Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 221221

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
621 AM CST Tue Jan 22 2019

.Updated for 12Z Aviation Discussion...
Issued at 611 AM CST Tue Jan 22 2019


.SHORT TERM...(Today through Wednesday)
Issued at 415 AM CST Tue Jan 22 2019

Main change was to lower forecast snowfall amounts across the region
for today. For that reason, ended the winter weather advisory sooner
across eastern Minnesota and western Wisconsin. Highs today and
tomorrow will be near 20 for most locations.

Early morning water vapor imagery with Rap13 500mb heights and winds
showed a broad longwave trough over the 4-corners region, with
southwest flow and a shortwave trough downstream over the Upper
Midwest. This shortwave was producing a few inches of snow across
northern Wisconsin and northern Minnesota, but central/southern
Minnesota and western Wisconsin remain in the dry slot and lacked
the deeper moisture and strongest forcing.

Part of the reason why the forecast area will receive less snowfall
today is due to a northern stream shortwave trough moving across
central Canada, and this will act to shear out vorticity. This will
hold off any redevelopment, so snow chances will be over for most
locations once the morning has passed. The exception is southeast
Minnesota and western Wisconsin, where we do expect a few bands to
develop this afternoon and bring them another inch or two of snow.
Forecast soundings show northerly wind gusts near 20 to 25 mph
which could lead to some blowing and drifting across southern
Minnesota, so held on to the winter weather advisory through
midnight tonight.

.LONG TERM...(Wednesday night through Monday)
Issued at 415 AM CST Tue Jan 22 2019

It is difficult to forecast during Winter months as little
moisture is available and subtle lifting mechanisms produce most
of the precipitation in Arctic air masses. Thus, the current
weather scenario had little moisture with it, and small deviations
from the upper forcing can alter snowfall amounts and location.

The forecast past Wednesday still remains uncertain in terms of how
cold it will be, and how to convey forecast uncertainties in a fast
northwest flow aloft. Confidence remains high that we will remain
below normal for the next 7 days, and possibly into the first week
of February. The reason for the high confidence is the consistent
pattern with an upper level ridge centered off the west coast, and a
strong upper low centered around Hudson Bay. The 5-day 500mb height
mean reflects this pattern and I can`t see any deviation from it.

The uncertainties come into play as where will the boundary between
the Arctic air mass, and the relatively milder Pacific air mass be
located. This boundary will be the key on where the most of the
unsettled weather will occur.

As with any forecast, trends in the models are a good starting point
on whether we have an increase, or a decrease in confidence on
impactful weather. The Arctic front moving across the Upper Midwest
Wednesday night, and early Thursday remains on track for the coldest
air of the season. However, models have trended toward a slightly
warmer forecast than previously. Therefore, extreme wind chill
values in the 35 to 40 below range maybe limited in far
western/southwest Minnesota where both wind speeds and temperatures
will enhance this scenario. Wind speeds have dropped off some from
previous model runs, but still high enough to warrant a concern of
areas of blowing snow in the typical areas of western/southwest
Minnesota. Blizzard conditions are not as likely, or maybe limited
to localized areas due to lower wind speeds and not as much snowfall
from the current weather system moving overhead tonight. It will
still be highlighted in the HWO but will downplay the significants
vs. a couple of days ago.

As discussed before, another Arctic air mass/front will move across
the area Friday evening, and another late in the weekend. The system
Friday night looks weaken and further to the southwest compared to
24 hours ago. However, late in the weekend, this system looks to be
more significant in terms of snowfall amounts and blowing snow. As
always, keep checking for updates as the forecast change frequently
in the Winter.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 611 AM CST Tue Jan 22 2019

Light snow with some patchy freezing drizzle this morning.
Eventually the precipitation will come to an end and become more
focused across western Wisconsin by this afternoon. Winds will
become northerly which will help scour out the moisture. Expect
VFR conditions to develop overnight as ceilings lift.

Most of the precipitation is over at KMSP, but could see some
lingering snow showers and light freezing drizzle. Little if any
accumulation is expected. Winds will become more northerly
throughout the morning, and expect cloud bases to remain above
1700 ft, with VFR condition by Wednesday morning.

WED...VFR. MVFR ceilings possible late. Wind S at 10 kts.
THU...VFR with MVFR-IFR and -shsn/blsn possible. Wind NW at
FRI...VFR. Wind NW 5-10 kts.


WI...Winter Weather Advisory until noon CST today for WIZ014-023.

     Winter Weather Advisory until midnight CST tonight for

     Winter Weather Advisory until 6 PM CST this evening for WIZ015-

MN...Winter Weather Advisory until noon CST today for MNZ052-053-

     Winter Weather Advisory until midnight CST tonight for MNZ078-

     Winter Weather Advisory until 6 PM CST this evening for



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