200
FXUS63 KUNR 182300
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
500 PM MDT Sat May 18 2024

.KEY MESSAGES...

- Warmer Sunday with thunderstorms. Strong to severe storms
  possible Sunday afternoon and evening across western South
  Dakota.

- Unsettled pattern continues through the coming week and weekend.

&&

.DISCUSSION...(This Afternoon Through Friday)
Issued at 1230 PM MDT Sat May 18 2024

Water vapor shows upper low along the ND/Canadian border, flat
ridge over the Northern Rockies, and upper low over southwest BC.
At the surface, high is building into western SD, with abundant
sunshine, some gusty northwest winds, and early afternoon temps in
the 50s/60s.

Warm front will lift back into the area after midnight tonight,
with 50kt low level jet and decent theta-e advection resulting in
a few late night showers/storms in our eastern and northern SD
zones.

On Sunday, upper low currently over southwest BC will dig into the
Northern Rockies, with southwest flow aloft through the Northern
Plains and temps rebounding into the 70s to mid 80s behind passage
of warm front. Cold front will work into far western during the
afternoon, with MLCAPE of 1000-2000J/kg. Scattered thunderstorms
will develop along the front first in the Black Hills then
spreading east onto the western SD plains through the afternoon
and early evening. The linear nature of expected storm development
along with inverted-v soundings would suggest more of a damaging
wind threat. Storms should exit the eastern zones by early
evening.

Next upper trof digs a little further south across the
Intermountain West on Monday. Northwest winds early will veer
northeast during the day as surface low develops over CO. Cloudy
skies and cool temps expected with highs in the 50s/60s. Lead
short wave will result in quite a bit of showers and non-severe
thunderstorm activity by late afternoon with precip chances
continuing through the night, with better chance for widespread
precip in southern half of zones. Cool/wet conditions likely to
continue into Tuesday as main upper low/trof shifts into the
Central Rockies.

Maybe a small break in precip chances on Wednesday behind first
departing upper trof, but next trof looks to work into the Rockies
by Thursday for more unsettled conditions. The unsettled pattern
with a nearly daily chance for showers/storms will continue into
next weekend. Temps should be close to seasonal averages.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 458 PM MDT Sat May 18 2024

VFR conditions are expected through most of the TAF period.
Isolated late night high based showers and thunderstorms will be
possible toward central SD. Otherwise, another low pressure system
will cross the region Sunday and support breezy winds and
scattered afternoon showers and thunderstorms, mainly across SD.
Local MVFR conds and gusty winds will be possible INVOF TS.

&&

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

$$

DISCUSSION/KEY MESSAGES...Johnson
AVIATION...JC