057
FXUS63 KUNR 301118
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
518 AM MDT Sun Jun 30 2024

.KEY MESSAGES...

-Moisture and warmer temps return today with slight chances for
 thunderstorms

-Stronger system will bring increased chances for storms Monday,
 some of which may be severe

-Unsettled pattern will bring near daily chances for storms the
 remainder of the week with temps around normal or slightly below

&&

.DISCUSSION...(Today Through Saturday)
Issued at 107 AM MDT Sun Jun 30 2024

Fairly active northern stream will prevail this week with near
daily chances for showers and storms as a frontal boundary wavers
over the region. Warmest day this week will be today as temps
surge into the 90s over the western third (approaching 100 at some
locations on the WY plains), much cooler in the east. LLJ with
pos theta-e adv may support a few showers/storms this morning
across scentral SD where some accas are in place. LL moisture will
increase through the day per gusty SE winds with winds
approaching adv levels over NW SD. Strong capping inversion will
be place today per sfc based convection. However, warm temps and
deep mixing will erode the cap in WY where isold TS are expected
in the afternoon as a shortwave approaches the region. TS may be
able to carry into far western SD this evening, but will likely
dissipate given lack of strong forcing and a strong cap in place.
Closer to the upper impulse, storms may adv into far NW SD
overnight, per outflow of an expected MCS to the north. Sfc cool
front will settle into the region Monday morning. However, the
next strong impulse will take aim at the region, supporting a
trend to LL easterly flow, allowing LL moisture to hold steady
across western SD. This impulse will support a good deal of LSA
and strong forcing, allowing TS to develop in the afternoon over
NE WY and far western SD. Storms should grow upscale into isolated
supercells and convective line segments, supporting large hail
and damaging winds given bulk shear of 50-60 knots. CAPE will be
somewhat limited in western SD topping out AOA 1000 J/kg, however
dynamic forcing should make up for the lack of sig CAPE there.
Deeper moisture will reside over central SD where storms will
likely intensify in the evening. Unsettled flow will persist the
remainder of the week with near daily chances for storms as some
monsoon moisture and GOMEX moisture interacts with passing
impulses and a sfc front wavers over the region. There will be a
few drier days mixed in and rain chances will at best be scattered
with the stronger impulses. Temps will reside around seasonal
norms with highs in the 70s/80s through the period.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 516 AM MDT Sun Jun 30 2024

Breezy southerly winds will be in place across the area; gusts to
30-40 knots are expected across the region. Isolated showers and
thunderstorms are possible after 18-20z this afternoon, especially
across NE WY and far western SD. Gusty, erratic winds and MVFR
conditions can be expected near any stronger cores. Otherwise, VFR
conditions will prevail.

&&

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

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...SE