Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 131106
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
506 AM CST Sat Jan 13 2018

.UPDATE...For 12z Aviation discussion below

&&

.SHORT TERM...(Today and tonight)
Issued at 237 AM CST Sat Jan 13 2018

Surface high pressure circa 1040mb is contributing to temps from
the mid teens to low 20s below zero this morning, although winds
are fairly light so wind chills are not as extreme as they could
be. Winds remain light today and temps will remain around 15 to 20
degrees below normal, with highs mostly from zero to 5 above.

Tonight we see increasing clouds and southerly flow developing
ahead of the approaching clipper system. Attendant snow looks to
hold off until after daybreak Sunday.

.LONG TERM...(Sunday through Friday)
Issued at 237 AM CST Sat Jan 13 2018

Main stories in the long term continue to be the clipper for Sunday,
another round of dangerously cold arctic air Monday and Tuesday,
then a considerable warm-up for the end of next week into next
weekend.

For the clipper, not much has changed with this forecast, with
models continuing to be in high agreement and having changed little
over the last 24 hours. We did lower QPF every so slightly as
moisture really looks to be lacking with PWATs around 0.2" and
mixing ratios on the 285K surface down between 1 and 1.5 g/kg.
Forecast soundings continue show deep DGZs on Sunday, so snow
rations in the 20-25:1 range seem reasonable. With those kind of
ratios, even a 0.02" reduction in QPF will take a half inch off your
snow totals, which is basically what happened. Still looks good to
see snow totals in the 2.5-3" across east central MN into western
WI. Based the track of the surface low, the St. Croix Valley still
looks to be where the greatest potential for seeing an isolated snow
amount near 4" resides, but that is the top end for this event.

In the wake of this clipper, it`s strong CAA Sunday night through
Monday as the next push of arctic air moves in. As the previous
discussion talked about, winds don`t look strong enough to produce
ground blizzard conditions behind the front, though there will be
some minor blowing and drifting as wind gusts topping out near 30
mph blow around the freshly fallen snow. The bigger issue though
with the cold air coming in next week looks to be wind chills. We`ll
have stronger winds with this push of arctic air than we have seen
with previous ones since the end of December, with apparent
temperatures forecast to bottom out Monday night/Tuesday morning
in the -40 to -45 range out in western MN. Looks like both Sunday
night/Monday morning and Monday night/Tuesday morning will require
wind chill warnings, with the Monday night into Tuesday period
having the potential to see the largest coverage, with current
forecast minimum winds chills of -35 or cold extending along and
west of a line from Albert Lea, to Buffalo and Milaca. It looks
unlikely the Twin Cities metro and western WI will get down to
that -35 wind chill threshold for a warning.

This arctic air will quickly get pushed out of here Wednesday as the
western ridge begins to push out on to the Plains. By Friday, the
ECMWF has h85 temps of +12C into southern MN, with it likely that we
see highs above freezing for most of the MPX area Thursday through
Saturday.  Beside the warmer weather, medium range ensembles
continue to point to a more active large scale weather pattern
setting in next weekend into the following week as we see the
western ridge/eastern trough pattern become a western trough/eastern
ridge. This is a considerably warmer pattern for us, so any system
we see then could very well have p-type issues as well. Still a long
ways out at this point, but it wouldn`t be a surprise if we start to
see a stronger storm system emerge in the models in the coming days
for the nations mid section for next weekend into the following
week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 507 AM CST Sat Jan 13 2018

High confidence in VFR conditions through the period, with clear
skies through this evening. Mid/high clouds approach from the
west tonight ahead of a clipper that will bring MVFR conditions
and snow on Sunday. Light and variable winds today become
southeasterly at 5-10 knots overnight.

KMSP...No concerns.

/OUTLOOK FOR KMSP/
Sun PM...MVFR with IFR/SN likely. Wind S 5-10 kts.
Mon...VFR with MVFR possible. Wind NW 15G20 kts.
Tue...VFR. Wind NW at 5-10 kts.
Wed...VFR. Wind SW at 5-10 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Chill Advisory until 9 AM CST this morning for WIZ014>016-
     023>028.

MN...Wind Chill Advisory until 9 AM CST this morning for MNZ041>045-
     047>070-073>078-082>085-091>093.

&&

$$

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


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