Extreme Cold in Minnesota, January 1, 2018

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1132 PM CST Sun Dec 31 2017

.UPDATE...
Issued at 1126 PM CST Sun Dec 31 2017

See the updated aviation discussion below.

UPDATE Issued at 824 PM CST Sun Dec 31 2017

Cold temperatures and windchill remain the concern this evening.
Winds have been decreasing across the western two thirds of the
CWA allowing for the radiational cooling to take over and
a rapid drop in temperatures to occur. Went ahead and dropped the
overnight low temperatures several degrees from the James River
Valley west, and then a couple more degrees along the James River
Valley. Haven't seen the lows drop as quickly out east due to
winds in the 10-15 mph range, but this region is also experiencing
wind chill values in the -30 to -40 range. No changes to the wind
chill warning which remains in effect though noon CST Monday.

&&

.SHORT TERM...(This Evening through Monday Afternoon)
Issued at 255 PM CST Sun Dec 31 2017

The region is still under the influence of an Arctic high pressure
with all locations reporting temps below zero. Light,
northwesterly winds are creating wind chill values of -25 to -30
degrees. With clear skies and light winds tonight, lows should fall
to 20 below, to 30 degrees below zero. Much like last night, the
coldest locations will likely be in the James Valley. There is some
low stratus over northern ND which could spread southward into the
CWA late tonight into the morning hours on Monday. Will maintain a
clear forecast for tonight as confidence on clouds is low.

An upper level trough of low pressure, currently over Alberta, will
track southeastward across the region on Monday with slightly warmer
temperatures expected. With 925 mb temps warming nearly 10 degrees
from 18Z today to 18Z Monday, highs should reach the single digits
on either side of zero.

While dry conditions are expected, lake effect snow has been ongoing
from Lake Oahe, with snow impacting KPIR. The lake effect snow
should continue this evening, or until winds weaken below 5 mph.

.LONG TERM...(Monday Evening through Sunday)
Issued at 255 PM CST Sun Dec 31 2017

The first half of the long term forecast will see temperatures
remaining below normal before a building upper ridge over western
North America shifts east and brings normal to above normal
temps to the area for next weekend.

Will see one more morning of very cold wind chills on Tuesday
morning as clear skies combine with increasing winds ahead of an
approaching clipper system to produce wind chills solidly in the
advisory criteria and potential warning criteria for the eastern
CWA. Have added wording into the HWO to highlight that headline
concern. Expect southwesterly winds to increase through the day
and occasionally gust into the 20-25kt range in the afternoon
(inversion around 930mb should keep the area from tapping into
the stronger winds aloft). In the favored sw wind downslope areas
of the Coteau, trended winds up some and gusts around 30kts are
possible. Those gusty winds will lead to some drifting snow across
area roadways and with plenty of sunshine, could be some potential
for melting of the drifting snow on dark roadways and then
refreezing as temps cool. Think this chance will be most likely in
central SD, where temps will warm towards the mid 20s and close
enough to allow the potential for melting on the roads. On the
east side of the Coteau, expect patchy BLSN with the stronger
gusts. The cold front associated with the clipper moving through
the northern Great Lakes will move across the region late Tuesday
afternoon and into the first part of the evening. Models have
seemed to trend up the moisture in a very narrow band that may
produce a brief (1-2 hr) period of light snow or flurries. With
the best chance over northeast SD and west central MN, have
trended PoPs up some and added a buffer of flurries as the front
moves through.

Behind the front, a surface ridge will slide south over the
eastern Dakotas from a high in Saskatchewan/Manitoba and slowly
slide east across Minnesota through Thursday. Still differences
between the CMC/GFS/GEFS (colder) and ECMWF and ECMWF Ensemble
members on how cold it will be Wed/Thurs. This appears to be tied
to differences in the cold air below the inversion near 925mb.
Will follow a general blend for now, with highs on Wed/Thurs in
the single digits above zero. Overnight lows during this period
will depend on those cold llvl temps and weak shortwaves with mid
level moisture moving through Wednesday night into Thursday.
Ensembles showing more temp spread due to this, so will continue
following blend for lows too.

The upper ridge shifting east should bring moderating
temperatures for next weekend and potential even rising to above
normal values. Still a variety of solutions in the fine scale
details (potential for some precip) and will have to tune
the forecast over the coming days.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1126 PM CST Sun Dec 31 2017

Still dealing with lake induced low clouds at the KPIR TAF site.
In fact, latest satellite imagery shows expansion in the stratus
in the last couple of hours. Therefore, expect IFR ceilings at
the KPIR TAF site through a majority of the TAF period. VFR
conditions will prevail at all other TAF sites.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Chill Warning until noon CST /11 AM MST/ Monday for
     SDZ003>011-015>023-033>037-045-048-051.

MN...Wind Chill Warning until noon CST Monday for MNZ039-046.

&&

UPDATE...Serr
SHORT TERM...SD
LONG TERM...SRF
AVIATION...Serr

Hazardous Weather Outlook...UPDATED
National Weather Service Aberdeen SD
209 PM CST Sun Dec 31 2017

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-011200-
Traverse-Big Stone-Corson-Campbell-McPherson-Brown-Marshall-
Roberts-Walworth-Edmunds-Day-Dewey-Potter-Faulk-Spink-Clark-
Codington-Grant-Hamlin-Deuel-Stanley-Sully-Hughes-Hyde-Hand-Jones-
Lyman-Buffalo-
209 PM CST Sun Dec 31 2017 /109 PM MST Sun Dec 31 2017/

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

.DAY ONE...This Afternoon and Tonight

Wind chill values of 35 below to 45 below zero are expected
through tonight.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Hazardous cold and dangerous wind chills will continue through
Monday morning.

Wind chills of 25 below to 35 below zero are expected late Monday
night into Tuesday morning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

SRF