702
FXUS63 KABR 021537 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1037 AM CDT Tue Sep 2 2025

.KEY MESSAGES...

- A cold front will move through on Tuesday, bringing the
  potential for severe weather. A Marginal Risk, level 1 of 5, is
  in effect throughout and east of the James River valley. Main
  threats are large hail up to an inch and strong thunderstorm
  wind gusts up to 60 mph.

- Smoke, both aloft and near the surface, is forecast to impact
  the region later tonight into Wednesday and then again Thursday
  and Thursday night.

- Below normal temperatures are expected after today. For the most
  part, highs will be in the upper 50s to lower 70s from Wednesday
  through next Monday. These temperatures are 10 to 20 degrees
  below normal. Low temperatures Thursday morning and again
  Saturday morning may dip into the upper 30s for some locations.

&&

.UPDATE...
Issued at 1026 AM CDT Tue Sep 2 2025

Still watching the western extent of widely scattered showers and
thunderstorms affecting Big Stone and Traverse counties. This area
is out ahead of the southward moving cold front which will move
through the region later this afternoon. Focus for storms is
still across the eastern CWA in region of best lift/instability
this afternoon, with better shear lagging further behind the
front. Other than some westward extension of PoPs in coverage and
time this morning, only some cosmetic changes to other wx elements
for today.

&&

.DISCUSSION...
Issued at 350 AM CDT Tue Sep 2 2025

At 3 AM CDT, skies are mostly clear and temperatures are in the
upper 50s to mid 60s. An area of low pressure moving south across
Minnesota this morning is trying to generate a few showers
near/(potentially)in the west central MN forecast zones right now.
Monitoring for potential fog development over the CWA this morning
as well. Analyzing a pre-frontal trof dipping down across the
international border into North Dakota; the front of interest still
moving south across the southern Canadian prairie.

More mid/upper level energy and an upper level jet streak to come
later this afternoon through tonight, as the previously mentioned
frontal boundary is progged to move south across the CWA during peak-
heating this afternoon. There should be some shower/thunderstorm
activity along this fropa by late this afternoon/early this evening.
1500-2500J/kg of MLCAPE (75-125J/kg 0-3km CAPE) and mid-level lapse-
rates increasing to 6.5-7C/km should be sufficient for robust
updrafts. But, deep layer shear appears to be the potential limiting
factor for severe weather today, with only ~20-25kts of deep layer
shear. Convective mode is expected to be mostly multi-cellular, with
a modest large hail/strong TS wind gust threat. Later tonight, a
swath of showers/embedded thunder is expected to sweep southeast
across the forecast area, produced and maintained primarily by
elevated, post-frontal, factors of forcing/lift associated with the
trailing upper level energy working through the region.

The upper level pattern that develops today into Wednesday appears
to pause through Friday morning, just long enough to allow another
mid-level shortwave, and its associated surface cold front, to sweep
southeast through the region, impacting this CWA on Thursday with
another strong cold frontal passage (potential for wind gusts up to
45 mph across north central South Dakota late in the day on
Thursday). There could be isolated shower potential Thursday
afternoon with the fropa, as well. Beyond that, ensembles and
deterministic tools depict a positive PNA upper level flow pattern
developing, with this CWA stuck pretty much in the dry/cool
northwest flow portion of the pattern.

RAP/HRRR/RRFS smoke progs depict a first round of smoke aloft and
near surface advecting down across the CWA later tonight into the
first half of Wednesday, before clearing off Wednesday
afternoon/evening over, at least, the east-River forecast zones.
But, with the Thursday frontal passage, another burst of smoke aloft
and near surface could be potentially sweeping east-southeast across
the CWA Thursday into Thursday night.

The growing season is still happening. So, with much below normal
air advecting down across the region Wednesday/night and
Thursday/night, watching how cold the potential low temperatures
Thursday morning and Saturday morning could get. For now, it does
not appear as though the center of surface high pressure sets up in
a favorable location to support max radiational cooling by Thursday
morning. Friday night may contain a little bit better potential.
Ensemble-based probabilities of the temperature falling below 40
degrees Wednesday night is generally in the 40 to 60 percent range
over portions of north central and northeast South Dakota. Similar
probabilities (4 days out) are a bit higher and more widespread
right now for Friday night/Saturday morning.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 618 AM CDT Tue Sep 2 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast for the next 6 hours of the TAF period.
There is a low chance of fog development for a few hours this
morning. Beyond that, the forecast challenges will revolve around
a front that is going to slowly sag south across the Dakotas and
Minnesota today. Showers and thunderstorms may develop along this
front during the peak daytime heating hours this afternoon and
persisting into this evening. Storms are most likely to impact
the KABR and KATY TAF sites, and will continue to better refine
timing and coverage as the day wears on. Also expect winds to
switch around to the north northwest behind the front, drawing
smoke, both aloft and near the surface, into the region later
tonight into Wednesday. The smoke may be dense enough to reduce
visibility to 5sm or less later tonight into Wednesday.


&&

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

$$

UPDATE...TMT
DISCUSSION...10
AVIATION...10