. Dewpoints are hovering in
the upper 60s and lower 70s in some places, therefore, some
light fog is not out of the question this morning. Some light
fog has already been reported between Mountain Grove and West
Plains in low spots along Highway 60/63.


Heat and humidity continue today:

With the ridge in place and 850 mb temperatures in the 20-22 C
range, high temperatures today will remain hot in the lower 90s.
Heat Indices will reach into the middle to upper 90s as humidity
remains high with dewpoints in the lower 70s. Continue to
exercise caution when being outdoors for extended periods of
time. Take frequent breaks, have methods of cooling available,
and drink plenty of water.


Low-end thunderstorm chances today (15-30%):

The MCS in KS/NE is forecast to weaken as it moves eastward
through the night. CAMs depict much of the remnant precipitation
staying north of our area where the better shear is, however,
there is a very low chance (<15%) that some isolated showers and
thunderstorms could reach into our northern counties early this
morning within the 6-10 AM timeframe. Confidence in this
scenario is currently very low as shear and instability will be
quite minimal and nocturnal inhibition will be well in place.
However, it is not out of the question if sufficient elevated
lift reaches into our region given MUCAPE values at 1000-1500
J/kg.

As the shortwave approaches the area behind the decayed MCS, an
associated surface mass response will begin lifting the
boundary northward as a warm front, reorienting it to NNW-SSE
generally along the MO/KS border. Along this boundary, dewpoints
will be in the low 70s, supplying an axis of 1500-2500 J/kg
MLCAPE west of Hwy 65 as noted by RAP and HREF soundings. This
will be the focus for isolated showers and thunderstorms this
afternoon (15-30% chance). With upper-level support from the
shortwave displaced to the north, convergence along the
boundary will be the main source of lift for these storms. RAP
and HREF suggest a weakly capped environment (0-25 J/kg MLCIN),
so if convergence is strong enough for updrafts to develop, the
resulting thunderstorms will be rather isolated to scattered in
nature.

Although the belt of faster winds associated with the mid-
level shortwave will stay north of the area, 15-25 kts of deep
layer shear will still be available within the region.
Additionally, although it isn`t prime pulse thunderstorm season
just yet, our Ozark Pulse Thunderstorm Index is moderate to high
at 4-7 west of Hwy 65. The Ozarks Pulse Severe Thunderstorm
Index is between 14-18 for the same region. These combined
factors suggest that any storms that do form will be capable of
producing sub-severe to marginally severe hazards including wind
gusts of 30-60 mph and small hail. This is supported by mid-
level lapse rates at 6.5-7 C/km (supportive of small hail) and
inverted-V soundings with low-level lapse rates at 7.5-8 C/km
(supportive of downbursts).

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 400 AM CDT Sat Jun 15 2024

Heat and humidity will continue through next week:

As the longwave ridge slowly progresses eastward, it is forecast
to stall over the eastern CONUS and build substantially,
creating a heat dome across the eastern US. ESATs are continuing
to signal near record high geopotential heights off to our
east. While the center of the upper-level high will not be over
our region, the western fringes of it will still produce enough
subsidence and subsequent adiabatic warming to keep temperatures
high. Additionally, being on the western fringes of the upper-
level high will allow SSW`ly mean flow, keeping a steady supply
of warm and moist air. These factors combined will keep daily
highs in the upper 80s to lower 90s and nightly lows in the
upper 60s to mid-70s.

The hottest days look to be Sunday and Monday with highs in the
lower 90s and lows in the lower to mid-70s. In the extended
range, the NBM is beginning to signal the "excessive heat" that
was messaged in the past few AFDs by the WPC. Forecast highs
Thursday and Friday are reaching into the mid-90s. During this
period, Heat Indices will be in the middle to upper 90s,
reaching near or above 100 F at times. Once again, with the
prolonged nature of this heat and humidity, heat stress will be
a constant hazard. This is backed up by constant lower to middle
80s Wet Bulb Globe Temperatures and a Moderate to Major (level 2
to 3 out of 4) Risk for heat-related impacts. Continue to
exercise caution when being outdoors for extended periods of
time. Take frequent breaks, have methods of cooling available,
and drink plenty of water.

After the 7-day period, heat and humidity is still forecast as
the ridge continues to have a hold over the eastern US. For the
moment, there looks to be no short-term end to the heat and
humidity save for if an isolated thunderstorm impacts your area.


Daily chances for isolated showers and thunderstorms (15-30%):

As previously mentioned, our region will be on the western side
of the building upper-level high next week, producing SW`ly
mean flow. This will create a constant stream of moisture into
our region. ESATs have our area constantly above the 90th
percentile for mean specific humidity and PWATs, and nearing the
99.5th percentile on some days, particularly Tuesday.
Additionally, deterministic models hint at weak tropical
disturbances coming out of the Gulf, rounding the upper-level
high. Even furthermore, with SW`ly mean flow just to our west,
subtle shortwaves from the polar jet may also come near our
region. These disturbances would interact with the hot and
humid air mass, and with the NBM giving 50-80% chances for CAPE
> 500 J/kg each day, there will be daily chances for isolated to
scattered showers and thunderstorms (15-30%).

Sunday will exhibit the lowest chance (<15%), however, with the
shortwave trough still exiting the region Sunday, and some CAMs
such as MPAS portraying isolated showers and thunderstorms,
there is still a low-end risk, generally in the eastern Ozarks.

Monday will exhibit the highest chance (15-35% east of Hwy 65)
as a tropical disturbance coming out of the Gulf advects
positive vorticity into the region. This could provide enough
lift for scattered showers and thunderstorms.

Wednesday will exhibit the most widespread chance (15-30% across
our entire CWA) as an additional wave of positive vorticity
advection coming out of the Gulf meets with a cold front across
the central Plains. Once again, these features could give
enough lift to generate scattered showers and thunderstorms.

After this, models diverge on the westward extent of the ridge
and where each disturbance ejects, however, chances still exist
for showers and storms through Friday (15-25% chances).

In the coming days, each round will become clearer with better
details in forthcoming short-term forecasts.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 540 AM CDT Sat Jun 15 2024

VFR conditions will prevail through the entire TAF period with a
15-30% chance of a brief interruption due to an isolated shower
or thunderstorm between 19-01Z. If a storm were to impact a TAF
site, lightning and modest gusts up to 40 mph will be the main
hazards. Additionally, heavy rainfall will decrease
visibilities. Otherwise, winds will generally be S`ly at 8-12
kts with gusts up to 15-20 kts at times this afternoon. Lastly,
some stratus over JLN and BBG at 4-6 kft should erode through
the next few hours, leaving just FEW to SCT high clouds for the
rest of the period.

&&

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

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Price