626
FXUS63 KABR 221952
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
252 PM CDT Wed May 22 2024

.KEY MESSAGES...

- A slight risk for severe storms (2 out of 5) exists as a low
pressure system nears the region Thursday afternoon. Threats include
damaging wind (~60-70 mph), large hail (~up to ping pong sized) as
well as a low tornado probability.

- Showers and weak storms are expected into early Friday. The
unsettled weather pattern then continues with additional chances of
moisture Saturday into Monday (30-50%).

- A chance of frost (30-40%) exits for north central South Dakota
Saturday morning.

&&

.SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/...
Issued at 236 PM CDT Wed May 22 2024

Weak upper level ridging will transition to southwesterly flow ahead
of another fast moving closed low system. As such, surface return
flow winds and warm air advection will develop tonight and into
Thursday. The combination of a low level jet, weak upper level
energy and WAA will be enough lift for some accas-y type cloud
development/thunderstorms early Thursday morning. As previous
forecasts mentioned, the hi-res models pick up on this and continue
to develop weak simulated radar returns.

Attention then turns to Thursday afternoon as the surface low
approaches the region. A fairly well defined warm front, surface
trough and trailing cold front appear to set up. Looks like a decent
CAP in the warm sector, but dewpoints will be rising into the upper
50s/60s and CAPE values a modest (but sufficient) 500-1500 J/KG.
Thunderstorms will likely be tied to the surface trough, giving a
somewhat limited window, but they will also be accompanied by an
upper level ~70-80 kt jet streak, and as such, 0-6 KM shear in the
50-60 KT range. Current trajectories suggest mean storm motion will
not allow storms to move off the surface boundary. Hodographs show
decent curvature from 0-3 km, so cannot rule out supercellular
development. However, it also looks like any right moving storms
will struggle to move off the boundary making it difficult to reside
in the more favorable environment. The exception may be areas just
north of the warm front or near the intersection of the warm
front/surface trough. This includes our northern CWA and
northward into North Dakota. Here storms may take on a more
discrete mode. Additionally, any supercell development would
likely be pretty shallow given the strong shear/low-medium CAPE
environment. Nonetheless, severe storms are expected. Current
threats include SPC 15% probs for wind (~60-70 mph) and hail (~up
to ping pong sized) as well as a 2% tornado probability.

Much colder air moves in behind the low pressure system, with
additional light rain showers possible into Friday morning.
Temperatures will drop into the mid to upper 30s across parts of
north central South Dakota, but breezy winds should prevent frost
development.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 236 PM CDT Wed May 22 2024

An upper level low continues to pass over the area Friday morning.
It will continue to move northeast across the region through
Saturday morning, though shortwave energy remains. The next low
comes through Monday. The GFS brings the center of the low right
over SD, but the Canadian and EC keep the center in ND. Tuesday
morning brings a ridge to the area that will continue through the
end of the period.

Rain chances will decrease through the day Friday as the low moves
to the northeast. Low level chances (20-25%) remain through Saturday
with the shortwave energy remaining in the region. Sunday afternoon,
higher chances (30-50%) return as the Monday low starts to move
towards the region. With these rain chances comes a chance of
storms. Mid level lapse rates are a little on the low side, sitting
at around 6.5 C/km. MLCAPE is also pretty low except in the Canadian
model in central SD. Given this, if storms do form, they will most
likely not be severe. Monday has some 20 to 30% chances as the low
moves through. Tuesday through the end of the period looks dry.

Temperatures through the first part of the long term will be below
average with highs in the 60s to low 70s. Once the ridge moves in
Tuesday, highs will start to warm up towards 80. We still have a
chance for freezing temperatures Saturday morning. Areas along the
ND/SD border in north central SD have a 10-20% chance of lows below
32 degrees. This has decreased in the last model runs and we will
continue to watch the trends. Winds Friday look to be strong with
gusts of 30-35 mph likely across most of the forecast area and 35+
mph possible in higher elevation areas. Winds will start to diminish
during the evening hours and remain around normal for the rest of
the period.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1228 PM CDT Wed May 22 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions for all terminals. Winds will shift to a southerly
direction tonight and a round of mid level accas/light rain
showers or weak thunderstorms may develop after 06Z. Minimal
impact to any TAF sites anticipated. The next round of strong to
severe thunderstorms is forecast for Thursday afternoon and
evening.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

SHORT TERM...Serr
LONG TERM...KK
AVIATION...Serr