451
FXUS63 KFSD 191140
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
540 AM CST Sun Jan 19 2025

.KEY MESSAGES...

- An Excessive Cold Warning for wind chills colder than -35F
  has been issued for portions of the US Hwy 14 and SD34/MN30
  corridors this morning. A Cold Weather Advisory remains in
  effect elsewhere through noon today, and for the entire
  forecast area late tonight through Tuesday morning.

- An arctic air mass has settled into the region and a second
  push of colder air moves in late tonight-Monday. Temperatures
  will be 15 to 30 degrees colder than normal through Tuesday
  morning, with periods of dangerously cold wind chills as low
  as -25F to -40F (coldest north of I-90).

- Temperatures moderate through mid to late next week with near
  to slightly above normal temperatures favored from Wednesday
  onward.

- A weak system Wednesday into Thursday may bring areas of light
  snow. Chances for more than an inch of snow (0.05" liquid)
  less than 30%.

&&

.DISCUSSION...
Issued at 350 AM CST Sun Jan 19 2025

With current temperatures slightly cooler than forecast, the
moderate (12-20 MPH) northwest winds have pushed wind chills
below our -35F Excessive Cold Warning criteria across portions
of east central SD and southwest MN early this morning, and we
upgraded areas from Brookings/Lake counties in SD, east through
Lyon/Murray counties in MN. The remaining Cold Weather Advisory
is on track and still looks good to expire at noon today as
temperatures slowly rebound back into the single digits above
zero this afternoon.

We should get a brief reprieve from cold advection through much
of today and into this evening which will allow winds to taper
off after sunset more than we have seen the past couple of days.
This will be short-lived, though, as a trailing wave will swing
southeast across the northern Plains later tonight into Monday.
This will bring a reinforcing shot of cold advection which will
allow winds to ramp up more quickly Monday morning and become
a bit stronger than today with gusts 25 to 35 mph possible.
The gusty winds will be accompanied by the coldest air mass of
the season thus far, with several areas struggling to climb
above zero on Monday despite our lack of snow cover. This will
lead to very little recovery in wind chills through the daytime
hours Monday with readings remaining in the -20F to -35F range
most of the day.

Although moisture is limited, cannot completely rule out some
isolated light snow showers/flurries in the wake of this cold
front Monday morning. However, only one or two CAMs are picking
up on the potential just yet, so will stick with a dry forecast
for now.

Winds subside again rather quickly Monday evening as a weak
surface ridge slides into the area. However, the lighter winds
and mostly clear skies will allow for a colder night with lows
firmly in the teens below zero throughout the CWA, and isolated
areas approaching -20F (air temperature) for Monday night`s low.
At these colder temperatures, even the lighter winds will be
sufficient to maintain wind chills well within Advisory levels.

The coldest air is pushed east of the area by early Tuesday with
warm advection allowing for temperatures rebounding back into
the teens to lower 20s by Tuesday afternoon, warmest in south
central SD. After a quick drop-off Tuesday evening, continued
warming aloft ahead of our next wave may very well result in
rising temperatures through the latter half of Tuesday night, on
the way to highs Wednesday in the upper 20s and 30s. The warmth
does not come without a small price, though, as the responsible
wave will likely trigger areas of light snow at times Wednesday
into Thursday morning. Ensemble probabilities show moderate
(50-70%) chances for measurable precipitation over that 24-hour
period. However, the probability of 24-hour precipitation
exceeding 0.05" (roughly equivalent to an inch of snow) is less
than 30%, so expect any accumulation to remain in the nuisance
range.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 540 AM CST Sun Jan 19 2025

VFR conditions are expected to prevail at TAF sites through this
period. However, could see thin MVFR ceilings at times in areas
east of I-29 over portions of southwest Minnesota/northwest Iowa.
Gusty northwest winds (generally peaking 18-25kt) will remain
prevalent through sunset, with speeds expected to subside quickly
this evening. A secondary cold front moves into southeast South
Dakota from the northwest late tonight, bringing gusts near 20kt
back to KHON and possibly KFSD by the end of this TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Cold Weather Advisory until noon CST today for SDZ038-039-050-
     052>054-057>071.
     Cold Weather Advisory from 3 AM Monday to noon CST Tuesday for
     SDZ038>040-050-052>071.
     Extreme Cold Warning until noon CST today for SDZ040-055-056.
MN...Cold Weather Advisory until noon CST today for MNZ081-089-090-
     098.
     Cold Weather Advisory from 3 AM Monday to noon CST Tuesday for
     MNZ071-072-080-081-089-090-097-098.
     Extreme Cold Warning until noon CST today for MNZ071-072-080-
     097.
IA...Cold Weather Advisory until noon CST today for IAZ001>003-
     012>014-020>022-031-032.
     Cold Weather Advisory from 3 AM Monday to noon CST Tuesday for
     IAZ001>003-012>014-020>022-031-032.
NE...Cold Weather Advisory until noon CST today for NEZ013-014.
     Cold Weather Advisory from 3 AM Monday to noon CST Tuesday for
     NEZ013-014.

&&

$$

DISCUSSION...JH
AVIATION...JH