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255
FXUS63 KUNR 170841
AFDUNR

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

.KEY MESSAGES...

-- Changed Discussion --
- 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.
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&&

.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...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1024 PM MDT Sun Jun 16 2024

Scattered to numerous thunderstorms will lift northeast across
southwest and south-central SD overnight, mainly near and south of
I-90, then diminish around sunrise. IFR conditions expected with
the strongest storms. Around sunrise, low stratus will develop
near and south of I-90 across western SD, with lower probability
of the stratus expanding into northeast WY. Widespread MVFR and
areas of IFR ceilings expected with the stratus. The low stratus
may linger through much of the day Monday, especially south and
east of the Black Hills.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Johnson