683
FXUS63 KABR 171125 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
525 AM CST Mon Nov 17 2025

.KEY MESSAGES...

- Above normal temperatures continue today, with highs in the mid 40s
  to the lower 50s. Cooler temperatures expected for Tuesday with
  highs ranging in the upper 30s to the upper 40s.

- There is a 60 to 90% chance of precipitation Monday afternoon
  into early Tuesday morning. Mainly rain is expected. However, a
  band of moderate rain or snow will be possible late Monday night
  into Tuesday morning, mainly over and along the eastern slopes
  of the Sisseton Hills through west central MN.

&&

.UPDATE...
Issued at 517 AM CST Mon Nov 17 2025

Updated discussion for the 12Z TAFs below.

&&

.SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/...
Issued at 349 AM CST Mon Nov 17 2025

Very tricky forecast with this upcoming banded system, especially
tonight through Tuesday morning. The main uncertainty is the timing
of rain to snow changeover tonight over portions of northeastern SD
into west central MN and the resulting snowfall accumulations. A
second uncertainty is the banded nature of this system, a more
intense band or bands will lead to higher snowfall
rates/accumulations along and east of the Coteau, especially from
Clark and eastward through Deuel Counties. By 12Z, models are in
better agreement of an elongated area of low pressure extending from
eastern Colorado and northwestward through Wyoming into western
Canada. By 18Z, a weaker low will be over southwestern SD with the
stronger stacked surface-500mb Colorado Low pushing a bit eastward
over NE/KS. By 00Z, the low over southwestern SD will continue to
track southeast and merge with the CO Low, with the center of this
low over the NE/KS by 00Z and continuing to track eastward through
KS/IA by 12Z Tuesday morning.

CAMs are in better agreement with rain bands moving in over
south central SD, around the midday or so, where they will track
north and northeast over the CWA through this evening and overnight
with additional development/intensity of rain changing to snow over
our southeastern CWA (Redfield-Deuel Counties) as we are on the
northern side of this low. HREF at 700mb has a west to east oriented
area of Fgen/WAA from Pierre to Miller at 21Z with this Fgen/WAA
band pushing north/northeastward and extending from Gettysburg to
Clear Lake by 00Z. By this time, the bulk of the banded precip is
forecasted from Dewey to Stanley Counties and eastward through Spink
and then east/southeast over our southeastern CWA. HiRes-ARW/RAP
seems to be the only CAMs that pull this precip a bit northward. By
02-03Z, this Fgen will be over our far southeastern CWA with
stronger forcing along FSD/MPX border. 850mb Fgen seems to be
located mainly over the Coteau during this time period. As the low
tracks east, the last of the precip will continue over our
southeastern CWA, exiting this area around 12Z. Its noted too that
with stronger lapse rates/MuCape/FGEN, HREF>40dbz shows paintballs
with these bands indicating stronger intensity. We are outlooked for
general thunder by SPC so cannot rule out a thunderstorm or two,
staying below severe limits. Due to low confidence, this has not
been added into the grids. Overall for the grids, incorporated ECAM
to the NBM blend through 12Z Tuesday, giving the highest pops of 60-
90% from central SD and eastward through our southeastern CWA.

The rain to snow changeover will be highly dependent on exact
temperatures during this time. NBM does a good job showing the
colder air filtering in behind this system this evening and
overnight but with collab from other offices, we added in
ConsShort/HREF to nudge things down a bit more. The majority of the
CAMs keep Ptype as rain through 00Z with NAM12/HiRES ARW indicating
a brief time in the transition period where we could see isolated
areas of freezing rain/sleet over the Leola Hills and over/eastern
slopes of the Coteau around ~06-09Z (Fram highlights this well)
before precip changes over to snow over our southeastern CWA. Storm
total ice does show a couple hundredths of an inch along the eastern
slopes of the Coteau, however, with the ground being warm, this
should keep any ice from accumulating. However, bridges and
overpasses could become slick. HiResArw is the quickest with the
changeover to snow while Fv3 seems to be the outlier and keeps
precip as all rain. It is interesting to note that with the stronger
Fgen over our southeastern CWA after 00Z, steeper lapse rates, and
the paintballs>40dbz highlight in this area, the Snowband
Probability Tracker highlights this area for the potential for
heavier snow bands between 03-09Z. NAM soundings for ATY do show
quite the saturated column hovering around 0C at the surface before
dropping to at or below freezing. With this potential we did bump up
snow ratio between 5-6:1 to show for this higher potential over our
far southeastern CWA.

The latest NBM has increased QPF and seems to handle this situation
well with amounts of 0.50-0.90" along and south of a line from
Redfield through Watertown to Clear Lake. This seems to match up
well with the grand ensemble HREF. 90th percentile has QPF of 1"-
1.25" which could be possible if we get stronger bands. HREF 25-75th
spread still runs about 0.40-0.50" for this area. There is a
difference between NBM and HREF on snow accumulation. HREF ensemble
highlights 1 to potentially 3 inches of snow from Wilmot to
Watertown and east/southeastward with a 25-75th spread of 4-5 inches
and 4-8 inches in the 10th-90th! HRW_ARW and HRRR both are showing
more of these higher ends amounts (up to 10 inches over portions of
our southeastern CWA!). NBM keeps snow accumulation under an inch
with the 90th percentile at an inch and 95th percentile of 2 inches
along and east of the Coteau. So very low confidence exists on snow
amounts as its all going to be temperatures dependent (if we cool
quicker=ptype changing to snow faster) and where the stronger
bands end up. Stay tuned!

&&

.LONG TERM /TUESDAY EVENING THROUGH SUNDAY/...
Issued at 349 AM CST Mon Nov 17 2025

Tuesday evening, we are under a somewhat weak upper level ridge.
This will transition into a zonal flow pattern Wednesday with a low
over California that will move east and a trough coming down out of
Canada. The NAM has by far the strongest trough, but the EC and
Canadian deterministic models also include this feature. Past
Thursday, models don`t really agree but the big picture seems to be
that the low from California will stay to our south and pass us by
as another low moves onto the Pacific Coast.

The PoP forecast has changed rather dramatically as the models have
shifted to keep that low from California to our south instead of
bringing it across the SD/NE border. As the trough from Canada
grazes our northern counties, that area will have a slight chance
(15-20%) for some rain showers mainly Wednesday evening into early
Thursday morning. Temperatures in the lower layers look to remain
above freezing, so precipitation should stay rain. However,
overnight low temperatures in this area (ND/SD border) are forecast
to be right around freezing (NBM probabilities of lows less than 32
degrees are between 55 and 80%) and if they dip below freezing,
could result in some slick surfaces, mainly bridges/overpasses. Past
Thursday, the forecast looks dry, but models don`t really have a
good handle on what will happen so this could change.

High temperatures through the period are currently expected to
remain above average, mainly in the mid to upper 40s, perhaps
reaching into the mid 50s on Wednesday ahead of the low and Saturday
as some models show us getting a blast of WAA. Winds will be rather
light, strongest on Thursday and Saturday with gusts up to 25 mph.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 517 AM CST Mon Nov 17 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast to prevail through this afternoon,
with MVFR CIGs to move northward through the region this evening
continuing early Tuesday morning as a storm system tracks to our
south. Rain is primarily forecast at KMBG, KPIR, and KABR while
rain will change to either a rain and snow mix or all snow at KATY
early Tuesday morning. Lowering Cigs to IFR to even LIFR are
possible around midnight through the end of the TAF period at
KATY.

&&

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

$$

UPDATE...MMM
SHORT TERM...MMM
LONG TERM...13
AVIATION...MMM