SPC AC 040049
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0749 PM CDT Thu Oct 03 2024
Valid 040100Z - 041200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TONIGHT ACROSS
PARTS OF SOUTHEASTERN IOWA...ADJACENT NORTHEASTERN MISSOURI AND WEST
CENTRAL ILLINOIS...
...SUMMARY...
An area of developing thunderstorms overnight may pose a risk for
small to marginally severe hail across parts of southeastern Iowa,
adjacent northeastern Missouri and west central Illinois.
...01Z Update...
Within the mid-latitude westerlies, one notable short wave trough is
forecast to continue digging across the northern Great Plains Red
River Valley toward the upper Great Lakes region tonight. The
southern periphery of the surrounding cyclonic mid/upper-level flow
currently curves across southern Nebraska through the Missouri/Iowa
border vicinity, where it is beginning to overspread an initially
quasi-stationary frontal zone. Models suggest that this regime will
become increasingly divergent late this evening into the overnight
hours, contributing to increasing forcing for ascent.
Lower/mid-level ascent is already increasing across Iowa and
surrounding portions of the Missouri Valley/Upper Midwest, in
response to warm advection. It appears that this will lead to
increasing thunderstorm development by 05-07Z across parts of
central/southern Iowa, where guidance indicates a corridor of modest
destabilization is possible associated with weak elevated moisture
return above the frontal zone.
Forecast soundings indicate most unstable CAPE may increase in
excess of 1000 J/kg along this corridor, in the presence of modest
potential cloud-bearing layer shear. Thermodynamic profiles may
include sufficiently cool mid-levels (and steep lapse rates) to
support a risk for marginally severe hail (up to around 1 inch or so
in diameter) in a few of the stronger storms.
..Kerr.. 10/04/2024
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