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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0258 PM CDT Tue Jul 19 2022

Valid 192000Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
UPPER MIDWEST AND UPPER GREAT LAKES...

...SUMMARY...
Severe thunderstorm gusts and large hail are possible over portions
of the Upper Midwest and upper Great Lakes regions late this
afternoon into this evening.

...20Z Update...
The western edge of the Marginal and Slight Risks have been trimmed
across northeast ND into northwest MN, based on the progression of
the cold front. Also, southern portion of the Slight Risk has been
trimmed across parts of WI, due to capping concerns and the general
lack of guidance supporting robust development that far south.
Otherwise, no changes have been made, see the previous discussion
below for more details, and MCD 1519 and WW 476 for more information
regarding the near-term severe threat in MN and northwest WI.

..Dean.. 07/19/2022

.PREV DISCUSSION... /ISSUED 1129 AM CDT Tue Jul 19 2022/

...Synopsis...
A co*pact upper wave is evident in mid-morning water vapor imagery
translating eastward across North Dakota. This feature will continue
east into the Great Lakes region through 12 UTC Wednesday, and will
be the focus for severe weather potential for today. A weakening
upper disturbance over the eastern U.S. will continue to lift
northeast into the western Atlantic, but residual influences from
this wave will support lower severe probabilities across the
Northeast and Southeast states this afternoon. Across the Southwest,
hot and dry conditions prevail under a Four Corners ridge, though
widespread monsoonal moisture will continue to support scattered
thunderstorm chances with the potential for damaging downbursts for
a couple of regions.

...Upper Midwest/Great Lakes...
Surface analysis reveals a deepening surface low across the northern
Red River Valley of the North with a cold front advancing east
across the eastern Dakotas. Ahead of this front, temperatures are
warming into the low 80s with widespread dewpoints in the upper 60s
and low 70s. While this air mass is undergoing some destabilization,
strong capping sampled in the 12 UTC ABR and MPX soundings will
likely limit the potential for open warm sector convection.
Thunderstorm development is more likely along the diffuse warm
frontal zone that is currently draped across northern MN into
western WI and where capping diminishes with eastward extent (per
the 12 UTC INL and APX soundings). Evidence of strong lift is
already evident across northern MN in satellite imagery with
thunderstorm initiation likely by late afternoon as lingering
inhibition is minimized. Deep-layer flow largely orthogonal to the
boundary co*bined with strong ascent should support semi-discrete
storm modes posing primarily a severe hail/wind risk. Storms along
the front will continue eastward towards northern lower MI and the
U.P. of MI overnight. While convection may beco*e elevated due to
diurnal cooling, forecast soundings show adequate MUCAPE and
effective shear to maintain a hail, and perhaps damaging wind,
threat. 

...Northeast...
Morning soundings across the region show poor mid-level lapse rates
with evidence of low/mid-level stability evident in visible
satellite imagery. However, upstream soundings from southeast Canada
reveal much colder temperatures aloft, which should advect east
through the day as the upper-level low shifts east/northeast. These
cooling temperatures, co*bined with diurnal insolation and a nearly
uni-directional wind profile featuring 30-40 knot winds will support
a conditionally favorable environment for organized severe storms.
While this favorable environment is noted, storm coverage remains
uncertain. Thunderstorm development is possible by mid/late
afternoon as a weak surface trough, currently just northwest of the
international border, moves across the region. However, latest
guidance continues to show sparse storm coverage, likely owing to
the weak forcing for ascent. Recent downward convective trends of
ongoing storms north of ME also limits confidence in storm coverage.
Consequently, the potential for a more widespread severe threat
appears too limited for a categorical upgrade. 

...Southeast...
The southern extension of the East Coast upper trough will continue
to drift east towards the Atlantic Coast through the day. This will
continue to provide lift across far eastern AL, GA, and the
Carolinas over an air mass that is currently destabilizing under
partly cloudy skies (with temperatures climbing into the upper 80s
with rich low-level moisture). The co*bination of adequate buoyancy,
sufficient lift, and modest upper-level flow should support a few
strong to severe storms with a predominantly damaging wind risk
(though sporadic severe hail is possible with the stronger
updrafts).

...Southern High Plains...
A deep, dry boundary layer are noted across the southern High Plains
on the edge of the monsoonal moisture plume. By late afternoon,
adequate mid-level moisture should support sufficient buoyancy for
isolated to scattered thunderstorms. With inverted-V signatures
noted in forecast soundings and a modest convective signal in most
CAM guidance, the potential for strong to severe downburst winds
appears sufficient to introduce wind probabilities. 

...Southeast Arizona...
A weak surface low over southern AZ is noted in morning surface obs.
This feature should maintain weak south to southwesterly flow across
southeast AZ through the day under modest easterly flow aloft. This
should support 20-30 knots of 0-6 km shear through the day, which
will aid in storm organization as convection develops off the
terrain of the Mongolon Rim and western Gila region this afternoon.
Similar to the southern High Plains, inverted-V low-level profiles
are noted in forecast soundings, which, when co*bined with the
slightly sheared environment, should support a few stronger storms
with severe wind potential.