Ice Storm Warning 1, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
444 AM CST Sun Jan 1 2023

.SHORT TERM...(Today and Tonight)
Issued at 340 AM CST Sun Jan 1 2023

KEY MESSAGES:

1. Quiet weather continues for New Years Day with slightly cooler
temperatures and light winds.

2. A major winter storm will affect the region on Monday and
Tuesday, with significant impacts expected in the form of heavy
snow, moderate icing, and near blizzard conditions possible by
Tuesday.

TODAY: One last quiet day across the area before a major winter
storm moves into the region for the start of the work week. Weak
surface high pressure will build into the area today, and with
continuing cold air advection temperatures will be cooler than
yesterday - playing out to highs in the upper 20s to mid 30s.

TONIGHT: The upper level trough presently situated over the
Intermountain West shifts eastward into the Rocky Mountain states
overnight. Although our area will remain primarily dry overnight,
increasing midlevel warm air advection and intensifying midlevel
frontogenesis through the MO river corridor could kick off some very
light snow through south central SD by very late tonight. Any
snowfall is expected to be less than half an inch over that area
through 12Z Monday. It will be another cold night across the area
with lows in the mid teens to mid 20s.

.LONG TERM...(Monday through Saturday)
Issued at 340 AM CST Sun Jan 1 2023

MONDAY-TUESDAY: A major winter storm remains in the offing for the
beginning of the week with significant impacts expected across the
region. The aforementioned upper level trough pivots into the
Northern Plains on Monday and Tuesday, while a deepening surface low
tracks from eastern CO to the western Great Lakes region through the
period. Models continue to converge on the placement and timing of
the surface low and upper level features - albeit with slight
variations. Although models continue to remain in their respective
camps of the past several model runs - with the GFS furthest north,
ECMWF the furthest south, and the Canadian in between - they are now
close enough that confidence is fairly high on the general placement
of the heaviest snow to affect the area during this time frame with
increasing upper level support provided by the upper level jet,
intensifying midlevel frontogenesis occurring north of Interstate 90,
and increasing midlevel theta e advection overspreading the region.
The GFS/GEPS/ECMWF ensembles all indicate probabilities of greater
than 70 percent for snowfall greater than 6 inches in the heaviest
band - which lends increasing confidence for heavy snowfall. All
that being said, current thinking has the greatest snowfall - in the
range of 8 to 12 inches, with locally higher amounts possible - from
south central SD northeastward to east central SD into southwestern
MN. Slight variations in the storm track will make a difference in
precipitation types, and the least confidence lies in how far north
freezing rain/sleet will occur on the south side of the system as
warm air aloft surges to the north on Monday into Monday night (as
this could cut down on snow amounts on the southern edge of the
snow/ice gradient). The greatest icing potential continues to be
situated over northwestern IA where two to four tenths of ice will
be possible on Monday afternoon through Monday night. By Tuesday,
precipitation should be in the form of all snow as colder air
sweeps in on the backside of the system. In addition to the
falling snow on Tuesday, winds are expected to increase - with
model soundings indicating momentum transfer winds of 20 to 25 kts
- which will result in areas of blowing snow - with near blizzard
conditions possible. In terms of headlines, in coordination with
surrounding offices, decided to leave the current Winter Storm
Watches in place for one more cycle until additional details are
further resolved.

WEDNESDAY-SATURDAY: As the system exits to the east, much colder air
will filter into the region for Wednesday and Thursday as Canadian
surface high pressure builds southward into the Northern Plains. By
the end of the week temperatures will begin to moderate as upper
level ridging builds over the region. Models are hinting at another
weak system tracking across the Central Plains on Saturday, which
could bring light precipitation to our area during that time
frame.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 441 AM CST Sun Jan 1 2023

Patchy LIFR fog through mid morning. Light snow may develop
through south central SD after 10Z tonight. Winds will be light
northerly through the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Watch from Monday morning through Tuesday afternoon
     for SDZ038>040-050-052>071.

MN...Winter Storm Watch from Monday morning through Tuesday afternoon
     for MNZ071-072-080-081-089-090-097-098.

IA...Winter Storm Watch from Monday morning through Tuesday afternoon
     for IAZ001>003-012>014-020>022-031-032.

NE...Winter Storm Watch from Monday morning through Tuesday afternoon
     for NEZ013-014.

&&

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

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
414 AM CST Sun Jan 1 2023

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-021015-
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-
414 AM CST Sun Jan 1 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...Today and tonight.

Patchy fog will continue through mid morning. In some areas,
visibility may be reduced under one half mile.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

A winter storm will impact the area beginning Monday morning and
continuing into Tuesday evening. While there remains some uncertainty
in the exact track of this storm system, confidence is high for the
potential of moderate to heavy snow amounts in the Tri-State region.
Additionally, some locations may see ice accumulation before snow
begins. At this time the greatest potential for icing is across
northwest Iowa and adjacent areas.

Continue to monitor your local forecast and be prepared for
impacts early this week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.