310
FXUS63 KFSD 202024
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
224 PM CST Mon Jan 20 2025

.KEY MESSAGES...

- Dangerous to life-threatening cold will continue into Tuesday
  morning. Wind chills values between -30 and -45 are possible.
  Cold related illness may happen in as little as 10 minutes.

- Temperatures warm slowly Tuesday, bringing in a risk for very
  light snow into Wednesday. Any accumulation will remain less
  than one half inch.

- No additional arctic outbreaks are expected through next
  weekend, with a continued  of above and below normal
  temperatures likely.

- No major snow storms on the horizon as well.

&&

.DISCUSSION...
Issued at 221 PM CST Mon Jan 20 2025

THIS AFTERNOON:  Mid-lvl vorticity within a broad upper trough
continues to moves through the Tri-State are this afternoon.
Soundings remain very cold.  In fact the 12Z ABR sounding set a new
daily minimum temperature at 850 mb at -25C.  Unfortunately this
isn`t even the coldest portion of the airmass to arrive, with
progged 850mb temperatures as low as -34C later this evening.    At
the surface, we continue to see isolated patchy of light snow
developing, briefly reducing visibility but with limited
accumulations. A better fetch of light snow is tied to some lake
effect snow coming off the Oahe Reservoir. This will avoid most
of the CWA and should lessen as low lvl winds turn westerly
this evening.

TONIGHT:  A VERY cold night is expected.  With this afternoon`s
passage of a secondary cold front, we`ve already started seeing
temperatures fall a bit, and this trend will amplify after dark.
Have pushed overnight low temperatures further down, especially as
winds turn light towards midnight.  Some -20F air temperatures could
be possible, certainly some of the coldest surface air temperatures
we`ve experienced with zero to a trace of snow.   Wind chills will
begin to also fall after sunset, but winds will generally weaken as
we approach 06Z. These weakening or even variable winds should
prevent most areas west of I-29 from reaching extreme cold criteria
(-35F), but areas along the higher elevations of the Coteau will
continue to see warning level conditions.  Have expanded the warning
into NW Iowa and the Sioux City metro (where criteria is a bit
lower), but not further west at this time given apparent
temperatures bottoming between -25 and -30F.

TUESDAY: Low level warm advection begins in earnest after midnight
as well, with surface winds turning southwesterly by daybreak.
This should bring a gradual rise in temperatures through the
morning, with fairly rapid improvement in apparent temperatures
after 8am. Areas most likely to linger near or below -25F will
be in the higher elevations of SW Minnesota and Iowa. Therefore
early cancellation of headlines could be possible. A slug of
Pacific moisture will cross the Dakotas Tuesday afternoon. A
very dry airmass remains in-place below this moisture layer, but
would not be surprised to see some flurries to light snow over
northern South Dakota by late afternoon/evening.

WEDNESDAY: A cold front moves through the Northern Plains early
Wednesday as another shortwave moves through the Rockies and into
the Plains on Wednesday.  Scattered light snow showers or flurries
may be possible at times through the day Wednesday, however the
probability of anything more than a half inch of snow is low (10-
15%).

THURSDAY-SUNDAY:  No dramatic chances to the forecast in the medium
range. We remain stuck in a pattern with stronger North Atlantic
troughing and eastern Pacific Ridging, which will bring several
upper troughs through a broad northwesterly flow. None of these
troughs will bring anything more than weak Pacific moisture with
them, and most of that will be scoured out across the Rockies.  The
end result will be an up and down temperature forecast, and periodic
light snow or flurry chances. The risks for meaningful snow are
low, with 24 hour probabilities of more than 0.5" never topping
15% in any one period through Sunday.


&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1059 AM CST Mon Jan 20 2025

MVFR level horizontal convective rolls may continue to develop
through the afternoon, very briefly reducing visibility to 2
miles or less. In snow showers ceilings may range from 1000ft
AGL to 2000ft AGL.

We`ll see skies only slowly clear this evening, with winds
turning light and variable overnight. Southwest winds will
arrive towards daybreak, with filtered high level clouds.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Cold Weather Advisory until 6 PM CST this evening for SDZ071.
     Extreme Cold Warning from 6 PM this evening to noon CST
     Tuesday for SDZ071.
     Extreme Cold Warning until noon CST Tuesday for SDZ039-040-055-
     056.
     Cold Weather Advisory until noon CST Tuesday for SDZ038-050-
     052>054-057>070.
MN...Cold Weather Advisory until 6 PM CST this evening for MNZ081-
     089-090-098.
     Extreme Cold Warning from 6 PM this evening to noon CST
     Tuesday for MNZ081-089-090-098.
     Extreme Cold Warning until noon CST Tuesday for MNZ071-072-080-
     097.
IA...Cold Weather Advisory until 6 PM CST this evening for
     IAZ001>003-012>014-020>022-031-032.
     Extreme Cold Warning from 6 PM this evening to noon CST
     Tuesday for IAZ001>003-012>014-020>022-031-032.
NE...Cold Weather Advisory until 6 PM CST this evening for NEZ013-
     014.
     Extreme Cold Warning from 6 PM this evening to noon CST
     Tuesday for NEZ013-014.

&&

$$

DISCUSSION...Dux
AVIATION...Dux