652 
ACUS01 KWNS 162001
SWODY1
SPC AC 162000

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0300 PM CDT Wed Jun 16 2021

Valid 162000Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE
UPPER MIDWEST AND SOUTH ATLANTIC COAST...

...SUMMARY...
Isolated severe hail and damaging winds will be possible through
early evening from north Florida to southern South Carolina, and
mainly tonight across southern Minnesota into Iowa.

...Discussion...
No appreciable change is needed to the previous convective outlook.

..Smith.. 06/16/2021

.PREV DISCUSSION... /ISSUED 1128 AM CDT Wed Jun 16 2021/

...Upper Midwest...
A shortwave trough moving east across the Prairie Provinces will aid
in suppression of the mid-level ridge across the Upper Midwest to
northern Ontario. A trailing cold front will advance east across the
central and eastern Dakotas into western MN, arcing southwestward
across northeast to southwest NE by tonight. Warm advection between
850-700 mb will likely maintain sufficient MLCIN to mitigate late
afternoon storm development along the front, owing to a confined
moderately rich boundary-layer moisture plume emanating north from
the Ozarks to Mid-MO Valley. The one exception may be in the
southeast SD vicinity where surface temperatures approaching 105 may
be adequate to remove MLCIN. Here, a conditional risk exists for a
high-based storm capable of severe wind and marginal hail. 

Otherwise, the main convective development should be driven by
low-level warm/moist-advection tonight across parts of MN/IA along
the periphery of the more stout EML farther west in the Great
Plains. Cloud-layer shear should be relatively modest with a fairly
uniform northwesterly flow regime lacking in appreciable
strengthening of winds above 500 mb. This should result in a
predominant cluster convective mode. Despite convection likely
initially being rooted closer to 700 mb, the steep lapse rate
environment above 850 mb should yield ample DCAPE, which may support
a threat for strong to locally severe winds in addition to isolated
severe hail overnight. Below-average confidence exists in the degree
of overnight severe coverage, as well as its spatial location,
mitigating an upgrade.

...FL/GA border to southern SC...
Despite a reduction in potential peak MLCAPE today after yesterday's
convective overturning, a plume of low 70s surface dew points
persists to the south of a stalled surface front. This buoyancy
reduction should be compensated by stronger deep-layer shear and
ascent tied to a shortwave impulse approaching from the southern
Appalachians. This renders enough concern for a few updrafts capable
of producing isolated severe hail and locally damaging winds to
warrant a cat 1/MRGL risk this afternoon into early evening.

$$