Scientific Forecaster Discussion
fxus63 kmpx 131031
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
431 am CST Wed Dec 13 2017
Update...for 12z aviation discussion below
Short term...(today and tonight)
issued at 409 am CST Wed Dec 13 2017
The surface trough is passing across the area this morning. For the
most part only areas along the northern/eastern periphery of this
feature have received measurable precipitation, with other areas
being too dry thus far. Continue to expect the majority of the
measurable precipitation to fall from north central Minnesota across west
central WI (generally north of I-94), where some light freezing
precip and 1-3 inches of snow are possible. Given the potential for
a slick morning commute in these areas, decided to issue a Winter
Weather Advisory through early afternoon.
Eventually the rest of the area will see a better potential for
light precip as low level moisture (clouds) wrap around the backside
of the system. However at that time the threat for freezing precip
will be diminishing and the lift waning.
Over western Minnesota, the Wind Advisory looks to be in good shape.
Expect winds of 25-30 miles per hour with gusts up to 50 miles per hour at times. Given
the measurable snow is falling east of the area with the strongest
winds and the biggest impact should be the winds, have kept it as a
Long term...(thursday through tuesday)
issued at 409 am CST Wed Dec 13 2017
A relatively quiet end to the week lies ahead. A wave will pass
south across the Dakotas Thursday, keeping the best chance of
steady snow to our west. Cyclonic flow within the trough through
Friday will allow for plenty of clouds and scattered flurries,
A better organized clipper will develop Friday across southern
Canada. Like the last several, a narrow band of snow along and
north of the track could bring some accumulations mainly north of
I-94. Meanwhile, another trough over the northern rockies may try
to phase with a cut off low over Mexico, bringing aggressive
moisture advection northward across the lower Mississippi Valley
into the Ohio Valley. Models currently depict the low getting
caught up in the strengthening southwesterly flow and shearing out
as it lifts quickly northeast. Additional energy remains back
over the Desert Southwest. If the energy from northern Mexico
phases with the trough approaching from the west, there could be a
big system over the center of the country this weekend. None of
the deterministic guidance is showing this currently, with the
progressive northern stream likely a culprit in orphaning energy
across the southwestern U.S. It's something to watch nonetheless.
Temperatures through the forecast period will be above normal, but
there are signs in the extended guidance toward the weekend of
Christmas that Arctic air could unload on the center of the
Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 430 am CST Wed Dec 13 2017
Ceilings will lower to MVFR level this morning, with light
precip wrapping around the departing trough. There is still a
chance of -fzdz this morning...although soundings are really dry
so precip amounts look meager. Periods of IFR cigs cannot be ruled
out, but look less likely than the prior issuance. South/southeast
winds will shift to the northwest throughout the morning and
increase to sustained 20-30kts with gusts to 40 kts.
the freezing drizzle threat has reduced due to dry lower levels.
The threat isn't entirely over, as we could see -fzdz or -fzdzsn
when the band of light precip swings through between 14z and 18z.
Any accumulations still look to be light given how dry the low
levels are (a couple hundredths of an inch of ice and less than
one half inch of snow).
/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.
WI...Winter Weather Advisory until 3 PM CST this afternoon for
Minnesota...Wind Advisory until 6 PM CST this evening for mnz041-047-048-
Winter Weather Advisory until 3 PM CST this afternoon for