Scientific Forecaster Discussion
fxus63 kmpx 130028
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
628 PM CST Tue Dec 12 2017
Update...for 00z aviation discussion below
Short term...(this evening through wednesday)
issued at 248 PM CST Tue Dec 12 2017
An active short term period ahead. First of all, we have an area
of light snow moving through the eastern portion of the area in
response to strong Theta-E advection spreading over the area ahead
of the incoming clipper that we've been discussing. This area of
snow is on a diminishing trend and don't expect much more than a
dusting across eastern Minnesota and western WI.
The aforementioned clipper is currently dropping southeast through
Alberta, and is well defined in current water vapor imagery and
indicates a decent pv anomaly with this wave. This wave is going
to race southeast this evening and reach western North Dakota
around midnight. The surface response will be a deepening low that
will move from extreme eastern North Dakota through Minnesota
from about midnight through 10am tomorrow. This still looks to
spread mainly snow along the northern flank of the low, with
western WI in the most favorable location to see 1 to 3 inches of
snow. Farther south, mid level drying leads to limited icing aloft
and hence the forecast of freezing drizzle. Thinking the quantitative precipitation forecast will
be light south of the I-94, but the roads will likely turn slick
for the morning rush. However, the lack of quantitative precipitation forecast inhibited the idea
of issuing a Winter Weather Advisory at this time, but will
continue to evaluate the possibility for a headline through the
We do feel more confident in the wind potential for western and
southern Minnesota tomorrow, so went ahead with a Wind Advisory. These
areas can expect winds of 25-30 miles per hour with gusts up to 50 miles per hour at
times tomorrow. The precip should mostly stay east of the area
with the strongest winds.
Long term...(wednesday night through tuesday)
issued at 248 PM CST Tue Dec 12 2017
The series of upper level shortwaves and surface clipper-type low
pressure systems will continue through the rest of this week into
the upcoming weekend. None of the systems will be particularly
strong or put down any significant amount of precipitation, each
acting to be primarily a nuisance to the area. The next upper
level wave looks to drop southeast through the area late Thursday
afternoon, followed by late Friday through Friday night, then
another on Sunday then potentially another on Tuesday. However,
each wave is rather progressive and not deep with moisture (some
not even enough to produce precipitation), thus pops are limited
to the low- end chance range at best throughout the extended
portion of the forecast. Not looking at any systems that may have
icy precipitation either, with each small round of precip a mix of
mainly rain & snow.
As for temperatures, virtually no change in airmass is expected
through the weekend which will keep Max temps in the lower 20s to
lower 30s. Starting early next week, a more east-west flow will take
hold (rather than a more north-northwest-south-southeast colder flow) which will allow for
modified Pacific air to be brought into the region, nudging the
temperatures up a bit across the area. Highs starting on Monday
look to climb into the 30s across the weather forecast office mpx coverage area.
Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 629 CST Tue Dec 12 2017
Somewhat of a repeat of last night, with MVFR ceilings shifting
east of the taf area during the first few hours of the taf period.
Then MVFR ceilings envelop the area on Wednesday in the wake of a
trough dropping across the area. Expect -fzdz to develop as well
overnight and eventually transition to -sn. Ceilings will degrade
to MVFR by 12z, with periods of IFR. South/southeast winds will
shift to the northwest on Wednesday and increase to sustained
20-30kts with gusts to 40 kts.
freezing drizzle looks like a decent possibility during the
morning push...10z-13z. Any accumulations look to be light (a few
hundredths of an inch). Light snow will be possible through the
afternoon, with total snow under one half inch.
/Outlook for kmsp/
Thu...chc MVFR. Wind northwest 10-15 kts.
Fri...chc MVFR. Wind west-southwest 5-10 kts.
Sat...chc MVFR. Wind SW 5-10 kts.
Minnesota...Wind Advisory from 6 am to 6 PM CST Wednesday for mnz041-047-048-