Mesoscale Discussion 1320
NWS Storm Prediction Center Norman OK
0317 PM CDT Tue Jul 20 2021
Areas affected...Parts of western through much of northern New York
State and adjacent northern Vermont
Concerning...Severe Thunderstorm Watch 384...
Valid 202017Z - 202215Z
The severe weather threat for Severe Thunderstorm Watch 384
SUMMARY...An organized cluster of thunderstorms will spread across
the St. Lawrence River through much of the Adirondacks vicinity,
along with continuing development across and southeast of Lake
Ontario by 5-7 PM EDT, accompanied by the risk for potentially
damaging wind gusts.
DISCUSSION...Moderate southeasterly low-level inflow of moist air
characterized by CAPE in excess of 1000 J/kg is maintaining vigorous thunderstorm development along the leading edge of an
east-southeastward advancing, convectively driven surface cold pool.
This continues to be aided by large-scale forcing for ascent
associated with a 30-50 kt westerly mid/upper jet streak, and will
overspread the upper St. Lawrence Valley through much of the
Adirondacks region by 22-23Z. As the temperature gradient across
the gust front increases at least a bit further, potential for
damaging wind gusts probably will also continue to increase during
the next hour or two.
Farther to the southwest, thunderstorms which initiated along the
trailing outflow boundary, and preceding lake breezes across the
Lake Ontario vicinity, may also begin to consolidate while spreading
into the unstable environment to the southeast of the lake. This
too may gradually pose increasing risk for damaging wind gusts
near/north of the Finger Lakes region through the Mohawk Valley by
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