Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 111157
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
557 AM CST Wed Jan 11 2017

.SHORT TERM...(Today and tonight)
Issued at 400 AM CST Wed Jan 11 2017

First band of snow came up on an elevated warm front characterized
by strong isentropic lift along the 290k surface and strong Fgen in
the h7-h6 layer. Steep mid-level lapse rates also gave us a weakly
stable environment above this forcing, with conditional slantwise
instability noted. Though narrow, this band packed a punch,
producing an inch of snow in less than an hour with visibilities
getting down to 1/2 mile. Looking back west, there is another band
of strong Fgen in the h7-h6 layer across SD. This is associated with
a narrow band of moderate to heavy snow from the Black Hills to the
east of Pierre, SD. This area of forcing will quickly move into MN
this morning. As this band of Fgen moves across the region, it will
coincide with favorable upper diffluence as we get into a couple jet
structure between one jet streak up over Lake Superior and another
nosing into western IA. This environment will allow for another band
of moderate to heavy snow to develop. Hi-res models are in good
agreement with this occurring between about 5am and 11am this
morning. Given the narrow nature of the band, relied heavily on
probability matched mean of short term models for QPF. This resulted
in a band of 2-4" of snow from the Twin Cities east, with amounts
near 5 inches out between Eau Claire and Ladysmith where there does
not look to be a break between the two bands of snow like we have
seen in the Twin Cities. Given these amounts and the timing of the
snow with respect to the morning commute, went ahead with issuing a
winter weather advisory from the Twin Cities on east due to expected
impacts to travel this morning.

This snow will end quickly this morning, with dry low level air
pushing in from the northwest as high pressure moves in from the
Dakotas. Though the low levels dry out, we will remain within a mid-
level baroclinic zone and associated mid/upper level cloud cover.
Tonight, we`ll see another shortwave work across IA/southern MN,
which will cause Fgen to redevelop overnight. However, the high
pressure moving in at the surface leads to a lot of uncertainty as
to if we will actually even see precip reach the ground, so
maintained mention of low pops down in southern MN tonight.
What did change for tonight was an increase in cloud cover and an
associated increase in overnight minimums, with said clouds keeping
us warmer than previously forecast. The one exception to this rule
looks to be up from Alexandria over toward Little Falls, where the
potential for less cloud cover supports the idea of lows in the
teens below zero there.

.LONG TERM...(Thursday through Tuesday)
Issued at 400 AM CST Wed Jan 11 2017

Concerns in the long term are centered around two features. The
first is arctic high pressure and the associated low temperatures
that occur Friday morning while the second is how models are now
handing a weather system coming at us from the southern plains for
early next week.

The period begins with a little light snow along the I-90
corridor early on Thursday. This is associated with the forcing
from a coupled upper jet lifting northeast from the central
plains. In its wake, arctic high pressure over Saskatchewan and
Manitoba will strengthen from 1031 mb to 1048 mb while moving to
central MN by daybreak Friday. The timing of the high and the
several rounds of fresh snow cover that will have occurred by
Friday morning are a recipe for very cold low temperatures Friday
morning. The one fly in the ointment is the insistence from the
GFS and ECMWF that there will be some increase in CI/CS during the
late night hours, especially across the southwest quarter of MN.
However, the damage may already be down with temperatures falling
quickly during the evening and early morning hours. I think we
have a good chance of seeing 30 below zero across our far northern
counties in central MN with 15 below to 25 below across southern
MN and west central WI. Overall, we lowered the FB lows several
degrees. Fortunately, this occurs with very light winds (less
than 5 mph) Friday morning, so the apparent temperatures are not
that ferocious with readings in the 30 below to 35 below range to
the west, north and east of the Twin Cities.

Temperatures will begin to moderate during the weekend as the
high moves off to the east with highs on Sunday near or above
seasonal normals. The trend of above normal temperatures will
persist next week as our mid/upper level flow become more
southerly. This is due to a cut-off low over Baja during the
weekend end that moves into Texas by Monday and then begins moving
almost due north through the plains through Wednesday. The 00z
runs of the GFS and ECMWF are now showing this low moving all the
way northward into MN and WI. This is farther north than previous
runs and means more precipitation early next week. Unfortunately,
because of the warming in the low levels, some of this may be
freezing rain/freezing drizzle along with some snow. Things look a
little messy from late Monday into Wednesday as the low moves
overhead. There is some potential for heavy snow due to
temepratures being near the critical mark. Based on the 00z cycle,
the chance for heavy snow would extend across eastern NE and
western IA on northward into west central MN. Plenty will change
between now and then, but this system will need to be watched
closely.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 557 AM CST Wed Jan 11 2017

Expect moderate snow to rapidly expand across the area within the
first 30 minutes as a band of snow sets up from RWF over to MSP,
RNH, and EAU per the HRRR and HopWRF. Followed these models to
time snow through this morning. Lower confidence on CIG trends
today, but do expect all sights to go VFR as dry high pressure
works in from the Dakotas. If anything, 12z TAFs may be holding on
to lower cigs for too long. This evening, we will have another
band of snow heading toward SW MN, but lots of uncertainty as to
if it will be able to overcome dry low level air to reach the
ground. RWF would have the best chance at seeing snow with this
between 2z and 6z.

KMSP...Still anticipate snow to rapidly expand here in the Twin
Cities and may very well need an AWW for snowfall rates between
3/4 and 1 inch per hour in the 1230z to 15z window. Snow looks to
end quickly between 15z and 16z with return to VFR cigs expected
shortly thereafter.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind NW 5-10 kt.
Fri...VFR. Wind variable 5 kt or less.
Sat...VFR. Wind S 5-10 kt.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until noon CST today for WIZ014>016-
     023>025-027-028.

MN...Winter Weather Advisory until noon CST today for MNZ053-060>063-
     068>070.

&&

$$

SHORT TERM...MPG
LONG TERM...RAH
AVIATION...MPG



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