Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 232206
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
406 PM CST Thu Feb 23 2017

.SHORT TERM...(This evening through Friday night)
Issued at 342 PM CST Thu Feb 23 2017

Surface analysis this afternoon shows development of a classic
mid-latitude cyclone over the TX/KS panhandles with an extended
surface front from the center of this system ENE into lower MI and
a trailing cold front over NM/AZ. Aloft, a large longwave trough
which moved onshore the lower CA coast has shifts atop the
central-southern Rockies. The upper trough is expected to deepen
over the central-northern Plains during the day tomorrow through
tomorrow night, helping add plenty of energy to the developing
surface low. The surface low will shift across KS tonight and over
northern MO tomorrow morning, on its way to lower Lake Michigan by
tomorrow evening then Lake Huron by Saturday morning. Deep Pacific
moisture will accompany this system, so much so that QPF amounts
for southern MN look to range 1.00-1.50" by the conclusion of this
system. Though there continues to be good model agreement (outside
of the NAM which has and remains a significant outlier) that SE MN
will be in the crosshairs for the highest snowfall totals, the
consensus track took another slight shift to the SE, thus lowering
the snow amounts and hence the impacts mainly N and W of the Twin
Cities metro. As such, some minor reconfiguring of the headline
products were made but the point must still be made that there
will be a very tight NW-SE gradient of snow amounts just to the
south of the Twin Cities metro. As an example, counties like Le
Sueur or Nicollet or Dakota or Brown could see as much as a 6"
difference in snow totals from NW to SE across each respective
county.

Snow has commenced in far SW MN this afternoon and snow will
gradually spread mainly E and slightly N as the overnight
progresses. There may even be a slight mixture with rain at the
immediate onset but any mixture of precipitation will have a short
duration before become all snow. As the surface low shifts ENE
and the upper level trough pivots to help enhance the surface
feature, snow coverage and intensity will increase during the
early morning hours, likely with rates increasing to 1-2"/hr for
several hours in far southern MN and into SW WI. The morning
commute for southern/eastern MN into western WI will likely have
ongoing snow then the snowfall will steadily diminish as the day
progresses. However, strong winds for much of the region will
contribute to the blowing snow issues, making for hazardous
travel conditions for much of southern MN. Another concern is
isolated thunderstorms could develop over far southern MN into
southwestern WI. Instability levels are not entirely zero given
the antecedent moisture levels plus the incoming surge and that
additional lift will be created by the pivoting upper level
trough. Confidence not high enough to include mention at this
point but some thunder cannot be ruled out.

Precipitation will end from west to east late tomorrow afternoon
through tomorrow night and the wind speeds will decrease as well,
resulting in partly to mostly cloudy skies for the start of the
weekend. As for temperatures, once temperatures drop below
freezing later this evening, they will remain below freezing
throughout the duration of this event. Lows tonight to highs
tomorrow will have a very small diurnal range, potentially 5
degrees or less from tonight through tomorrow. As colder air wraps
around this system as it departs, lows will drop into the teens
tomorrow night, temperatures this area has not seen in some time
but will be actually right on par with climatological norms.

.LONG TERM...(Saturday through Thursday)
Issued at 342 PM CST Thu Feb 23 2017

Temperatures will warm through early next week. A fairly large
storm will develop over the Upper Midwest, but thermal profiles
should be warm enough to have mostly rain, especially if the
system translates westward with time.

A weak clipper system will sweep through the region on Sunday and
could bring some snow across MN/WI. On Monday the southern stream
will develop a storm to the southeast over the Ohio river valley.

This will be followed by a third system Tuesday into Wednesday.
This mid-week storm will have a favorable temperature gradient
to work with and should develop strong cyclone. However, there is
a lot of warm air with this storm, so the primary p-type will be
rain, with perhaps some snow mixed in. There is still uncertainty
with this storm, but as of now it appears that the chance is quite
low for this system to develop into a winter storm for the Upper
Midwest.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1234 PM CST Thu Feb 23 2017

Potent winter storm still on track to impact 4 of the 6 WFO MPX
TAF sites (KAXN-KSTC look to remain out of the crosshairs as the
models are still putting SE MN in the crosshairs for heaviest snow
with a sharp dropoff going NW). MVFR to IFR conditions will
develop overnight with some periods of heavy snow over southern MN
into parts of western WI. Winds will also kick up overnight and
remain elevated through tomorrow with speeds increasing to
15-20G30kt for much of the coverage area. These speeds may well
created BLSN concerns for RWF-MSP and potentially the WI TAF
sites. Slow improvement will take place late tomorrow afternoon
through tomorrow evening (mainly past the end time of the 24/18z
TAFs).

KMSP...Timing/durations of IFR look to be less, mainly confined to
around the Friday morning push through midday Friday. Some
ceilings around that time could also drop into IFR levels which
would be lower than currently advertised. The strong winds may
well create visibility issues due to blowing/drifting for much of
the day.

/OUTLOOK FOR KMSP/
Sat...VFR. Wind NW 10-15 kts becoming W.
Sun...VFR. Chc MVFR/-SN. Wind SW-W 5-10 kts.
Mon...VFR becoming MVFR. Chance afternoon -RASN. Wind S 5-10 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning from 9 PM this evening to 6 AM CST Saturday
     for WIZ015-016-023>028.

     Winter Weather Advisory from 9 PM this evening to 6 AM CST
     Saturday for WIZ014.

MN...Winter Storm Warning from 9 PM this evening to 6 AM CST Saturday
     for MNZ063-069-070.

     Winter Weather Advisory from 9 PM this evening to 6 AM CST
     Saturday for MNZ060-062-065>068-073.

     Blizzard Warning from 9 PM this evening to 6 AM CST Saturday for
     MNZ074>078-082>085-091>093.

&&

$$

SHORT TERM...JPC
LONG TERM...JRB
AVIATION...JPC



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