Valid 060100Z – 061200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO
THE OVERNIGHT HOURS ACROSS PARTS OF THE UPPER MIDWEST INTO THE
MIDDLE MISSOURI VALLEY…
…SUMMARY…
Thunderstorm activity may continue to develop and overspread
portions of the Upper Midwest and middle Missouri Valley this
evening into the overnight hours, accompanied by a risk for strong
surface gusts and some hail.
…01Z Outlook Update…
…Upper Midwest into mid Missouri Valley…
The short wave perturbation digging across the central Canadian/U.S.
border area, which provided support for the initiation of ongoing
storms across the Upper Midwest/Great Lakes region, appears to be in
the process of turning eastward across the upper Great Lakes, and is
forecast to continue into southeastern Ontario/southwestern Quebec
overnight. In its wake, large-scale mid/upper support for
convection across the Upper Midwest into the middle Missouri Valley
becomes increasing unclear, but a corridor of moderate to large
boundary-layer CAPE lingers this evening ahead of the thunderstorm
activity, which has generally become focused along a southeastward
advancing cold front.
Due to veering of wind profiles with height, deep layer shear along
this corridor appears relatively strong, but northwesterly ambient
deep-layer mean flow is fairly modest (near or below 30 kt). The
lack of the development of a deeper, stronger convectively generated
surface cold pool probably has limited the risk for strong surface
gusts to this point. It is possible that this still could increase
somewhat this evening, particularly across parts of western and
central Iowa, where strongest potential instability exists,
mid-level inhibition does not appear overly strong, and a
west-southwesterly low-level jet may contribute to a southward
propagation of convection later this evening into the overnight
hours
..Kerr.. 08/06/2019
$$