234
FXUS63 KABR 182054
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
354 PM CDT Mon Aug 18 2025

.KEY MESSAGES...

- There is a slight risk (level 2 out of 5) for severe weather for a
portion of central SD tonight. A marginal risk (level 1 out of 5)
for severe weather has been posted for areas between the James and
Missouri Valleys tonight. Main threats are for damaging winds and
large hail.

- Patchy to areas of fog will be possible early Tuesday morning
across northeast SD and west central MN. Some fog could become
locally dense prior to and just after sunrise.

- Dry and warmer conditions will set up through the middle of the
week with the next round for showers and thunderstorms expected by
later Thursday into early Friday.

&&

.DISCUSSION...
Issued at 354 PM CDT Mon Aug 18 2025

One more round of scattered thunderstorms will affect portions of
the forecast area for one more period before we get into a quiet
pattern for a couple of days. As of 20Z this afternoon, a few
isolated showers have been confined to north central SD, around the
Mobridge area. However, vsbl satl imagery has shown a field of CU
developing across parts of northwestern SD the first half of this
afternoon along a sfc frontal boundary and now this CU field has
become agitated enough to lead to scattered thunderstorm development
north of the Faith area back to the southwest around the Black
Hills. Increasing instability across areas of western and central SD
with MLCAPE values up to 2000 J/kg and effective bulk shear values
up to 45 kts has been noted and will remain the case going through
the rest of the afternoon into the evening. Low and mid lvl lapse
rates of 7-9 C/km is in place with the higher values just off to the
west of our forecast area.

SPC has posted a slight risk for severe weather (level 2 of 5) for
portions of central SD back to the west into the western portion of
the state. A marginal risk for severe weather (level 1 of 5) has
been issued for areas along and west of the James Valley into
central SD for tonight. The main threats will be large hail
initially before turning into a more damaging wind threat with time.
Uncertainties still exist in coverage of storms across our western
zones going through the remainder of the day. CAM solutions haven`t
been much help in this regard with timing and placement of any of
this convection currently underway and going out in time into this
evening. Nonetheless, best chances of any severe convection are
likely to remain across our western zones into this evening and
we`ll have to continue to monitor trends going through the remainder
of the afternoon.

By late this evening and overnight, the active weather should begin
to wane and we`ll be left with partly to mostly cloudy skies. Low
stratus and fog is expected to develop again by daybreak across
northeast SD and west central MN. Some of this fog could be locally
dense, as it was in some areas this morning. After this burns off by
mid morning, we will be left with a quiet stretch of weather through
midweek. A ridge of high pressure will build and expand across the
Rockies and High Plains during this time. This will lead to a more
west to northwest flow aloft locally and result in warming
temperatures through Thursday. Wednesday and Thursday look to be
particularity hot across central SD with highs in the 90s to around
100 degrees. The next disturbance is expected by Thursday afternoon
into Thursday night in the form of a cold front. This will give our
area the next chance for showers and thunderstorms. Increasing
instability at that time is likely going to increase our potential
for the next round of severe convection. We`ll just have to keep an
eye on trends the next couple days to get a better idea of what to
expect by Thursday night into Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1239 PM CDT Mon Aug 18 2025

Terminals KABR,KATY,KPIR,KMBG

VFR will generally remain the prevailing conditions for all
terminals during this TAF cycle. The exception will be at
KABR/KATY during the early morning hours on Tuesday due to low
stratus and fog. MVFR/IFR cig and vsby`s will be possible at
these two TAF sites. There is an isolated shower west of KMBG
early this afternoon. Will have to monitor and amend the forecast
at this terminal if it continues on its current trajectory. There
remains some uncertainties with respect to more organized
convection expected across western and central South Dakota later
this afternoon. If it materializes, some of this activity could
affect KPIR/KMBG late this afternoon and this evening, but with
low confidence left it out of the forecast at this time.

&&

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

$$

DISCUSSION...Vipond
AVIATION...Vipond