623
FXUS63 KABR 211824
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
124 PM CDT Tue Jul 21 2026

.KEY MESSAGES...

- A weak disturbance aloft will bring a 50-70% chance of rain
  showers, with an occasional rumble of thunder, over south
  central SD late tonight through Wednesday morning. Probability
  of rainfall in excess of 0.10" is 40-70% along and south of a
  line from Mission Ridge to Chamberlain. Additional rain is
  possible Thursday for this same location.

- A cooler air mass in place through Thursday, which will result in
near normal temperatures. However, hot and dry conditions are
expected to return Friday through the weekend, with highs in the 90s
to the lower 100s.

&&

.DISCUSSION...
Issued at 123 PM CDT Tue Jul 21 2026

Currently, fair weather cumulus is over much of the CWA per daytime
heating along with mid to high clouds moving from the northwest and
over central SD per downstream side of the ridge. A hazy sky
continues due to ongoing smoke aloft with HRRR smoke model
continuing to indicate periods of elevated smoke through at least
Thursday. This has been incorporated in the sky grids.

The Northern Plains remains in northwest flow with a ridge over the
western CONUS and trough over the eastern CONUS. Not much movement
expected with this pattern aloft for the next several days. At the
surface, the CWA remains on the southern/southeastern side of a high
pressure system, with the center over ND/MT/Saskatchewan as of 18Z
keeping the area dry. This high will broaden over the Northern
Plains as it drifts southeast through tonight with the center of the
high over the eastern Dakotas/MN by 12Z Wednesday with the CWA on
the western side of it by Wednesday evening with overall dry
conditions continuing. However, with a weak wave rounding the top of
the ridge then downstream in this northwest flow aloft, CAMs agree
overall on a band or bands of elevated showers (and maybe a rumble
of thunder) tracking across central SD, with the bulk of the QPF
over south central SD late tonight through Wednesday morning.
Probability of QPF>0.10" is 40-70% along and south of a line from
Mission Ridge to Chamberlain with the highest percent over Jones and
Lyman Counties. Prob of at least 0.25" at 20-40% for this same
location. Additional elevated showers and weak thunderstorms (pops
20-40) are possible over south central SD once again Thursday
through Thursday evening per another weak wave aloft rounding the
ridge. Probability of 0.10" is less this time around at 20-40% over
south central SD. Slight pops (20% or less) are possible late
Saturday into early Sunday with a passing frontal boundary/weak low,
however, the ridge and heat may influence this potential so low
confidence as of now.

The good news with this high is that temperatures will be a bit
cooler giving us a break from the heat and humidity with highs for
Wednesday only in the upper 70s to the mid 80s, warmest over north
central SD. Highs for Thursday will increase by a few degrees across
the CWA, ranging in the lower to upper 80s. However, the ridge out
west will shift eastward Friday and similar to last week will park
itself right over the central CONUS over the weekend through at
least the middle of next week as the top of the ridge will amplify
well into Canada with its mid level high extending from central
Rockies through the Central Plains. Highs are forecast to reach the
90s west of the James River on Friday and upper 90s to lower 100s
across the CWA this weekend with the hotter day being Saturday where
some portions of north central SD could reach up to 106! Dewpoints
look to be similar to last week overall ranging in the upper 50s to
the upper 60s, highest James Valley and eastward. Closer to time, we
will see how the humidity/peak evapotranspiration will affect high
temps for this area as more humidity will equal overall highs being
"cooler". Drier air over central SD should allow for temps to reach
the triple digits easily. Once again, GFS is running a few degrees
hotter than the EC at this time for surface temps-850mb both
Saturday and Sunday. Example, 850mb temps peak heating Saturday
afternoon is 34C GFS vs 29C EC at KABR. Looking at NBM 5.0 vs 5.2,
there is only about a degree difference in high temps over central
SD this weekend (giving higher confidence on achieving these highs)
whereas there is a 1-3 degrees spread James Valley and eastward with
NBM 5.2 being lower trying to correct this bias, therefore giving
lower confidence in exact highs. So closer to time, we may need to
lower the temps James Valley and eastward like we did last week as
all the models were running several degrees higher than what
actually occurred. Currently, the 25-75th spread per NBM is 5-7
degrees for the weekend. HeatRisk these days will range from
Moderate to Major meaning this heat will affect those sensitive to
heat or without cooling/hydration. Closer to time, a Heat Headline
will likely be needed as heat indices look to be in the triple
digits (with the exception of the higher elevations of the Coteau)
Saturday and central SD Sunday. Temps will still remain hot over the
CWA with highs ranging in the 90s early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1212 PM CDT Tue Jul 21 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast through the end of the TAF period.
Mid to high clouds currently overspread portions of central SD
tracking northwest to southeast on the downstream side of the
ridge. Otherwise, rain chances are possible for KPIR between
~08-16Z Wednesday associated with a weak wave aloft. Winds will
remain out of the north/northeast through this evening
switching to southerly by Wednesday morning.

&&

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

&&

$$

DISCUSSION...MMM
AVIATION...MMM