598
FXUS63 KMPX 091830
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1230 PM CST Tue Dec 9 2025

.KEY MESSAGES...

- Strong system to bring an intense and narrow band of heavy
  snow this afternoon and evening along and north of the I-94
  corridor. The rain/snow line looks to setup over the Twin
  Cities metro, with a strong snowfall gradient expected from
  southwest to northeast across the metro.

- A 2-4 hour period of freezing rain/drizzle will be possible
  along and just south of the I-94 corridor as precipitation
  initially moves in today.

- Strong winds are expected Tuesday evening southwest of the
  low track, with gusts of 40-50 mph possible south I-94 in
  Minnesota. Uncertainty remains high with how blowable the snow
  pack in southwest Minnesota will be after they see highs
  above freezing with rain and drizzle today.

- Multiple bouts of light snow will be possible Wednesday
  through Saturday. Only minor accumulations would occur with
  any additional snowfall we see after today.

- Very cold temperatures settle in by this weekend with wind
  chills approaching advisory criteria Friday night and Saturday
  night.

&&

.UPDATE...
Issued at 1048 AM CST Tue Dec 9 2025

As of 10AM this morning, our sfc low which is driving
today`s wintry mess was located in northwestern North Dakota and
moving east-southeastward. The forecast remains on track with the
eastern periphery of the precipitation shield now making its way
into western MN. Light snowfall rates this morning will increase to
1.0-1.5"/hour, especially along and north of the I-94 corridor as
early as 2 to 3 PM this afternoon and persisting through the evening
commute. Farther to the southwest, including the Twin Cities metro,
a short period of freezing rain mainly between 2-4 PM is expected to
occur prior to transitioning to all snow after 6 PM. Across SW`rn
MN, cold rain will transition to freezing drizzle this evening and
then change over to all snow tonight. With wind gusts approaching 50
to 55 mph, potential blowing snow could make traveling very
difficult.

&&

.DISCUSSION...
Issued at 320 AM CST Tue Dec 9 2025

As one clipper exits stage right over Lake Superior, the next one as
already queued up just off stage. Water vapor imagery shows a deep
plume of moisture coming off the northeast Pac and across the Can/US
border into the Dakotas. Within this plume of moisture, a
shortwave currently over southern Albert deepen and dig south
through the day. This is what will result in the deepening
surface low moving across MN this afternoon/evening. Spread
remains higher than normal in the models for being within 24
hours of storm onset with the eventual track of the surface low.
In a broad sense, we have a southern camp and a northern camp.
The southern camp is where you will find the majority of your
traditional deterministic models (GFS, ECMWF, Canadian...),
ensemble systems, and AI driven models. The northern camp is
almost being completely driven by CAMs (HREF). For this update,
we continue to favor an ECMWF AIFS/EPS solution, with not much
weight put into the northern, CAM driven solution. The biggest
reason for this is recent verification, with the AIFS in
particular performing very strong in correctly placing where
heavier precip swaths end up going back to the pre-Thanksgiving
winter storm. The resulting forecast is still very complex,
with a threat for an initial burst of freezing rain, heavy snow
this evening, then strong winds and potential for blizzard
conditions tonight.

Initially this morning, we will have to deal with some very minor
freezing drizzle with saturated low levels that are experiencing
lift from WAA. There have been lots of BR (mist) reports from the
airports overnight, which is a classic freezing drizzle signal,
which is what the human observes have been noting all night at MSP.
This bout of freezing drizzle will diminish when a location sees
winds switch to the northwest, which will cutoff the WAA, at least
momentarily. Precipitation will be moving quickly into western MN by
the late this morning. As this band of WAA driven precip moves
in, warm noses in soundings confirm what we are seeing with
model p-type depictions, with a 2-4 hour window at precipitation
onset where the predominate p-type will likely be freezing rain
basically along and just south of the I-94 corridor. Although
any ice accumulations are minor, there is some higher end
potential out toward Alexandria and Glenwood in northwest
portions of our CWA where ice accumulation over a tenth of an
inch will be possible. After this initial burst of
precipitation, it becomes a rain or snow question based on
surface temperatures. Given it`s heavy inclusion of CAMs, the
NBM looks too aggressive with how far northeast it drives the
freezing line this afternoon/evening and we used hourly
temperatures from the GFS to help suppress this warm nose from
the NBM. This resulted in a rain/snow line basically setting up
from Glenwood, to Minneapolis and Durand in western WI. Besides
the warm temperatures, the I-94 corridor will also be about
where the mid-level dry slot terminates, so not only does the
I-94 corridor have to deal with uncertainty in terms of the
thermal environment on p-types, but there will be issues with
cloud ice being present as well. The highest snow totals are
expected to fall just north of where the freezing line and
termination of the mid-level dry slot ends up, which right now
would place Long Prairie to the northeast Twin Cities metro and
Chippewa Falls, WI in the most likely region to cash on the snow
amounts around 7 inches. These higher snow amounts will be
driven by a heavy band of snow, where snowfall rates of near and
above 1 inch per hour will occur in a 4-6 hour window (centered
in the 5-10pm timeframe). With this continued southward drift
in where the heaviest snow is expected, we did add Washington,
St. Croix, Dunn, and Eau Claire counties into the Winter Storm
Warning.

