SPC AC 190600
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Wed Sep 19 2018
Valid 201200Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM IOWA AND
SOUTHEAST MINNESOTA INTO WISCONSIN AND SOUTHERN UPPER MICHIGAN...
Severe storms will be possible Thursday from portions of the central
Plains northeastward to the Upper Great Lakes region.
While a ridge aloft persists over the eastern U.S., eastward
progression of a trough out of the Rockies and across the central
U.S. is expected Thursday. At the surface, the progression of this
trough will result in a deepening surface cyclone, progged to shift
northeast out of the Plains and across the Upper Great Lakes through
the second half of the period. A trailing cold front should focus a
band of strong/locally severe storms, peaking in coverage and
intensity in the late afternoon and evening hours.
...Parts of Kansas northeast into the Upper Great Lakes...
Surface low pressure initially over the central Plains is expected
to deepen with time as it shifts northeastward across the Upper
Mississippi Valley and Upper Great Lakes area. As this occurs,
diurnal heating ahead of the low -- and trailing cold front -- will
result in afternoon destabilization, likely maximized from the upper
Midwest into the Upper Great Lakes area.
As the cold front advances across the central Plains and
mid-Missouri Valley, scattered afternoon thunderstorms are likely to
initiate along the cold front. Upscale growth into a frontal squall
line is expected to occur through the afternoon, such that by
evening a fairly solid line of storms should be crossing western
portions of the risk area. Here, damaging winds and hail risk is
expected, given relatively strong flow aloft progged to be spreading
east ahead of the upper trough. Across northern portions of the
risk area -- i.e. central Wisconsin and into southeast Minnesota,
more isolated storms may persist just ahead of the low and
eastward-extending warm front. Here, some risk for tornadoes may
evolve, along with hail/wind risk.
As the low continues moving quickly northeastward along with the
associated warm front through the evening hours, continued eastward
advance of the cold front -- and associated band of storms -- is
expected. Gradual weakening of the storms, and corresponding
decrease in severe potential, should begin later in the evening as
the band of storms moves across the upper Mississippi and Mid
...MAXIMUM RISK BY HAZARD...
Tornado: 5% - Slight
Wind: 15% - Slight
Hail: 15% - Slight
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z