447
FXUS63 KUNR 031738
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1138 AM MDT Thu Apr 3 2025

.KEY MESSAGES...

- Temperatures to remain below seasonal norms through the end of
  week

- A weak system will bring chances for light rain and snow late
  today into Friday.

- Warmer and drier pattern setting up for later this weekend
  into next week

&&

.DISCUSSION...(Today Through Wednesday)
Issued at 307 AM MDT Thu Apr 3 2025

Current sfc analysis depicts strong low sitting over the Great
Lakes region with cold front arcing southward from WI to AR. Upper
level low is centered over northern MN/southern ON. Further west,
an upper level trough sits over the Four Corners region.
Nighttime RGB shows lingering upper level moisture contributing to
high clouds over most of the CWA.

Slightly warmer today with highs in the 40s to low 50s. Steep
lapse rates and weak instability (SB CAPE approaching 100 J/kg)
should support a few rain or snow showers over the Black Hills and
across northwestern SD into northeastern WY this afternoon. Weak
disturbance will move northward into the region from NE late today
with modest lift and moisture contributing to more substantial
chances for rain across southern SD tonight. Meanwhile, a northern
stream shortwave will sweep across the Northern Plains late
tonight into Friday with attendant cold front pushing through the
CWA through the day Friday. As the front moves into northwestern
SD, modest fgen and saturating moisture profiles will support a
decent burst of rain/snow as the front moves through. Snow
accumulations won`t be too impressive with HREF probs depicting
around 20-40% chance for 10:1 snow totals to exceed an inch over
northwestern SD. North-northwest flow will support a short period
of upslope snow as the front crosses the Black Hills. Again, not
expecting anything too impressive out of this with HREF probs
showing a 70-100% chance for 10:1 snow totals to exceed 2" and a
50-70% chance for 10:1 snow totals to exceed 4" across the
northern slopes/foothills. As the front pushes through the region,
it will meet with the southern stream disturbance and push the
bulk of the lift eastward. This will mean that the western SD
plains and most of the Black Hills won`t see too much precip out
of this event. 3 hr pressure rises of 2 to 4 mb behind the front
will support gusty northwest winds across the western SD plains
Friday. Widespread gusts of 30+ mph will be likely (HREF probs
80-100%) though advisory level gusts of 45+ mph are unlikely (HREF
probs at around 0%).

Very cool once again on Friday with highs in the 30s to low 40s.
As the trough exits and upper ridge builds into the western US
through this weekend, warmer temps and drier conditions will
return to the region. Deterministic models in general consensus of
upper level pattern transitioning to unsettled northwest flow by
mid week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1135 AM MDT Thu Apr 3 2025

VFR conditions are expected through much of today, the exception
being chances for rain/snow over the Black Hills this afternoon.
The next system will bring chances of rain and snow tonight into
Friday, along with widespread MVFR/IFR conditions, starting to
move in around 00-04z Friday.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...Dye