131
FXUS63 KABR 171829
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
129 PM CDT Sun May 17 2026

.KEY MESSAGES...

- Slight Risk for severe weather (2 of 5) focused across far
  northeast South Dakota and west central Minnesota this
  afternoon/evening. Marginal Risk for severe weather (1 of 5)
  includes parts of the northeast and central South Dakota.
  Main threats are large hail, damaging winds and an isolated
  tornado or two.

- Colder air returns Monday through Wednesday, with high
  temperatures around 15 to 20 degrees below normal.
  Temperatures Wednesday morning may drop to near or below
  freezing, bringing the potential for frost.

&&

.DISCUSSION...
Issued at 120 PM CDT Sun May 17 2026

After the first round of showers and storms moved through portions
of central SD this morning, most of the forecast area has been in
between areas of precipitation with the second round now moving into
our south/west zones. This is in association with the next upper
wave and inverted sfc trough that has poked northward into central
sections of SD. The main low pressure center remains to our south
across parts of NE/KS and it is progged to shift northeast by late
this afternoon into Sioux Falls/Sioux City area. Of the
aforementioned area of precip, an area of stronger elevated
convection across north central NE at midday is progged to track
northeast into SD through the early afternoon. This area of
convection appears to be located around a meso low and attendant
cold front that is centered and draped north to south toward the
parent low across the NE/KS border. RAP guidance shows an
instability gradient set up in the vicinity of this convection
across northern NE into far south central SD. This guidance progs
this gradient to track northeast from Ainsworth, NE toward Mitchell
and Huron SD the first part of the afternoon and then on into our
far southeast zones around the Watertown area mid to late afternoon.

North of the elevated convection, we see an area of moderate to
embedded heavy rain shifting into the Pierre area(I-90 corridor) and
points north toward Mobridge. These rains will be just that and not
pose any severe threats to central SD through the afternoon. Visible
Sat shows extensive cloud cover(mostly stratus) along and west of
the James Valley through central SD. Clear to partly cloudy skies
have developed across east central and southeast SD which will help
to contribute to destabilization and a more favorable environment
for strong/severe convection this afternoon. RAP model does prog
MLCAPE values of 1000-1500 J/kg across east central SD/west central
MN by mid to late afternoon with ample bulk shear values of 45-55
kts. CAM solutions track that elevated convection northeast from
south central SD into parts of southeast SD with additional
development possible to the north that would affect some of our
forecast area such as Miller to Redfield, Clark, Watertown and
Ortonville through the course of the afternoon hours. The main
concern with any of the stronger convective cells will be large hail
and damaging winds with a more isolated risk for a tornado or two
and of course locally heavy rainfall.

By late this afternoon and evening, guidance progs this activity and
any generic showers and storms located farther north and west to
shift eastward into the James Valley and points east. By early to
mid evening, most of the this activity is expected to begin to shift
east and out of our forecast area into western MN. A break in the
precip is then expected tonight into Monday morning before the next
round of moisture shifts north and east back into our region for
Monday afternoon and Monday night. This will be more strato-form
rainfall with no risk for severe weather expected. Increasing
northerly breezes and temperatures cooling into the upper 40s to mid
50s is about as best we be able to manage for Monday. By Tuesday
morning, most if not all the precip will be gone and we should be
left with mostly dry conditions albeit still cool. This cooler than
normal air mass will maintain itself across our area Tuesday night
into Wednesday. In fact, we should see 2 overnight`s worth of frosty
or near frosty like temperatures in the 30s. Late Tuesday night into
Wednesday morning still looks to be the coldest with forecasted
overnight lows in the upper 20s to mid 30s. More guidance has
latched onto this idea leading to higher confidence that a good
portion of our forecast area will see frost.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 120 PM CDT Sun May 17 2026

Terminals KABR,KATY,KPIR,KMBG

Chances for showers and thunderstorms will become more prevalent
this afternoon and early evening at all four TAF sites. MVFR/IFR
cigs will remain a consistent trend through this forecast cycle.
MVFR vsbys are expected in more of the general strato-form type
rains with IFR vsbys possible in the heavier or heaviest
shras/tsras by late this afternoon into early evening. Southeast
winds across northeast SD will become north to northeast with
time while central SD sees a predominant north to northwest
wind through this TAF valid period. Gusts as strong at 25 kts
are expected with locally higher gusts possible near/close to
any heavy thunderstorms.

&&

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

&&

$$

DISCUSSION...Vipond
AVIATION...Vipond