114
FXUS63 KABR 011128 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
628 AM CDT Mon Jun 1 2026

.KEY MESSAGES...

- After a brief break today, the active weather pattern
  continues, starting again Tuesday. Chances for showers and
  thunderstorms are in place through the end of the work week.

- There is a Slight Risk (Level 2 of 5) for severe weather
  Tuesday, mainly along and west of the Missouri River. There
  is a Marginal Risk Level 1 out of 5) for severe storms for
  locations between the Missouri and James River. Large hail of
  1-2" in diameter is the main threat. Wind gusts of 60 mph and
  tornadoes cannot be ruled out as possible threats either.

- Another Slight Risk (Level 2 of 5) for severe weather is in
  place for Wednesday for parts of north central and
  northeastern South Dakota. Large hail of 1-2" in diameter and
  wind gusts of 60 mph are the main threats. Areas west of the
  Missouri River and east of the James River Valley are under a
  Marginal Risk (Level 1 of 5).

&&

.UPDATE...
Issued at 611 AM CDT Mon Jun 1 2026

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

&&

.DISCUSSION...
Issued at 246 AM CDT Mon Jun 1 2026

Storms are moving out of the area early this morning, and are not
expected to produce any additional severe wind or hail. An upper-
level low over the western CONUS will remain in place over the next
couple of days, but will begin to wobble slightly to the north
through the day today. This wobble will bring the vorticity maximum
that is supporting current showers up to the north along with the
low, giving the area a bit of a break from showers and storms today
until another jet streak and vorticity maximum will move into the
area and bring the return of showers and storms late this evening.
Hi-res model guidance does not keep storms around for very long this
evening, due to poor mid-level lapse rates (barely above the moist
adiabatic lapse rate) leading to a poor CAPE environment. Therefore,
confidence is low on thunderstorms development, and even lower on
chances for severe weather chances.

A Slight to Marginal Risk for storms returns Tuesday, mainly over
central and north central South Dakota. The environment Tuesday
evening appears favorable for hail development due to a CAPE/Shear
combo of ~2000 J/kg and 30-40 knots respectively. Decent mid-level
lapse rates of 7 C/km will also be present, supporting hail growth
aloft. A little lower confidence on the wind threat, but some DCAPE
as high as 1500 J/kg will likely be present. The potential drawback
is that this DCAPE is expected over central South Dakota, while the
best potential severe threat is over north central South
Dakota, so it will depend on how things line up. There does
appear to be a tornado threat in the evening, as 0-1km shear of
>20 knots, low-level helicity of 200 m2/s2, and LCLs below
1000m all appear to line up over north central South Dakota.
Future forecast shifts will likely be able to provide more
clarity on the specific timing and location of this possible
tornado threat as high-resolution guidance comes more into
focus, as there is still a bit of disagreement among them at
this time.

One commonality between hi-res models Tuesday evening is that storm
motion is likely going to be from southwest to northeast, with the
potential for training storms to develop if storms don`t progress
eastward quickly enough. At the moment corfidi upshear vectors and
mean cloud layer wind appear to be high enough to help alleviate
concerns (both around 30 knots). However should training storms
develop, conditions will be favorable for flooding. PWATs around
1.3-1.4", warm cloud layer >10k feet, moist mid-levels, and a
long, skinny CAPE profile are all possible. North central South
Dakota does not have very saturated soils currently, which may
also help alleviate concern, but that was also the thought
process ahead of yesterday evening`s convection before flooding
was observed over eastern McPherson county. A notable difference
however is that the ABR observed sounding had a corfidi upshear
vector of 10 knots, which made things much more favorable for
training storms to develop than what is being forecast for
Tuesday evening. All that to say, can`t rule anything out just
yet, but nothing widespread is currently anticipated in terms of
the flooding threat.

By mid-week, the upper-level low over the western CONUS begins to
break down, and the Northern Plains will see the return to more
zonal flow aloft. Precipitation chances will continue, in part due
to the potential for a couple of shortwaves to move over the area
during this zonal flow regime. Additional chances for severe weather
will exist through the end of the week with these shortwave
supported storms, and most medium range machine learning models
place at least a 5% chance (equivalent to a Marginal Risk from SPC)
over part of the Aberdeen forecast area. Beyond that point, there is
fairly strong consensus in the ensembles in another trough
developing over the western CONUS and potentially continuing the
rain chances and severe potential for the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 611 AM CDT Mon Jun 1 2026

Terminals KABR,KATY,KPIR,KMBG

After a few hours of MVFR/IFR cigs/visbies at KABR and KATY this
morning, VFR conditions will prevail at all four terminals.
Toward the end of the TAF valid period, rain shower chances
start to pick up at KPIR.

&&

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

&&

$$

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