Chalk Butte, South Dakota Weather Forecast Discussion

960
FXUS63 KUNR 171719
AFDUNR
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1119 AM MDT Wed Sep 17 2025
.KEY MESSAGES...
-Cool and unsettled through Thursday with scattered showers and
 isolated thunderstorms
-Rainfall amounts of one half inch to one inch expected on much
 of the western SD Plains
-Dry and warmer this weekend into next week
&&
.DISCUSSION...(Today Through Tuesday)
Issued at 117 AM MDT Wed Sep 17 2025
Slow moving upper low will support widespread rains across the
area today and tonight. Deeper upper trough in the northeast Pac
will then kick the western NOAM ridge east this weekend, with
warmer and dry conditions. Upper low over WY continues to support
deep layer southerly flow over the region aloft with moisture
ladden Gulf flow. Convective complex to the south in NE/KS has
jammed up moisture transport for now. However, that will change
later this morning as the systems slowly shifts east and
convection wanes. Expect showers to develop later this morning,
becoming more widespread this afternoon. System deformation zone
will then concentrate lift across western SD later this afternoon
and evening with decent rain fall amounts of one half inch or more
expected under this feature. Right now, model consensus places
this feature from the Black Hills into north central SD. Hence,
tailored the highest pops and highest QPF amounts there. Dry air
on the west side of this system will support a sharp cutoff to
precip as the deformation zone intensifies this evening, with
portions of northeast WY drying out tonight. Rain will persist
overnight into Thur morning with things beginning to dry out in
the western half of the FA as the system shifts east. With all the
rain and clouds, cool conds can be expected with highs in the 50s
and 60s most areas today and Thursday where clouds and rain
persists. Where the sun does make it out, low 70s can be expected
(mainly northeast WY Thur). Breezy north winds can also be
expected the next two days, esp on the Plains east of the Black
Hills where gusts over 30 mph are forecast. Things dry out this
weekend with warmer temperatures, as highs climb back into the 70s
and 80s as the ridge shifts east, warmest Sunday. A fast moving
upper trough will then support a cool front across the region
Monday, with breezy winds and slightly cooler temps. Another sharp
ridge looks possible next week over the Rockies with the FA on
the eastern side of the ridge. This would support warm and dry
conds locally most of the week, with chances for rain returning
toward the end of the week.
&&
.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1114 AM MDT Wed Sep 17 2025
A low pressure system will bring deteriorating flight conditions
across much of the region today. MVFR/IFR conditions expected to
develop across most of western SD with local LIFR around the Black
Hills by late afternoon/early evening in rain and isolated
thunderstorms. Areas MVFR CIGS will slide into northeastern WY at
times as precipitation rotates through. Breezy north winds will
continue through Thursday across western SD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...JC
AVIATION...Helgeson

NWS UNR Office Area Forecast Discussion