As for the Winter Storm Watch for Blizzard conditions, we decided to
leave that as is. What is certain is that we`ll see wind gusts of 40
to 50 mph (plus a few 50+) from west central through south
central MN from roughly 1z through 8z (7pm through 2am). What is
much less certain is how blowable that snow will be coming off
a day where highs make a run at 40 with periods of rain and
drizzle as well. Looking at the WSSI for blowing snow, it
doesn`t even show minor blowing snow impacts across southwest
MN this evening. This region will likely see additional light
snow, but that does not look to arrive late in the night Tuesday
night, after the strongest winds have moved through. Although
you can`t rule out ground blizzard conditions, there are too
many question marks in place to be putting out a headline
(Blizzard Warning) that would have the effect of shutting down
southwest MN tonight. Unfortunately, we`re not really going to
know how this snow will behave until we hit it with these winds.
At the moment, there`s too much of a chance that we just get
some minor blowing, but not enough lofting of snow particles to
create the visibility restrictions needed to support a blizzard.

After this system, it`s back into the deep freeze through next
weekend. The coldest day looks to be Saturday, when a high of zero
looks like it will be difficult to attain everywhere in the MPX
area. This will also see wind chill values down in the -25 to -35
range Friday night/Saturday morning and again Saturday night/Sunday
morning, with the need for at least Extreme Cold Advisories
both periods looking all but certain. Besides the cold, there
will be more chances for light snow. Wednesday looks like your
typical snow shower setup as we have well mixed boundary layers
that have thermal profiles completely withing the dendritic
growth zone. Thursday, a weak upper wave will move along the
thermal gradient, laying down a quick band of light snow. Right
now, this looks most likely to impact Iowa into southern MN.
Friday, we should see another round of light snow move through
with the passage of the arctic cold front. Saturday brings yet
another wave embedded in the northwest flow that will work with
the strong thermal gradient to create another swath of light
snow, which at the moment is again favored for Iowa or southern
MN.

Next week, a pattern shift still looks to be upon us as we see the
eastern Canadian trough push into the north Atlantic, which
allows upper ridging to move into the central CONUS. This looks
to result in the active storm track shifting to the north, with
milder Pacific airmasses moving in, with the cold easing as
well. There`s lots of snow to our south across Iowa, so it will
be tough for us to warm significantly, but we`ll take highs
returning to the 20s and 30s for a little bit of a reprieve from
the deep winter cold.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1149 AM CST Tue Dec 9 2025

Very complex forecast this afternoon & evening, mainly relating
to where the rain/snow/ice transition line will setup this
afternoon & how the track of the low pressure center will impact
winds speeds this evening.

Generally, precipitation will spread from western Minnesota
into eastern Minnesota & western Wisconsin through the
afternoon. Maybe a 30 minutes to an hour of freezing drizzle or
a wintry mix is possible as the precipitation begins, but that
will quickly change over to snow. The snow will be heaviest
across central Minnesota, where a few hours of visibility below
1 SM & rates around 1"/hr are likely. Across southern Minnesota
(RWF/MKT), the snow will likely change back over to rain, then
potentially end completely as a dry slot moves over the region.

