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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0754 AM CDT Mon Jul 04 2022

Valid 041300Z - 051200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN ROCKIES/PLAINS AND OVER PORTIONS OF THE MIDWEST AND GREAT
LAKES REGIONS...

...SUMMARY...
Isolated to scattered severe thunderstorms are expected over parts
of the northern Rockies/Plains and over portions of the Midwest and
Great Lakes regions this Independence Day. Large hail and damaging
winds should be the main threats, with a tornado or two possible in
the Midwest.

...Synopsis...
The large-scale pattern in mid/upper levels will continue to feature
mean troughing over northwestern North America, southward across the
Pacific west of CA.  Within that regime, a small cyclone is evident
in moisture-channel imagery over the coastal Olympic Peninsula. 
This feature and is forecast to drift northeastward to southwestern
BC and weaken through the period, while another low digs
southeastward from the Gulf of Alaska and intensifies well offshore.

Downstream ridging will strengthen in place over the central/
northern High Plains, despite being traversed by several weak
vorticity maxima ejecting from the southwest-flow sector of the
Northwest cyclone.  Meanwhile, a slowly strengthening anticyclone
will persist over the Mid-South, lower Mississippi Valley and
central/western Gulf Coast States.  East of the ridge, MCVs were
evident in radar co*posites over southeastern ND, the southern SD/MN
border area, and northwestern IA.  With the middle/northern MCVs
embedded in faster flow, these should align better as the day
progresses.  Most synoptic guidance accordingly (and reasonably)
yields a coherent, negatively tilted shortwave trough from this
phasing, with the perturbation reaching Lower MI and eastern Upper
MI by 00Z.

At the surface, 11Z analysis showed a cold front offshore from
eastern NC, across southern NC and eastern TN, beco*ing a wavy warm
front northwestward over central KY and southern IL to southern/
central MN.  A secondary/developing warm front was drawn from
central MN east-southeastward over southern WI and southwestern
Lower MI, and should beco*e the main warm front through the day in
that region.  This boundary should move northeastward over central
portions of WI, Lake Michigan and western/southern Lower MI.  An
elongated/co*plex low-pressure area over the central Dakotas should
consolidate through the day and move/redevelop eastward along the
warm front to Lake Huron by the end of the period.  A weak cold
front should move southeastward out of the Dakotas to northern/
central NE and east-central/north-central WY before stalling.

...Upper Mississippi Valley/Great Lakes...
Scattered to locally numerous thunderstorms are expected to shift
across the area today and tonight, roughly from west to east. A mix
of storm modes is expected, including the potential for a few
supercells with the full range of severe hazards (gusts, hail,
perhaps a tornado or two).  Upscale evolution of afternoon
convection into a wind-dominant MCS is possible this evening into
tonight across portions of WI, Lake Michigan and Lower MI.  If
confidence increases in a more-specific track and timing for such a
co*plex, a mesoscale concentration of greater probabilities may be
needed in a future outlook update.

Downstream from the mid/upper ridge, west-northwesterly to westerly
flow aloft will orient slightly across the warm front, toward its
cool side.  However, with slow northward motion of the front,
effectively the flow aloft will be front-parallel, helping to
support convective growth/maintenance, as low-level theta-e
advection and diurnal heating destabilize the convective inflow
sector.  This will occur amidst a regime of increases in large-scale
ascent and vertical shear related to the approaching MCV-related
shortwave trough.  Forecast soundings show 35-50-kt effective-shear
magnitudes and occasional areas of large hodographs with 300-400
J/kg effective SRH, in support of both supercellular and QLCS
tornado potential.

Meanwhile the area of clouds/precip now over southern MN/IA should
move eastward and slowly break up, allowing increasing moisture
south of the front, and pockets of favorable diabatic heating. 
Accordingly, MLCAPE values in the 1500-2000 J/kg range are possible
west of Lake Michigan, decreasing with eastward extent into Lower MI
where the preconvective air mass has less time to destabilize. 
Still, warm/moist advection may support surface-based effective-
inflow parcels and a residual well-mixed boundary layer well into
southern Lower MI tonight, supporting damaging to severe gust
potential with any co*plex after crossing the lake.

...Northern Rockies/Plains...
Despite weak height rises aloft, widely scattered thunderstorms are
expected to develop this afternoon into early evening -- initially
over portions of western/southern MT and perhaps the Black Hills
region.  In those area, MLCINH will be preferentially reduced by
diabatic heating of higher terrain.  Seasonally strong mid/upper
winds will support both favorable deep-layer shear and fast storm
motions onto the northern Great Plains, and near a postfrontal
moisture/instability axis over southern/western SD and south-
central/southeastern MT.  As that occurs, activity should offer
severe gusts and hail, with a blend of supercellular and
multicellular/bowing modes expected.

Surface heating near the moist axis will yield steep low/middle-
level lapse rates and a well-mixed boundary layer, beneath about
1000-1500 J/kg peak MLCAPE.  Strong veering of winds with height
will yield lengthy hodographs and 45-60 kt effective-shear
magnitudes, supporting supercell potential.  Some upscale clustering
and cold-pool growth also may occur from eastern MT into the western
Dakotas, with small-scale corridors of severe-gust potential aided
by strong ambient flow aloft.

..Edwards/Goss.. 07/04/2022