853
FXUS63 KUNR 211844
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1244 PM MDT Tue May 21 2024

.KEY MESSAGES...

- Relatively active pattern expected through Memorial Day weekend.

- Somewhat drier and warmer early to mid next week with upper
  ridge building in.

&&

.DISCUSSION...(This Evening Through Tuesday)
Issued at 1228 PM MDT Tue May 21 2024

Water vapor shows upper trof extending from SASK through the
Central Rockies, with upper low over WY. Short wave is ejecting
from the Central Plains into the Midwest. At the surface, high is
building in from the northwest. Scattered showers continue across
much of the area early this afternoon with temps in the 40s/50s.

Showers and a few thunderstorms will continue to increase in our
western zones this afternoon and evening as upper low over WY
shifts east. Best lift with this low will extend from northeast
WY through the Black Hills into southwest SD. Precipitation should
end from west to east overnight. Clearing skies and light winds
could lead to some frost overnight, especially over northeast WY.

For Wednesday, a short wave ridge overhead will bring mostly dry
and warmer conditions to the area, with only a small chance for
showers/storms over the Black Hills.

Next trof crosses the Northern Rockies on Thursday and into the
Northern Plains Thursday night. There will be enough return
flow/instability for some stronger to severe storms along the
associated cold front across our eastern third of zones in the
afternoon/evening, with good chances for showers/storms through
the night especially across our northern zones.

Friday looks drier behind departing upper trof, with next trof set
to arrive late Saturday into Sunday for more unsettled weather.
Medium range guidance is suggesting a ridge building in for early
to mid next week, which would result in somewhat drier and warmer
conditions.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1119 AM MDT Tue May 21 2024

Scattered showers and isolated thunderstorms are expected through
today with MVFR/local IFR ceilings and visibility. Conditions will
trend toward VFR across the forecast area after 22-00z tonight.

&&

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

$$

DISCUSSION/KEY MESSAGES...Johnson
AVIATION...SE