SPC update on severe thunderstorm watch #455.


Concerning…Severe Thunderstorm Watch 455

Valid 272317Z – 280115Z

The severe weather threat for Severe Thunderstorm Watch 455

SUMMARY…The severe threat continues across eastern portions of
WW455 in far eastern Wisconsin and northeast Illinois with severe
wind as the primary threat. Strong/severe storms may move out of the
watch across portions of eastern Lake Michigan, southwest Michigan,
northeast Illinois, and northwest Indiana.

DISCUSSION…A line of thunderstorms capable of producing severe
wind continues to move eastward across far eastern Wisconsin and
northeast Illinois. Norther portions of the line are beginning to
weaken as storms encounter weaker instability while the southern
portion continues to develop new storms amid MLCAPE of 1500-2000
J/kg. These storms will likely continue until sunset taking
advantage of the insolation driven instability and steep low-level
lapse rates in the area.

The low-level jet will be stronger farther west, which will limit
the ability for the storms to continue into the evening across this
area. However, the southern part of the line will likely continue to
be strong/severe across southern Lake Michigan and northeast
Illinois and may move into portions of southwest Michigan and
northwest Indiana later this evening. Convective trends will
continued to be monitored for a possible watch expansion/extension
or if a new watch may be needed.

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