724
FXUS63 KUNR 021857
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1257 PM MDT Mon Jun 2 2025

.KEY MESSAGES...

- There is a marginal (level 1 of 5) mainly along the SD/NE border
  for this afternoon and evening. Main threats will be large hail
  and damaging winds.

- Chances (40-60%) for showers and some storms Wednesday and
  Thursday

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 1255 PM MDT Mon Jun 2 2025

WV imagery depicts upper low centered over central Canada with
upper shortwave and secondary front draped across western ND into
northwestern SD and northeastern WY. A line of weak showers has
developed along this front and is currently moving across the
western half of the CWA. This line should continue to move
eastward through early afternoon, though low instability and weak
shear should prevent any stronger convection from occurring. RAP
reanalysis depicts corridor of 1000-1500 J/kg SB CAPE nudging into
southeastern SD as a sfc low develops over central SD. The
strongest instability will remain east of the CWA though near term
guidance does indicate 500-1000J/kg CAPE developing over portions
of Tripp County and along the SD/NE border. CAMs keep pretty much
all of the convection this afternoon just over the border in NE.

Cooler airmass moves in on Tuesday, keeping highs in the mid 60s
to low 70s. Next system moves through Wednesday as a shortwave
trof crosses the region. This system will bring showers and storm
to the region, though severe weather risk is minimal. Main
forecast challenge on Wednesday will be highs as cloud cover and
rain may keep temperatures lower than current guidance suggests.
The LREF and NBM have 25-75%-ile spreads of 4-7F for Wednesday
afternoon across much of the region. Regardless, it will be a mild
and rainy Wednesday for the CWA. Another weak disturbance will
move through the region Thursday afternoon with again, with
chances for showers and a few thunderstorms being the main weather
impacts.

Upper level ridge builds over the west coast bringing warmer and
drier conditions to the region by Friday into the weekend.
Deterministic models are showing an upper low grazing the region
later this weekend which would bring a slight cool down and slight
chances for precip to the CWA.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1137 AM MDT Mon Jun 2 2025

A secondary cold front will move through the area today with
increasingly gusty northerly winds behind it. SHRA/TS will develop
today, especially this afternoon/evening with local IFR
conditions. MVFR/local IFR CIGS will develop behind the front over
northeastern WY, spreading into southern SD this afternoon and
tonight.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...Dye