946
FXUS63 KUNR 011921
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
121 PM MDT Wed May 1 2024

.KEY MESSAGES...

-Cool/unsettled weather continues through Friday

-Warmer this weekend

-Strong storm with wet/windy conditions early next week

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 100 PM MDT Wed May 1 2024

Water vapor shows broad upper lower southern ALTA/SASK and MT,
with short wave ejecting from the Central Rockies. At the
surface, inverted trof extends through eastern WY into northwest
SD. Widespread -shra have been ongoing since early this morning
across southwest through central SD.

Showers and a few storms will continue to develop this afternoon
and evening as short wave ejects northeast through the Northern
Plains, with the best chance for widespread precipitation from the
Black Hill eastward. Northwest winds will be on the increase as
surface trof pushes through tonight. Precipitation should quickly
end from west to east later this evening and overnight.

Aforementioned upper low will slowly move eastward along the
US/Canadian border through Friday. Should be plenty of subsidence
on Thursday behind the departing short wave, although diurnal
showers and a few storms will remain possible, especially from the
Black Hills into northwest SD. Better chance for showers/storms on
Friday will be from the Black Hills through southwest/south-
central SD with arrival of next short wave. Both days will see
breezy west/northwest winds and highs in 50s to lower 60s.

Upper trof axis will finally shift through on Friday night with
main upper low ejecting northeast towards the Hudson Bay. Upper
ridge axis building in for Saturday will bring dry and warmer
conditions to start the weekend.

Upper ridge axis shifts east on Sunday as strong upper low digs
into the Intermountain West. Gusty southerly winds will likely
develop across the area Sunday with temps pushing well into the
70s at many locations. Showers/storms will become more likely
Sunday afternoon across northeast WY into the Black Hills,
spreading eastward Sunday night.

Strong upper low will track through the Central Rockies and out
into the Northern Plains by Monday before possibly getting cut-off
from the main flow. The result will be wetter/cooler/windy
conditions for early next week. Exact track of the low will
determine how much precipitation we receive, and those details
will likely become more clear with time.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1130 AM MDT Wed May 1 2024

Scattered to numerous showers, and a few thunderstorms, are
expected through this evening. LCL MVFR conditions are possible,
especially with the stronger showers and storms. AREAS MVFR/LCL
IFR conditions will develop over parts of western and south
central South Dakota after 06Z tonight. With conditions gradually
improving from west to east and becoming all VFR conditions after
16Z on Thursday morning.

&&

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

$$

DISCUSSION/KEY MESSAGES...Johnson
AVIATION...10