517
FXUS63 KABR 181829 CCA
AFDABR

Area Forecast Discussion...CORRECTED
National Weather Service Aberdeen SD
129 PM CDT Sat Jul 18 2026

.KEY MESSAGES...

- Heat advisory for the James Valley and points west Sunday.
  Temperatures in the 90s to around 100 degrees and dewpoints in
  the 60s resulting in heat index values around 100 to 105.

- Storms expected along a cold front late Sunday evening into
  early Monday. A Slight Risk (2 of 5) covers the northern tier
  counties of South Dakota, with a Marginal Risk (1 of 5) for the
  rest of the forecast area. Main threat is high winds. Not
  expecting a lot of moisture overall either.

- Heightened Fire Weather threat for Monday. Lightning starts
  from storms Monday morning possible. Northwest winds of 25 to
  40 mph during the day, with drier air. Afternoon humidity
  down to around 20% across the Missouri Valley region, 30-40%
  across Northeast South Dakota.

&&

.DISCUSSION...
Issued at 112 PM CDT Sat Jul 18 2026

Precipitation wise, we have our ridge rider system for tomorrow, with
elevated skinny CAPE in NAM BUFKIT profiles early in the day. The
CAMS are latching onto some convection late morning coming in from
the west so added some low POPs. The actual ridge rider late in the
day has better potential for convection up in North Dakota with CAMS
indicating this then migrates southeast into the CWA. Some also
indicate convection also coming in from the west as well.  NAM
BUFKIT profiles likewise point to elevated skinny CAPE in
moderate/high speed mid level flow (around 50kts). This suggest fast
moving convection and overall not much rainfall potential, with a
high wind threat.

NBM temperatures/humidity support a heat advisory for Sunday.
NBM temperatures back into the 90s (northeast) to low 100s
(central/north central). The wave to the north is helping advect
a plume of elevated mixed air out of the west across at least
central South Dakota with 700mb temperatures somewhere between
+12 and +15C. Model dewpoints still only in the 60s east river
and only upper 50s to near 60 west river so not "over the top"
humid again and falls well in line with the trends we`ve seen
over the last few of weeks. Even if NBM is overdone, will still
be close enough for a heat advisory.

As we go into Monday, fire weather is the priority, with the
lack of consistent moisture. Flagging vegetation and a
lightning threat Sunday night/early Monday are then compounded
by weak cold/dry air advection and northwest winds enhancing
mixing. NAM BUFKIT mixed winds are up around 25-35kts.

Regarding smoke, there are multiple source regions to contend with
that we will need to watch over the next several days, though the
current surface high pressure does`t have much smoke contained
within or pivoting around. Focus for smoke shifts to Monday where a
plume of elevated smoke from the Pacific Northwest/Western Canada
starts to move into the region. There is a reflection at the surface
at the tail end of the RAP/HRRR runs moving into North Dakota and as
such can be supposed to continue towards CWA so something to watch.

Tuesday onwards, the upper pattern remains persistently a
northwest flow regime resulting to closer to seasonal
temperatures with low humidity. Low confidence on any
precipitation chances with subtle waves mid-week and the wave
that slips in under the ridge loop in around the upper high late
Thursday. This is because much of this moisture is pivoting
around the ridge taking the long way through the Intermountain
West before kicking out into the Northern Plains.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 112 PM CDT Sat Jul 18 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions. East winds gradually shift to southerly. Low
chances for moisture during the TAF period for KPIR/KMBG
tonight/early Sunday.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from 1 PM CDT /noon MDT/ to 9 PM CDT /8 PM MDT/
     Sunday for SDZ003>006-009-010-015>018-033>037-045-048-051.
MN...None.

&&

$$


DISCUSSION...07
AVIATION...07