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992
FXUS63 KUNR 171122
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
522 AM MDT Mon Jun 17 2024

.KEY MESSAGES...

- Non-severe storms and showers move out of the region later this
  morning.

- Re-development of showers and storms possible later today, some
  storms may be severe.

- Below normal temperatures continue for much of the week, warming
  up towards the weekend.

&&

.DISCUSSION...
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(Today Through Sunday)
Issued at 215 AM MDT Mon Jun 17 2024

Current surface analysis shows the boundary causing our overnight
storms and showers now east and south of the forecast area, with a
surface high located over southwestern ND. Behind the boundary,
some showers and storms still continue for southwestern and
south central SD, and will move out later this morning. At the
upper levels, southwest flow sits over the region, with a Low over
the PAC NW. Temperatures sit in the 50s early this morning, with
light and variable winds.

Through the day, PAC NW low swings over the northern Rockies.
Surface low swings into WY by mid-day into this evening. Warm
frontal boundary setting up ahead of the trough may fire up some
thunderstorms over northeastern WY this afternoon. As for western
SD, shower and storm potential will be highly dependent on cloud
cover throughout the day. While models all agree on a stratus deck
covering much of western SD, they do differ on extent and timing
of clouds clearing out. Areas without stratus, or with the stratus
deck breaking up earlier in the day will have a better for
potential for severe storms. Main threats for severe storms today
will be large hail and strong winds, however south central SD may
be a prime location for tornado development with the better low
level helicity near the boundary.

Upper trough swings over the northern plains Tuesday, and
precipitation chances will continue, mainly over northwestern SD
and south central SD. Southwest flow aloft sticks around for the
remainder of the week, with models showing mild disturbances
riding the flow near daily. This will allow for active weather to
continue into next weekend, though some days precipitation may be
very isolated. Low level flow becomes predominantly out of the
south-southeast midweek and later, and we can expect a warming
trend towards the weekend.
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&&

.AVIATION...
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(For the 12Z TAFS Through 12Z Tuesday Morning)
Issued At 518 AM MDT Mon Jun 17 2024

Scattered thunderstorms with local IFR conditions over
western/south-central SD will lift northeast and diminish this
morning. Behind the storms, MVFR/areas IFR stratus will develop
over the western SD plains on easterly boundary layer flow,
possibly pushing into far northeastern WY. Late this afternoon
into the evening hours as a cold front moves through,
thunderstorms with local IFR conditions will develop with erratic
gusty winds and hail possible through 06z Tuesday. Behind the cold
front, areas of MVFR stratus will develop overnight.
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&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Helgeson