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000
FXUS63 KUNR 140412
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1012 PM MDT Sat Apr 13 2024

.KEY MESSAGES...

- Warm with elevated fire weather conditions this weekend.

- Severe thunderstorms possible Monday.

- Unsettled, windy, and gradually colder weather expected for
  much of next week.

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 214 PM MDT Sat Apr 13 2024

Upper level ridge continues to shift east today as the thermal
ridge passes over the region. Expect a shift to much cooler and
unsettled flow this upcoming week as mean troughing develops over
the western CONUS. Temps have risen well into the 80s today at
many locations, with a few 90s in scentral SD. Mixed out BL with
sufficient CAPE is in place supporting some convection on the
Black Hills. Still expecting a few isolated showers and maybe a TS
as a weak shortwave advects through the flow late this afternoon.
Slightly cooler, but still well above normal temps Sunday with
another day of 70s/80s expected under dry flow. Winds will shift
back to the SE in response to the ejecting deep upper trough and
reflected sfc low. SE upslope winds will limit temps to some
extent. Upper ridge will begin to break down early next week as a
deep upper trough pushes into the western CONUS. Sfc low will
cross SW SD with increasing SE flow ahead of the inverted sfc
trough. As the upper trough and associated strong upper jet streak
nears the region, LSA will ramp up by afternoon. The sfc trough
will then provide the focus for showers and TS. Appreciable ll
moisture with 50s dewpoints will advect into the FA ahead of the
trough, supporting plenty of CAPE (around 1000 J/kg) by afternoon.
Deep bulk shear in excess of 40 knots will be more than
sufficient for rotating updrafts and resultant low topped
supercells by late afternoon/early evening. Some hires models
suggest that there could be a small window for a tornado threat in
far SW SD given increasing 0-1 km shear as the ll flow backs per
diurnal cooling and sfc low deepening. Something to definitely
keep an eye on. However, the main threat will mainly be isolated
large hailers. Severe threat will quickly wane by later in the
evening with increasing chances for showers and isolated TS
overnight. Main cold front will then cross the region Tues with a
potential high wind event in the making given expected pressure
rises, CAA, and eastern BH squeeze. Some models are suggesting
that gusts in excess of 65-70 mph will be possible on the plains
east of the BH Tues on the backside of this system. Otherwise,
showers chances will wane through Tues. Unsettled westerly flow
will persist through the remainder of the week as a series of
impulses cross the region. Much colder air will arrive after Wed,
with precip chances shifting to snow, esp in NE WY and the BH
where some light accums will be possible. Cool conds will then
persist into next weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1012 PM MDT Sat Apr 13 2024

VFR conditions are forecast through the TAF period.

&&

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

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...Helgeson