965
FXUS63 KUNR 022242
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
442 PM MDT Thu May 2 2024

.KEY MESSAGES...

-Cool and unsettled through Friday

-Breezy/windy and warmer this weekend, with potential for high
 winds on Sunday

-Strong storm early-mid next week with windy/wet conditions

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 1251 PM MDT Thu May 2 2024

Water vapor shows main upper low near the SASK/MT border with
distinct short wave over the Dakotas, and next upstream short wave
over OR. At the surface, broad low covers ND with gusty westerly
flow across our area. Very steep lapse rates attributing to
scattered showers generally near/north of I-90 early this
afternoon.

Showers and wind will diminish quickly with loss of insolation
early this evening. Next upstream short wave (currently over OR)
will quickly shift into southern ID overnight and may bring a few
showers to our southwestern zones towards morning.

Showers will become more likely on Friday as short wave across WY
and towards western NE by later in the day. Best forcing will be
across our southern 2/3rds of zones, but lack of deep moisture
should keep qpf under 0.25 in south-central SD and under 0.10
across the rest of the area. Thermal profiles continue to remain
cold enough for some snow across the Black Hills and northeast WY
but any accumulations should remain minor.

Dry and warmer weather expected on Saturday with surface high
over the Dakotas and upper ridge over the Rockies. Even warmer on
Sunday with thermal ridge overhead, with highs in the 60s/70s.
However, a very impressive surface pressure gradient between
ridging over the Upper Midwest and trof coming off the Rockies
will likely result in strong southerly winds across the area and
wind highlights may become necessary.

Strong upper low shifts from the Great Basin on Sunday into the
Central Rockies on Monday, then lifting north into the Northern
Plains on Tuesday. Showers/storms will become likely by late
Sunday in our western zones, with continued very unsettled weather
through early-mid next week as upper low becomes somewhat cut-off
across the Northern Plains. Determinstic and ensemble solutions
continue to wobble around with the placement of the upper low,
which have big impacts on qpf amounts. Confidence for significant
qpf is highest over our northwest zones, including the northern
Black Hills, and lowest across our southern zones. NBM
probabilities for greater an inch are in the 40-60 percent range
generally north of I-90 as well as the Northern Black Hills and
15-30 percent further south.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 434 PM MDT Thu May 2 2024

Scattered -SHRA and perhaps an isolated TSRA will continue over
the forecast area through this evening. These showers/storms will
dissipate after 02z. Expect locally MVFR conditions and erratic
and gusty winds around any showers. VFR area wide overnight with
areas of MVFR conditions associated with -SHRA encroaching on the
southern portions of NE WY and SW SD into western SD after 12z as
another disturbance passes through from west to east.

&&

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

$$

DISCUSSION/KEY MESSAGES...Johnson
AVIATION...Wong