Promise, South Dakota Weather Forecast Discussion

543
FXUS63 KABR 242342
AFDABR
Area Forecast Discussion
National Weather Service Aberdeen SD
642 PM CDT Wed Sep 24 2025
.KEY MESSAGES...
- Patchy fog is possible early Thursday morning over portions of
northeastern SD and west central MN.
- A prolonged period of dry and warm conditions continue through at
least early next week. Temperatures are forecasted in the 70s and
80s (5 to 15 degrees above normal).
&&
.UPDATE...
Issued at 641 PM CDT Wed Sep 24 2025
Limited changes are expected to the ongoing forecast as shallow
cumulus clouds continues to fade over the Prairie Coteau. Fog will
again be the main concern in the morning, with forecast guidance
continuing to downplay time and coverage area, as the focus will
mainly be south of ATY for the potential for dense fog.
&&
.DISCUSSION...
Issued at 211 PM CDT Wed Sep 24 2025
As of 2pm temps range in the 70s with dewpoints in the 50s to the
lower 60s. Satellite indicates fair weather cumulus clouds starting
to pop up east of the Missouri River with high pressure dominant
over the region. No major changes to the forecast through the
extended with overall dry conditions expected and ongoing warmer
than averages temperatures. Fog is once again possible east of the
James River early Thursday morning with some of that fog possibly
being dense (down to a 1/4 mile visibility) at times in localized
areas. Ridging continues over the region through early Friday with
more of a wavy zonal flow pattern over Canada with winds aloft over
the region out of the north, turning northwest Thursday, then out of
the southwest by Friday. This wavy pattern is due to a series of
shortwaves that will track west to east across Canada through the
weekend. The passing second wave will bring weak mid level troughing
over the Northern Plains late Friday as its surface low will also
track east and dry cold front passing northwest to southeast over
the CWA Friday late afternoon/evening. GEFS is a little faster on
the passage of the fropa than ENS at this time.
Otherwise ridging builds in behind the trough with a -PNA pattern
setting up Sunday through early next week with the trough over the
Pacific (and a strong mid level low over the Gulf of Alaska) and a
broad negative tiled ridge building over and east of the Rockies.
This broad ridge is forecasted to shift more eastward by the middle
of next week. Clusters even out to Day 6 have a good handle on this
pattern. By Day 7 onward, there are differences on exact location
and amplitude of this ridge and strength of the low/trough over the
Pacific/West Coast. Otherwise the CWA is forecasted to be on the
right side of a lee surface trough Sunday-Tuesday with this lee
trough possibly pushing eastward by the middle of week. Models
continue to keep the pattern dry into early next week.
With the cold front Friday, pressure gradients will be somewhat
tighter over the area which will increase winds as NAM soundings
indicate the top of mixed layer (inverted V sounding) up to around
20kts between 850-750mb across the CWA by the afternoon. So as the
previous shift mentioned, kept the trend of a 50/50 blend of
NBM/NBM90 for Friday. Gusts are forecasted between 20-30kts with
weak CAA moving in late Friday through early Saturday behind the
fropa. Our warmest days will be Thursday and Friday of this week as
850mb temps will range from +17 to +20C Thursday and +18 to +22C
Friday with southerly winds. This runs about 1 standard deviation
above climo per NAEFS. With daytime heating and mixing of drier air,
highs are forecasted in the upper 70s to mid 80s on Thursday and
overall in the 80s on Friday! Upper 80 readings are possible over
south central SD and portions of the James River Valley. To show
this, per previous shift, blended in warmer guidance as we
overachieved the straight NBM by several degrees yesterday in
Aberdeen. With the fropa, temps will cool back into the 70s
Saturday, but warming right back up Sunday through early next week
with highs overall in the upper 70s and 80s per the pattern setup
mentioned above. NAEFs indicates 500-850mb temps running about 1
standard deviation above climo. Would not be surprised if NBM is
underachieving highs, especially over the James River Valley, and
may need to be bumped up closer to time.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 641 PM CDT Wed Sep 24 2025
Terminals KABR,KATY,KPIR,KMBG
VFR conditions will continue for the majority of the period. Fog
will again be a concern at both ABR and ATY from around daybreak
to 14-16Z. Forecast guidance has less fog at ABR, and have opted
to keep the potential at 5SM. ATY will continue to have a higher
chance of fog, with visibility falling at or potentially below 2SM
at times (TEMPO) from 12-14Z Thursday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...06
DISCUSSION...MMM
AVIATION...06

NWS ABR Office Area Forecast Discussion