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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0751 AM CDT Sat Jul 16 2022

Valid 161300Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE CENTRAL PLAINS...LOWER MISSOURI VALLEY...MD/DC/VA REGION...AND
SOUTHERN AZ...

...SUMMARY...
Isolated severe thunderstorms are possible over the central Plains 
this afternoon and evening, and possibly across the lower Missouri
Valley overnight.  Damaging to isolated severe gusts are also
expected this afternoon from Maryland southward across Virginia, and
over southern Arizona.

...Synopsis...
Mid/upper-level height falls, related to shortwave activity in the
central Plains, will lead to a slight westward shift of the major
anticyclone now over the southern Rockies, relocating its center to
the Four Corners area by the latter half of the period.  A series of
small perturbations -- some convectively induced/enhanced -- is
apparent from the Dakotas across portions of WY, CO and NE.  The
most prominent of these in moisture-channel imagery extends
initially from western SD to southwestern WY, and should shift
eastward to southern MN and northeastern to southwestern NE by 00Z. 
By 12Z tomorrow, phasing of this and a few smaller vorticity lobes
should lead to a better-defined height trough from WI to the lower
Missouri Valley.  Downstream, a shortwave trough apparent from Lake
Erie to eastern TN should extend from southern NY down the
Appalachians to the western Carolinas by 00Z. 

At the surface, 11Z analysis showed a wavy, mostly quasistationary
frontal zone -- interspersed with convective outflows -- from NJ
across OH to central IL, northern MO, and central/southwestern KS. 
An elongated area of low pressure on the KS frontal segment should
consolidate today over southwestern KS, then move slowly eastward
through the remainder of the period, with a trough extending
northward across portions of NE and eastern SD.  

...Central Plains and lower Missouri Valley vicinity...
Isolated to scattered thunderstorms are possible this afternoon
through evening across the western/middle parts of the outlook area,
with additional convection possible overnight near the front over
the lower Missouri Valley.  At least isolated damaging gusts and
large hail are possible.  A better-focused concentration of severe
potential may develop, especially near the trough and front, but
uncertainty on placement of any upscale clustering preclude an
embedded area of greater probabilities on this outlook cycle. 

Relatively maximized boundary-layer convergence should develop near
the low, front and trough, as MLCINH also weakens via diabatic
surface heating throughout the afternoon.  This will contribute to
convective development, as should heating and sufficient moisture 
behind the front over the High Plains of eastern CO and western KS. 
Along and north of the front, east of the trough, and removed from
the hot/mixed air mass south of the boundary, surface dewpoints in
the mid 60s to mid 70s F should be co*mon.  This, along with subtle
large-scale ascent preceding the mid/upper perturbation(s), will
support MLCAPE co*monly in the 1500-2500 J/kg range, and locally
higher.  MLCAPE will decrease to around 1000-1500 J/kg range in the
post-frontal trajectories wrapping northwest through west-southwest
of the low over the High Plains, but still supporting strong/
isolated severe potential.  Somewhat-enhanced vertical shear  and at
least transient supercellular structures are possible along and
north of the front over KS and near the trough, as midlevel flow
increases ahead of the shortwave trough, and atop weak but backed
near-surface winds.  Additional convection should develop tonight as
a modest LLJ impinges on the frontal zone above the surface, over
the lower Missouri Valley, with sporadic hail and strong gusts
possible. 

...MD/VA and vicinity...
Widely scattered to scattered thunderstorms should develop during
mid/late afternoon over western/central portions of the outlook area
and move generally eastward, offering sporadic damaging wind -- with
isolated, marginally severe (50-55-kt) gusts and hail possible. 

As the Ohio Valley/Cumberland Plateau shortwave trough approaches,
increasing large-scale ascent/cooling aloft will overlie a diurnally
heated, destabilizing, favorably moist boundary layer (with surface
dew points in the mid 60s to near 70 F and very weak MLCINH), east
of the Blue Ridge.  Accordingly modified forecast soundings indicate
a corridor of 800-1200 J/kg MLCAPE atop a shallow but well-mixed
boundary layer.  The eastern rim of the favorable cooling aloft may
shift east with the convection, contributing to persistence into the
evening hours and the Chesapeake Bay region.  Weak low/middle-level
winds and related lack of shear should preclude a better-organized
severe event. 

...Southern AZ...
Widely scattered thunderstorms should develop this afternoon on the
higher terrain east of the PHX-TUS-OLS corridor and move westward to
west-southwestward over the adjoining lower deserts.  Potential for
isolated severe gusts will exist across south-central AZ, especially
where activity can aggregate outflow pools locally.  

The strong-severe gust threat will be supported by a deep/well-mixed
boundary layer, with sufficiently great antecedent moisture (lower-
elevation dewpoints in the upper 50s to mid 60s this morning) to
maintain deep surface-based buoyancy.  Forecast soundings indicate
500-1000 J/kg MLCAPE developing atop the mixed layer, amidst a deep
(essentially the entire troposphere above 700 mb) layer of
easterlies.  The borderlands also will be on the northern fringe of
a speed max in the 500-mb easterlies (around 25-30 kt along the
international border, weaker northward), related to a shortwave
trough in the easterlies over northwestern MX.  This speed max may
contribute to some faster storm motion and downward momentum
transfer over southern areas.

..Edwards/Mosier.. 07/16/2022