SPC Aug 22, 2021 1730 UTC Day 2 Convective Outlook – Weather Shelby Ohio

SPC 1730Z Outlook Day 2
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1227 PM CDT Sun Aug 22 2021

Valid 231200Z - 241200Z


Isolated severe thunderstorms are possible across portions of the
northern and central Plains Monday afternoon into early Tuesday

Subtropical ridging centered over east TX is forecast to build
throughout the day on Monday, expanding northward into more of the
central Plains as well as northeastward into more of the OH Valley
and southwestward into more of Mexico. Broadly cyclonic flow aloft
will persist north of this ridging from the West Coast through the
Upper MS Valley while the modest upper trough in place from the
Northeast Coast through the Mid-Atlantic gradually shifts

At the surface, a weak cold front is forecast to extend from a low
over southern Manitoba southward across MN and then back
southwestward across NE into eastern CO. This front will likely
retreat back north as an effective warm front throughout the day, as
moist southerly low-level flow increases across the central Plains
in response to a deepening lee trough. By Monday evening,
cyclogenesis is expected across the northern High Plains, with the
resulting surface low then progressing eastward into the northern
Plains overnight Monday/early Tuesday morning.

...Central Plains/Mid MO Valley...
A conditional severe threat appears likely during the afternoon and
evening across portions of the central Plains and Mid MS Valley.
Low-level moisture advection is expected to bring upper 60s/low 70s
dewpoints into the region, especially those areas near the warm
front where boundary-layer mixing will be more tempered. Moderate to
strong instability is forecast to develop in these areas, with
MLCAPE over 3000 J/kg possible. Limiting factors for storm
development are the lack of stronger forcing for ascent and
potential capping resulting from warm temperatures aloft. Despite
these limiting factors, potential for at least isolated convective
initiation is high enough to introduce 5% wind/hail probabilities
with this outlook. Higher probabilities may be needed in later
outlooks if the potential for thunderstorm development becomes more
certain. Any storms that do develop should quickly develop intense
updrafts capable of producing hail and/or water-loaded downbursts.
Vertical shear will be modest, suggesting a predominantly
outflow-dominant storm mode.

...Northern High Plains...western Northern Plains Monday
In contrast to the areas farther east, forcing for ascent will be a
bit stronger across the northern High Plains on Monday, although
still relatively modest given the limited strength/amplitude of any
embedded shortwave troughs. Deep boundary layer mixing should result
in a largely uncapped environment and any storms that can overcome
the limited buoyancy and strong dry air entrainment will likely
produce strong outflow capable of damaging wind gusts.

...Northern Plains later Monday evening and overnight...
Ascent is expected to increases across the northern Plains Monday
night into early Tuesday morning ahead of the strong shortwave
trough moving across the Canadian Prairie Provinces. This ascent
should be augmented by increasing warm-air advection along the warm
front associated with the surface low moving into region. As a
result, an increase in thunderstorm coverage is expected. The
environment should be characterized by steep mid-level lapse rates
and moderate vertical shear, and a few storms may be
strong/organized enough to produce hail.

..Mosier.. 08/22/2021

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