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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0750 AM CDT Fri Jul 01 2022

Valid 011300Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
WYOMING ACROSS THE BLACK HILLS REGION TO THE NEBRASKA SANDHILLS...

...SUMMARY...
Severe gusts and isolated large hail will be possible this afternoon
and evening from northeast Wyoming across the Black Hills region to
the Nebraska Sandhills.

...Synopsis...
In mid/upper levels, a mostly low-amplitude synoptic pattern will
characterize the prevailing westerlies across the northern half of
the CONUS, downstream from a slow-moving cyclone and trough located
offshore from the Pacific Coast.  Ridging should amplify somewhat
over the northern Rockies, while another mid/upper low shifts
largely eastward over the southern coastline of Hudson Bay. 
Associated cyclonic flow will shift eastward across the Great Lakes
and Northeast through the period, with gradual height falls much of
today and tonight over the Lower Great Lakes region, northern
Appalachians and most of New England.  An embedded shortwave trough
-- evident in moisture-channel imagery across portions of Upper MI,
WI and southern/central MN -- should move eastward across Lower MI
and southern ON today, then over northern New England tonight.  A
minor perturbation preceding that is located over southwestern QC
and parts of eastern ON, and should move down the St. Lawrence
River/estuary near ME today.

At the surface, 11Z analysis showed a wavy cold front from Lake
Huron across southern Lake Michigan, northern IL, extreme
southeastern NE, and western KS.  This front should move to
southeastern ON, northern IN, central portions of IL/MO, and
southwestern KS by 00Z.  By 12Z tomorrow, the cold front should
extend from northern NY across OH to parts of southern IL, beco*ing
quasistationary across southern MO and southern/southwestern KS.

...High Plains...
Scattered to widely scattered thunderstorms are possible this
afternoon into early evening around the Black Hills in WY/SD,
spreading into parts of northwestern NE this evening before
weakening.  Severe gusts are possible, along with isolated large
hail.

Diurnal heating, and moist advection with 50s F surface dewpoints,
should underlie 7-8 deg C/km midlevel lapse rates, contributing to
MLCAPE in the 1000-1500 J/kg range.  Even though low-level winds are
not forecast to be very strong (generally less than 10 kt through
the boundary layer except very near convection), substantial veering
with height is expected beneath the midlevel west-northwesterly
flow.  This will support a blend of multicells and at least
transient supercellular characteristics, with attendant severe-gust
and large-hail threats.  Some aggregation of this activity is
possible into the evening, with localized reinforcement of severe-
gust potential, before the convection moves into a nocturnally
stabilizing boundary layer and wind potential diminishes.

Farther south, and close to the mid/upper-level subtropical ridging,
flow aloft and deep shear will be weak.  Nonetheless, clusters of
convection -- forming over higher terrain during the afternoon --
may shift eastward across the central High Plains atop a very well-
heated/mixed boundary layer and steep low-level lapse rates, with
isolated severe gusts/hail possible.

...Northeastern CONUS to KS and lower Missouri Valley...
Isolated to scattered thunderstorms are possible along/ahead of the
cold front this afternoon into evening.  Isolated severe gusts/hail
may occur in the most intense multicell storms/clusters and/or short
convective bands.  Multiple relative concentrations of convection
and/or severe potential are possible on the mesobeta-scale, but
predictability remains too limited to highlight any within the
broader 5%/marginal outlook corridor at this time.  A small midlevel
perturbation and related MCV -- now apparent in radar imagery over
central/north-central KS -- may enhance shear and low-level lift
somewhat over parts of the middle Mississippi/lower Ohio Valley
regions today.

Ahead of the cold front, favorable moisture should remain over the
lengthy region, with surface dew points co*monly in the 60s F and
locally around 70 over the lower Ohio/middle Mississippi Valley
regions, where localized water-loaded downdrafts are the most likely
potential source of damaging to marginally severe gusts.  Hotter
conditions with better-mixed subcloud layers (but also weaker CAPE
due to modest midlevel lapse rates) are expected over some areas
over and east of the Alleghenies in the eastern parts of the
corridor, and across parts of KS and western MO.  Though south of
the main belt of westerlies over most of this corridor, effective-
shear magnitudes of 25-35 kt in the west, and 30-40 kt elsewhere,
should support some multicellular organization.  Diurnal heating and
low-level lift near the front will be the main foci for convection,
though some persistence of loosely organized, cold-pool-driven
activity may occur this evening in the eastern Ohio Valley/central
Appalachians region.

...Northern ME...
Isolated to widely scattered thunderstorms - perhaps including a
supercell or two -- may move across northern ME this afternoon into
early evening.  Isolated severe hail and/or damaging gusts are
possible.

An area of clouds/precip this morning -- related to a zone of strong
low-level warm advection/isentropic ascent -- should depart the
region through the remainder of the morning.  Diabatic surface
heating and continuing warm advection will contribute to gradual
destabilization throughout the day, as mid/upper ascent subtly
increases with the passage/approach of the low-amplitude shortwave
troughs.  Mid/upper-level lapse rates will remain modest, but
low-level theta-e should increase enough to support the development
of 500-1000 J/kg MLCAPE.  Meanwhile, increasing mid/upper-level flow
will boost effective-shear magnitudes into the 40-50-kt range. 
Veering of boundary-layer winds with height also may produce 150-200
J/kg effective SRH and curved hodographs.  Diurnal heating
(including effects along differential-heating/outflow boundaries)
and prefrontal surface troughing may provide sufficient lift over
and west of this area to support initiation.

..Edwards/Goss.. 07/01/2022