Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 100053

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
653 PM CST Mon Jan 9 2017

.UPDATE...For 00z Aviation discussion below


.SHORT TERM...(This evening through Tuesday)
Issued at 343 PM CST Mon Jan 9 2017

Light snow today will continue shifting eastward and gradually end
from west to east this evening and overnight. Another area of
precipitation will develop across southern MN Tuesday morning, and
thermal profiles support a wintry mix. Areas to the north will have
snow later in the day, and should see another couple of inches for
most locations.

Higher totals are possible in western Wisconsin, so may need to
consider winter weather headlines if a quick 3 to 5 inches becomes
more likely with the next set of model runs. The wave driving this
precip is taking on a negative tilt which means more focused area of
ascent, higher QPF, and therefore potential for higher snow totals.
Bufkit soundings show a deep layer of omega in eastern MN and
western WI which produced a quick 2 to 5 inches of snow Tuesday

.LONG TERM...(Tuesday night through Monday)
Issued at 343 PM CST Mon Jan 9 2017

The active weather pattern this week should become less
active/milder next week as the main upper jet core, and weather
system hold well south or north of the Upper Midwest.

This pattern change is also conducive for a warm-up which the Upper
Midwest can get from time to time in January. This is typically
called a "January Thaw" which happens as winds aloft become more
westerly and more Pacific air masses dominate the Northern
Plains/Upper Midwest, or anywhere east of the Rockies.

There remains model differences on how mild the air mass becomes
next week, however, the trend remains the same as the core of the
coldest air over Canada, retreats further to the north/northeast. In
addition, the anomalous upper ridge that has dominated western
Alaska over the past week or two, and provided for very mild
temperatures, will break down this week. A deep upper trough is
forecast to form where the upper ridge was situated which means much
colder temperatures for Alaska. Further to the south across the
eastern Pacific, the persistent trough and anomalous very wet
pattern for the west coast, and interior mountainous region will dry
out as a large ridge begins to build. This ridge will again lead to
a more westerly/southwesterly flow aloft over then northern United
States, leading to much milder conditions for the Upper Midwest.

For this week, only subtle differences are noted with a strong short
wave and associated cold front, moves across the region Tuesday
night/Wednesday morning. Although QPF amounts are fairly low and
under a tenth of an inch, the air mass behind Tuesday front is much
colder leading to higher snowfall ratios. A tenth of an inch could
easily be a few inches of snow depending upon the strength of the
thermo boundary and upper level jet support. Therefore, I have
increased percentages to high chance category from St. Cloud to the
Twin Cities, northeast into east central Minnesota, and west central
Wisconsin. Again, due the persistent high thermo boundary gradient,
the QPF amounts maybe underestimated, and also the snowfall ratios
could be much high (15 to 25-1).

No other changes in the extended period. Depending upon the amount
of snowfall over the next three days and where the core of the
coldest air mass resided Friday morning, lows could be on the
conservative side. I would not be surprised to see lows colder than
the cold air mass we had around the 18th of December.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 654 PM CST Mon Jan 9 2017

Light snow will be possible through most of the period at the TAF
sites, but the main window for snow that will accumulate and lower
vsbys will be after 11z Tuesday. Other than a brief scattering in
the low cloud (MVFR) deck from central MN into west central WI
this eve, expect MVFR and IFR cigs to become prevalent overnight,
with vsbys lowering to IFR with the snow on Tuesday as well.
Southeast winds 08-15 knots with gusts into the lower 20s shift to
northwest Tuesday with gusts into the mid 20s developing.

Other than the possibility of flurries, precip has ended until the
early morning hours. May see a bit of a wintry mix prior to
daybreak, but we are more confident on the snow which will arrive
around 12z. Cigs/vsbys will be prevalent mvfr with the snow with
occasional reductions during the morning to around or slightly
below 1SM (similar to today). The snow should taper off by 00z
Wed. Southeast winds with gusts to around 20kts this eve become
lighter and variable by daybreak, the shift to the northwest by
the afternoon and increase. Expect gusts to around 25 kts during
the afternoon.

Wed...VFR. MVFR with -SN possible late. Wind W 5-10 kt bcmg N.
Thu...VFR. Wind NW 5-10 kt.
Fri...VFR. Wind variable 5 kt or less.




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