Day 1 Severe Weather Outlook

Valid 271300Z – 281200Z


Isolated severe thunderstorms are possible across parts of west
Texas during the late afternoon and evening, and from east-central
Minnesota to Upper Michigan this afternoon.

…West TX…
A decaying, southward-moving MCS is ongoing across north-central to
northeast TX. Guidance generally agrees that this MCS will further
decay as it shifts into progressively weaker upper-level flow with
southern extent and becomes separated from isentropic ascent focused
across the low-level baroclinic zone that lingers farther northwest
in OK.

Potential for late afternoon to evening thunderstorm development
should be focused farther west from western North Texas to the
Permian Basin. Reinvigorated low-level warm advection on the cool
side of the front might support a cluster of elevated convection,
with possibly a separate area of development farther southwest where
convergence should be maximized along the surface front. Deep-layer
shear will be modest and weaker with southwest extent despite
veering of the wind profile with height. Steep mid-level lapse rates
will support an isolated severe hail risk, while hot surface
temperatures south of the front may yield a few severe wind gusts,
mainly in the evening.

…Upper Great Lakes…
As pronounced mid-level DCVA occurs ahead of a shortwave impulse
moving from the SD/MN border to eastern WI, scattered low-topped
convection will develop this afternoon. The bulk of strong
southwesterlies aloft should reside in the upper portion of the weak
buoyancy profile, which would curb effective shear values.
Steepening low-level lapse rates will support mixing of moderate
700-mb flow despite predominant west-southwesterly boundary-layer
winds. Setup could foster locally damaging winds from strong gusts
along with marginally severe hail.

…Lower MS Valley to OH…
Scattered thunderstorms should redevelop along residual outflows
from remnant early-day convection, most likely across the Lower MS
to TN Valleys where boundary-layer heating should be more
pronounced. Weak deep-layer shear in these regions should preclude
an organized severe risk, but pulse microbursts are possible.

Farther north into OH, pervasive cloudiness in morning visible
imagery should limit boundary-layer heating. Given weak mid-level
lapse rates, buoyancy will likely remain below 1000 J/kg. In
combination with modest deep-layer speed shear, overall setup
appears unlikely to yield an appreciable organized severe risk.

..Grams/Mosier.. 08/27/2019


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