226
FXUS63 KFSD 121120
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
520 AM CST Wed Feb 12 2025

.KEY MESSAGES...

- A Winter Weather Advisory remains in effect for portions of
  far southeastern SD, far northeastern NE, and northwestern IA
  through this evening.

- Periods of light snow will continue through this evening across
  areas south of a Chamberlain to Madison to Marshall, MN line.
  Additional accumulations will range from a dusting to 3
  inches with the highest amounts focused along the Highway-20
  corridor and portions of the Missouri River Valley. Minor
  travel impacts will be possible.

- An area-wide Cold Weather Advisory will be in effect from
  tonight into Thursday morning with wind chill values between
  -20 to -35 expected.

- Temperatures will remain below normal through the week
  although Friday will be closer to normal. Saturday into early
  next week continue to trend well below normal.

- Confidence continues to increase in renewed snow chances from
  Friday afternoon through Saturday morning with measurable
  accumulations possible along and east of I-29.

&&

.DISCUSSION...
Issued at 352 AM CST Wed Feb 12 2025

Another cold and dreary day will be on tap for the day! Taking a
look across the area, flurries to light snow continue to develop
across portions of the area this morning with the focus being along
the Missouri River Valley and portions of northwestern IA mostly in
response to increasing mid-level frontogenesis with the left exit
region of an upper-level jet overhead. From here, expect snow cover
to expand through the morning with areas south of a Chamberlain to
Madison to Marshall line expected to receive light (and sometimes
moderate) accumulations throughout the day. Looking at the
environment, 12.00z deterministic guidance has sightly increased QPF
across portions the Missouri River Valley and northwestern IA with
the gradient of a 0.10" to 0.20" of an inch stretching roughly south
of a Tyndall to Worthington, MN line with the highest amounts along
the Hwy-20 corridor.

Given the fully saturated DGZ depicted in soundings this makes more
sense, so decided to slightly bump up our QPF where the highest POPs
were throughout the day. With SLR expected to be between 18-20:1 in
this event, this slightly increased our overall snowfall amounts
which will likely range between a dusting to 3 inches with isolated
pockets of 4 inches when its all said and done. Getting more
specific with amounts, between 2-4 inches are expected along and
south of the highway-18 corridor with a few isolated pockets of 4+
inches possible along the highway-20 corridor. Areas north of
highway-18 can expect between a dusting to 2 inches of snow.
However, accumulative amounts will sharply decrease the further
north you go. Given the slight increase in snowfall amounts decided
to add Plymouth county (northwestern IA) and Union county
(southeastern SD) into the Winter Weather Advisory which remains in
effect through 6 pm tonight. Otherwise, expect accumulations to
gradually come to an end from west to east closer 6 pm this evening.
Taking a look at impacts, be prepared for periods of reduced
visibility and slippery road conditions as the falling snow
accumulates especially across the highway-20 corridor.

Looking into tonight, the main concern continues to be colder
temperatures as another surface high moves overhead. The combination
of fresh snow cover, lighter winds, and clearing skies will lead to
another cold night with sub-zero overnight lows expected. Given the
similarities to the previous night, decided to use the BCCMC to
lower overnight temperatures from the previous package putting our
lows between -12 to -20 below zero for the night. Dangerous wind
chills are expected to accompany these colder conditions with values
between -20 to -35 degrees expected by Thursday morning. With this
in mind, went ahead and issued a cold weather advisory for our
entire county warning area (CWA) from 9 pm tonight through 9 am
Thursday. From here, expect a temperatures to gradually increase
heading into Thursday afternoon as increasing warm air advection
(WAA) and southerly surface winds usher in warmer air. With this in
mind, highs should top out in the teens to upper 20s with the
mildest conditions west of the James River.

By Valentines Day (Friday), temperatures will temporarily return to
our seasonal normals as a warm front lifts through the area
resulting in highs in the mid 20s to mid 30s. However, the warmer
condition will also be accompanied by another mid-level wave which
will likely lead to more snow chances mainly east of I-29. While a
few details are still uncertain, the 12.00z run of deterministic
guidance has slightly sped up the progression of the wave likely
leading to increasing snow chances from the afternoon onwards. As a
result, most ensemble guidance continues to have high confidence
(70%-90%) in at least measurable snowfall from Friday afternoon
through Saturday morning. Lastly, the colder conditions will
continue through Tuesday with daily highs in the single digits to
teens and sub-zero overnight lows. Similar to the last few days,
we`ll have to continue to watch the wind chill values on both Sunday
night and Monday night because we could easily dip into cold weather
criteria given lighter winds and increasing snowpack.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 513 AM CST Wed Feb 12 2025

Mostly VFR/MVFR conditions will transition to mostly MVFR and
lower this TAF period due to increasing snow chances. Taking a
look at satellite imagery, most areas continue to sit underneath
a thick later of stratus as flurries to light snow develop
across the area this morning. Expect the snow chances to persist
through this evening promoting MVFR to IFR vsbys and ceilings
throughout the area through about 00z before predominantly VFR
conditions return for the rest of the TAF period. Lastly, light
and variable surface winds will become marginally breezy
northwesterly winds by this afternoon to end the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Cold Weather Advisory from 9 PM this evening to 9 AM CST
     Thursday for SDZ038>040-050-052>071.
     Winter Weather Advisory until 6 PM CST this evening for SDZ071.
MN...Cold Weather Advisory from 9 PM this evening to 9 AM CST
     Thursday for MNZ071-072-080-081-089-090-097-098.
IA...Cold Weather Advisory from 9 PM this evening to 9 AM CST
     Thursday for IAZ001>003-012>014-020>022-031-032.
     Winter Weather Advisory until 6 PM CST this evening for
     IAZ020>022-031-032.
NE...Cold Weather Advisory from 9 PM this evening to 9 AM CST
     Thursday for NEZ013-014.
     Winter Weather Advisory until 6 PM CST this evening for NEZ013-
     014.

&&

$$

DISCUSSION...05
AVIATION...05