SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0121 AM CDT Fri Jul 11 2025
Valid 111200Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING ACROSS PARTS OF NORTHEASTERN KANSAS...MUCH OF NORTHERN
MISSOURI...SOUTHEASTERN IOWA...NORTHERN ILLINOIS...ADJACENT SOUTHERN
WISCONSIN AND NORTHWESTERN INDIANA...AND PARTS OF SOUTHWESTERN LOWER
MICHIGAN...
CORRECTED FOR TYPOS
...SUMMARY...
Strong thunderstorms are likely to impact a corridor from the lower
Missouri Valley into southern portions of the Great Lakes region
this afternoon and evening, accompanied by a risk for damaging wind
gusts, a few tornadoes and some hail.
...Discussion...
While mid/upper ridging across the subtropical into southern
mid-latitudes remains at least a bit suppressed for the time of
year, models indicate that the stronger westerlies will remain
confined to the higher latitudes. It does appear that one notable
short wave trough, now digging to the lee of the Canadian and
northern U.S. Rockies, will progress eastward along the central
Canadian/U.S. border vicinity today through tonight, and gradually
pivot from a positive to neutral tilt. As it does, preceding weak
mid-level troughing, and at least a couple of embedded convective
perturbations, are forecast to accelerate northeastward within weak
to modest ambient flow backing to a southwesterly component across
the lower Missouri Valley vicinity into the Great Lakes region.
At the same time, northwesterly mid-level flow will be maintained
with weak height falls across the southern Rockies into adjacent
Great Plains, while gradual mid-level height rises are forecast
across the Appalachians into Atlantic Seaboard.
In lower-levels, the primary short wave trough may support a modest
developing surface low across northwestern Ontario, with cooler and
drier air in its wake overspreading much of the northern Great
Plains by 12Z Saturday. Another low emerging from the central Great
Plains is forecast to migrate northeast of the lower Missouri Valley
toward the upper Great Lakes, along an initially diffuse low-level
baroclinic zone.
...Lower Missouri Valley into Great Lakes...
The low-level baroclinic zone may still be a focus for weakening
convective development at the outset of the period. However, as the
convection dissipates further, models suggest that the boundary will
become better defined with strengthening differential heating.
Surface dew points near and above 70F, beneath modestly steep
mid-level lapse rates, are forecast to contribute to CAPE on the
order of 2000-3000 J/kg along and south of the boundary, gradually
tapering to the north, beneath a lingering belt of convectively
augmented mid-level flow (on the order of 30-50 kt in the 700-500 mb
layer). Coupled with modest, clockwise-curved low-level hodographs
developing in advance of the migratory low, the environment may
become conducive to supercell structures posing a risk for a few
tornadoes across parts of northern Missouri and southeastern Iowa
into northern Illinois, before damaging wind gusts become the more
predominant potential hazard as convection tends to grow upscale
into clusters through this evening.
...Southern Rockies into the Great Plains...
Thermodynamic profiles characterized by modest low-level moisture,
but with generally steep lapse rates, including fairly deep
boundary-layer mixing, may become conducive to scattered
thunderstorm clusters posing a risk for severe wind and hail late
this afternoon and evening. This may be aided by modest shear
beneath the northwesterly mid-level flow, with thunderstorm activity
mostly initiating off the higher terrain of the Front Range through
Sangre de Cristo Mountains. However, low-level convergence within
surface troughing across southern Kansas through the Oklahoma/Texas
Panhandle vicinity may also become sufficient for thunderstorm
initiation during the peak late afternoon heating.
..Kerr/Thornton.. 07/11/2025
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