Sisseton, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

070
FXUS63 KABR 262003
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
303 PM CDT Thu Jun 26 2025

.KEY MESSAGES...

- Severe storm chances return Friday afternoon through Friday night,
with a slight risk (level 2 of 5) for severe weather across the
entire forecast area. Main threat includes large hail, potentially
2" in diameter or larger, wind gusts between 60-70 mph, and a few
tornadoes.

- Additional chances for severe weather continue Saturday/Saturday
night with a slight risk (level 2 of 5) for severe weather mainly
along and south of Highway 12.

- Temperatures will remain rather warm along with higher levels of
humidity on Friday through the weekend. Drier conditions will be
possible early next week as warm temperatures continue.

&&

.DISCUSSION...
Issued at 302 PM CDT Thu Jun 26 2025

The main concern in the forecast package will be the scattered
severe storms possible Friday and Saturday over the forecast area
and the return of summer like temperatures these days. As of 3pm,
radar indicates light to moderate rain continuing to fall mainly
east of the Coteau with the last of the rain forecasted to exit the
far northeastern CWA this evening. We are seeing some clearing over
western SD and portions of central SD on the backside of this
system. The ongoing low level moisture and post-rain will lead to
more fog overnight into early Friday morning. EC meteograms
highlight this well with Conshort indicating a bit more broader in
coverage than what we saw this morning, mainly along and east of the
Mo River. Some of this fog could be dense at times especially over
the James River Valley and Coteau. This has been added to the grids
and an advisory may be needed if we see visibilities drop to less
than 1/4 mile.

The shortwave and its associated low pressure system will be off to
our east this evening with zonal to slight northwest flow aloft as a
low amplitude ridge moves in over the area this evening and shifting
eastward into MN on Friday, bringing a relief to the soggy weather.
A weak amplitude trough sets up and extends over the Pacific
Northwest this evening through Friday. Within this trough, a
stronger shortwave will push east/northeast on the downwind side of
the trough. The axis of this shortwave is forecasted to be over
MT/WY and western Dakotas into Canada by 00Z Saturday. Winds will be
increasing to 40-50kts from 300-500mb and 700mb winds increasing to
25-35kts with these winds highest over MT/ND. By Friday evening, its
center of the low looks to hover the Saskatchewan/Manitoba border
with central to portions of northeastern SD within the warm sector
between the warm front and cold front, will will be over western SD
along with a lee low. So with upper air support and lift from the
front will aid in convection, however, the better lift looks to be
over ND and northward, closer to the low.

Within the warm sector, return flow at 850mb will bring in more low
level moisture and warmer air with winds between 20-30kts and
dewpoints rising between 10-15C by the afternoon and evening with
temperatures 20-25C in this area. With this WAA, surface temps are
expected to rise in the 80s the lower 90s, warmest over central SD,
with dewpoints in the mid to upper 60s to possibly the lower 70s.
This will lead to moderate to strong instability (and help break the
daytime cap as 700mb temps range from 9-12C) as HREF Surface/MUCAPE
will increase between 1000-3000j/kg, with the 2-3K values over
central SD. The potential max values could be up to 4000-5000 j/kg
in this area! EC EFI highlights values 0.6-0.8 for CAPE and CAPE-
shear over central SD for this enhanced threat. With the increased
winds aloft, bulk shear will run between 30-40kts and mid level
lapse rates between 7-8C. STP values between 1-2 run from north
central SD through southeastern SD where we see the greatest 0-1km
SRH (up to 100m2s2). HREF 2-5 UH>75m2s2 paintballs indicate
organized convection could fire up as early as late afternoon (~22Z)
but more in two areas to start. One area over north central SD into
ND and the other area over central/south central SD into southern
SD/northern NE. This northern convection, per HREF, becomes more
numerous as it pushes eastward. UH>150m2s2 indicates these cells
could be right moving supercells over central to northeastern parts
of SD. So if we can get convective initiation, it will not take much
for these storms to become severe with what was mentioned for severe
parameters. The SPC has expanded the slight risk (level 2 out of 5)
and now covers the entire CWA. The main threats include large hail
with a 10% hatched area along and west of a line from Aberdeen
through Redfield, meaning 10% or greater chance for hail to be at
and over 2" in diameter within 25 miles of a point (due to this
supercell potential). There is also the threat for a few tornadoes
with any supercells with a 2% chance within 25 miles of a point
along and west of the James River to the Mo River. Winds gusts
between 60-70 mph is also a threat.

The embedded shortwave will be over the southern portions of
Canada/Northern CONUS by Saturday afternoon and evening with the
surface low/boundary shifting eastward. Temperatures are expected to
rise into the upper 80s to the lower 90s and dewpoints in the upper
60s into the lower 70s with similar instability/shear setup as
Friday. EC EFI has a larger area of 0.6-0.8 for CAPE from southern
SD through northeastern SD into MN with a shift of tails of zero.
With this ongoing instability, severe storms are possible again
as SPC has a slight risk (2/5) mainly along and south of Highway 12.

Lastly, we continue in this moist setup as PWAT values will still 1-
2 standard deviations above climo Friday and Saturday with values up
to 1.25" along and east of the Mo River Saturday and along and east
of the James River Sunday. Mean specific humidity still ranges about
2 standard deviations above climo from 850-925mb. So with any
thunderstorm that forms, it does have the potential to produce heavy
downpours. Any training of these storms could lead to an increase
potential for flooding.

Overall dry weather expected Sunday into early next week with temps
in the 80s to lower 90s.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1226 PM CDT Thu Jun 26 2025

Terminals KABR,KATY,KPIR,KMBG

Light to moderate rain showers continue over the James River
Valley and eastward, with the rain continuing its path northeast
into ND/MN.The last of the rain should exit the eastern portions
of SD by this evening with dry conditions tonight into Friday
morning. With ongoing low level moisture and post rain, fog is
possible (could be dense in some areas of the James River
Valley/Coteau) Friday morning. Cigs remain at IFR/MVFR at
KPIR/KMBG with KABR improving to MVFR/VFR later on this afternoon.
KABR may fall back to lower cigs if the fog forms early Friday
with KATY remaining in IFR to possibly LIFR tonight into early
Friday morning.


&&

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

$$

DISCUSSION...MMM
AVIATION...MMM