SPC AC 191234
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0734 AM CDT Tue Oct 19 2021
Valid 191300Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDDLE MISSOURI VALLEY...
Strong thunderstorms posing a risk for isolated severe hail are
possible late tonight (early Wednesday morning) across parts of
northeastern Nebraska and southeastern South Dakota into
...Middle Missouri Valley including portions of NE/SD/IA...
A closed low centered over Utah/western Colorado this morning will
continue eastward and reach the central High Plains by evening. The
progression of this system will influence modest surface
cyclogenesis across Kansas/Nebraska in tandem with the sharpening of
an eastward-moving cold front that will cross the region tonight
into Wednesday. Pre-frontal moisture advection into the region will
be modest overall given limited source region availability, but
middle 50s F surface dewpoints could develop into the middle
Missouri Valley late tonight.
These forcing for ascent/moisture trends are likely to influence a
nocturnal maximization of thunderstorms, with initial isolated
development across northern Nebraska/southern South Dakota becoming
a bit more numerous (scattered) into the overnight in areas near the
front and near/north of the surface low, including northeast
Nebraska/southeast South Dakota and northwest Iowa. Steepening
mid-level lapse rates atop stable but moistening low-levels could
support MUCAPE near/above 1000 J/kg. Owing to strong deep-layer
southwesterly winds, very strong shear through the cloud-bearing
layer could support some elevated supercells capable of isolated
severe hail overnight.
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