Area Forecast Discussion
Issued by NWS Twin Cities, MN

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480
FXUS63 KMPX 010446
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1046 PM CST Tue Feb 28 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 405 PM CST Tue Feb 28 2017

The main concern during the short term period is the chance for
snow tonight through Wednesday morning.

A northern stream wave is expected to impact the area this
eve/tonight while much of the area comes under the influence of
forcing from the upper jet. The GFS/NAM/ECMWF all depict light
snow to spread east/southeast across central/southern MN and west
central WI tonight and Wednesday morning. A period of light rain
and/or a mix is also possible this eve until cooler air works into
the region in the wake of the cold front. One red flag for
accumulating snowfall, however, is the trends the hi-res models
have been showing, which are much less supportive of snow. This is likely
due to the moisture displacement with the convection that`s
occurring to the south/southeast of the area (IA/IL/IN)
associated with the southern stream. Have therefore gone more
conservative with snowfall amounts tonight through Wednesday
morning, with 1-2 inches seeming the most likely.

Widespread cloud cover from tonight through much of Wednesday will
yield limited temperature changes, with lows in the 20s overnight
and highs in the low/mid 30s on Wednesday.

Although lingering weak shortwave energy could yield a few snow
showers into Wednesday afternoon, for the most part measurable
precip should end during the morning hours.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 405 PM CST Tue Feb 28 2017

Models have been fairly consistent in the long wave pattern
through the early part of the weekend, but diverge by early next
week. This means that confidence remains high for a cool period
from Wednesday night through Friday morning, with temperatures
moderating over the weekend. However, by Monday, as models remain
uncertain on the evolution of the long wave pattern change, a
strong storm system will eject out of the Rockies, taking aim on
the Northern Plains, and Upper Midwest.

Both the EC/GEM remain close (better consistency) to a potent storm
system moving into the Upper Midwest late Sunday, and into Monday.
The GEM is much further to the south leading to a snow scenario,
with the EC a mixture at the beginning, but rain for the GFS. In
addition, the GFS is much further to the north and slower than the
GEM/EC.

The differences in the long wave pattern is related to how
fast and sharp short wave energy moves across the Rockies over the
weekend. The GEFS mean 50H keeps the pattern more progressive and
weaker across the Rockies, leading to the northward route of the
storm system of the GFS. As with the previous discussion, kept a
blend of the models for early next week.

As for the upcoming weekend, the upper ridge will allow for above
normal temperatures to resurges northward with standard deviations of
the 85T between 2 % 3. The GEFS plumes suggest highs on Sunday
approaching 60 degrees in the Twin Cities.

As for an "Alberta" type clipper progged to affect the Upper Midwest
Wednesday night, and into Thursday... there will be a sharp and
narrow band of 1 to 3 inches of fluffy type snow in southern
Minnesota. Timing remains close but location still remains uncertain
based on how these systems have a narrow band of snow on the
northeast side of the surface low location.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1045 PM CST Tue Feb 28 2017

Main concern overnight is whether or not snow will develop from
south central MN through the Twin Cities and on across west
central WI. Short term guidance from this afternoon and evening
have not done well with the snow that occurred in central MN
during the late afternoon and for the snow that should be
occurring now across west central MN. However, overnight there
will be a mid/upper level trough move east from SD while an
inverted surface trough strengthens from southern WI on northwest
across MN. Hence, still feel that snow, with low MVFR/IFR
ceilings and visibilities will develop after 08z from KRWF through
the Twin Cities and on across KRNH and KEAU. This band should
slowly pivot ESE through the mid morning. This would bring the
worst conditions and most snow accumulation to KEAU. MVFR ceilings
will slowly rise to BKN VFR during the late afternoon and early
evening. NE winds near 10 knots overnight becoming NW 12g18kts on
Wednesday.

KMSP...Best snow chances overnight are in the 10z-13z time frame.
This could result in 1.5 inches of snow. The snow ends after 14z
with increasing NW winds and ceilings rising from 015 to 025.

/OUTLOOK FOR KMSP/
THU...Chc MVFR/-SN. Winds NW 5-10 kts.
FRI...VFR. Winds S 5-15 kts.
SAT...VFR. Winds SE 10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...LS
LONG TERM...JLT
AVIATION...RAH



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