208
ACUS01 KWNS 240600
SWODY1
SPC AC 240558

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Mon Jun 24 2024

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
MIDWEST TO THE CENTRAL PLAINS....

...SUMMARY...
Scattered severe thunderstorms will be possible over parts of the
Upper Midwest, this afternoon and continuing overnight. A cluster of
severe storms potentially capable of producing destructive wind
gusts may develop over parts of Minnesota into Wisconsin though
there remains significant uncertainty.

...Upper Midwest to the central Plains...
A broad upper low with several embedded vort maxima and moderate
west/southwestern flow over the Canadian prairies is forecast to
move eastward and consolidate across portions of the Upper Midwest
this afternoon and evening. Weak ascent will overspread a developing
surface low and warm front lifting into the eastern Dakotas and
western MN. Rich boundary-layer moisture (low 70s F surface
dewpoints) is forecast to surge northward from the central Plains
into the lower Red River Valley. Very warm temperatures (at the
surface and aloft), steep mid-level lapse rates, and the returning
moisture will prime an extremely unstable, but strongly capped
troposphere, potentially supportive of all hazards.

Multiple convective scenarios appear possible from late this
afternoon through the overnight. Isolated surface-based
thunderstorms may develop along the occluded front in eastern ND or
near the triple point/warm front across northeast SD and western MN.
While uncertain given the large inhibition, any storms that do form
will likely organize into supercells given strong veering wind
profiles and the very large buoyancy (MLCAPE >4000 J/kg). Large to
very large hail, damaging winds and perhaps a tornado would be
possible with any supercells, especially near the warm front with
backed surface winds. Some CAM guidance suggests a cluster of storms
could then track southeast along the warm front, potentially growing
upscale into an MCS, with a damaging wind and hail risk into the
overnight hours across the western Great Lakes.

A second, potentially more significant, scenario may evolve if
convection remains suppressed through the afternoon and instead
develops along the southeastward surging cold front over the eastern
Dakotas and western MN, or elevated storms intensify north of the
warm front. With the 4000-5000 J/kg of MUCAPE present, rapid upscale
growth into a damaging MCS/bow echo could result in the risk for
widespread severe winds. This scenario remains highly uncertain
given the warm temperatures aloft and unpredictable mesoscale storm
interactions, but is reflected in several hi-res model solutions and
by general pattern recognition. Should this occur, a swath of
significant damaging winds may evolve along or just north of the
buoyancy gradient across southern MN, southern/central WI and into
portions of northern IL by 12z Tues. Considered an upgrade to
level-3 Enhanced but uncertainty in storm development and evolution
remains too high.

...Central Plains and Black Hills...
Very warm surface temperatures are expected ahead of the weakening
cold front across central NE and northern KS. Deeply mixed profiles
may overcome very warm H7 temperatures to support widely scattered
high-based storms. With generally weak mid-level flow across the
region, storms may quickly become outflow dominant, but steep
tropospheric lapse rates will support isolated severe gusts. The
strongest updrafts may also be capable of producing some hail.

High-based storms are also possible over the Black Hills where weak
upslope flow is occurring behind the front. Limited moisture and
only glancing upper-level support suggest storm coverage will remain
isolated. Still, the deeply mixed air mass could support damaging
gusts with any sustained storms.

...Carolinas...
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 along a weak
surface cold front. Enhanced flow aloft and surface convergence near
the front should be sufficient for transient storm organization into
multi-cell 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.

..Lyons/Wendt.. 06/24/2024

$$