670
FXUS63 KABR 311143 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
643 AM CDT Sun May 31 2026

.KEY MESSAGES...

- Active pattern continues, and chances for showers and
  thunderstorms are in place through at least mid-week.

- Probability of additional rainfall of half an inch or greater
  through Monday is roughly 30-50% over northeastern South
  Dakota and western Minnesota, increasing to around 60-80% over
  central and north central South Dakota.

- There is a Marginal Risk (Level 1 of 5) for all of central and
  portions of northeastern South Dakota this afternoon and
  evening. Main threats include wind gusts of 60 mph and hail up
  to an inch in diameter.

- Another Marginal Risk (Level 1 of 5) is in effect for Monday
  for parts of northeastern South Dakota. Wind gusts of 60 mph
  and hail up to an inch in diameter are the main potential
  threats.

&&

.UPDATE...
Issued at 638 AM CDT Sun May 31 2026

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.DISCUSSION...
Issued at 236 AM CDT Sun May 31 2026

Currently (~06Z) keeping a close eye on a line of storms moving into
central South Dakota early this morning. Over the past hour, surface
observations indicate that win gusts are consistently in the 40-50
miles per hour range, with some stray gusts upwards of 50 (remaining
sub-severe for the moment). Expectations over the next couple of
hours based on hi-res models are that storms will continue moving
into north central South Dakota, gradually deteriorating as they go.
Mesoanalysis seems to agree with this assessment based on the idea
that shear will decrease moving north. There is still some decent
DCAPE (topping out around 900 J/kg) over parts of north central
South Dakota that storms are expected to move into over the next
couple of hours, so until storms dissipate, an isolated severe gust
may still be possible.

Attention then turns to this evening`s severe threat, with currently
a Marginal Risk for severe storms in place. Storms are expected to
take the form of more individual cells, with the best chances for
the severe threat located along the James River Valley. A plume of
roughly 1500-2000 J/kg of MUCAPE will be in place, and mid-level
lapse rates around 7 C/km will also help to support the hail threat.
Shear may be a bit of a struggle, but still expecting around 20-30
knots of 0-6km shear lining up with the plume of CAPE (albeit with
some local variability). Therefore, can`t rule out the potential for
severe hail in the areas of strongest shear. Conversely, areas of
weaker shear will likely hold the strongest wind threat, mainly due
to the potential for collapsing storms. However other than some
marginal DCAPE in the 750-1000 J/kg range, not much in the
environment points towards the severe wind threat. Low-level lapse
rates will be fairly poor (6-7 C/km) and PWATs fall a bit short of
the ideal 1.5" for microbursts. That said collapsing storms may be
able to produce a stray gust or two, hence the greater potential on
the weaker end of the shear. In terms of the potential tornado
threat, generally expecting the area of best shear/helicity to be
disconnected from the lowest LCLs until later in the evening (as
well as fairly low 0-1km shear where storms are present, struggling
to get up to 20 knots). The area where all the ingredients could
potentially line up appears to be over parts of central South Dakota
around sunset and/or over far northeastern South Dakota. However,
there is not great consistency between model guidance at this point,
so confidence on both the existence and location of possible
tornadoes remains quite low.

In terms of rainfall totals still to come, the highest rainfall
totals are still expected over central and north central South
Dakota. The majority of remaining rain is expected with this
morning`s convection moving in currently, but scattered showers this
evening may also dump an additional quarter to half an inch (though
totals will be highly locally varied). Probability to see another
half an inch through Monday sits around 30-50% over northeastern
South Dakota and western Minnesota, increasing to 60-80% over
central and north central South Dakota.

Through the start of the work week, the upper-level low over the
western CONUS will continue to bring chances for rain, with perhaps
a bit of a break Monday afternoon and evening. The Storm Prediction
Center has drawn a Marginal Risk up into parts of northeastern South
Dakota Monday, and there does appear to be some CAPE/shear
combination in the area during the evening time frame. However,
confidence remains quite low due to very few models actually
displaying convective initiation, and those that do keeping showers
very weak. Both Tuesday and Wednesday evenings show perhaps some
better potential for some alignment between CAPE and shear within
the Aberdeen forecast area, and severe storms may be possible during
those periods. Flow aloft will transition to more zonal by mid to
late week. Beyond that point, there is fairly strong consensus in
the ensembles in another trough developing over the western CONUS
and potentially renewing the rain chances and severe potential for
the end of the week to the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 638 AM CDT Sun May 31 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail more often today than MVFR will.
Remaining showers/embedded thunder are working through the KATY
terminal this morning. There are also pockets of IFR fog/cigs
forming across the Missouri River valley where clouds have
cleared out. This should be a brief/temporary condition this
morning.

By late this afternoon, scattered showers and thunderstorms are
expected across mainly portions of north central and northeast
South Dakota. Some storms may become strong to severe with hail
up to an inch and thunderstorm wind gusts up to 55 knots
possible.

&&

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

&&

$$

UPDATE...10
DISCUSSION...BC
AVIATION...10