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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0750 AM CDT Tue Jul 19 2022

Valid 191300Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE UPPER MIDWEST AND UPPER GREAT LAKES REGIONS...

...SUMMARY...
Severe thunderstorm gusts and large hail are expected over portions
of the Upper Midwest and upper Great Lakes regions.

...Synopsis...
A large, well-developed, mid/upper-level anticyclone will persist
over the Southwest through the period, while weak, messy mean
troughing continues in the East.  A shortwave trough is evident in
moisture-channel imagery over southern/southwestern QC, and should
pivot eastward across portions of New England and adjoining areas of
Canada today.  Upstream, a co*pact, well defined mid/upper-level
cyclone is located initially over extreme northeastern MT, with its
circulation straddling the international border.  The 500-mb low
should move east-southeastward past the FAR-GFK corridor before 00Z,
to the Keweenaw Peninsula by 12Z tomorrow, with a trough trailing
south-southwestward for about 400-500 nm from each position. 
Farther southeast, a weak mid/upper-level shortwave trough --
initially from eastern KY to central MS -- will move eastward to the
Carolinas and GA through the period. 

The 11Z surface analysis depicted a weak low over ME with slow-
moving cold front across southern parts of QC/ON, beco*ing a warm
front over Upper MI and northern MN.  An occluded low was drawn over
southwestern MB with short occluded frontal segment to the warm-
frontal junction near the eastern ND/MB line.  A cold front extended
from there through a low between JMS-FAR, then across northeastern
SD to northwestern NE.  The main/occluded low should shift
east-southeastward to near the MN Northwest Angle by 00Z, with
occluded/cold front arching over the Arrowhead, western WI,
southwestern IA, and central/southwestern KS.  By 12Z, the low
should be near Thunder Bay, with occluded/cold front over eastern
Lake Superior, northern IL, central MO, northern OK, and the TX
Panhandle.  

...Upper Midwest/Upper Great Lakes...
The trailing portion of an arc of convection near the MB/ON border
extends into northwestern MN, and may still be capable of gusts to
near severe limits as it crosses the Lake of the Woods region
eastward to near INL this morning.  Potential should be limited to
an isolated/marginal severe threat by weakening buoyancy with
southward extent, and strong MLCINH.

Behind the morning activity, an arc of convection is expected to
develop this afternoon from near the MB low southeastward to
southward near the surface cold front.  This activity should expand
(backbuild) southward while the entire arc shifts eastward across
northern MN and into area surrounding the western half of Lake
Superior.  Considerable uncertainty remains regarding how far the
convection will develop southward into a regime of decreasing
frontal convergence and strengthening capping of the prefrontal
boundary layer.  However, any sustained thunderstorms will pose a
threat for severe hail and gusts, and a tornado cannot be ruled out.

Strong mid/upper-level height falls and DCVA are likely ahead of the
mid/upper cyclone/trough, spreading eastward to near the frontal
position.  The associated mass response will contribute to low-level
convergence, as well as favorable deep shear, with 40-50 kt
effective-shear magnitudes co*mon across the region.  As the front
impinges on a diurnally heated boundary layer, rich boundary-layer
moisture will support a narrow corridor of 1500-2500 J/kg of
preconvective/prefrontal MLCAPE.  The convective arc may persist to
at least marginal severe levels as far east as eastern Upper MI and
western/northern Lower MI overnight. 

...Northeast...
Widely scattered thunderstorms with strong to briefly/marginally
severe thunderstorms are possible near the trough over northern New
England through midday, as well as this afternoon over northern NY
into northwestern New England.  Light and generally westerly near-
surface winds will minimize convergence, limiting overall convective
coverage behind the morning/midday passage of the mid/upper
perturbation; however, only minimal and brief DNVA/subsidence is
progged in its wake.  Cool mid/upper temperatures (around -10 to -11
C at 500 mb) and steep 500-300 mb lapse rates will overlie a
diurnally heated and favorably moist (60s F dewpoints) boundary
layer with minimal MLCINH.  Deep-layer flow will be nearly
unidirectional, but with sufficient mid/upper winds to support
effective-shear magnitudes in the 30-40-kt range.

...Southeast...
Modest large-scale ascent preceding the mid/upper trough will
overspread a very moist and heated boundary layer over parts of the
southeast today, supporting scattered to widely scattered
thunderstorms.  Aside from almost randomized/very isolated potential
for water-loaded pulse downdrafts to approach severe limits in
discrete cells, some potential exists for aggregation of multicell
clusters to at least loosely organize and concentrate wind
potential.  Foci for such development should be near outflow/
differential-heating boundaries related to nonsevere convection now
over northern parts of MS/AL/GA, shifted eastward over parts of
AL/GA to the sea-breeze regime in SC.  A deep troposphere, strong
surface heating in cloud breaks, and surface dewpoints co*monly in
the upper 60s to mid 70s F should support 2000-2500 J/kg MLCAPE
(locally higher), with modest deep shear.

..Edwards/Mosier.. 07/19/2022