Heavy Snow and Winter Weather in Minnesota, December 13 to 16, 2022

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1127 PM CST Mon Dec 12 2022

.UPDATE...
Issued at 838 PM CST Mon Dec 12 2022

Forecast is on track. More widespread and heavier pcpn looks
poised to move into the CWA overnight, per latest radar and sat
pix, plus model data. Some pretty hefty ice amounts still look
possible over portions of the northeast. Temperatures won't change
much through the night.

&&

.SHORT TERM...(This Evening through Tuesday Afternoon)
Issued at 356 PM CST Mon Dec 12 2022

Forecast challenges surround coverage of drizzle/freezing drizzle
into late this evening before transition to heavier plain old rain
and freezing rain (rain to snow across the northwest and far west
forecast zones late) tonight, and ultimately where the liquid/frozen
p-type line sets up from late tonight through the end of the day
Tuesday. Additional challenges include where/when the CWA
experiences thunder over the next 24 hours (EC EFI CAPE shift of
tails and 12Z/12th HREF 1in/hr snowfall rates progs).

At 2 PM CST, skies are overcast and sfc obs/reports have been coming
in of drizzle and freezing drizzle now throughout the region. The
regional radar mosaic reveals the drizzle look and feel on radars
from Colorado to Iowa up into the Dakotas, with the KABR radar
showing a notable drizzle signature on it (especially to the west of
the radar currently). Temperatures have warmed to above freezing
across portions of the CWA from the James River valley westward.
Noticing a tremendous surge of surface/low level moisture advecting
northward into South Dakota, including the southwestern third of the
CWA this afternoon.

This low level moisture surge seems to hold the key to how tonight's
and Tuesday's forecast pans out. If more low level moisture advects
up through the western two-thirds of the CWA and warms the Tw up to
above freezing, then precipitation likely remains liquid
(drizzle/rain) for much longer and there is less of a chance of snow
across the west overnight. Up on the Prairie Coteau, the set up is
much more probable for conditions to be light freeing
drizzle/freezing rain overnight into Tuesday morning, so the Ice
Storm Warning headline there looks good. The breezy to windy
easterly component winds/gusts forecast for overnight and Tuesday up
on the Coteau will combine with freezing precipitation to create
simply treacherous driving conditions, especially on north-south
roads.

It still looks like by Tuesday morning, saturation aloft should have
the CWA north and west of a line from Murdo to Gettysburg to
Frederick in all snow. The trend still shows up for that
liquid/frozen precipitation line to gradually shift south and east
throughout the day on Tuesday, with a lot of snow accumulation
potential across the northwestern/western half of the CWA on Tuesday
as multiple bands of moderate to heavy precipitation rotate north
and west into the CWA. There is "cold air instability" showing up in
some of the hi-res rapid update models later tonight and on Tuesday.
Between the latest trends in extreme forecast potential (CAPE) off
the ECMWF ensemble system and the HREF's hourly snow rates in excess
of an inch/hour and this cold air instability availability, thunder
occurring somewhere over the CWA between midnight tonight and 6 PM
CST Tuesday is definitely worth a mention in the grids. So, added
some in across the western half of the CWA Tuesday afternoon where
the highest snow-rates are progged.

Take a snapshot of the current temperatures/dewpoints over the CWA,
because they are not likely to fluctuate but perhaps 3 or 4 degrees
over the next 24 to 30 hours.

.LONG TERM...(Tuesday Evening through Monday)
Issued at 356 PM CST Mon Dec 12 2022

The complex weather situation revolving around this compact winter
storm will continue and spill over into basically the first half of
this period. All weather types, temperatures and winds will be the
key challenges during this portion of the forecast, especially
through the end of the week. Starting things off Tuesday night, the
classic Colorado low pressure system will be tightening up as it
tracks basically in the vicinity of the Nebraska/South
Dakota/Iowa/Minnesota border region from Tuesday night, through the
day Wednesday and into the first half of Thursday. This system will
remain virtually stacked through this entire period with the
mid/upper level lows and features right on top of each other.
Multiple shortwaves of energy will be rotating around the region as
the mid-lvl slowly moves across the aforementioned areas above. It
won't be until late Thursday through Friday before the sfc and upper
level features of this complex storm begin to pull away from our
forecast area.

Still a challenging and uncertain p-type situation is anticipated on
the front side of this period, particularly across our eastern
zones(along and east of the James Valley) going from Tuesday night
into Wednesday. Initially, on Tuesday night, we anticipate the
precip scenario will be steadier, more pronounced falling snow,
freezing rain or a rain/snow mix across those locales. As the system
tracks north and east during the morning hours Wednesday, we could
see drier air in the mid/upper levels get pulled into the system.
The effects of this potential dry slotting in our east will have a
couple ramifications. For one, we'd loose saturation aloft in the
DGZ leaving only the low levels saturated meaning drizzle/freezing
drizzle would be possible again. Secondly, the drier upper levels
would mean QPF amounts will be cut back in these eastern zones. This
isn't to say eastern zones won't get in on some snow accumulations
of their own by the time this is all said and done because we are
expecting light snowfalls to persist through the end of the week.

