Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 110959
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
359 AM CST Thu Jan 11 2018

.SHORT TERM...(Today and tonight)
Issued at 359 AM CST Thu Jan 11 2018

Temperatures are plummeting in the wake of the cold front. Areas
of drizzle will continue to transition to freezing drizzle and/or
snow. In the meantime, untreated roads/pavement will likely
"flash freeze" given the residual moisture from earlier
precipitation, as is being observed along I-35 near Albert Lea.
Therefore even though anticipated snowfall totals in most areas
alone would not justify continuance of the winter weather
advisory, the impacts from the freezing do warrant it. Have moved
up the ending time for MN counties to 18z given blowing snow
concerns will be less given notably lower accums. The highest
snowfall accumulations in the deformation band still look to just
barely clip the eastern fringes of the forecast area, with 4-5
inch amounts the maximum. Have therefore downgraded the warning to
an advisory.

Temperatures will either remain steady (west central MN) or fall
through the day (elsewhere). In the wake of the snow, most areas
will see single-digit temperatures by late afternoon, likely even
below zero in west central MN (near Alexandria). While northwest
winds do look to lose their gusts during the evening, they should
stay in the 5-7 knot range overnight. These winds combined with
temps falling into the single digits to teens below zero will make
for very cold wind chill values tonight. Areas generally west of
Interstate 35 look to see wind chills falling into Advisory
criteria range, so anticipate headlines will likely be needed
later today.

.LONG TERM...(Friday through Wednesday)
Issued at 359 AM CST Thu Jan 11 2018

The long range period will be dominated by arctic air through
Tuesday, before we start working our way out of it. The northwest
flow bringing the arctic air will send a couple of clippers Friday
and again Sunday.

Starting with temperatures, the lack of snow we are getting out of
the system moving through now will definitely limit the punch of
this arctic out break, especially with overnight lows. Even then
though, 925-850mb temps will not be as cold as what we saw at the
beginning of the month, so sub-zero highs will be fairly uncommon.
We will get a brief warmup on Sunday with WAA ahead of the
clipper, but outside of that, we`ll see highs around 20 degrees
below normal Fri, Sat, Mon, and Tue. For lows, to see -10F or
colder, you`ll need snow, so central MN and west central WI will be
the only places that see those kinds of lows. Of course with arctic
air comes wind chill headlines. Any wind chill headlines needed for
tonight will need to be continued through Friday morning. Friday
night will be another wind chill headline worthy night before high
pressure moving in Saturday allows the winds to drop off. WAA ahead
of the clipper on Sunday will give us a break from wind chill
headlines Saturday night and Sunday. Behind the clipper though, we
will likely see wind chills drop to -20 to -35 once again, so wind
chill headlines will likely be needed again Sunday night through
Tuesday night.

For snow chances, models continue to push the clipper for Friday
farther southwest and this now looks to stay southwest of MN. Sunday
will see a potent shortwave deepening as it drops down from Canada
and looks to be a bit more giving in the snowfall department. This
looks like your standard clipper, with a pretty broad 1-3" of snow
falling. Soundings show the DGZ extending from the surface to nearly
10k feet, so we should see some healthy snow ratios with this snow,
likely in excess of 20:1.

For the end of the period, we will be on a warming trend. In fact,
by the end of the next week, it is looking like we could see more
highs above the freezing mark. As we saw recently, the one advantage
to having little snow cover is we can warm up quickly.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1108 PM CST Wed Jan 10 2018

Quite the complex forecast with multiple precip types changing to
-SN, possibly SN to +SN at times for southern MN into western WI,
 then with BLSN for much of the day on Thursday. Conditions this
 evening will start out as IFR or worse for much of central MN
 into western WI where -DZ/BR/FG with low stratus is prevailing
 while western MN, having already shifted to NW winds with
 plummeting temperatures, has improved to MVFR. The trend will be
 to have precip change over from DZ/BR/FG to -SN/BR, but there may
 be a brief period of -FZDZ in the 06z-12z period between the two
 other prevailing p-types and trying to capture that period will
 be quite problematic. But, once the p-type changes over to -SN,
 the visibility will be mainly derived from any falling snow while
 ceilings will slowly rise through the MVFR levels. Nevertheless,
 flight conditions will likely remain as IFR-or-worse for at least
 the first half of the day tomorrow. Conditions will slowly
 improve tomorrow evening to VFR and remain as such going into
 Thursday night.

KMSP...Expect IFR-or-worse conditions through at least the first
half of Thursday, starting out due to ceilings and -DZ/FG then
transitioning to falling and/or blowing snow. There may also be
some icing, not only due to falling precipitation, but simply due
to ground/pavement moisture freezing with temperatures expected to
fall so quickly. P-type will change over to -SN by or shortly
after with precipitation continuing until late afternoon. Snow
amounts have been decreased such that it may be a stretch to even
get an inch of snow accumulation.

/OUTLOOK FOR KMSP/
Sat...VFR. Wind NW 5 kts.
Sun...MVFR with -SN likely. Wind S 5-10 kts.
Mon...VFR. Wind NW 10 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 PM CST this evening for
     WIZ014>016-023>028.

MN...Winter Weather Advisory until noon CST today for MNZ041>045-
     047>070-073>077-082>084-091-092.

     Winter Weather Advisory until 6 PM CST this evening for MNZ078-
     085-093.

&&

$$

SHORT TERM...LS
LONG TERM...MPG
AVIATION...JPC



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