823
FXUS63 KABR 181151
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
651 AM CDT Mon Aug 18 2025

.KEY MESSAGES...

- There is a slight (level 2 out of 5) to marginal risk (level 1 out
of 5) for severe weather over central SD today. Main threats are for
severe wind gusts of 60 mph and large hail.

- Patchy to areas of fog are reducing visibilities over north
central and northeastern SD. This fog should dissipate by mid-
morning.

&&

.UPDATE...
Issued at 309 AM CDT Mon Aug 18 2025

A dense fog advisory has been issued for a fair amount of the
area excluding MN counties, I-90 corridor, as well as Brown and
Spink. These areas will continue to be monitored to see if they
need to be added to the advisory later.

&&

.DISCUSSION...
Issued at 226 AM CDT Mon Aug 18 2025

As of 07z, there are storms moving through southeastern SD, and most
of these storms should stay out of northeastern SD. However the
northern edge of the storms could still build into southern
northeastern SD and some smaller storms that develop ahead of the
main area of storms could affect that area too. The other concern
for this morning is the fog that is developing over central and
eastern SD from the excess moisture left by yesterday`s
precipitation. This fog could reduce visibilities in areas, and
those driving should take caution. The fog should dissipate during
the morning once the sun rises.

The lee of the rockies surface trough continues to sit over western
SD while the frontal boundary stays parked over southern SD today.
The environment over central and eastern SD continues to stay fairly
wet as well as unstable, with CAPE values forecast to get above 2000
J/kg Monday evening, especially over central SD. The surface trough
over western SD could help to develop and push storms east into
central SD, while the frontal boundary over southern SD could
develop storms that affect south central SD. Models are also showing
bulk shear values of 30-40 kts over south central SD Monday
afternoon, which could help with storm organization. The bulk shear
and CAPE values start to decrease later in the evening, which could
help to decrease storm chances during overnight. Storms will mainly
have the risk for strong to severe winds and large hail. On another
note, elevated wildfire smoke continues to move into central and
eastern SD today. This elevated smoke should stay aloft and not
reach the surface.

The upper and mid levels start to shift and build high pressure over
AZ/NM Monday evening into Tuesday. This then helps to develop a
ridge that reaches up over western SD and parts of central SD by the
mid-week. At the surface, the frontal boundary finally decides to
start moving overnight into Tuesday with some weak high surface
pressure building in behind the front. Despite there being some high
pressure over central and northeastern SD, there is still a moist
environment with some instability present through the day Tuesday
that could help with shower and storm development. The lack of
fronts and lifting mechanisms helps to reduce the chances for
development, however there is still the possibility that something
could try to pop up. The models are also showing there to be weaker
bulk shear values in the area, which will help to reduce the ability
for storms to organize if they do get started.

As the ridge builds to the north, some drier air is push up in to WY
and western SD, with some variation in the models as to any of the
drier air moving into central SD. Even without the drier air in
central and eastern SD, there should thankfully be a break in the
storms and precipitation Wednesday into Thursday afternoon. Though,
the occasional pop-up showers cannot be fully ruled out at this
time. Temperatures will also be affected by the ridge, with them
starting to increase. The warmest temperatures are forecast for
Thursday, reaching the low to mid 90s over central SD and low to
upper 80s over northeastern SD.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 651 AM CDT Mon Aug 18 2025

Terminals KABR,KATY,KPIR,KMBG

Other than morning fog, with IFR to LIFR conditions at all sites
through 12-15Z this morning, VFR conditions will return. Light
winds around 10kts or less will continue through the period.
Another round of IFR fog is expected Tuesday morning, mainly at
ATY.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 9 AM CDT /8 AM MDT/ this morning for
     SDZ003>005-007>011-015>017-019>023-033>037.

MN...None.
&&

$$

UPDATE...12
DISCUSSION...12
AVIATION...06