Dense Fog Advisory 15, NWS Twin Cities, MN

684 
WWUS73 KMPX 250548
NPWMPX

URGENT - WEATHER MESSAGE
National Weather Service Twin Cities/Chanhassen MN
1148 PM CST Fri Dec 24 2021

WIZ015-016-025>028-250700-
/O.EXP.KMPX.FG.Y.0015.000000T0000Z-211225T0600Z/
Barron-Rusk-Dunn-Pepin-Chippewa-Eau Claire-
Including the cities of Rice Lake, Ladysmith, Menomonie, Durand, 
Chippewa Falls, and Eau Claire
1148 PM CST Fri Dec 24 2021

...DENSE FOG ADVISORY WILL EXPIRE AT MIDNIGHT CST TONIGHT...

Fog has dissipated and visibilities have been consistently above
1/4 mile.

$$

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
149 PM CST Fri Dec 24 2021

.DISCUSSION...(This evening through Thursday)
Issued at 148 PM CST Fri Dec 24 2021

Key Messages:

- Saturday, light snow expected. Most locations will see less than
an inch, but 1 to 2 possible from Alexandria to Mora.

- Sunday into Monday, confidence remains high on a band of moderate
to heavy snow blossoming across the region Sunday evening/night.
Heaviest amounts along and north of I-94, generally 3-5". This snow
could be followed by some freezing drizzle into Monday morning.

- Tuesday night into Wednesday - Another plowable snow possible,
with much colder air to follow.

Saturday - Overall the previous forecast remains very much on track.
A shortwave trough will move across the Dakotas toward Lake
Superior. H850 theta_e advection ahead of this wave will lead to
isentropic ascent, saturation, and precipitation. The strongest
forcing for ascent is from western Minnesota to northern Wisconsin.
Forecast soundings show snow as the main precipitation type. Expect
several hours of light snow, with amounts generally ranging from 1
to 2 inches across the northern part of the forecast area, namely
from Alexandria to Mora. Meanwhile areas to the south could get a
few hours of snow showers, but the forcing weakens with time as it
moves across, so not anticipating much more than a dusting. Did
increase pops a bit from the previous forecast, since the chance of
seeing some snow is higher than seeing nothing, but overall not
anticipating significant travel impacts. Could see some slick spots
on roads and reduced visibility, but winds will be relatively light
and temperatures will be in the teens north and near 30 south.

Sunday into Monday - This remains the time frame when the most
impactful weather is expected. Confidence remains high that a band
of snow on the leading edge of fairly strong warm air advection will
develop across western Minnesota Sunday afternoon. This area of
snowfall will blossom across the region Sunday evening and lift
northward out of the region Sunday night. Snowfall rates of around
an inch per hour for a few hours seem plausible as this band of
moderate to heavy snow moves through. The highest amounts will along
and north of I-94. Probabilistic guidance suggests a 60 to 80
percent chance of seeing at least 2 inches north of I-94, with
around a 50 percent chance of seeing at least 4 inches. The chance
of seeing more than 6 inches is around 10 percent, meaning that
confidence is high in accumulating snowfall, but amounts should be
less than 6 inches because the system is moving quickly. Winds will
be out of the east/southeast at 20 to 25 mph as the snow falls, so
could see some blowing and drifting snow.

One other thing worth mentioning is that the chance for freezing is
decreasing Sunday afternoon and evening. However, as the system
departs Sunday night into Monday morning, could see the snow
transition over to a light freezing drizzle due to the loss of ice
crystals, not so much a melting layer aloft. Any icing amounts
should be minimal, but this could lead to a light glazing on top of
the snow. The icing is a lower confidence forecast, but wanted to at
least mention the possibility. The winds will become northwest
around 15 to 20 mph toward Monday morning.

