Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 282359
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
559 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 00Z TAFS through 00Z Wednesday evening)
Issued at 559 PM CST Tue Feb 28 2017

Short term guidance has shifted things around late this afternoon
with more focus on snow across central MN early tonight and then
across southern MN and adjoining areas of west central WI late
tonight and Wednesday morning. It seems that a H7 low is moving
northeast from KABR at this time with a fairly strong band of mid
level frontogenesis across central Mn and northern WI. This area
is also in the right entrance region of the upper jet over LSUP.
Therefore, kept snow longer tonight for KAXN and KSTC. Once the
mid level low moves northeast, the trailing trough axis will shift
south with snow for later this evening through Wednesday morning.
Hence, low MVFR/IFR ceilings and visibilities will be the rule
through much of the period. NE winds 10-15 knots backing to the
northwest on Wednesday with gusts to 20 knots or so for the
afternoon.

KMSP...MVFR ceilings steadily lowering this evening to 012. Some
light rain skimming the airfield as well this evening, mainly to
the north, with a more steady snow developing during the overnight
hours and lasting through much of the morning on Wednesday.
Ceilings during this period will be IFR. Accumulations up to 2
inches, but confidence is low.

/OUTLOOK FOR KMSP/
WED night...VFR. Winds NW 5-10 kts.
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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