525
FXUS63 KUNR 271723
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1123 AM MDT Sat Apr 27 2024

.KEY MESSAGES...

- Isolated showers/storms possible this morning and afternoon,
  more widespread precipitation moves in this evening through
  Sunday afternoon.

- More seasonable temperatures move in early next week, along with
  near daily chances for showers/storms

&&

.DISCUSSION...(Today Through Friday)
Issued at 134 AM MDT Sat Apr 27 2024

Current Water Vapor and upper air models show first shortwave
over eastern SD into MN, while second wave sits over the four
corners region. At the surface, low pressure sits over the SD/MN
border, with another low over southwestern WY. Low clouds cover
much of the western SD plains. Temperatures currently sit in the
40s across the forecast area this morning.

Out ahead of the next wave, CAMs hint at isolated showers
possible later this morning and afternoon across the western South
Dakota plains, while bulk of expected precipitation moves in this
evening into Sunday as the upper trough swings into NE eventually
eastern SD. Ensembles continue to prog the wave a bit more to the
east, highlighting a sharp cutoff on QPF potential, with
northwestern SD remaining mostly dry. The better forcing continues
to be east and south of our forecast area, however will be enough
lift to see widespread precipitation. Areas east and south of
Rapid City may see amounts 0.25-0.75 inches of rainfall.
Precipitation tapers off from west to east Sunday afternoon.

Behind this weekend system, a more active near-zonal flow sets up
over the region, bringing chances for daily showers/storms. Weak
disturbance is progged to track north of the forecast Monday
evening into Tuesday. Chances for showers and storms will be
possible mainly over the Black Hills and northwestern SD. Weak
instability will keep severe chances low through mid-week.
Deterministic models become more divergent on the overall pattern
later in the week, however still point to potential for active
weather in the region.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1119 AM MDT Sat Apr 27 2024

MVFR CIGS over most of western SD will persist into the evening,
becoming IFR tonight as upslope flow lowers CIGS and patchy fog
develops. Isolated showers are possible this afternoon, but
widespread rain will develop east of the Black Hills tonight with
isolated thunderstorms over south-central SD. Over northeastern
WY, expect mainly VFR conditions this afternoon, except persistent
MVFR ceilings over the Bear Lodge mountains. Then redevelopment
of MVFR ceilings later tonight.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...15