Tuesday and beyond - Another snow event looks likely for Tuesday.
This system has a few moving parts in terms of how things come
together, so did not make and changes to the blended guidance. The
current probabilistic indicates another 2-4" snowfall event, but
this could go up if the system develops more quickly across the
region, or it could go down if the system is more progressive. One
thing that is more certain is colder weather to follow for the rest
of December into early January.

A typical winter cool down will follow Tuesday's snow, with
overnight lows going below zero across western Minnesota, and into
the single digits across eastern Minnesota into western Wisconsin
Tuesday night. Wind chills Wednesday night could approach 15 to 25
degrees below zero. This cooler temperature trend will continue
through the weekend into early next week.
&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1110 AM CST Fri Dec 24 2021

Areas of LIFR in stratus, BR, -RA/DZ will affect areas from KFRM-
MKT-KMSP-KRNH and eastward through the afternoon, with conditions
rapidly improving once winds shift to the SW/W. West-central Wi
(KEAU-KRCX) will likely see the LIFR improve to IFR/MVFR by 21z, with
VFR after 23z. NW winds will develop over western Mn during the
afternoon, and shift eastward during the late afternoon over west
central Wisconsin. I introduced -SN at KRWF-KAXN after 15z Saturday
as the next system approaches from the west.

KMSP...

An hour or less of MVFR cigs will affect mostly areas to the east-
southeast of the terminal. Once winds shift to the SW/W conditions
will improve to VFR thru the rest of the TAF period. Some -SN is
possible Saturday afternoon, but currently only MVFR vsbys are
expected.

/OUTLOOK FOR KMSP/

Sat night...VFR. Chc MVFR cigs. Wind NNW 5-10 kts.
Sun...VFR. IFR with SN evening/overnight. Wind E 15G30 kts.
Mon...MVFR in mrng. Winds W 15G25 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&

DISCUSSION...JRB
AVIATION...JLT

Hazardous Weather Outlook
National Weather Service Twin Cities/Chanhassen MN
158 PM CST Fri Dec 24 2021

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
252000-
Douglas-Todd-Morrison-Mille Lacs-Kanabec-Stevens-Pope-Stearns-
Benton-Sherburne-Isanti-Chisago-Lac Qui Parle-Swift-Chippewa-
Kandiyohi-Meeker-Wright-Hennepin-Anoka-Ramsey-Washington-
Yellow Medicine-Renville-McLeod-Sibley-Carver-Scott-Dakota-
Redwood-Brown-Nicollet-Le Sueur-Rice-Goodhue-Watonwan-Blue Earth-
Waseca-Steele-Martin-Faribault-Freeborn-Polk-Barron-Rusk-
St. Croix-Pierce-Dunn-Pepin-Eau Claire-
158 PM CST Fri Dec 24 2021

This Hazardous Weather Outlook is for portions of central and
southern Minnesota, and west central Wisconsin.

.DAY ONE...This Afternoon and Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Light snow is expected Christmas Day, 1 to 2 inches of snow
possible in central Minnesota.

A stronger system will impact the area late Sunday afternoon into
Monday morning. Heavy snow at times, with accumulations in excess
of 3 inches likely along and north of the I-94 corridor, with 6
or more inches possible across central Minnesota into northwest
Wisconsin. In addition to the snow, this precipitation may end
with a period of freezing drizzle near I-90.

Another plowable snow is possible Tuesday into Tuesday night.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation will not be needed.

jrb

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
225 PM CST Fri Dec 24 2021

WIZ016-025>028-242230-
Rusk-Dunn-Pepin-Chippewa-Eau Claire-
Including the cities of Ladysmith, Menomonie, Durand,
Chippewa Falls, and Eau Claire
225 PM CST Fri Dec 24 2021

...LOCALIZED DENSE FOG THROUGH LATE AFTERNOON...

An area of fog and low clouds continues to affect areas over west
central Wisconsin with localized dense fog patches this afternoon.
Conditions are expected to improve during the late afternoon once
winds shift to the northwest and colder air arrives.