Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0736 AM CDT Sat Jun 21 2025
Valid 211300Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
MICHIGAN AS WELL AS NORTHERN NEW YORK...
...SUMMARY...
Thunderstorms associated with marginally severe wind gusts and hail
will be possible today from Michigan into the Lower Great Lakes
region. Isolated severe storms could also occur across the northern
High Plains and Middle Missouri Valley.
...Great Lakes...
Outflow and remnant convection from last night's severe MCS over the
northern Plains and Upper Midwest is currently moving over Upper MI
and northern MI, while the vorticity maximum is moving through far
northwestern Ontario. General expectation is for the vorticity
maximum to continue eastward through central Ontario and southern
Quebec, with some ascent associated with this system glancing the
Lower Great Lakes region tonight. The low-level jet is expected to
persist, helping to maintain an isolated severe potential with the
activity ongoing on the Upper Great Lakes region for the next few
hours. There is some chance the reintensification occurs along the
outflow later this morning across Lower MI where daytime heating
will contribute to strengthening buoyancy. A Slight Risk was
maintain for this scenario, although warm low/mid-level temperatures
and resultant capping cast doubt to its viability.
Farther east across the Lower Great Lakes region, a few late
afternoon storms are possible as the convection currently over Lower
MI reaches the region. Limited buoyancy should keep any severe
threat with these storm isolated. Additionally, as previously
mentioned, some ascent should glance the Lower Great Lakes vicinity
late tonight/early tomorrow. Forecast soundings depict moderately
steep mid-level lapse rates and unidirectional wind profiles
supportive of a few strong to severe storms.
...Eastern MT into Western ND...
A few elevated storms are currently ongoing across eastern MT,
within a region of strong large-scale ascent ahead of an approaching
shortwave trough. These isolated storms will likely persist this
morning, with a few additional storms possible later this afternoon.
Instability will be modest, limited in the overall severe potential,
but strong shear will support organization within an updrafts than
can mature. Isolated hail and/or damaging gusts are the primary
severe risk.
...Central NE/SD/ND into the Upper Midwest...
Surface low currently over central SD is expected to drift slowly
eastward throughout the day, with notable low-level moisture
advection across throughout the warm sector east of this low. This
will allow the airmass to recover from the overnight MCS while also
contributing to a sharpening warm-frontal zone. Strong to extreme
buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by
this evening along this warm front from the ND/SD border vicinity
eastward through central MN into northern WI. Some low-level
convergence is anticipated in this region, but height rises are
anticipated within the large-scale environment. Additionally, warm
mid-level temperatures (i.e. 16 to 17 deg C at 700 mb) are expected,
capping the airmass to deep convection. Given these factors and the
lack of convection within any of the convection-allow guidance, the
Marginal Risk was removed from the majority of the region. The only
exception was from central NE into southeast SD and far southwest MN
where some late night elevated storms capable of hail are possible.
..Mosier/Leitman.. 06/21/2025
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