SPC AC 190732
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 AM CDT Thu Sep 19 2019
Valid 211200Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS
KANSAS...NORTHERN MISSOURI AND IOWA...
Severe storms are possible across parts of the Plains on Saturday,
most notably from Kansas into Iowa.
An upper trough will move east across the northern Plains and toward
the Great Lakes, with a broad zone of strong southwest winds aloft
encompassing much of the central and northern Plains, upper MS
valley and Great Lakes. The primary surface trough will extend from
northern ND and MN into Ontario, with a cold front roughly from MN
to KS by Saturday afternoon. Ahead of this front, mid to upper 60s F
dewpoints will be widespread, and will contribute to areas of
moderate instability. The most favorable combination of instability,
lift, and shear appears to be from KS northeastward into IA and
northern MO, although severe storm potential exists as far north as
MN and WI.
Upper 60s to near 70 F dewpoints are forecast to move north over OK,
KS, MO and IA, with a cold front roughly from central KS into
western IA by peak heating. Given the very moist air mass, capping
will be minimal and storms may form early in the day from KS into MO
in the moist sector with isolated severe possible. Veering winds
with height and favorable effective SRH may favor a couple
supercells producing either strong wind gusts or a brief/weak
tornado. The most likely time for concentrated severe storms will be
during the late afternoon and evening, beneath a strengthening 40-50
kt low-level jet centered over KS. Good model agreement exists
within the zone from KS into northern MO and IA depicting
significant storm coverage. Damaging wind appears to be the main
concern during the evening, and storms may persist into IA and even
western IL given strong westerlies aloft.
...Upper Mississippi Valley...
Scattered storms are expected throughout the day from MN into WI.
Early day storms may be associated with warm advection at 850 mb,
with a secondary area of storms along the cold front as it moves
across MN during the day. Marginal instability is forecast, with
long hodographs suggesting a wind or marginal hail threat. It
appears that a dry slot will move over the region during the day,
with veering winds above the surface. In addition, 850 mb wind
convergence will focus farther north into Ontario, with some models
showing speed divergence over MN. Therefore at this time, only
isolated severe storms are forecast.
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z