840
FXUS63 KUNR 291112
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
512 AM MDT Sat Jun 29 2024

.KEY MESSAGES...

- Frontal passage this afternoon will bring chances for isolated
  storms.

- Cooler, drier, and breezy through Saturday.

- Warming up for Sunday with chances for storms, with a chance
  for severe storms especially around the Black Hills

- Warmer through next week with near daily chances for storms

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 147 PM MDT Fri Jun 28 2024

Current wv imagery depicts upper low centered over central MT. A
sfc low sits over northern MN with a cold front extending
southward into KS. CU has developed over the Black Hills along a
sfc boundary, more clouds have also developed in northwestern SD,
associated with a secondary cold front moving through the region.

This front will move through the northern plains this afternoon,
bringing the potential for an isolated storm or two this
afternoon. Moisture is limited with sfc dews in the low 40s to 50s
and forecast soundings show only a little bit of mid-level
moisture. This will inhibit storm development this afternoon. NAM
does depict a narrow band of 250-500 J/kg MUCAPE across western SD
by this evening. In the unlikely event any storms do get going,
they`ll have 50-60 kt of 0-6km shear to work with. Behind the
front, modest 3hr pressure rises of 3mb and CAA will bring breezy
winds to the area. BUFKIT soundings also show the potential for
some of the stronger winds aloft to mix down, which could result
in advsy level gusts up in northwestern SD this evening.

Upper ridge builds into the region Saturday with temperatures
steadily warming through Sunday thanks to low level southerly flow
advecting warmer temps into the region. Highs by Sunday and
Monday will reach into the 80s to 90s.

Next system moves in Sunday afternoon with approaching upper
level trof and mid-level shortwave crossing the region. Ample low
level moisture return (Tds in the mid 50s to 60s), warm sfc temps,
and modest low and mid level lapse rates (on the order of 7-8
C/km) will lend to instability during the afternoon hours on
Sunday. NAM depicts narrow band of 1500-2500 J/kg MUCAPE setting
up over far western SD with 0-6km shear ranging from 35 to 55 kt.
Limiting factor will be a strong cap at 700 mb (as evident on NAM
fcst soundings). Still, instability and shear will be supportive
of rotating updrafts late Sunday with the greatest risk for storms
over the Black Hills where the cap is weaker.

LREF depicts broad troughing over the northern plains through
early next week with a transition to more zonal flow in the mid
week. Deterministic guidance depicts disturbances moving along the
upper flow which will bring near daily chances for showers and
storms, though the timing/location of said disturbances remain
nebulous at this time.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Sunday Morning)
Issued At 511 AM MDT Sat Jun 29 2024

Low clouds and MVFR cigs will persist across portions of far NE WY
and NW SD this morning, although no impacts are expected at KGCC
or KRAP. Otherwise, VFR conditions are expected through the
forecast period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...SE