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000
ACUS01 KWNS 160539
SWODY1
SPC AC 160538

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1238 AM CDT Tue Apr 16 2024

Valid 161200Z - 171200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MIDWEST...

...SUMMARY...
Scattered severe thunderstorms are likely today, centered mostly
over the midwestern states of northern Missouri/Iowa/northwestern
Illinois. Hail, wind, and tornadoes are expected in this corridor.
More isolated activity could develop as far south as the Ozarks of
northern Arkansas.

...Midwest...

Upper low is currently located over southeast CO, and will soon
begin ejecting northeast in line with latest model guidance into the
central Plains. By 18z this feature should advance into eastern NE
as 90kt 500mb speed max translates through the base of the trough,
across northern OK, into northwestern MO. In response to this
dynamic system, strong LLJ will focus across the eastern Plains
early then shift into the mid/upper MS Valley by 18z.

Low-level warm advection is expected to prove instrumental in
early-day convection, in association with the LLJ. This activity
should be ongoing at the start of the period, focused over the
mid-MO Valley. Subsequent movement/development is expected
downstream across IA/southern MN as the warm conveyor shifts east.
While strong shear will support this convection, the primary concern
will be with secondary development in association with a pronounced
mid-level dry slot. Latest model guidance suggests surface-3km lapse
rates will steepen to near 9 C/km across southeast NE/northeast KS
by 18z. Leading edge of this steeper lapse-rate plume will advance
across western IA, immediately ahead of the surface low. As a
result, boundary-layer heating will contribute to substantial
buoyancy and some areas may experience MLCAPE near 2000 J/kg.
Surface-based parcels are forecast to be uninhibited by 17-18z
across western IA. Current thinking is scattered convection should
develop within this zone of destabilization then spread northeast.
Surface warm front is expected to serve as a northern limit to
surface-based convection, along with any appreciable tornado risk.
Large hail can be expected with supercells, and favorable shear will
support the potential for tornadoes, a few potentially strong. This
activity will spread across IA/extreme northern MO into northwestern
IL during the evening.

Farther south into the Ozarks, severe threat is much more
conditional. Forecast soundings exhibit poor lapse rates and at
least weak inhibition through much of the period. It`s not real
clear how robust updrafts will be, despite the strong shear, given
the marginal lapse-rate environment. Will maintain SLGT Risk into
this portion of the lower MS Valley but convection may struggle much
of the period.

..Darrow/Lyons.. 04/16/2024

$$