Dakota Dunes, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

424
FXUS63 KUNR 202056
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
256 PM MDT Sun Jul 20 2025

.KEY MESSAGES...

- Marginal risk (level 1 of 5) to a slight risk (level 2 of 5)
  for severe thunderstorms late this afternoon/evening.
- Daily chances for at least isolated thunderstorms, some of
  which may be strong to severe.
- Warm and muggy conditions to continue.
- Heat indices at or above 99 degrees Monday over south central
  South Dakota.

.DISCUSSION...(This Evening Through Sunday)
Issued at 226 PM MDT Sun Jul 20 2025

At the upper levels, a positively trough extends through the
Pacific Northwest as a broad ridge remains over the southern CONUS
extending upward into the Mississippi River Valley. Water vapor
satellite shows a weak wave over south central Montana, which
should clip northern portions of the forecast area later this
evening. The latest surface analysis has a low over south central
South Dakota, with a stationary boundary extending east and west
from the low and a trough extending southward into west central
Nebraska.

Isolated storms are expected again this afternoon and evening.
The highest shear is located closer to central South Dakota, with
30-40 kt effective bulk shear. This area seems to have the highest
potential for severe storms along the boundary and ahead of the
surface low. Already a few isolated storms have already formed
over the Black Hills, but these storms dissipated quickly as they
moved onto the plains. Additional storms are possible tonight over
the northern portions of the forecast area. These would be
associated with the shortwave that is currently moving across
Montana. These storm look possible after 00Z.

Mid level flow will continue to strengthen across the northern
Rockies into the northern Plains as the western trough amplifies on
the Pacific Northwest Coast. This will create a southwest flow
pattern across the forecast area by Monday afternoon. At the
surface, the frontal boundary will stretch across the forecast
area on Monday afternoon, providing a focus for storm development.
Most CAMS are showing some convection across the area, but there
is some uncertainty given the inhibition associated with the
elevated mixed-layer. However, some of the models indicate a
subtle shortwave could move through the flow, posing a risk for an
isolated severe storms. With the ridge amplifying, temps in the
90s and dew point temperatures around 70 degrees, heat indices
will push 100-105F over south central South Dakota. Thus a heat
advisory has been issued for Mellette, Todd, and Tripp Counties.

A weak cold front moves slowly through the area on Tuesday. Behind
the front winds will shift to the north, temperatures will be
slightly cooler, and there will be a chance of showers and storms.
However, south central South Dakota will remain on the warm side,
with another hot and muggy day. The main upper trough swings through
the region late Wednesday and Wednesday night, keeping chances for
shower and storms and cooler temperatures in the forecast.

Zonal flow prevails for the rest of the week, with temperatures
gradually warming and chances for storms continuing.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1100 AM MDT Sun Jul 20 2025
Isolated to scattered thunderstorms are possible across the
western South Dakota Plains through 09Z, mainly from K2WX-KICR
with IFR conditions, gusty erratic winds, and hail in and near
storms. Otherwise, VFR conditions will prevail.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from noon to 8 PM CDT Monday for SDZ046-047-049.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Smith
AVIATION...Smith