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000
FXUS63 KUNR 251057
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
457 AM MDT Thu Apr 25 2024

.KEY MESSAGES...

- Thunderstorms expected this afternoon and evening. Heavy rain,
  small hail, and gusty winds possible.

- More widespread precipitation expected Friday through much of
  the weekend.

- Warmer and dry conditions move in early next week.

&&

.DISCUSSION...(Today Through Wednesday)
Issued at 218 AM MDT Thu Apr 25 2024

Current Water Vapor and upper air models show mild upper ridge
over the northern and central plains this morning, while weak
upper low sits over the southwest CONUS. At the surface, high
pressure sits over eastern NE, with a surface low over north
central CO. Temperatures this morning sit in the mid 40s to mid
50s, with light winds.

Return flow and WAA will raise dew points this afternoon into the
upper 40s and low 50s over much of western SD. With daytime
heating and added moisture, expect storms/showers to develop late
this morning into the afternoon. Severe parameters aren`t co-
located well, with the better CAPE today being over far western
SD, and the best 0-6km shear over south central and central SD.
Black Hills and southwestern SD sit in marginal risk for today,
where the better instability (1000-1500 j/Kg) and weaker capping
is expected. As storms travel east into the better shear
environment, larger hail may be possible.

Later Thursday night into Friday morning, upper wave swings
through CO and into NE. Wrap-around precipitation will fill in
over much of the forecast area. Then later Saturday into Sunday, a
secondary wave swings up from the four corners into the plains.
While precipitation diminishes early Saturday from the first
system, expect redevelopment over much of the region.  A more
northerly track coupled with less moisture will keep the higher
QPFs over this round east of the CWA. NAEFS probabilities keep us
in the 99.5% Friday morning through the first half of Saturday,
dropping to the 90th percentile through Sunday. Widespread 1-2"
QPF will be possible through the weekend. Following passage of
this system, 2-3mb/3hr press rises will make for a breezy Sunday.
Expect temperatures to also cool off for the weekend with these
systems passing through, with highs mainly in the 40s and 50s.

Moving into next week, upper flow becomes quasi-zonal, with drier
conditions expected. By mid-week, upper ridge builds back into
the northern/central plains, with temperatures gradually warming
back into the 70s by Tues/Weds. Long-range models hint at upper
trough swinging across southern Canada into the northern plains
towards next weekend, and we may see a return to unsettled
weather.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Friday Morning)
Issued At 453 AM MDT Thu Apr 25 2024

VFR conditions are expected through early afternoon. Showers and
thunderstorms will increase in coverage and intensity after 20Z.
MVFR/IFR conditions are expected with the heavier precipitation.
Widespread MVFR/local IFR conditions expected tonight with
expanding area of stratus and showers.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...7