Valid 051630Z – 061200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
IOWA INTO SOUTHERN MINNESOTA AND MUCH OF WISCONSIN…
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
THE UPPER MIDWEST AND GREAT LAKES REGION AS WELL AS OVER A PORTION
OF THE CENTRAL HIGH PLAINS…
…SUMMARY…
Organized severe-storm clusters will pose a threat mainly of severe
winds today, across upper parts of the Midwest, Mississippi Valley
and Great Lakes. Other strong to severe storms with downburst winds
and hail are possible over a portion of the northern and central
High Plains.
…Upper Midwest and Great Lakes region…
An MCS continues eastward through northwestern WI this morning and
is associated with a progressive MCV that is embedded within the
base of an amplifying upper trough. The moist boundary layer
downstream continues to destabilize with 2000 J/kg MLCAPE expected
this afternoon. Destabilization in conjunction with increasing
mid-upper flow within the amplifying trough suggest intensification
of the current activity and/or redevelopment along the residual
outflow boundary should foster organized severe storms into the
afternoon from northern WI into upper MI. Farther south and west,
across southern WI, MN into northern IA surface dewpoints are near
70 F which will support 2500-3000 J/kg MLCAPE as diabatic heating
of the warm sector continues. Storms are expected to redevelop along
and south of the southeast-advancing cold front this afternoon.
Vertical wind profiles with 30-40 kt effective bulk shear will
support organized storm structures that will eventually evolve into
lines and bowing segments with damaging wind and hail into the
evening.
…Northern and central High Plains…
Severe thunderstorms appear most probable later this afternoon into
early tonight from northeastern WY across parts of southwestern SD
into northwestern NE. Activity is forecast to form over the terrain
of northern WY in a regime of upslope flow and diabatically
minimized MLCINH. Severe hail and wind gusts will be the main
concern, though uncertainty remains regarding storm longevity and
potential support from self-sustaining cold-pool processes.
Convection should follow a moisture/instability axis southeastward
at least into parts of the Black Hills/Sandhills area this evening,
with forced ascent along the cold pool.
..Dial/Bentley.. 08/05/2019
$$