822
ACUS01 KWNS 241302
SWODY1
SPC AC 241300

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 AM CDT Mon Jun 24 2024

Valid 241300Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
MIDWEST...

...SUMMARY...
Scattered severe thunderstorms are expected over parts of the Upper
Midwest this afternoon into tonight. Storms will be capable of large
hail, and a cluster potentially capable of destructive wind gusts
could develop over parts of Minnesota into Wisconsin.

...Upper Midwest...
A mid-level trough will continue to transition eastward and modestly
amplify over the Canadian Prairies, with southern-peripheral height
falls and strengthening westerlies from North Dakota/northern
Minnesota toward the Upper Great Lakes through tonight. In this same
corridor, a weak MCV may be evolving this morning over eastern North
Dakota/northwest Minnesota, while these scattered thunderstorms will
probably also influence and somewhat hinder the effective
north-northeastward of a warm front later today across Minnesota and
Wisconsin.

A very moist (low 70s F dewpoints) and unstable air mass will
otherwise develop northeastward regionally in tandem with the warm
front as surface cyclogenesis occurs across the Siouxland and
southern Minnesota through evening. Upwards of 3000-5000 J/kg MLCAPE
is expected within the warm sector, with very warm mid-level
temperatures associated with the elevated mixed-layer plume likely
limiting warm sector development away from (south of) the immediate
triple point and cold front/warm front vicinity.

Multiple convective scenarios are possible late this afternoon
through tonight. For one, as the air mass recovers from the early
day storms, widely scattered surface-based thunderstorms may develop
by late afternoon near the eastward-advancing cold front within the
relatively narrow warm sector from far eastern North Dakota into
northern/western Minnesota. Any storms that do develop will likely
organize into supercells given strong wind profiles and the large
buoyancy. Large to very large hail, damaging winds and perhaps a
tornado would be possible with any supercells, especially with
storms in proximity to the warm front.

Additionally, on the southern fringe of the early scattered early
day convection (and related cloud cover) from eastern North Dakota
into northern Minnesota, storms may form near an effective triple
point/differential heating reinforced warm front. Such initial
development could occur across south-central/southeast Minnesota,
with robust instability/seasonally strong shear potentially
supportive of an initial mode of intense supercells, with subsequent
upscale growth in an MCS with heightened damaging wind potential.

Additional mostly elevated storms could form tonight from eastern
Minnesota into northern/central Wisconsin, on the immediate cool
side of the surface baroclinic gradient as a nocturnally
increasingly low-level jet heightens isentropic ascent. These storms
may also pose a large hail and damaging wind risk through the
overnight.

An upgrade to Enhanced Risk (Level 3/5) may be warranted pending
morning observational/guidance trends, potentially including a
corridor across south-central/southern Minnesota and west/southwest
Wisconsin, where a semi-focused swath of potentially significant
damaging winds appears plausible.

...Central Plains and Black Hills...
Very warm surface temperatures are expected ahead of the weakening
cold front across central Nebraska and northern Kansas. At least
isolated high-based storms are expected to develop within a
hot/deeply mixed boundary layer environment. With generally weak
mid-level flow across the region, storms may quickly become outflow
dominant, but steep low/mid-tropospheric lapse rates will support
isolated severe wind gusts. The strongest updrafts may also be
capable of producing some hail.

Other potentially severe storms will also be possible over the Black
Hills/northeast Wyoming with weak low-level upslope flow in the
post-frontal environment. Modest low-level moisture and only
glancing upper-level support suggest storm coverage will remain
isolated, although severe hail/strong winds will be possible.

...Carolinas and far southeast Virginia...
At the base of departing east coast trough, subtle height falls atop
a warm and unstable air mass will support scattered afternoon
thunderstorms across much of the eastern Carolinas and far southeast
Virginia along a weak surface cold front. Enhanced flow aloft and
surface convergence near the front should be sufficient for
transient storm organization into multicell clusters or a weak
supercell. Steepening low-level lapse rates and the high PWAT air
mass will favor heavily water and hail-loaded downdrafts capable of
isolated damaging gusts. Storms should begin to move offshore by
early evening ending the severe risk.

..Guyer/Mosier.. 06/24/2024

$$