Vivian, South Dakota Weather Forecast Discussion

877
FXUS63 KABR 140458
AFDABR
Area Forecast Discussion
National Weather Service Aberdeen SD
1158 PM CDT Sat Sep 13 2025
.KEY MESSAGES...
- Marginal Risk (threat level 1 of 5) for severe storms across
  central SD this evening/overnight. Hail around quarter size,
  winds to 60 mph, and heavy rain are the main threats.
- Fog possible late tonight into Sunday morning across portions
  of central and northeast SD into west central MN. Visibility may
  be reduced to below one-half mile at times.
- Marginal Risk (threat level 1 of 5) for severe storms across
  the entire forecast area on Sunday. Similar threats as tonight,
  although a very low end (2%) tornado threat exists over the
  region.
&&
.UPDATE...
Issued at 805 PM CDT Sat Sep 13 2025
No changes planned to the tonight period forecast.
Showers/thunderstorms will develop/move north into central and
then north central South Dakota overnight. Probably two rounds of
convection, with the first attached to the shortwave noted moving
up through Nebraska at this time. Expecting precipitation to be
moving/developing up into the southern/southwestern forecast
zones after 04Z this evening. Additional shortwave energy is seen
lifting out of Colorado, and is expected to be draw a second
batch of showers/storms into the southern/southwestern forecast
zones after 09Z tonight. There may be enough instability/shear
accompanying these shortwaves` forcing/lift to generate a few
embedded stronger cells capable of hail up to an inch or wind
gusts up to 60 mph. But, with pwats observed between 1.25in and
1.50in (KABR 00Z RAOB pwat of 1.42in is above the 90th percentile
for today), suspect torrential/heavy rain potential stands atop
the list of convective weather hazards tonight into Sunday
morning.
On a separate note, while MLCAPE on Sunday may not be all that
much (skinny CAPE), a surface low moving north with 75-150J/kg 0-3
CAPE and 15-30kts of 0-1km shear (current RAP13 progs) suggests
that daytime-heating initiated, boundary-layer rooted convection
could carry with it a tornado risk, especially from north central
South Dakota over into northeast South Dakota. BUFKIT soundings
prior to and during surface low passage show a goodly amount of
0-1km curve in them.
UPDATE Issued at 634 PM CDT Sat Sep 13 2025
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.DISCUSSION...
Issued at 318 PM CDT Sat Sep 13 2025
Water vapor imagery shows the upper level trough across the
Rockies/Great Basin, with south-southwest flow aloft across the
Northern Plains. Broad/weak surface low pressure sits over eastern
SD while the first wave of showers/storms tries to exit northward
out of SD and into southern ND. Still quite a bit of cloudiness
across central SD, thus limiting the degree of destabilization
somewhat. Models continue to suggest central SD may be one of the
last locations to see a decrease in the low-level cloud cover by
late afternoon and early evening. CAMs continue to suggest any
redevelopment of convection may hold off until this
evening/overnight as the next wave of low pressure begins to move
into the region. HREF composite reflectivity (>40 dBZ) ensemble
paintball output shows much of the activity should be confined to
central SD, which is where rainfall chances are highest. It also
appears fog/low clouds are possible once again late tonight into
Sunday morning, especially over portions of central/northern SD into
west central MN. Have inserted mention of this into the forecast as
well.
On Sunday, low pressure over the region will bring continued showers
and thunderstorms, with development a bit further east into the CWA
by early afternoon. Expecting morning clouds once again, so will
have to see how the lower clouds erode and where pockets of
instability develop. Generally tall/skinny CAPE profiles in
soundings along with 6-7 C/km lapse rates may bring weak/moderate
updrafts with any cells that develop Sunday afternoon. Enough shear
seems to be present as well to perhaps bring a low end severe storm
potential. Cannot rule out an isolated tornado given the fact the
surface low will be right over SD, which could be impinging on the
low-level jet.
Unsettled weather looks to continue at least into the middle portion
of the upcoming week as upper level troughing remains in place over
the Northern Plains. Good agreement in the overall larger scale
mid/upper level pattern amongst the GEFS/GEPS/ENS into the middle of
next week, showing the upper level trough over the Northern Plains.
Inherited PoP grids generally show precip chances ranging from 30-
50% by Tuesday night already as Monday may see a brief break between
systems. Don`t really see any cold air intrusions through the 7-day
forecast, so threats for a frost/freeze look to hold off for a
little while yet.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1158 PM CDT Sat Sep 13 2025
Terminals KABR,KATY,KPIR,KMBG
By 09Z, sub-VFR conditions (both cigs and visbies) should be
developing across the region, and will eventually find their way to
the KPIR/KMBG and KABR terminals, where they are expected to persist
through at least 15z. Gradual improvement is expected beyond that.
Showers and thunderstorms, off and on, will occur throughout the
overnight hours and on into Sunday. KPIR and KMBG should receive the
brunt of the precipitation tonight, starting out at KPIR by 08Z
before spreading up into KMBG by 12Z Sunday. Additional
showers/thunderstorms are expected Sunday afternoon and evening.
Expect sub-VFR conditions to accompany the precipitation tonight
into Sunday. There is a low probability of hail up to an inch/strong
wind gusts up to 60 mph accompanying tonight`s thunderstorms. But
torrential/heavy rainfall holds the greatest threat heading into
Sunday morning.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...10
DISCUSSION...TMT
AVIATION...10

NWS ABR Office Area Forecast Discussion