258
FXUS63 KABR 150537
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1237 AM CDT Sun Sep 15 2024

.KEY MESSAGES...

- Several chances for precipitation next week. Greatest confidence
  for widespread rainfall will be Tuesday night into Wednesday
  with 50-70% chances.

&&

.UPDATE...
Issued at 647 PM CDT Sat Sep 14 2024

The overall trend with the ongoing storms over and east of the
Missouri River has been a diminishing one. There are a couple of
exceptions over Lyman County and west of Stanley/Jones County,
where we have been seeing strengthening storms over the last hour
that will need to be monitored for gusty winds of 50-60mph and
quarter sized hail with the strongest storms. To the east, the
outflow surged east and across Aberdeen-Redfield with gusts around
35 mph. Limited precipitation is expected east of this area
(Aberdeen-Redfield).

&&

.SHORT TERM /THIS EVENING THROUGH SUNDAY NIGHT/...
Issued at 316 PM CDT Sat Sep 14 2024

The region will be between ridging over the eastern part of the
country and a digging trough over the west coast through the near
term period. This will keep a southwesterly flow over the Northern
Plains, with some shortwave energy tracking across the CWA this
evening, then again across central South Dakota Sunday night.

At the surface, already seeing thunderstorms develop across parts of
southwestern South Dakota this afternoon. These storms are
developing along a boundary associated with low pressure over far
western South Dakota and in an area where MUCAPE values are in the
1000-1500 J/kg and bulk shear is around 30 knots. The stronger
instability looks to diminish through the afternoon, but will see
about 700-900 J/kg remain over central South Dakota this evening,
along with 35 to 45 knots of bulk shear. This will likely be enough
to keep convection going through 03Z or so. Weak high pressure will
bring quieter conditions overnight and through the day Sunday, then
another boundary will set up from southwestern to central South
Dakota. The best shear and instability will be over central South
Dakota, but will not really be aligned timewise. CAMs hinting at
some convective development, but the HRRR is currently the only one
that shows any decent areal coverage, so will stick with POPs in the
20 to 40 percent range for now.

Low temperatures tonight will range from the mid 50s across north
central South Dakota to the mid 60s across northeastern South
Dakota. High temperatures on Sunday will be in the mid 80s to the
lower 90s. Lows Sunday night will be in the mid 60s.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 316 PM CDT Sat Sep 14 2024

The long term starts out Monday morning with a low pressure system
to our west over MT. This low will move northeast and enter Canada
before reaching our area. However, its warm and cold fronts will
move more easterly and impact the area Wednesday afternoon through
at least Wednesday. Thursday and Friday we are stuck in a blocking
pattern with a low on the western side of the Rockies, a high over
the Great Lakes region, and another low over the Carolinas. The EC
ensemble shows a low moving west southwest across Canada on Saturday
will help to break this pattern and another cold front will move
across the area. The CMC ensemble and GEFS have some members showing
a low in Canada but mostly lean towards a surface low circulating in
the lee of the Rockies on Thursday and lasting through the end of
the period. There is still a lot of time for models to come into
agreement since this is at the far end of the period.

There are several waves of possible precipitation through the
period. The first starts early Tuesday with pretty light PoPs from
the NBM of 20-30%. These chances move out of the region by late
morning to early afternoon, leaving the rest of the day dry.
Starting early Wednesday morning, another band comes through with
much higher PoPs. Highest chances (70-75%) stay mainly south of I-90
with a band of 50-70% moving west to east across SD, decreasing to
30-45% as it moves into west central MN during the afternoon hours.
Probability of more than 0.25" is generally between 50 and 60%, with
slightly lower chances across north central SD. The next wave starts
early Friday morning with widespread 30-40% chances that will stick
around through the day Saturday. There is a lot of uncertainty with
this event which accounts for the lower PoP values.

Temperatures will be slowly decreasing through the period. Monday
and Tuesday will continue our current pattern of above normal
temperatures with highs in the mid 80s to around 90. Wednesday,
Thursday and Friday are expected to be slightly cooler with highs in
the upper 70s to low 80s. After a few days of clouds and rain
chances, along with some fairly strong CAA, Saturday looks to be
much more fall-like with highs in the mid 60s to low 70s. Afternoon
wind gusts Monday and Tuesday are expected to be between 30 and 40
mph, mainly over central SD on Monday, but spreading to all of
central and northeastern SD on Tuesday. Wednesday could see some
gusts about of similar strength in higher elevation areas, but are
expected to die out in the afternoon. The rest of the period is
expected to be less windy.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1235 AM CDT Sun Sep 15 2024

Terminals KABR,KATY,KPIR,KMBG

A low level jet across the area will result in wind shear
conditions for a few hours tonight/early morning. Otherwise VFR
conditions with some passing showers and decaying thunderstorms
for the KABR/KATY terminals tonight.

&&

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

$$

UPDATE...KF
SHORT TERM...Parkin
LONG TERM...KK
AVIATION...Connelly