National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KUNR 182006
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
206 PM MDT Thu Apr 18 2024

.KEY MESSAGES...

- Temperatures remain below normal through Saturday with breezy
  conditions and periodic light precipitation.

- Quick moving clipper Monday will bring windy conditions and
  chances of light precipitation.

- Warmer Sunday through next week with chances of thunderstorms by
  late next week.

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 202 PM MDT Thu Apr 18 2024

Water vapor imagery shows closed upper low centered over southern
Manitoba with a subtle shortwave clipping the forecast area and
subsidence/drying in its wake. A well-mixed boundary layer coupled
with upper level ascent from this shortwave has resulted in
scattered rain/snow showers across from the northern Black Hills
into the western South Dakota plains; although precipitation has
been light and will tapering off this afternoon. Surface winds
are gusty given the well-mixed boundary layer - widespread gusts
30-45 mph will persist through the evening hours before mixing and
strong winds cease.

Cool, breezy, and unsettled weather will persist Friday as the upper
low slowly shifts eastward. While large-scale forcing will be
largely absent Friday, steep low-level lapse rates will result in
breezy northwesterly winds and may provide enough impetus for
isolated rain/snow showers during peak heating along the northern
third of the CWA. Given the lack of larger scale forcing, have
kept the forecast dry.

Northwesterly flow will persist through Saturday. An upper trough
axis will drop through the Northern Plains late Saturday,
although moisture will be limited - main impacts will be continued
breezy conditions and increased cloudiness. Low-to-mid- level
flow will turn westerly early Sunday with warm air advection in
earnest by daybreak Sunday. Temperatures will surge into the 50s
across the Black Hills into the 60s across the WY and SD plains.

A robust clipper will drop out of western Canada late Sunday into
Monday. LREF guidance (GEFS/GEPS/EPS) keeps much of the
precipitation off to our east, with less than 5-10% of chance of
measurable precip across the forecast area. The main impact with
this clipper will be the cold front that arrives near daybreak
Monday with slightly cooler air (temps in the 40s to around 60F)
along with breezy northwesterly winds.

Large-scale ridging will quickly build behind this clipper as
temperatures surge back into the upper 60s to near 70 for the
latter half of the week. Chances of thunderstorms return Wednesday
into next week as southerly surface/low-level flow brings warmer,
more theta-e rich air back into the region.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1121 AM MDT Thu Apr 18 2024

Mainly VFR conditions expected through period. Local MVFR
conditions may occur near any showers over far northwest SD this
afternoon. Gusty northwest winds (35-40kt gusts) will subside this
evening.

&&

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

$$

DISCUSSION/KEY MESSAGES...SE
AVIATION...Helgeson