293
FXUS63 KUNR 162334
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
534 PM MDT Wed Apr 16 2025

.KEY MESSAGES...

- Precipitation chances increase this evening through Friday
  morning.

- Active pattern will bring seasonable temperatures and unsettled
  weather through early next week.


&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 213 PM MDT Wed Apr 16 2025

Current Water Vapor and upper air models show upper low/trough
centered over northern Idaho this afternoon, with southwest flow
aloft the FA as upper ridge flattens off to our east. Surface
charts depict low pressure over northwestern ND with a cold
frontal boundary running through southwestern MT. Temperatures
currently sit in the 70s to low 80s

Tonight into Thursday, upper trough digs into the Rockies and
slides eastward. Surface cold front moves into the FA as well.
Some isolated showers may be possible ahead of the front this
evening, but bulk of the precipitation comes in post frontal
Thursday. Still some uncertainty on QPF amounts, as some
deterministic models go up in the 1" plus range. Ensembles
trending a bit lower and have tamed down amounts a bit. Both HREF
and NBM probabilities of QPF >= 0.5" max out at around 40 to 60
percent over the Black Hills and parts of northeastern WY,
dropping off quickly elsewhere. Little to no signal for prob 1"
QPF potential. Low level CAA will transition the Black Hills and
northeastern WY to snow early Thursday, while other areas can
expect rain or a rain snow mix. Given the time of year, warmer
ground temperatures, and bulk of QPF looking like it will be
during the day Thursday, have opted away from any potential snow
headlines for areas outside of the Black Hills. WSSI probabilities
shows 50 to 60 percent chance for minor impacts to the higher
elevation northern Black Hills areas where 3 to 6 inches could be
possible through Friday morning, have issued a Winter Weather
Advisory for this area. Low end wind headlines may be necessary
during the day Thursday following the frontal boundary. Forecast
thermal profiles do not quite reach criteria, however ensemble
guidance does point to 50-60 percent chance of >= 45 mph over some
of our western SD plains area.

Dry and cool conditions are then expected later Friday through
Saturday. Progressive flow is expected the first half of next
week, maintaining seasonable temperatures and unsettled weather.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 534 PM MDT Wed Apr 16 2025

VFR conditions are expected through this evening. A cold front
will move through after midnight, bringing some MVFR/IFR/LIFR
conditions and rain/snow to northeastern WY and northwestern SD
after 08Z. Additionally, northwest winds will be 15 to 25 mph
with gusts up to 40 mph with the front. There is a chance for some
VCFG at the KGCC site by 18z.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 6 AM Thursday to 9 AM MDT Friday
     for SDZ024.
WY...Winter Weather Advisory from 6 AM Thursday to 9 AM MDT Friday
     for WYZ057.
&&

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Woodward