ACUS02 KWNS 241704
SPC AC 241703
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1203 PM CDT Mon Jul 24 2017
Valid 251200Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN SD TO
CENTRAL MN AND NORTHWESTERN WI...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
NORTHERN HIGH PLAINS TO THE UPPER GREAT LAKES...
A few severe thunderstorms with damaging winds and large hail will
be possible across portions of the northern Plains and the Upper
Mississippi Valley Tuesday afternoon and evening.
...Northern Plains and Upper MS Valley Tuesday afternoon/evening...
A closed midlevel low over AB/SK will translate eastward across MB
to western ON, as an associated surface cold front moves
southeastward across the Dakotas and MN. Some increase in low-level
moisture is expected through advection from the south and regional
evapotranspiration, beneath a plume of steep midlevel lapse rates
from the west. The net result will be a corridor of moderate-strong
buoyancy (MLCAPE values of 2500-3500 J/kg) ahead of the cold front,
when convective inhibition will be reduced by late afternoon.
In addition to the southern fringe of the height falls with the
Canadian shortwave trough, other embedded speed maxima will eject
eastward from the northern Rockies, on the northwest periphery of
the southern High Plains ridge. Thunderstorms should form by late
afternoon along the front and persist into the overnight hours,
maintained by warm advection on the nose of a nocturnal low-level
jet across the central Plains. The substantial buoyancy will
support strong updrafts and the potential for large hail in the
steep lapse-rate environment, though vertical shear and the mode of
initiation will perhaps favor clusters/bands of storms with damaging
winds (especially toward southern MN and eastern SD), as opposed to
discrete supercells. The severe-storm threat will diminish
gradually by 06z.
Scattered thunderstorms will continue from the Great Basin into the
Rockies, within a persistent monsoonal moisture plume around the
western periphery of the southern High Plains ridge. Isolated
strong outflow gusts may occur across NV where low-level lapse rates
will be steep and deep-layer shear will be a little stronger,
immediately east of the weak closed low over northern CA. Largely
diurnal convection will occur again across the Southeast, along and
south of a weakening stalled front. Isolated strong downburst winds
cannot be ruled out during the afternoon with multicell storms.