115
ACUS01 KWNS 280603
SWODY1
SPC AC 280602

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0102 AM CDT Fri Jun 28 2024

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL PLAINS AND MID MISSOURI VALLEY...

...SUMMARY...
Severe thunderstorms may develop from parts of the central Plains
into parts of the Middle and Upper Mississippi Valley today and
tonight. Large hail, damaging wind, and a few tornadoes will be
possible.

...Synopsis...
An upper trough over the northern Rockies is forecast to intensify
as it moves south and east over the northern Plains and Upper
Midwest. Accompanying the trough, a zone of enhanced mid-level flow
will overspread the northern and central High Plains, reaching the
Great Lakes region by 12z Saturday. At the surface, a mature cyclone
over the Dakotas will slowly fill through the day as it moves east
along the international border. A cold front will trail the cyclone
to the southwest, intersecting a secondary low over central KS. Rich
low-level moisture and QG ascent from the advancing upper-level wave
will support scattered severe thunderstorms over several areas of
central CONUS near the front this afternoon and evening.

...Mid MO Valley and Midwest...
Early in the period, widespread convection is expected to be ongoing
across parts of the upper Midwest and western Great Lakes associated
with overnight mid-level warm advection. This should result in a
broad area of remnant cloud cover and delayed diurnal heating across
parts of northern IA, IL, MN and WI. However, rich low-level
moisture ahead of the approaching cold front may support at least
modest destabilization through the day in the wake of the earlier
storms. While it is uncertain if sufficient destabilization can
support organized storms, 35-45 kt of deep-layer shear would allow
for clusters or transient supercells capable of damaging gusts, if
more robust convection evolves.

To the southwest, substantial heating is likely over the southern
and central Plains near the secondary surface low in KS. A warm
front will lift north into eastern KS and western MO, with rich
boundary-layer moisture (70s surface dewpoints) supporting MLCAPE of
2500-3500 J/kg by late this afternoon. Though forcing for ascent
will not be overly strong, robust heating and surface convergence
near the low will support isolated to scattered thunderstorm
development across north-central KS, and along the cold front in
eastern NE by mid to late afternoon. Veering wind profiles with
height near the low will support semi-discrete supercells across the
mid MO Valley. Backed surface winds, rich low-level moisture and
plentiful low-level vorticity/CAPE near the triple point may create
a favored mesoscale corridor for a few tornadoes from northeast KS,
into northwest MO, and southern IA/NE. While some hail is also
possible, given the potential for rotating storms, thermodynamic
profiles are not overly favorable, with only modest mid-level lapse
rates and large water loading.

The initial semi-discrete convection should gradually grow upscale
into clusters or a small MCS, moving east/southeast across parts of
the Mid MO Valley this evening. Damaging winds and a QLCS tornado
will be possible. Storms should begin to weaken overnight as they
encounter progressively more stable conditions across
central/eastern MO and western IL.

...Central Rockies/High Plains...
As the upper trough and surface low advance eastward across the
northern Plains, the trailing cold front will weaken as it moves
south through the central Rockies and adjacent High Plains. Behind
the front, weak upslope flow will develop with east/northeast
surface winds through the early afternoon. Subtle ascent from the
departing trough, along with diurnal heating of the moist
post-frontal air mass, will support scattered thunderstorm
development over northern/eastern CO, western SD and southeast WY.
Moderate mid-level flow behind the trough will favor straight, but
elongated hodographs favorable for organized clusters and
supercells. Steepening low and mid-level lapse rates, and forecast
MLCAPE of 1000-1500 J/kg will allow for isolated to widely scattered
severe storms to evolve with a risk for damaging winds and hail
across portions of the central High Plains. Significant hail of
2-2.5 inches and damaging gusts greater than 70 mph may also occur
with the more organized storms.

..Lyons/Squitieri.. 06/28/2024

$$