872
FXUS63 KMPX 250037
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
637 PM CST Sun Nov 24 2024

.KEY MESSAGES...

- Rain changes to snow overnight into Monday morning, which
  could slow down morning commute as temperatures fall below
  freezing.

- Accumulations of 1-2 and icy roads expected across central MN
  & western WI. More of a wintry mix & trace snowfall
  accumulations could occur from the Twin Cities south

- Temperatures sharply fall into the teens through the day
  tomorrow. Below normal temperatures continue through
  Thanksgiving weekend, with even colder temperatures expected
  to start December.

&&

.UPDATE...
Issued at 609 PM CST Sun Nov 24 2024

Snow tonight into Monday...Confidence remains high in an area
of rain changing over to snow tonight into Monday morning. The
previous forecast remains on track, so did not update much in
the way of timing or snowfall amounts.

However, one area of concern is the potential for a burst of
snow across the Twin Cities around 3-6am, shifting over to
western Wisconsin and Eau Claire around 4-7am. Snowfall amounts
would be light, generally less than a half inch. However,
temperatures will be falling below freezing, so wet roads could
become ice-covered leading to a slow and slippery morning
commute. This is not a sure thing, but some of the HiRes
guidance has been developing an area of precip right across the
Twin Cities and western WI. Will continue to monitor the trends
overnight.

&&

.DISCUSSION...
Issued at 235 PM CST Sun Nov 24 2024

The forecast still remains on track this afternoon for light
snow developing tonight across central Minnesota & western
Wisconsin, and light rain eventually changing over to snow by
tomorrow morning across the rest of southern Minnesota & western
Wisconsin. Surface forcing is generally weak with this system,
with only a slight pressure trough at the surface extending
northwards from a low over the mid-Mississippi valley. However,
enough curvature develops in the flow aloft tonight for
widespread light precipitation/drizzle to develop as the entire
atmosphere moistens in response to the increasing vorticity over
the region. Temperatures will be cold enough across northern &
central Minnesota and northwest Wisconsin for the light
rain/drizzle to quickly transition over to light snow by
tonight. Farther south, temperatures will stay warm enough for
precipitation to remain liquid through the night. Some
uncertainty still remains on how far south the freezing line
develops, and thus where snow accumulations of an inch or two
are most likely. Our confidence for accumulating snow tonight is
highest along and north of the US-8 corridor of WI, west
through St. Cloud & Morris. This line will dip south after
midnight, likely as far south as the northern Twin Cities metro
& I-94/US-12 corridor through Wisconsin. Eventually light
rain/drizzle will change over to light snow elsewhere across
Minnesota & western Wisconsin as colder air arrives by mid-
morning Monday, but potential accumulations will be quite light
with most of the moisture already out of the area.

As mentioned above, confidence in accumulating snow tonight is
highest north of a line from Morris & St. Cloud through the US-8
corridor in WI. Precipitation amounts have trended a little
higher with the latest guidance this morning, meaning confidence
continues to increase in forecast snowfall amounts of 1-2
along and north of this line. Where snow develops overnight, as
far south as the northern Twin Cities metro & the I-94 corridor
of WI, amounts of up to 1 are possible by tomorrow morning.
Elsewhere to the south, only trace amounts are expected, mainly
during the morning hours. While the snowfall amounts and rates
are not expected to be heavy, strong cold advection as the snow
begins means that temperatures will plummet through the the 20s
& into the teens overnight through tomorrow morning. This drop
will be most pronounced across central MN where the most snow is
expected, meaning we could see classic flash freeze conditions
creating icy roads & other paved surfaces for the morning commute
tomorrow. While these conditions will be worst across central
Minnesota & northwest Wisconsin, slick roads are possible area-
wide through tomorrow morning as temperatures fall below freezing.

The light snow will come to an end from west to east tomorrow
morning as frigid & drier northwest flow develops ahead of a
sprawling region of cold Canadian high pressure. Temperatures
will quickly fall through the 20s & into the teens, with wind
speeds of 20-30 mph creating wind chills in the single digits by
afternoon across western Minnesota & evening elsewhere. This
cold air sticks around through Thanksgiving weekend, with
several days of highs generally around 30 & lows in the teens
to low 20s. A weak surface low tracks south of the area on
Wednesday, but the forecast generally looks dry leading up to
Thanksgiving outside of occasional flurries as cloud cover
builds back into the region Wednesday & Thursday. Thanksgiving
Day looks dry, but cold, with sub-freezing temperatures during
the day meaning youll be safe to use the garage as extra fridge
space. The really cold air arrives Thanksgiving night into
Black Friday, as ensemble & deterministic guidance remains
consistent in a sprawling region of Canadian high pressure
moving into the Upper Midwest & staying over the area through
the first several days of December. Ensemble temperature
anomalies bottom out at 15 to 20 degrees below normal by the
start of December, meaning were looking at several days with
highs in the teens & lows in the single digits, potentially
lower if we are able to get some more snowpack over southern
Canada & the northern Dakotas/MN this week. A few light snow
events cant also be ruled out if any clippers develop in the
cold northwest flow regime.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 609 PM CST Sun Nov 24 2024

Expect MVFR conditions to become more widespread as clouds lower
ahead of the incoming precipitation that is expected to spread
across the region overnight. Most areas will see rain at the
start, then changing over to snow. KAXN, KSTC and KRNH could see
IFR/LIFR conditions. The remaining sites should have less snow.
Northeast winds will become northwest, with gusts 20 to 25 kts.

KMSP...Main change from the previous TAF was to lower the
visibility to IFR early Monday morning. A heavy band of rain to
snow is possible, with a quick burst of up to a half inch of
snow and reduced visibility. Northeast winds will become
northwest, with MVFR clouds expected to continue throughout the
TAF period.

/OUTLOOK FOR KMSP/
TUE...VFR. Wind NW 5-10 kts.
WED...VFR with MVFR/-SN possible. Wind NE 5-10 kts.
THU...VFR/MVFR, with -SN possible. Wind NW 5-15 kts.

&&

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

&&

$$

UPDATE...JRB
DISCUSSION...ETA
AVIATION...JRB