887
FXUS63 KUNR 171720
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1120 AM MDT Tue Jun 17 2025

.KEY MESSAGES...

-Scattered showers and thunderstorms today

-Warming and drying trend the remainder of the week, with
 temperatures approaching 100 by the end of the week on portions
 of the SD Plains

-Cooler and unsettled next week

&&

.DISCUSSION...(Today Through Monday)
Issued at 142 AM MDT Tue Jun 17 2025

Unsettled westerly flow will support one more day of scattered
showers and thunderstorms today, before mean ridging ensues over
the Rockies. Departing impulse and associated showers and storms
will be followed by yet another wave today. Main frontal boundary
and associated deep moisture has shifted south of the FA, per
several recent impulses. However, weak CIN will be in place over
the southern 2/3 of the FA today, with yet another wave expected
to traverse the region. Sufficient lingering moisture combined
with diurnal heating will also for increasing chances for
convection today. The weakest CIN and best chances for
showers/storms will be over the Black Hills, esp the southern BH
where LL convergence will be in place per northerly flow. Outside
and away from the BH, convention will be more scattered to
isolated. A few stronger cells will be possible, supporting gusty
winds and small hail given ML CAPE 500-1000 J/KG. However, bulk
shear will be lacking, with storms expected to be of a pulse
nature. Much cooler temps can also be expected across the BH into
portions of northeast WY today given clouds and showers. Activity
will peak this afternoon, then shift east and wane through
evening. Weak high pressure will advect into the region overnight,
supporting clear skies and light winds. Some patchy fog will be
possible on the Plains as well. Northeast Pac upper low will shift
south and support downstream ridging over the Rockies. This will
allow for height rises to shift east into the region, supporting
dry weather and warm weather the rest of the week. There is medium
confidence for temps to break 100 on the SD Plains Thur-Sat, east
of the Black Hills into scentral SD, esp if very dry westerly
flow spreads across the southern FA akin to GFS progs. Right now,
things look dry for the FA Wed through Sat. However, as impulses
traverse the northern side of the ridge, MCS clusters look
possible esp given the degree of LL moisture progged across
eastern SD into ND. These clusters cloud certainly clip NW SD this
weekend if the frontal boundary is biased enough south by these
systems. A stronger trough will eventually force the front south
into the region by early next week, with unsettled and cooler
conds likely.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1118 AM MDT Tue Jun 17 2025

A disturbance will bring scattered/numerous shra/TS to the region
this afternoon/evening, most numerous this afternoon over/near the
Black Hills. Local MVFR conditions, gusty winds, and hail will
occur with the stronger cells. Outside of storms, VFR conditions
will prevail. Patchy fog will be possible later tonight into
Wednesday morning, particularly well east of the Black Hills.

&&

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

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...Helgeson