414
FXUS63 KABR 201140
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
640 AM CDT Wed Aug 20 2025

.KEY MESSAGES...

- Heat index values will top out in the upper 90s to around 104
degrees today, and possibly again Thursday across portions of
central South Dakota.

- The passage of a low pressure system and cold front late Thursday
afternoon through Thursday night will bring a 40 to 70 percent
chance of precipitation, with a marginal risk (level1 out of 5) of
severe storms.

- Temperatures Saturday through Tuesday of next week will be around
10 to 15 degrees below normal. Lows Sunday morning and through
Tuesday morning are forecast to fall into the 40s over much of the
area.

&&

.DISCUSSION...
Issued at 406 AM CDT Wed Aug 20 2025

Mainly dry conditions will continue. The surface high has shifted
over the northern MN/Ontario border by 09Z, with the ridge extending
southeast across the SD/MN border. While fog is again occurring in
the light wind and high relative humidity environment, it has been
less abundant than the last 2 nights. Still, pockets of patchy to
areas of fog will remain possible mainly east of the Missouri River
through 15Z.

Low pressure over eastern MT and western WY will move east to the
ND/SD border with MT and WY by 21Z as the surface ridge shifts into
MN while the area of high pressure settles over Lake Superior. Winds
will shift out of the east to southeast this afternoon, with the
increased pressure gradient helping to bring afternoon gusts of 20
to 30 mph to central South Dakota this afternoon. The heat and humid
conditions will continue. Dewpoints in the upper 60s to low 70s and
temperatures well into the 90s will result in heat index values in
the 100 to 104 degree range over portions of central SD (mainly
Dewey, Stanley, Sully, Hughes, Jones, and Lyman Counties). A Heat
Advisory has been posted for this afternoon for those counties.

An upper-level shortwave will be moving over Saskatchewan during
the day Thursday, which will start to push the upper-level ridge
out of SD while also supporting a cold front moving southeastward
through the state. This frontal boundary is forecast to start
moving into SD on Thursday, with models varying the time of
arrival slightly between mid-morning to mid-afternoon. Moisture
over central and eastern SD in combination with growing
instability from diurnal heating in combination with the lift the
front will provide the needed ingredients for shower and storm
development during the late afternoon into the evening and
overnight. With there being shear along and behind the front,
there is the potential for these storms to organize and become
severe. There is an SPC marginal risk for severe storms over most
of the forecast area.

Thursday is a little trickier with respect to the heat and
humidity with the winds shifting out of a northerly direction
over central SD during the mid to late afternoon hours. While
temperatures are still expected to top out in the 90s to near 100
degrees, dewpoints may be falling a little during the afternoon
hours, which would result in heat index values not getting as high
as today. We`ll continue monitor the latest trends and timing for
another possible heat advisory Thursday afternoon. Fire weather
wise, the quick wind shift was noted in our fire weather forecast
products to give a heads up if there are any ongoing fires at that
time.

After the front moves out of central and eastern SD, cooler
temperatures will start to move into the area on northwesterly winds
through the weekend. The temperatures are forecast to be the coolest
on Sunday when the are about 10 to 15 degrees colder than normal for
this time of the year. The high temperatures over central SD will
around the low to mid 70s and northeastern SD will see high
temperatures in the low to mid 60s.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 640 AM CDT Wed Aug 20 2025

Terminals KABR,KATY,KPIR,KMBG

Mainly VFR to MVFR conditions are occurring with fog at times at
ABR and ATY until 14-15Z. Winds will increase this afternoon with
gusts 20-25kts at MBG/PIR. Otherwise, no significant weather is
expected during this TAF period.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from 1 PM CDT /noon MDT/ this afternoon to 8 PM
     CDT /7 PM MDT/ this evening for SDZ015-033>035-045-048.

MN...None.
&&

$$

DISCUSSION...06/12
AVIATION...06