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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0756 AM CDT Sun Aug 07 2022

Valid 071300Z - 081200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
ARIZONA...THE UPPER MIDWEST AND CENTRAL HIGH PLAINS...

...SUMMARY...
Isolated severe thunderstorm gusts are possible across parts of
Arizona, the Upper Midwest and central High Plains this afternoon
and evening.

...Synopsis...
In mid/upper levels, a zonally elongated anticyclone -- initially
from parts of the central Plains to northern AZ -- will be the
dominant feature for this period.  The western end of the associated
ridging is expected to shift somewhat northward over southern CO and
northern AZ, with weakly increasing heights.  Meanwhile, farther
north, a strong shortwave trough was apparent in moisture-channel
imagery over portions of southern SK to central MT and the WY/ID
border region.  This perturbation is forecast to move eastward to
the Dakotas by 00Z, then beco*e aligned from Lake Superior to
northern IA by 12Z tomorrow.

At the surface, 11Z analysis showed a cold front from southwestern
QC across northern Lower MI, central WI, southeastern MN (behind a
great deal of convective outflow there), to a weak low near HLC, and
across parts of east-central/north-central CO.  By 00Z, the front
should extend from a weak low over the Upper Mississippi Valley
southwestward across central IA (possibly where another weak low may
be located), then over southeastern NE, north-central/southwestern
KS, to north-central NM.  By 12Z, the front should extend from a low
over eastern WI to near a DBQ-MKC-ICT-TCC line.

...AZ...
Widely scattered to scattered thunderstorms are forecast to develop
from midday through afternoon, initially over the Mogollon Rim and
other higher terrain of central/southeastern AZ.  As the
aforementioned northward shift of mid/upper ridging occurs, flow in
those layers will beco*e more easterly than in previous days, even
northeasterly near anvil level.  This will encourage convection to
move southwestward over lower elevations, where a strongly heated,
favorably moist, yet well-mixed subcloud layer will encourage both:
1) Strong-severe gusts from early convection moving off the higher
terrain, and
2) Discrete propagation/redevelopment of activity along successive
outflow surges -- and especially, outflow-boundary collisions where
lift will be maximized on mesobeta and smaller scales.

The preconvective environment over the lower deserts should be
characterized by 500-1500 J/kg MLCAPE (locally/briefly higher), atop
steep low-level lapse rates supporting around 1000-1500 J/kg DCAPE
at peak surface temperature.  Deep shear will increase with
southward extent away from the ridging aloft, into associated
easterly/northeasterly gradient winds, airing with organization and
faster cell motion.  That, along with higher moisture content in the
southern AZ storm-inflow region, also may support marginally severe
hail.  Convection may persist into the evening over southern/western
areas, especially if any clustering/small-MCS evolution can occur. 
Some portion of this area may be considered for an upgrade, if
mesoscale trends and shorter-fused convective guidance lessen the
evolutionary uncertainty.

...Upper Midwest...
Widely scattered to scattered thunderstorms are expected to develop
this afternoon, most probably along the remnant outflow/differential
heating boundaries now evident south of the front across portions of
IA.  Multicellular modes are expected, with gusts being the main
concern.

Potential northward into southern MN is more uncertain and
conditional, given the persistent stabilizing effects of precip
between the boundaries and the front, the southward movement of the
front, and the uncertainties on boundary retreat and heating into
what is now relatively stable air.  Near and south of the outflow
boundaries, surface dewpoints will remain co*monly in the 70s F,
acting in concert with heating to offset modest mid/upper-level
lapse rates, and boost peak MLCAPE into the 1500-3000 J/kg range. 
Water-loaded downdrafts, into enough of a well-mixed subcloud layer
to maintain or accelerate them, may offer damaging to isolated
severe gusts.

...Central High Plains...
Widely scattered thunderstorms should develop this afternoon over
portions of central and southeastern CO, focused mainly near the
southeastward-moving front and over a post-frontal upslope-lift
regime near the Palmer Divide.  Strong/isolated severe gusts are the
main concern.

Diurnal heating of the elevated terrain, and around the frontal
convergence maxima, should co*bine with favorable moisture for that
altitude (surface dewpoints in the 50s to low 60s F) to render a
favorable buoyant environment.  Despite modest midlevel lapse rates
near the ridging aloft, MLCAPE values co*monly 1000-1500 J/kg,
locally near 2000 J/kg, are possible, atop a well-mixed boundary
layer.  Though midlevel winds will be around 10-20 kt, post-frontal
low-level northeasterlies will contribute to about 25-35-kt
effective-shear magnitudes in support of multicellular organization.
Nonsupercellular "landspout" tornado potential also may exist,
especially near the front and any mass-convergence lines farther
northwest, where pre-existing low-level vorticity can be stretched
in early updraft stages.

..Edwards/Marsh.. 08/07/2022