512
FXUS63 KUNR 091037
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
437 AM MDT Sun Jun 9 2024

.KEY MESSAGES...

- Marginal risk for strong to severe storms across northeastern
  WY this afternoon and evening

- Better chances for severe weather on Monday as a stronger
  wave moves through the region

- Near to above average temperatures with near daily chances
  for showers and storms through the end of the week.

&&

.DISCUSSION...(Today Through Saturday)
Issued at 232 AM MDT Sun Jun 9 2024

Upper air analysis depicts the northern plains under west-
northwest flow. A weak shortwave is crossing over WY with a few
thunderstorms struggling to develop given the limited moisture.
This shortwave will continue to cross through the region early
this morning, bringing low chances for showers/storms across
northwestern SD this morning. Dewpoints across northeast WY have
climbed into the 50s as low level moisture begins to advect into
the region, this should be sufficient for some low stratus/fog to
develop through the early morning hours. A stronger wave is
developing over the PacNW with more moisture to work with and
there`s some convection that`s developed over eastern OR into
western ID.

For Today: Shortwave from the PacNW passes through the region
later today with chances for showers and storms across most of
northeastern WY and northwest SD this afternoon. Decent plume of
moisture advects into NE WY with 55-60F dewpoints across most of
northeastern WY by mid afternoon. ML CAPE of 500-1000 J/kg and 0-6
bulk shear of 35-45kt should be sufficient for isolated strong to
severe storms. The limiting factor to convection this afternoon
will be high CIN (-50 to -100 J/kg) and drier air in the mid to
upper levels. Forcing doesn`t look too strong either with some
weak 850- 700 mb frontogenesis providing the bulk of the lift for
storms this afternoon.

For Monday: Trough moves on shore from PacNW and crosses Rockies,
ejecting over the northern plains by late Monday. Strong
southerly sfc flow advects ample GoMex moisture into the CWA with
dewpoints in the 60s and temps in the 80s. With strong upper level
winds providing decent shear (30-40 kt of 0-6 km bulk shear) and
ML CAPE reaching 1000-2500 J/kg across much of western SD by 21z
Monday - we have a decent shot at scattered strong to severe
storms Monday afternoon. Tornado threat is very low with damaging
wind gusts and large hail being the main threats. Another threat
will be heavy rain with PWAT values of 1-1.2" which are 150-175%
of normal for this time of year.

Rest of the upcoming week: Stalled out low over SK/MB gets
dislodged by the western trough as it crosses the Rockies. As this
low moves further east, the ridge flattens out with flow across
the northern plains becoming more zonal by the mid week. In terms
of sensible weather impacts through the end of the week: near to
slightly above average temperatures with daily chances for storms
as periodic disturbances cross the region.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 434 AM MDT Sun Jun 9 2024

Areas of MVFR and local IFR ceilings from far southwest SD into
northeast WY will gradually dissipate this morning. Scattered
showers/thundershowers this morning from northeast WY into
southwest SD will dissipate by late morning. Additional
showers/thunderstorms are possible across the region this
afternoon and tonight. Local MVFR conditions possible with
stronger storms.

&&

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

$$

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