The greatest uncertainty lies between these two areas (MSP/EAU),
which will light right along the transition zone from snow to
rain along with the edge of the dry slot. A few hours of
moderate to heavy snow looks likely this afternoon into early
evening, but precipitation then likely transitions to a light
rain/snow mix, or even ends completely this evening. Eventually,
light snow returns late tonight along with gusty northwest
winds as the warp-around region of the system moves through the
area. This snow ends during the early morning hours, with
another round of lights snow looking likely from mid-morning
into early afternoon.

Winds are very complex with this system, owing to uncertainty
with the track of the surface low over the area. This
afternoon, winds will remain southeasterly to southerly with
speeds between 10-20 kts. As the surface low tracks over central
Minnesota & western Wisconsin this evening, winds will likely
become light & variable for a few hours (STC/MSP/RNH/EAU).
Tonight, gusty northwest winds develop as the system exits the
area, with gusts of 40-50 kts across southwest Minnesota
(RWF/MKT) & generally 25-30 kts elsewhere. A few hours of LLWS
is also likely this evening before the gusty Northwest winds
develop late tonight, with northwest shear around 50 kts at
FL020. The winds will be strongest late tonight into a few hours
after midnight, then gradually decrease closer to 20 kts into
the morning.

KMSP...Very uncertain forecast regarding the details, as
discussed above. Could see roughly half an hour of freezing
drizzle at the onset of precipitation between 2-3 PM, but this
only cause light glazing on untreated surfaces. Moderate to
heavy snow should quickly develop by 3-4 PM, with visibility
likely below 1 SM & snowfall rates around 0.5" to 3/4"/hr. It
remains uncertain how long this moderate to heavy snow will
last, as a sharp cutoff with the dry slot of this system will
setup somewhere over the Twin Cities metro. Best forecast for
now suggests that the snow will begin tapering off by 6-7PM,
when precipitation will either transition to a light rain/snow
mix or end completely for a few hours. A second round of light
snow then returns late tonight, likely 10-11 PM, which will
have lighter rates, but gustier winds resulting in visibilities
down to around 1-2 SM.

Winds this evening are probably the most uncertain part of the
forecast. Confidence is high in SE to S winds into this evening
with gusts around 20 kts early this evening. It then looks
increasingly likely that winds will become variable for several
hours tonight as the low moves overhead with speeds generally
below 10 kts. Northwest winds then develop late tonight with
the second round of snow, with northwest winds gusting to 25-30
kts into tomorrow morning. During the time of the likely lull in
winds at MSP, very gusty northwest winds will develop in the
dry slot across southern Minnesota, & these winds could extend
into the southern Twin Cities metro. While it seems unlikely at
the moment that we will see these surface gusts at the terminal,
a few hours of LLWS is likely with W to SW shear of 50-55 kts
in the lowest 2000-3000 ft.

/OUTLOOK FOR KMSP/
THU...MVFR. Chc -SN. Wind NW 5-10 kts.
FRI...MVFR/SN early. VFR late. Wind NW 10-15G20 kts.
SAT...VFR. Wind NW 10G20kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Winter Weather Advisory until 6 AM CST Wednesday for Douglas-
     Kandiyohi-McLeod-Meeker-Pope-Stearns-Stevens-Swift-Wright.
     Winter Storm Warning until 6 AM CST Wednesday for Anoka-Benton-
     Chisago-Isanti-Kanabec-Mille Lacs-Morrison-Sherburne-Todd-
     Washington.
     Winter Storm Watch from 9 PM CST this evening through
     Wednesday morning for Blue Earth-Brown-Chippewa-Faribault-
     Freeborn-Lac Qui Parle-Le Sueur-Martin-Nicollet-Redwood-
     Renville-Sibley-Waseca-Watonwan-Yellow Medicine.
     Winter Weather Advisory from 3 PM this afternoon to 6 AM CST
     Wednesday for Carver-Dakota-Goodhue-Hennepin-Ramsey-Rice-
     Scott-Steele.
WI...Winter Storm Warning from 3 PM this afternoon to 9 AM CST
     Wednesday for Barron-Chippewa-Dunn-Eau Claire-Polk-Rusk-
     St. Croix.
     Winter Weather Advisory from 3 PM this afternoon to 9 AM CST
     Wednesday for Pepin-Pierce.

&&

$$

UPDATE...Dunleavy
DISCUSSION...MPG
AVIATION...ETA