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 Forecast Discussion


000
ACUS03 KWNS 181113
SWODY3
SPC AC 181112

Day 3 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0612 AM CDT Tue Sep 18 2018

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
PLAINS AND MIDWEST TO THE UPPER GREAT LAKES...

CORRECTED THUNDER LINE

...SUMMARY...
Severe storms will be possible Thursday from portions of the central
Plains northeastward to the Upper Great Lakes region.

...Synopsis...
Stout upper ridging is progged to persist Wednesday over the eastern
states, which will result in the advancing trough being shunted to
the northeast with time as it exits the Rockies and crosses the
north-central states.  By the end of the period, the deamplifying
trough should be centered over the Upper Great Lakes region, while
the dominant ridge remains centered over the Southeast.

At the surface, a low initially progged to be crossing the
Mid-Missouri Valley/upper Midwest should deepen as it shifts across
the Upper Great Lakes toward southern Ontario/western Quebec.  A
trailing/advancing cold front will focus a zone of thunderstorms --
and some severe risk -- from the central Plains to the Upper Great
Lakes region.  

...The Mid-Missouri and Upper Mississippi Valleys, and Upper Great
Lakes...
Diurnal heating of the pre-frontal boundary layer is expected, as
the low -- and warm front -- shift northward into/across the Upper
Great Lakes.  Resulting destabilization, combined with large-scale
ascent focused near the surface cold front will support afternoon
storm development -- from Kansas northeast to the Upper Great Lakes.

With strong southwesterly flow aloft spreading atop the frontal zone
-- particularly from roughly Iowa northward, a few stronger storms
appear likely to evolve through the afternoon, possibly growing
upscale with time into a line/band of locally severe convection. 
Large hail and locally damaging winds appear to be the primary risk
with stronger updrafts, with risk likely diminishing gradually after
dark into the Midwest and toward the lower Great Lakes.

..Goss.. 09/18/2018

$$