NZUS99 KABR 231956
WRKABR

Primary focus of the long term part of the forecast will be the
transition from Fall to Winter on Tuesday, which will remain through
the start of December. The transition will be driven by a strong
shortwave over the Pacific that will move into the PacNW tonight and
then quickly move east into the northern Plains Monday night and
depart Tuesday evening. Expect this shortwave and associated weak
surface low (around 1009mb) to bring an initial push of light rain
to northern SD on Monday night (generally north of US-14, but may be
some lingering rain in southwest MN from tomorrow's precip). Then as
the low moves east Tuesday and intensifies over eastern MN and
western WI during the afternoon, it will wrap in much colder air on
Tuesday morning, switching the rain to snow from northwest to
southeast and eventually putting the eastern SD and southwest MN
(largely north of I-90) in wrap around snow into the evening. The
combination of the snow, with strong N-NWrly winds, may lead to some
travel impacts along/north of US-14/81 on Tuesday.

First for the winds. The initial surge of cold air advection behind
the front will lead to the strongest winds over central and
especially south central SD on Tuesday, where 0.5km winds are in the
35-45kt range. Thus, expect gusts easily in the advisory range for
areas along and especially west of the Missouri River on Tuesday.
Wouldn't be surprised to see some High Wind Warning gusts for
Gregory and maybe Brule/Charles Mix counties, which is supported by
the NBM 24hr wind gust probabilities of 55mph or greater being over
60-80%. Farther east to the James River Valley, think that area
should see some gusts to advisory level (NBM has 24hr probs on
Tuesday around 70%) and they too may eventually need an advisory.
That matches up with the EC-EFI data highlighting much of SD, except
the northeast, with 0.7-0.8 values, which traditionally lines up
with advisory winds for our region. Will need to watch the
tightening pressure gradient Tuesday aftn/evening near the MN/SD
border areas, as the surface low strengthens. This could lead to an
enhanced 6hr period of winds with gusts reaching advisory level.

The strong winds and dry fuels will lead to elevated fire weather
concerns for locations that don't experience precipitation on
Tuesday. That looks to primarily be in south central SD, so despite
RH values being up towards 60%, the strength of the winds may
support the need for a Red Flag Watch/Warning, or at least enhanced
messaging in wind products and social media.

Finally, some additional details on the snow side of the forecast. As
mentioned previously, expect to see a steady transition from rain to
snow from northwest to southeast on Tuesday afternoon, as the cold
air surges into the area. At the present time, ensembles have a
decent cluster that have QPF amounts of 0.15" or less along US-14,
but there are members that show amounts up towards 0.25-0.4". This
appears to be tied to the members that have a farther south shift
with the snow. So will need to watch that for any potential
southward trends over the next 24 hours. That being said, the
current probabilities of 1" of snow or more along US-14 is around
20% and then increases as you head north towards Watertown and US-
212. Thus, expect the overall impacts from the snow to be limited at
this time.

For the rest of the week...

A high moves in on Wednesday and remains into Thursday. Could be
some light precip moving into western SD later Thursday and sliding
southeast with time into Friday, associated with an shortwave
dropping southeast through the northwest flow aloft (and mid level
WAA). Still some uncertainty in the ensembles on the location and
amounts, but in general, seems like snow accumulations will be light
(NBM 24hr probs of 1 inch or greater is 50-70%). Beyond that,
uncertainty remains into the weekend, as an upper trough deepens
over the southwest CONUS this weekend and remains in the first part
of next week. Ensembles are consistent on the upper trough being
present, but differ on the location of the trough axis and how
amplified it will be. That being said, with the baroclinic zone
setup to the southwest of our area, stretching from western MT
through southwest SD and into central NE, we'll still have the
potential for periods of light snow this weekend (30% chance). In
addition, high temperatures will be 10-15 degrees below normal and
in the 20s.