Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 232253
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
453 PM MDT Tue Apr 23 2024

.KEY MESSAGES...

- Mainly dry and warmer weather through Thursday morning.

- Unsettled, windy, and cooler conditions return late week, with a couple
  of systems bringing showers and some thunderstorms Thursday
  afternoon through the weekend.

- Warmer and drier weather quickly develops during the first half of
  next week.

&&

.DISCUSSION...(This Evening Through Tuesday)
Issued at 250 PM MDT Tue Apr 23 2024

Current surface analysis shows low pressure over the northern
Great Lakes, with high pressure moving over the northern high
Plains. Winds have been slowly decreasing this afternoon from west
to east as the high approaches the area. Upper level analysis
shows ridging over the Rockies, with trough well east of the
region. Another trough is located off the west coast. Skies are
mostly sunny with seasonable temps, mostly in the 50s to around 60
degrees early this afternoon.

Ridging to the west will bring warmer conditions to the region over
the next couple of days. Highs will reach into the 60s and lower 70s
Wednesday, with mostly 70s on Thursday. As far as pcpn chances are
concerned through early Thursday, would not rule out very isolated
showers and possibly a thundershower from the Black Hills into
southwest SD late Wednesday into Wednesday evening, with a few
showers and thundershowers also possible later Wednesday night into
early Thursday across southern SD as low level jet intensifies over
the central Plains into SD. Breezy conditions can be expected later
Wednesday morning into Thursday, especially east of the Black Hills.

As the ridge shifts east of the region later Wednesday night and
Thursday, trough off the west coast now will move quickly through
the southwest US and into the southern/central Rockies by late
Thursday. Energy ahead of the trough will push north-northeast into
the area Thursday afternoon and night as Pacific cold front
approaches from the west during the day. This will lead to increased
chances for showers and thunderstorms Thursday afternoon and
especially by the evening. Forecast MUCAPE values are expected to
reach 500 to 1000 j/kg in at least far northeast WY and much of
western SD during the afternoon, as low level moisture increases
ahead of the front. Shear looks rather weak across the area at this
time, which would limit organized storm potential. However, buoyancy
would be sufficient for at least briefly strong storms with some
hail and gusty winds. Will continue to monitor potential for any
stronger storms. As the trough moves northeast into the high plains,
a closed low is likely to develop over the central high Plains and
track fairly quickly across NE, eastern SD, and MN. This general
track with above average precipitable water values in place would
bring beneficial rainfall to many areas later Thursday night and
Friday, especially from the Black Hills area eastward, where chances
for a half inch or more of rainfall are 40 to over 80 percent. One
inch or more of rainfall has a 20 percent to over 50 percent chance
from the northern Black Hills to much of southwest/south central SD
right now. Gusty northwesterly winds will develop behind the front
into Friday, but chances for advisory level winds are mostly less
than 50 percent across the western SD plains. On the heels of this
system, another low is progged to develop over the central Rockies
Saturday and move east-northeast through the central Plains, likely
a bit further south and east than the first one. Better chances for
rainfall, at least more significant rainfall, should be southeast of
the Black Hills Saturday night and Sunday. Cooler air arrives for
Friday and especially the weekend, with highs Saturday and Sunday
only in the 40s and 50s. There could be at least a mix of rain and
snow over the higher Black Hills later Saturday night into Sunday.

The second system moves quickly out of the region Sunday night, with
warmer and drier weather quickly returning during the first half of
next week. Above average temperatures are expected early next week
as ridge builds back over the Rockies and Plains. There could be
some low chances for PM showers and thunderstorms Monday and
Tuesday, especially over the Black Hills, but most medium range
models are trending drier during this time.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Wednesday Evening)
Issued At 453 PM MDT Tue Apr 23 2024

VFR conditions will continue through the TAF period.

&&

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

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...10


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