Hail in Wyoming, June 12, 2022

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
145 PM MDT Sun Jun 12 2022

.DISCUSSION...(This Evening Through Sunday)
Issued at 145 PM MDT Sun Jun 12 2022

Upper level and water vapor analysis show broad upper ridging over
the western half of the US with deep high pressure centered over
western Texas. Further upstream, an amplifying upper trough is
pushing onshore across the CA and OR coasts this afternoon. Ahead of
this trough, ample mid-level moisture is evident on water vapor and
IR imagery streaming through ID and into MT and northern WY. Embedded
shortwaves will push through the Northern Plains this afternoon and
evening, although overall large-scale forcing will be weak as
evidenced by neutral 500 mb height tendencies. At the surface, weak
high pressure is in place across the CWA with an area of low pressure
situated across eastern WY. As the afternoon progresses, low-level
temperature and moisture advection will continue into the evening
with south-southeasterly low-level flow.

Active weather will continue today despite the meager upper level
forcing. As the upper wave slowly pivots through the western US,
upper level flow has begun to shift west-southwesterly over the
forecast area. A weak boundary (sfc to ~850mb) resides across the
north-central portion of the CWA, stretching back into southern MT
and central  WY. This boundary will push southeastward with time
later this afternoon and evening. A favorable thermodynamic
environment is in place today with theta-e rich air situated below
steep mid-level lapse rates (700-500 mb lapse rates ~7-9C/km). As
such, MUCAPE of 2000-3000 J/kg will be in place through the evening
hours. This buoyancy will coincide with effective bulk shear
magnitudes of 50-70 knots, resulting in a favorable environment for
supercellular convective modes through the evening hours. While
some upscale growth is expected later tonight as storms interact
and cold pools consolidate, residual capping (via KUNR 19z RAOB,
where a subsidence inversion is evident from ~820mb-780mb) and weak
forcing is expected to keep initial storms discrete. Given the
overall environment, all hazards will be possible with any severe
convection today, particularly large hail and damaging wind gusts.
The greatest threat for tornadoes will stretch from NE WY through
the Black Hills into far NW SD along a nose of high theta-e air.
These areas will see the best overlap of low-level instability and
surface vorticity; 0-6/0-8 km bulk shear; and associated long,
looping hodographs with ample effective inflow-layer SRH in the
lowest few kilometers. Additionally, very heavy rainfall is likely
with these storms as PWATs are again 150-200% of normal.

Storms will exit the CWA after 06-08z tonight with areas of fog
developing, especially across NE WY, the Black Hills, and the
western SD plains. The severe weather threat will continue Monday as
the upper trough pivots through the central and northern Rockies.
Upper flow will become increasingly meridional Monday as the
trough approaches, ejecting embedded shortwaves through the region.
Strong thermal advection will result in temperatures pushing well
into the 90s for portions of the western SD plains into south-central
SD. Ample instability will be in place across the region, with
MUCAPE values ranging from 500-3000+ J/kg, highest across western
and central SD. While the strongest 0-6 km effective bulk shear will
be displaced northwest of the greatest instability, sufficient shear
(>35 knots) will be in place across much of the CWA for supercells
and severe convection. A strong cold front will push through from NW
to SE late afternoon into the evening. This front coupled with shear
vectors oriented parallel to the front will result in storms becoming
increasingly linear with time. A more significant severe weather
threat (2+ inch hail, 75+ mph wind gusts, and/or tornadoes) will
exist with any supercells that are able to outpace or remain
relatively discrete ahead of the front in the warm sector,
particularly NE WY and portions of NW SD.

Following the passage of the cold front late Monday, cooler and
unsettled weather will continue into Wednesday as upper trough
lingers over the region. This upper trough will slide east of the
area by Thursday morning with broad ridging centered over the
Northern Plains, north of an upper high centered over the central
and southern plains. Expect much warmer temperatures (90s to around
100) Friday into the weekend.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1101 AM MDT Sun Jun 12 2022

More thunderstorms are expected to develop this afternoon/evening,
with some of the storms becoming strong to severe with large hail
and damaging winds possible. MVFR/IFR cigs/vsbys are expected with
the stronger storms. Aft 08z look for MVFR/IFR cigs to again
develop behind the exiting storms. The lowest conds will be found
around the northern Black Hills and northwest SD/northeast WY.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

DISCUSSION...Eagan
AVIATION...Hintz

Hazardous Weather Outlook
National Weather Service Rapid City SD
424 AM MDT Sun Jun 12 2022

SDZ001-002-012>014-024>032-041>044-072>074-WYZ054>058-071-131300-
Harding-Perkins-Butte-Northern Meade Co Plains-Ziebach-
Northern Black Hills-Northern Foot Hills-Rapid City-
Southern Foot Hills-Central Black Hills-Southern Black Hills-
Custer Co Plains-Pennington Co Plains-Haakon-Fall River-
Oglala Lakota-Jackson-Bennett-Sturgis/Piedmont Foot Hills-
Southern Meade Co Plains-Hermosa Foot Hills-Northern Campbell-
Southern Campbell-Western Crook-Wyoming Black Hills-Weston-
Northeastern Crook-
424 AM MDT Sun Jun 12 2022

This Hazardous Weather Outlook is for portions of western South
Dakota and northeastern Wyoming.

.DAY ONE...Today and Tonight

There is a slight risk (level 2 of 5) of severe thunderstorms
today, meaning that scattered severe storms are possible. Primary
hazards include large hail, damaging winds, and isolated
tornadoes.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There is a slight risk (level 2 of 5) of severe thunderstorms
Monday, meaning that scattered severe storms are possible.
Primary hazards include large hail, damaging winds, and isolated
tornadoes.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today.

&&

Stay tuned to NOAA weather radio for further updates...or check
our web site at weather.gov/rapidcity

SDZ046-047-049-131300-
Mellette-Todd-Tripp-
524 AM CDT Sun Jun 12 2022

This Hazardous Weather Outlook is for portions of south central
South Dakota.

.DAY ONE...Today and Tonight

There is a slight risk (level 2 of 5) of severe thunderstorms
today, meaning that scattered severe storms are possible. Primary
hazards include large hail, damaging winds, and isolated
tornadoes.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There is a marginal risk (level 1 of 5) of severe thunderstorms
Monday, meaning that isolated severe storms are possible. Primary
hazards include large hail and damaging winds.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today.

&&

Stay tuned to NOAA weather radio for further updates...or check
our web site at weather.gov/rapidcity