NWS Forecast Discussion

Below is the latest Area Forecast Discussion from the Twin Cities National Weather Service office in Chanhassen, MN. It gives insight into why the forecasters are making the predictions you read in your local forecast. The overall "big picture" of the atmospheric setup is well described, as well as the forecasters' interpretation of the various Computer Atmospheric Models (CAMs). Sometimes, very specific information is available here that is not available, or otherwise generalized, in the public forecast.

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FXUS63 KMPX 012323
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
523 PM CST Sat Feb 1 2025

.KEY MESSAGES...

- Light snow lingers across parts of central MN and WI into
  tonight, with minor accumulation possible.

- Another round of accumulating snow late Sunday night into
  Monday morning. 3 to 6 inches are possible in a narrow band,
  but confidence in where it sets up remains low.

- Much colder next week with additional chances for light snow.

- A potentially more significant system could impact the region
  Friday night and Saturday.

&&

.DISCUSSION...
Issued at 254 PM CST Sat Feb 1 2025

Snow continues to progress across central MN and is beginning
to reach northwest WI. Visibilities at times have been reduced
to 1/2 mile or less, signaling moderate to heavy rates. Drier
air south of a line from Olivia to the Twin Cities and Rice Lake
has limited the amount of snow able to reach the ground,
although radar reflectivity is finally filling in over the
metro. The bulk of the steadiest snow will exit to the northeast
during the next couple hours. Some light snow may linger
tonight across WI and parts of central MN, but any additional
accumulations after the main batch this afternoon will be light.
Temperatures will rise into the 30s following the snow and
should remain steady tonight as the warm sector overspreads the
region.

A cold front will pass through Sunday. Before it does so, we`ll
have an opportunity to warm back into the 40s across southern/
eastern MN and WI. Cold air advection does not look as strong
behind the front as yesterday thanks to modest mid level height
rises. This has had major implications for the W-E oriented band
of snow Sunday night. Deterministic and hi-res models have
continued their trend of shifting north. Central MN and the
northern two thirds of WI now stand the best chance at several
inches of snow, but confidence remains low. Ensemble guidance
exhibits large spread in QPF, largely due to latitudinal
differences. At MSP, GFS ensembles of QPF range from 0 to 0.5
inches, EC ranges between 0 and 0.4 inches, and the CMC 0 to 0.3
inches. Farther north, the same applies, but there are fewer
zero solutions. This suggests wherever the band sets up will
probably produce a max of 0.3 to 0.4 inch QPF with a sharp
cutoff on the north and south sides. This also suggests the
northern half of the CWA, mainly north of the metro, has a
better chance than farther south. PoPs have been increased north
and decreased across southern MN. DGZ depths are nowhere near
as impressive as yesterday given a much milder airmass below 10
kft. However, snow ratios within the heart of the band will
likely reach 15:1 given the strong frontogenetic forcing and
heavy snow rates. It is expected a swath of 4 to 6 inches will
fall somewhere (perhaps just a county wide), but without much
confidence yet on where, had to stick with a wider swath of 2 to
4 inches for now. The snow will exit to the east Monday
morning.

Zonal flow will persist for next week across much of the CONUS,
with a trough digging deeper down the West Coast as the week
goes on. Weak shortwaves embedded in the fast westerly mid level
flow could bring light snow chances any time one passes
through. These wouldn`t be very impactful. However, there are
two systems in the longer term that bear watching. The first is
Wednesday and Wednesday night. A southern stream shortwave may
interact with a Polar stream shortwave across the northern U.S.
Their phasing could produce some steadier snow across the Upper
Midwest during that time. Just how much these two interact will
determine whether snow will be widespread and heavy enough to
bring any impacts. For now, nothing significant is expected but
it is still 4 days out. The second, a more robust trough, comes
Friday night through Saturday night. The western trough will
kick east late week and spawn a Colorado low over the central
Plains. A Polar airmass will remain entrenched across the
northern U.S., while the southern U.S could reach the 70s and
80s next weekend. A large fetch of tropical moisture will be
drawn northward as the low tracks east across the mid
Mississippi Valley. Widespread precipitation should break out
north of the track. Such a pattern can bring some of our
healthier snow storms if the trough doesn`t ultimately shear out
downstream of the Rockies.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 523 PM CST Sat Feb 1 2025

Snow has largely moved out of the area with mixed MVFR and VFR
CIGS reported. Outside of a few hours of IFR visibility at AXN,
this will continue through the evening. Winds will also remain
gusty with gusts up to around 30 knots this evening. Winds will
calm and the flight category will drop tonight. IFR ceilings and
some chance for fog to reduce visibility as well, but it will be
a mainly ceilings based IFR. Winds ramp up again tomorrow from the
northwest as a front passes through. Near the end to just after
the period the next round of snow will move in. Check for future
TAF issuances to start getting details on this snow. Overall it
does look to be more impactful that what we got today.

KMSP...The gusty southeast winds will continue through the
evening. High MVFR to low VFR ceilings expected as well. Winds
will calm tonight and ceilings will come down into IFR. Some
visibility reduction possible as well with mist, but mainly a
ceiling based IFR. Tomorrow morning ceilings will rise back into
VFR and winds will shift to the northwest. There could be a
period of crosswind in the morning as the winds shift. Snow is
expected to move in on Sunday night at the end of this TAF
period into Monday. Kept it out of the 00Z TAFs as the main time
for the snow will be in the hours after this TAF ends.

/OUTLOOK FOR KMSP/
MON...IFR/-SN in mrng. VFR aftn. Wind NW 10-15 kts.
TUE...VFR, bcmg MVFR. Chc IFR/-SN. Wind NE 5-10 kts.
WED...MVFR, chc IFR/-SN aftn. Wind E 5-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Winter Weather Advisory until midnight CST Sunday night for
     Kanabec-Mille Lacs.
WI...None.

&&

$$

DISCUSSION...Borghoff
AVIATION...NDC

NWS MPX Office Area Forecast Discussion