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000
FXUS63 KUNR 250858
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
258 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 06Z TAFS Through 06Z Thursday Night)
Issued At 944 PM MDT Wed Apr 24 2024

Isolated light showers are possible over northeastern Wyoming,
the Black Hills area and southwestern South Dakota tonight through
Thursday morning. Showers and thunderstorms will increase in
coverage and intensity after 20Z on Thursday afternoon. VFR
conditions will continue through Thursday morning. Widespread MVFR
CIGS will develop over south central South Dakota after 20Z on
Thursday afternoon and will continue through the evening. Mainly
VFR conditions are expected over the rest of the area with LCL
MVFR conditions possible with the stronger showers and
thunderstorms on Thursday afternoon.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...10