782
FXUS63 KABR 172334
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
634 PM CDT Fri Oct 17 2025

.KEY MESSAGES...

- Winds increase Saturday out of the northwest, with gusts of 30 to
40 mph. The winds will cause elevated fire danger over portions of
central and north central South Dakota.

- Lows for Saturday night will be near or at freezing ranging in the
30s.

- Windier conditions for Monday and elevated fire danger returns
over portions of north central and central SD. Probability of wind
gusts at or over 45 mph is 50 to 90%, highest over central SD.

- Seasonal temperatures this weekend will be followed by slightly
cooler readings early next week.

&&

.UPDATE...
Issued at 632 PM CDT Fri Oct 17 2025

No major changes to the forecast. See update to the aviation
discussion below...

&&

.DISCUSSION...
Issued at 314 PM CDT Fri Oct 17 2025

Overall westerly flow will continue at the surface and aloft this
evening as the CWA is southwest of the nearly stacked departing low
that will continue to track northeast over Canada. Models agree that
our next shortwave will move in from western Canada/Pacific
Northwest tonight, and track southeast over the Northern Plains
through Saturday. Its positive tilted surface trough/cold front will
also track southeast, with the front forecasted to be over north
central SD ~04-06Z and exit our southeastern CWA by 12Z. Winds will
switch out of the northwest with northwesterly flow continuing
through Saturday evening both at the surface and aloft as a high
pressure system sets up over the Intermountain West.

This weak system really lacks any moisture as PWAT`s ahead of the
cold front range from 0.5-0.6" and decreasing to 0.2-0.3" behind it,
per HREF. GEFS/ENS/HREF models do agree on some sort of elevated
light rain showers passing through behind the front, associated with
the shortwave. Cams actually highlight this potential well and
overall agree on timing with just minor differences in the spread of
these rain showers/intensity. The first of the precip is forecast to
move in over Corson County around ~6-8Z. The precip will then track
southeast over the CWA through the late morning with HRRR/ARW/RAP
indicating additional showers/wrap-around behind the main line. The
last of the precip is forecast to exit our southeastern CWA by ~00Z
Sunday. NBM did a pretty good job with the pops over south central
to east central SD but I added ECAM to the mix for better coverage
since the CAMs were consistent. Probability of QPF>0.10 is only 10-
20% over south central SD, where the "bulk" of the precip will fall.

Behind the cold front, GFS indicates pressure rises between +4 to
+6mb/6hrs at 15Z, highest over central SD, with the highest pressure
rises shifting southward by the afternoon. The strongest CAA (-8 to -
10C/12HR EC) is between 06-12Z, trailing right behind the front as
it tracks southeast. This colder air and pressure rises with lead to
the steepening of low level lapse rates early in the morning with
winds becoming breezy over central SD. Add in daytime mixing and
winds will increase through the afternoon. Luckily winds aloft are
not too strong with HREF grand ensemble soundings indicating the top
of the mixed layer around 825mb at KABR/KATY and around 750-800mb at
KPIR/KMBG with speeds at the top of the ML ranging between 25-35kts.
Went with previous guidance and did mix in some NBM90 to show for
this better mixing over central SD with overall gusts of 20-35kts,
highest over central SD. 90th Gusts (for max potential) is 35-45
mph, highest again for central SD. Comparing to NBM5.0 and winds are
pretty similar with really only a difference of 2-3kts giving better
confidence. With the gusty winds and drier fuels, the Grassland Fire
Danger Index is High for portions of north central though south
central SD for Saturday. Winds will diminish a bit Saturday night.
With this cold front, highs will range in the 50s and lows in the
30s with James River and westwards potentially around the freezing
mark.

By Sunday, a ridge will move in aloft and at the surface, ushering
in return flow/WAA. This will bring temps back up into the upper 50s
to the mid 60s, warmest over south central SD. This ridge will exit
east late Sunday night with our next wave moving in from the west.
Its surface low and cold front will sweep northwest to southeast
over the Northern Plains through early Monday bringing with it a
chance of light precip (NBM 25-40%) mainly over north central SD as
of now. As winds turn northwest behind the front Monday morning,
CAA/pressure rises/mixing will lead to an increase in winds. This
looks to be a windier day than Saturday as winds aloft will be
stronger to mix into (850mb winds ~40kts, 700mb winds 40-50kts). So
in collab and continuing with previous shift, used NBM/NBM90th.
Probability of wind gusts>45mph is 50-90% and up to 50% for prob of
wind gust over 55 mph, mainly over the higher elevations in central
SD. Comparing to NBM5.0 and 5.0 has wind speeds/gusts about 6-10kts
higher than deterministic NBM (gusts 30-48kts), leading to higher
confidence on a windier day. So will need to monitor closer to time
for any wind headlines. Otherwise, an overall dry forecast looks to
be the theme Tuesday into the middle of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 632 PM CDT Fri Oct 17 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions for all terminals. Winds will remain primarily out
of the west and pick up again tomorrow. Could be some light shower
activity tomorrow as well, though confidence is too low for most
terminals to include in TAFS.

&&

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

$$

UPDATE...07
DISCUSSION...MMM
AVIATION...07