Winter Storm Watch 2, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Sioux Falls SD
1054 PM CST Wed Jan 25 2023

.SHORT TERM...(This Evening through Thursday)
Issued at 333 PM CST Wed Jan 25 2023

KEY MESSAGES:

1. Light snow is likely for Thursday night, with any accumulation
expected to be an inch or less.

2. Confidence is growing in a much more impactful system for Friday
night into Saturday, with the biggest impacts being south of
Interstate 90.

2. Much below normal temperatures will follow that system, impacting
the region for the upcoming weekend into the middle of next week.

TONIGHT: A cold front has pushed through the region this afternoon,
and with strong cold air advection, temperatures have generally been
falling through the day. Light snow/flurries continue east of
Interstate 29 this afternoon with an upper level low situated over
western IA, though we will see this activity diminish by evening as
the feature pulls away. Otherwise, surface high pressure builds into
the region tonight, and as the surface pressure gradient slackens,
gusty northwesterly winds will diminish. Another shortwave will
slide southward through western and central SD later tonight, and
this could produce light snow over those areas. Most of this will
remain to the west of our CWA, though it cannot be ruled out that a
few tenths will fall in our southwestern most zones of south central
SD overnight. With the cold air advection and lighter winds, it will
be a cold night with lows in the single digits above zero to single
digits below.

THURSDAY: Surface ridging slides to the east on Thursday, with a
southerly flow returning to the area on the backside of the high.
This will bring about a much milder day, as highs climb into the
lower to mid 30s from the Interstate 29 corridor and westward. East
of there where the warm air advection will be delayed, highs will
remain in the 20s.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 333 PM CST Wed Jan 25 2023

THURSDAY NIGHT AND FRIDAY: The shortwave train continues on Thursday
night as yet another wave drops into the Northern Plains. Strong
midlevel theta e advection will overspread the area out ahead of the
feature, with light snow spreading eastward across the area
overnight. With increasing winds and the warm air advection,
temperatures are expected to actually rise for a period as the
system moves across the region, and with that, could see rain mix
with the snow for a brief time. Any snowfall that does occur will be
light, with ensembles supporting snow amounts of generally an inch
or less - with the higher amounts north of Interstate 90. With winds
gusting at around 30 to 35 kts, patchy blowing snow will be possible
- especially when snow is falling. Colder air begins to feed
southward behind the system on Friday, with high temperatures most
likely occurring early in the day, then falling in the afternoon.

FRIDAY NIGHT AND SATURDAY: Confidence is growing on an impactful
winter storm for Friday night into Saturday - with greatest impacts
being felt south of Interstate 90. Another upper level shortwave
will track through the Central Plains, with strong midlevel
frontogenesis lifting northward into our area during this time
frame. Deterministic models are in fairly decent agreement on the
heaviest snowfall axis being situated through the MO River corridor
(the exception being the NAM which is shifted farther to the south).
Interestingly, GEFS/GEPS/and ECMWF ensembles have the higher
probabilities of receiving 3 inches or more located mainly south our
CWA, and ensemble plumes also indicate a wide spread in potential
snowfall amounts, so some uncertainty remains. In spite of that, it
is becoming likely that some type of headlines will be issued in the
coming forecasts.

SATURDAY THROUGH WEDNESDAY: With the passage of this, the main theme
will be a prolonged period of very cold temperatures as Canadian
high pressure builds into the region. Both the NAEFS and ECMWF
ensembles continue to show 700/850 mb temperatures in the 10th
percentile or lower with respect to climatology for this period.
This will play out to highs in the single digits above to single
digits below zero for that time period, with lows in the single
digits below to teens below zero. Other than Saturday, winds do not
look overly strong, which will lessen wind chill affects - though
anyway you look at it, it will be cold. There do not look to be any
significant storm systems through the period, with ensembles showing
only very low probabilities of receiving greater than a tenth of an
inch of precipitation for any one 24 period through the middle of
next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
Issued at 1048 PM CST Wed Jan 25 2023

Mid level stratus continues to gradually spread in from the west.
MVFR ceilings will slowly creep eastward from central SD
underneath. Introduced MVFR stratus near the I-29 corridor by 12z
(at FSD/SUX). Although confidence is lower in how widespread it
will be and how long it will linger near and east of I-29 (could
be most of the day Thursday), stayed with a more optimistic TAF
for now.

Behind departing sfc high pressure, winds will swing west and
eventually southwesterly during the daylight hours Thursday with
gusts of 15-25 kts developing by late afternoon. A front passes
through Thursday evening, bringing chances for light snow or rain
and gusty northwesterly post frontal winds.

&&

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

SHORT TERM...JM
LONG TERM...JM
AVIATION...BP

Hazardous Weather Outlook...UPDATED
National Weather Service Sioux Falls SD
643 PM CST Wed Jan 25 2023

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-261245-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory-
Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook-
Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton-
Union-
643 PM CST Wed Jan 25 2023

This Hazardous Weather Outlook is for northwest Iowa, west central
Iowa, southwest Minnesota, northeast Nebraska, central South
Dakota, east central South Dakota, south central South Dakota and
southeast South Dakota.

.DAY ONE...Tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Light snow is expected with a passing front on Thursday evening and
night. Gusty northwest winds behind the front coupled with light
snow could reduce visibility at times and cause hazardous travel.

Confidence is growing regarding a much more impactful system Friday
night into Saturday. The biggest impacts would likely be south of the
Interstate 90 corridor where the heaviest snow is looking most likely
to occur, however, confidence in details is low at this time.

Much colder air moves in Saturday through at least early next week.
This brings daily high temperatures in the single digits either side
of zero and nighttime wind chills dipping into the teens and 20s
below zero.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.