Speaking of snow farther west, along and west of the James Valley,
confidence remains much higher on the outcome of this event. P-type
is anticipated to be all snow in these area by the time we get into
Wednesday morning, especially after daybreak. From that point on
through the end of the event late Thursday/early Friday, it will be
all snow. Chances will remain likely through the end of the day
Wednesday into early Thursday. PoPs will then begin to dwindle down
gradually through the day Thursday and should all come to an end by
late Thursday/early Friday. Throughout this period, an additional 5
to 8 inches of snow will be possible west of the James Valley
through our West River counties. Winds will become more of a concern
with time across these zones by later in the day Wednesday,
especially Wednesday night through Thursday evening. Probabilities
for seeing max wind gusts in excess of 40 kts are highest across our
West River zones, particularly across our southwestern zones. With
falling snow initially Wednesday night and/or the already
accumulated snow on the ground will pose blowing snow and reduced
visibility impacts to those zones.

Back in our eastern zones(James Valley and points east), any
leftover freezing precip will come to an end toward late Wednesday
into early Thursday. A transition to all snow will take hold and
continue for the remainder of the event. This is the point where an
additional 3 to 6 inches will be possible. Some enhancement along
the Prairie Coteau will be possible with perhaps some locally higher
values. High pressure will eventually work its way back into the
region by late in the period on Sunday into Monday. Temperatures
will be relatively mild until the weekend when much cooler air is
anticipated to shift into the forecast area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1125 PM CST Mon Dec 12 2022

Terminals KABR,KATY,KPIR,KMBG

IFR cigs/MVFR vsbys will prevail for most of the night. FZDZ/FZRA
will be prominent overnight, becoming a mix late, and then mostly
snow for KPIR/KMBG late tonight. The mix of pcpn types will
continue at KATY/KABR into Tuesday.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Warning until 6 AM CST /5 AM MST/ Thursday for
     SDZ003>006-009-010-015>018-033>037-045-048-051.

     Ice Storm Warning until 6 PM CST Tuesday for SDZ007-008-011-
     019>023.

     Winter Storm Warning from 6 PM Tuesday to 6 AM CST Thursday for
     SDZ007-008-011-019>023.

MN...Winter Storm Warning until 6 AM CST Thursday for MNZ039-046.

&&

UPDATE...TDK
SHORT TERM...Dorn
LONG TERM...Vipond
AVIATION...TDK

Hazardous Weather Outlook...CORRECTED
National Weather Service Aberdeen SD
1013 PM CST Mon Dec 12 2022

MNZ039-046-SDZ003>006-009-010-015>018-033>037-045-048-051-140415-
Traverse-Big Stone-Corson-Campbell-McPherson-Brown-Walworth-Edmunds-
Dewey-Potter-Faulk-Spink-Stanley-Sully-Hughes-Hyde-Hand-Jones-Lyman-
Buffalo-
1013 PM CST Mon Dec 12 2022 /913 PM MST Mon Dec 12 2022/

This Hazardous Weather Outlook is for west central Minnesota,
central South Dakota, north central South Dakota and northeast
South Dakota.

.DAY ONE...Tonight.

Overnight, expect rain and freezing rain and then over to snow into
the day Tuesday

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday we will see our heavier accumulations of snow. 40mph
winds will also result in blowing and drifting. Improving
conditions are unlikely until some point Thursday. Arctic air
follows the system for a prolonged period with highs in the single
digits and lows below zero through the weekend and into next
week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

SDZ007-008-011-019>023-140415-
Marshall-Roberts-Day-Clark-Codington-Grant-Hamlin-Deuel-
1013 PM CST Mon Dec 12 2022

This Hazardous Weather Outlook is for northeast South Dakota.

.DAY ONE...Tonight.

Precipitation intensity and coverage increases during the evening
and overnight with more ice accumulation possible due to freezing
rain and freezing drizzle.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday and Tuesday night we will see a transition to snow. 40-50mph
winds will also result in blowing and drifting. Improving conditions
are unlikely until some point Thursday. Arctic air follows the
system for a prolonged period with highs in the single digits and
lows below zero through the weekend and into next week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ABERDEEN SD
922 PM CST MON DEC 12 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 PM     FREEZING RAIN    1 NW BRISTOL            45.35N 97.76W
12/12/2022  E0.01 INCH       DAY                SD   LAW ENFORCEMENT

            ICY ROADS FROM FREEZING DRIZZLE LED TO A
            SEMI CRASH ON US HIGHWAY 12 NEAR BRISTOL.
            RELAYED VIA SOCIAL MEDIA WITH PHOTO.
            APPROXIMATE TIME AND LOCATION.

&&

RL