425
FXUS63 KSGF 162331
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
631 PM CDT Fri Aug 16 2024

.KEY MESSAGES...

- Slight (2 out of 5) risk for severe thunderstorms this
  evening through tonight, mainly over far SE KS and far SW MO.
  Damaging wind up to 60-70 mph, large hail up to golf ball
  size, and localized flooding are the main severe weather
  risks.

- Heat Index values up to 95-105 F remain a hazard today and
  Saturday, especially along the Missouri-Arkansas and Missouri-
  Oklahoma/Kansas borders.

- 15-30% chance for showers and thunderstorms Saturday evening
  and through the night. Large hail and damaging winds are the
  main threats. Additional non-severe storm chances Sunday night
  (20-40%).

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 325 PM CDT Fri Aug 16 2024

A belt of W`ly upper-level flow is currently setup across the
central CONUS with broad (but rather low-amplitude) ridging
across the western CONUS and a trough dropping SE through the
north part of the Midwest. Between these features, a localized 40-50
kt mid-level jet is spread across NE KS/N MO. At the surface, an
E-W stationary boundary is progged across south-central KS and
MO. Elevated showers and thunderstorms are along and north of
this boundary in central KS, moving east. These have been slowly
dissipating as they move east, but dropping outflow boundaries
in their wake. These features will be the focus for additional
thunderstorm development, with some possibly being severe,
across SW MO this evening into tonight.


Slight risk of severe thunderstorms this evening through tonight:

A lone sub-severe storm along with some other showers are
currently tracking through SE KS. An SPC discussion is out for
this cell, highlighting the possibility for its outflow to
generate new convection within a weakly capped environment
characterized by 1000-2000 J/kg MLCAPE and 40-45 kts of
effective 0-6 km bulk shear. A 40% chance is given for a severe
thunderstorm watch just west of our CWA. If this scenario pans
out, isolated severe storms may enter into extreme SE KS and
extreme SW MO, however, the main chance for higher coverage of
thunderstorms in our region will be later this evening into
tonight.

As the aforementioned trough drops to the SE this evening, flow
aloft will increase and become NW`ly. Synoptic-scale ascent
will overspread SW MO along with this feature. A 25-30 kt
nocturnal LLJ will simultaneously develop and overspread the
stationary boundary draped across the region. Moisture
advection from the LLJ and convergence along the boundary, aided
by large- scale ascent, will force numerous showers and
thunderstorms across SW MO and SE KS (60-80% chance), especially
after 9 PM when the nocturnal LLJ begins intensifying. Isolated
to scattered thunderstorms are still possible (30-40% chance)
before this timeframe (generally in the 6-9 PM timeframe along a
line from Osceola to West Plains and westward), but the highest
coverage will be across the Joplin to Branson area between 12-5
AM tonight where a Slight (2 out of 5) risk is currently
situated.

These storms will largely be elevated with supercells supported,
especially with the storms after 9 PM. HREF mean model
soundings depict larger dewpoint depressions near the surface
above the nocturnal inversion, with ample dry air aloft above
the moist layer. This should favor downbursts with damaging wind
gusts up to 60-70 mph. Additionally, despite largely curved
hodographs in the low-levels overnight with the LLJ, the
elevated storms will effectively create longer and straight
hodographs with 40-60 kts effective bulk shear. This, along with
1000-2000 J/kg MUCAPE largely in the hail-growth zone, and
modest lapse rates at 6-7 C/km, large hail up to the size of
golf balls are also possible with any supercell. Lastly, the
NW`ly flow will largely be parallel to the boundary, so as long
as forcing stays consistent, storms will likely train, bringing
localized flash flooding as another hazard. Areas with storms
will see 1-2" of rain with localized areas up to 3-6". Storms
should be out of the area by 5-8 AM.


Heat Index values up to 100-105 F today and Saturday:

Current obs have temperatures in the lower 90s across the area.
Dewpoints in the lower 70s are contributing to Heat Index values
in the 100-105 range (currently at 100 F in Springfield and 102
F in Joplin). While a Heat Advisory is not issued, heat is still
a hazard given localized areas having values flirting with the
105 F threshold. The same situation will occur Saturday as highs
creep into lower to middle 90s. Heat Index values along the
MO/AR and MO/KS/OK borders are forecast to be near or above 105
F, but given only localized pockets reaching above 105 F along
with uncertainty from leftover cloud cover from storms tonight,
have held off on issuing a Heat Advisory for Saturday.
Nevertheless, heat will still be a hazard and everyone should be
aware of the associated risks and preparedness.

Lows will also be somewhat mild in the middle 60s to lower 70s
tonight and tomorrow night, with the warmer temperatures to the
south.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 325 PM CDT Fri Aug 16 2024

15-30% chance for showers and thunderstorms Saturday night:

With the stationary boundary setting up just to our south and
west, and the nose of a 25-30 kt LLJ revving up during the
overnight hours again, there is a low-end chance (15-30%) for
showers and thunderstorms Saturday night over southern MO. The
main uncertainty is whether forcing along the front will be
enough to overcome right-exit region subsidence aloft.
Currently, all CAMs keep us dry except for the RAP/HRRR, so will
need to monitor trends closely. However, if storms do form, RAP
model soundings support a very conditional threat for very large
hail as mid-level lapse rates are at 7-9 C/km, MUCAPE at
2500-3500 J/kg, and effective bulk shear at 50-70 kts. Damaging
wind gusts up to 60 mph will also be possible. These threats
are on the lower end of the risk spectrum (2-5%).


Additional non-severe storm chances Sunday night (20-40%):

As mentioned in previous, with the NW flow pattern in place, any
source of lift across the surface stationary boundary to our
south and west could force showers and thunderstorms, especially
overnight as the overlapping LLJ intensifies. As such, chances
are on the increase for showers and thunderstorms Sunday night,
west of Springfield. At the moment, severe weather is not
anticipated.

After Sunday night, more rounds of nocturnal thunderstorms are
possible, yet chances dwindle as high pressure strengthens
across the area and the front drops further to the south along
with a sagging trough to our east. This will bring calm weather
next week with highs down into the lower to middle 80s with
lows in the mid-50s to mid-60s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 630 PM CDT Fri Aug 16 2024

Convection has developed across far northwestern Arkansas and
also across central to southeastern Kansas early this evening.
The convection across Arkansas should mainly remain south of the
area. The showers and thunderstorms in southeastern Kansas will
continue to move southeast and move across extreme southeastern
Kansas and southwestern Missouri this evening. Gusty winds,
brief heavy rainfall will occur with the storms. This activity
will likely impact the TAF sites this evening.

Shower and storms will likely continue to develop across
portions so northeastern Oklahoma/southeastern
Kansas/northwestern Arkansas/far southwestern Missouri
overnight. This activity could impact the TAF sites overnight
into early Saturday morning, but questions still remain how far
north this activity overnight develops and if it affects the TAF
sites. As this evenings storms could produce an outflow south of
the area which could be the focus for storms tonight.

Outside the storms VFR conditions are expected through the rest
of the TAF period.



&&

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

&&

$$

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