NWS Forecast Discussion

335
FXUS63 KMPX 080459
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1059 PM CST Fri Feb 7 2025

.KEY MESSAGES...

- Narrow Winter Storm Warning issued across central Minnesota
  into northwest Wisconsin.

- Accumulating snow late this eveningthrough Saturday morning
  and early afternoon.

- Widespread snow amounts around 3 to 5 across central Minnesota
  and western Wisconsin. Pockets of higher amounts (6+) are
  possible, especially across western Wisconsin.

- Well below normal temperatures will move in behind the
  Saturday system, with sub-zero lows Sunday night and even
  colder lows (negative teens to 20s) Monday through Wednesday.

&&

.UPDATE...
Issued at 639 PM CST Fri Feb 7 2025

We decided to upgrade a narrow swath of our area into a Winter
Storm Warning. This follows near where the HRRR is showing storm
total QPF near 0.4", which when converting to snow with an
expected ratio of 16 or 17 to 1 pushed snow totals up into the
6-7" range over about a 20-30 mile wide west-east oriented band.
This enhanced snowfall is being largely aided by the appetizer
of snowfall we`ve seen develop over central MN within a strong
zone of h7-h6 fgen. With the main entree still back over
southern NoDak (where the SPC issued an MCD for heavy snowfall),
we felt comfortable enough to squeeze a very narrow extension
of the Winter Storm Warning out of the south end of the Grand
Forks NWS coverage area across the northern boundary of ours.

This may not be the only headline update needed though. We`ll
see what the 00z HRRR does, but right now, there is little
difference in our snow forecast between Mankato and Albert Lea
and Fairmont, so we may be looking to add the I-90 corridor into
the advisory as well since there is currently little difference
in the forecast for the I-90 corridor and the advisory off to
its north.

&&

.DISCUSSION...
Issued at 251 PM CST Fri Feb 7 2025

The forecast has not changed much over the last 12 hours, with
accumulating snow moving into western Minnesota by this evening.
A deepening surface low to the south will provide weak warm air
advection at the same time high pressure moves south from
Canada. This setupwill lead to a frontogenetically-driven snow
event for the Upper Midwest. As is often the case with fgen
driven snow, there will be bands of higher QPF/snow amounts.
Determining exactlywhere those bands will set up can be
difficult, but a general consensus between the models indicates
it will be just north of the Twin Cities Metro (but south of
Duluth). From a timing perspective, light snow will begin in
western Minnesota as early as 7-8PM, but the more intense snow
wont start for a few hours after that. The Metro area likely
wont see much snow accumulate prior to midnight, but the rates
will peak shortly after in the 2-7AM timeframe. Western
Wisconsin likely wont see anything until after midnight,but
things will linger slightly longer into the early afternoon
hours on Saturday. All-in-all, this event will take place when
the vast majority of people are sleeping, which is good from an
impact point-of-view. Areas in western Wisconsin may see more
travel impacts due to the later arrival and shift into more of
the daylight hours.

As mentioned above, there will be a band of higher QPF in
central/eastern MN and western WI. Guidance continues to
indicate 0.3 to 0.4 QPF will fall within this band, tapering to
0.25 in the Metro, and quickly dropping to 0.15 or less for the
far southern portion of Minnesota (Mankato and south). This will
be a more light and fluffy snow, with snow to liquid ratios
slightly above the climatologicalnorm in the 14-18:1 range. The
lower ratios will be in areas just south of the Metro as weaker
forcing and drier air will inhibit anything higher. Equating
this to snow amounts, 3 to 5 can be expected for most across our
forecast area, with lesser to the south.Again with the fgen
banding, the location of the band will be where we see the
highest ratios and snow rates. These locations are also most
likely to see 6+ of snow. Although QPF amounts have
noticeablydropped since forecasting for this event began,
whether or not a specific location sees 5 or 6 wont make a
difference in terms of impacts. The biggest takeaway should be
that it will snow and it will need to be plowed for the majority
of southern and central Minnesota and western Wisconsin. Taking
a look at current Winter Weather headlines, we have expanded
the Winter Weather Advisory to cover our entire area, minus the
southernmost tier of counties in Minnesota (along I-90). This
advisory is mostly due to expected snow amounts and associated
travel impacts. There is a limited potential for blowing snow in
SW MN, but nothing major due to lower snow amounts and a short
time frame of concern.

Looking to Sunday and beyond, things will get cold. Canadian
high pressure will settle in behind the departing low, dropping
high temperatures into the single digits with even colder
apparent temps. Monday, Tuesday, and Wednesday night lows will
be the coldest of the week, with wind chills in the negative 20s
in western Minnesota. Western Wisconsin will be roughly 10 to
15 degrees warmer, but still below zero. Looking into longer
term chances at any more weather makers, there is decent
agreement between ensembles for a few systems over the next two
weeks, but none of which are looking significant. This means our
pattern of a light dusting to half inch here and there will
continue beyond this weekends system.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1054 PM CST Fri Feb 7 2025

Main change with the 6z TAFs was to delay by an hour or two the
arrival of snowfall at RWF, MKT, MSP, & EAU. Snow band across
central MN and NW WI will remain stationary for the first few
hours of the TAF, with snow expected to blossom over southwest
MN between 8z and 10z and quickly shift east across southern MN.
Primary snowfall is expected between 12z and 18z on Saturday.
There will be a period of MVFR cigs behind the snow, but skies
are expected to clear out Saturday evening.

KMSP...Dry air is taking a bite out of the snowfall for MSP,
with snow start time possibly coming as late as 11z. Because
we`ve taken some snow out of the front end of this event, snow
totals for MSP have dropped into the 2-3 inch range. Heaviest
snow, with occasional vsbys down to 3/4sm is expected between
13z and 17z.

/OUTLOOK FOR KMSP/
SUN...VFR. Wind NW 5-10 kts becoming SW.
MON...VFR. MVFR ceilings possible late. Wind NW 5-10 kts.
TUE...VFR. Wind NW 5-10 kts.

&&

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

&&

$$

UPDATE...MPG
DISCUSSION...PV
AVIATION...MPG

NWS MPX Office Area Forecast Discussion

Script by Ken True @Saratoga-Weather.org