Day 1 Severe Weather Outlook

Valid 071300Z – 081200Z


Thunderstorms associated with wind damage and isolated large hail
will be possible across parts of the Upper Mississippi Valley and
central Plains today. Additional storms with isolated damaging wind
gusts may occur from parts of the Carolinas northward into the

…Upper Mississippi Valley…
An upper-level trough will move across western Ontario and the upper
Mississippi Valley today as northwest mid-level flow remains over
the Upper Midwest. At the surface, a cold front in northern
Minnesota and eastern South Dakota will advance southeastward
reaching Upper Michigan, northern Wisconsin, southern Minnesota and
eastern Nebraska this afternoon. As surface heating takes place
ahead of the front, surface dewpoints in the mid to upper 60s F will
contribute to an axis of moderate instability. Thunderstorm
development will be possible along the instability gradient near the
front during the mid to late afternoon. Convection is first expected
to initiate in Upper Michigan ahead of the upper-level trough with
storms developing west-southwestward into northern Wisconsin. It is
uncertain how far west convection can develop but at least a few
storms will be possible in southern Minnesota.

RAP forecast soundings along the axis of instability late this
afternoon show 0-6 km shear near 35 kt, steep lapse rates in the
lowest 1 km AGL and veered west-southwesterly winds just ahead of
the front. This setup should be sufficient for damaging wind gusts
with the multicell line segments that organize and move
southeastward during the late afternoon and early evening. Hail will
also be possible with convection that develops in the strongest

…Central Plains/Ozarks…
Northwest mid-level flow will remain in place today across the
central states as a couple of minor shortwave troughs move
southeastward across the region. The southern shortwave trough is
forecast to move into the lower Missouri Valley today. Thunderstorms
are ongoing ahead of this feature in eastern Kansas. Substantial
uncertainty exists concerning how long the severe threat with the
MCS will be maintained. Some models suggest that the MCS will become
marginally severe by the time it reaches southeast Kansas. Some of
the same models regenerate storms by afternoon near the instability
axis in south-central Nebraska and move this new convection
southeastward into central Kansas. Deep-layer shear along this
corridor along with steepening low-level lapse rates could result in
the development of another cold pool. If that happens, then a
wind-damage threat can be expected to redevelop late this afternoon
into early this evening from north-central Kansas southeastward into
far northeast Oklahoma and far southwest Missouri.

…Eastern Seaboard…
An upper-level trough will move across the eastern states today as
southwest mid-level flow remains in place ahead of the trough from
the Mid-Atlantic into New England. At the surface, a cold front will
advance slowly southeastward across the lower Great Lakes. A
pre-frontal trough will deepen across the Eastern Seaboard. Surface
dewpoints ahead of the pre-frontal trough will be in the upper 60s F
to near 70 F. As surface temperatures warm today, a corridor of
instability will develop from the eastern Carolinas northward to
eastern New York and western New England. As the upper-level trough
approaches, scattered to numerous thunderstorms should develop west
of the strongest instability with convection moving
east-northeastward across the region. Although deep-layer shear is
forecast to be in the 20 to 30 kt range in much of the eastern
states, steep low-level lapse rates will make conditions favorable
for damaging wind gusts with the better-organized multicell line
segments. The severe threat should be maximized in the mid to late

..Broyles/Edwards.. 08/07/2019


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