213
FXUS63 KABR 012356
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
656 PM CDT Fri Aug 1 2025

.KEY MESSAGES...

- Showers and thunderstorms expected across central and north
  central SD late into this evening. There is a marginal to
  slight risk (level 1 to 2 out of 5) for severe weather, mainly
  in and west of the Missouri river valley. All hazards are
  possible.

- A Flood Watch is in effect from 4 PM CDT to 10 PM CDT this
  evening for possible flash flooding conditions across portions
  of central SD.

- There is a 40 to 60 percent chance of showers and thunderstorms
  Saturday night and Sunday night.

- Surface smoke from wildfires is expected to persist across much
  of the region through Saturday. Monitor the latest from the EPA
  and state agencies, as there may be impacts for those sensitive
  to smoke.

&&

.UPDATE...
Issued at 641 PM CDT Fri Aug 1 2025

Watching bowing convection associated with the MCV (mesoscale
convective vortex) across northwest SD, now moving into western
Corson county. Made some updates to PoPs to better match radar
trends/expectations. Will continue to watch progression of MCV
into the evening hours, with low confidence on overall storm
coverage and flooding threat. Southern portions of the severe
thunderstorm and flood watches are in question, although some
CAMs do suggest further development southward into the evening,
but have a feeling convection may be tied in closer proximity to
the actual MCV circulation.

&&

.DISCUSSION...
Issued at 216 PM CDT Fri Aug 1 2025

At 2 PM CDT, skies are a mix of sun and clouds and smoke aloft. Near
surface smoke also continues, reducing visibility to 4-7 miles.
Temperatures are warming through the 70s, and winds are generally
out of the south 10 to 25 mph with gust up to 35 mph. A line of slow-
moving showers are moving into Corson/Dewey counties.

There is a compact low pressure circulation spinning over northwest
South Dakota. CAM guidance generates thunderstorms over the western
half of the CWA by late this afternoon, furthering convection across
central South Dakota overnight. Models show a low level jet
overnight over the region, transporting of low level
moisture/instability over toward northeast and east central South
Dakota. 20-35 knots of deep layer shear, but generally less than
600J/kg CAPE are available, so perhaps low topped supercells or
multi-cellular convection would be possible this afternoon into late
this evening throughout the Missouri River valley region. 0-1km
shear increases from around 10 knots at 20Z to around 20knots at 02Z
throughout and west of the Missouri River valley. 0-3km CAPE ranges
from 50-100J/kg at 20Z mainly over Corson/Dewey to around the same
over western Corson/nw Dewey counties at 02Z. So, while low level
shear is currently progged to increase into this evening, low level
CAPE appears to be relegated mainly to portions of north central
(west river) South Dakota. So, if there is any semblance of tornado
risk with this cyclonic circulation, Corson/Dewey counties would be
the most likeliest candidates for where. The western forecast zones
continue in a slight risk (level 2 out of 5) for severe
thunderstorms into tonight. Otherwise, seeing major slow storm
motion under this regime, so any heavy rain-producing thunderstorms
this afternoon/tonight will need to be watched closely for flash-
flooding potential. A Flood Watch has been issued for portions of
central and north central South Dakota from 4 PM CDT to 10 PM CDT
this evening.

On Saturday, similar set-up. Any remaining morning convection will
be waning. There will be a west-east oriented surface boundary
around in the afternoon to force storms on. Again, appx 20-35 knots
of deep layer shear, but increased/higher amounts of deep layer
instability (generally 750-2500J/kg CAPE) than today. So, perhaps
taller supercellular mode storms could happen on Saturday capable of
large hail and damaging thunderstorm wind gusts. If convection
happens on Saturday, it could be maintained into the overnight with
a low level jet in play again over the region.

Smoke is still modeled to stick around through Saturday, with some
improvement expected Saturday night into Sunday, both near surface
and aloft. Temperatures tonight through Saturday night should
continue near to below normal.

The rest of the 7-day consists of this semi-flat/dirty ridge, almost
zonal flow aloft, pattern where (almost daily) diurnally driven
convection could impact (some portion of) the CWA. Low level WAA
(supported by 850hpa temp anomalies) does appear to resume by
Tuesday of this upcoming week, with daytime highs getting back into
the 80s and 90s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 641 PM CDT Fri Aug 1 2025

Terminals KABR,KATY,KPIR,KMBG

Areas of smoke (FU) will continue to affect the region through the
TAF period, with VSBY generally between 4-6SM while it`s in place.
Otherwise, will see an area of SHRA/TSRA and possible +TSRA across
north central/central SD this evening, more likely affecting KMBG
early in the period. Heavier showers are capable of MVFR/IFR VSBY
and perhaps MVFR CIGs. The same disturbance bringing precipitation
to central SD this evening will be near KABR on Saturday with
potential SHRA/TSRA.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Flood Watch until 10 PM CDT /9 PM MDT/ this evening for SDZ003-
     009-015-016-033>036.

MN...None.
&&

$$

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