North Sioux City, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

865
FXUS63 KFSD 111735
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1135 AM CST Wed Dec 11 2024

.KEY MESSAGES...

- Arctic air settles into the Northern Plains for today and
  Thursday, bringing the chance for sub-zero temperatures and
  wind chills as low as -10 to -20 degrees F this morning.

- A narrow band of snow is possible across the Missouri River
  Valley Thursday morning. However, amounts look to be light,
  below half an inch of snow.

- Chances for snow, freezing rain, and sleet across portions of
  the area Friday night into Saturday. Ice amounts up to a tenth
  of an inch possible, with snowfall amounts up to an inch.

&&

.DISCUSSION...
Issued at 406 AM CST Wed Dec 11 2024

Last push of light snow is currently traversing the I-29 corridor
here at 2:30 AM as the vorticity maximum from a strong upper level
low slides by from northwest to southeast. As has been the case,
expect only minimal accumulations under half an inch of snow, with
most areas only seeing a dusting to a tenth of an inch. The strong
push of cold air has started to move into the region, with Huron
falling almost 10 degrees over the past two hours down into the
positive single digits. As the winds remain breezy, wind chills
below zero are expected area wide later this morning, with areas
along and north of I-90 expected to have wind chills in the -20 to -
10 degree range. Be sure to bundle up before heading out the door
today, as daytime highs will only reach up into the positive single
digits to teens, with breezy winds continuing to send wind chills
into the negative teens to positive single digits throughout the day.

Drier air aloft quickly moves in behind the exiting vorticity
maximum bringing an end to the snow showers for most this morning
prior to sunrise. The exception today is for areas along and east of
highway 59, where a stripe of snow showers may linger off and on
throughout the day. This is expected as a narrow corridor of weak
isentropic ascent will likely keep producing a stratus deck in the
dendritic growth zone (DGZ), keeping chances for flurries/light snow
into the afternoon hours before dissipating. A surface high pressure
starts to slide down into the northern plains during the late
afternoon hours, allowing winds to decrease as they transition to
become out of the east-southeast throughout the morning hours on
Thursday. The coldest overnight temperatures from this cold spell
are expected overnight into Thursday given the clear skies, weak
winds, and fresh push of arctic air...producing low morning
temperatures on either side of zero. While winds will be weak, any
increase in winds will send the wind chills into subzero territory
throughout the morning hours.

Also occurring overnight into Thursday, frontogenesis (f-gen) in the
mid-levels will be strengthening over the Missouri River Valley, but
will need a few hours to saturate the low levels before snow starts
to reach the surface. With precipitable water values in the 0.3-0.4"
range, even after the lower layers are saturated, there isn`t a lot
of moisture to work with so snowfall accumulations are expected to
remain on the light side. Areas south of a line from Huron, SD to
Sioux Falls, SD to Spencer, IA have the highest chance of seeing at
least a trace (20-50%) according to the HREF, with probabilities for
an inch at 0%. So, similar to the recent events, expect less than
half an inch of snow with most only seeing a tenth or two. Chances
for snow quickly dwindle into the afternoon hours, with the main
story continuing to be the cold temperatures parked across the
region. Daytime highs will again only reach up into the upper single
digits to teens, and with the weaker winds wind chills remain on
either side of zero.

Temperatures start to rise on Friday as the surface high pressure is
bumped off to our east, allowing for southeasterly return flow to
bring some slightly warmer air into the region. Daytime highs will
only reach up into the lower to upper 20s, with the warmest
temperatures expected late in the day and overnight as a warm front
pushes northwards from eastern Nebraska. Aloft, a progressive
shortwave will be traversing the region and lifting a surface low
pressure onto the central plains, bringing our next chances for
precipitation Friday night into Saturday morning. While areas well
north of the warm front will only see snow, portions of northeastern
Nebraska, northwestern Iowa, and far southern portions of
southwestern Minnesota will likely see periods of freezing rain as a
warm-nose (indicating above freezing temperatures) extends
northwards into the area, with a cold-nose (sub-freezing
temperatures) beneath the aforementioned warm-nose. We`ll need to
keep an eye on the depth of both the warm-nose and cold-nose, as
both will determine what precipitation types end up falling. Given
the complex temperature profiles, freezing rain, sleet, and snow are
all possible across portions of the area mentioned above. Currently
expecting ice amounts up to a tenth of an inch, with snowfall
amounts up to an inch.

Temperatures look to jump back up into the 40s for Sunday as ridging
takes place aloft, with uncertainty rising into the beginning of the
week as models struggle to agree how the shortwaves navigate through
the zonal flow.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1134 AM CST Wed Dec 11 2024

Latest satellite imagery shows a mix of clear skies and a few areas
of MVFR stratus across the area. The bulk of the MVFR stratus lies
west of a Huron, South Dakota to Sioux Falls, South Dakota to Storm
Lake, Iowa line. This area of MVFR stratus will push southeastwards
and looks to avoid KHON and KFSD. It could graze KSUX but confidence
is not high enough to put in KSUX`s TAF at this time. Trends will be
monitored. Northwest winds will continue to gust up to 20-25 knots
through the bulk of the afternoon hours before dropping off by
sunset. Winds will go light and variable overnight but mid level
stratus will push northeastwards during the overnight hours. This
increasing cloud cover may bring light snow to locations along the
Missouri River Valley. Have included a PROB30 group for light snow
at KSUX during the morning hours tomorrow. Aside from the light snow
potential, light easterly winds will finish out the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...APT
AVIATION...Meyers