Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
FXUS63 KMPX 111000

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
400 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


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1131 PM CST Tue Jan 10 2017

Skies have cleared behind the snow and strato-cu from this
afternoon, but the mid-high clouds have already started spreading
into western MN this evening - ahead of the next 1-2 bands of
light to moderate snow that will affect the TAF sites late tonight
and tomorrow morning. The first snowband has already spread into
KRWF with ceilings going from 10000ft to 2400ft and 3/4SM -SN. This
will likely be the trend with the snow this morning. There will be
a quick first band...then a lull...then a more pronounced 2nd band
that will mostly affect eastern MN and western WI. MVFR/IFR is
likely with the first band...with IFR/LIFR likely with the second
band that moves in later on this morning.


Another snow filled morning is looking more likely. There will
likely be an initial band for a couple hours before the morning
push (we sped up the timing of this lead band a little)...then a
lull...followed by a steadier and heavier band of snow that takes
shape before mid morning - possibly leading to visibility below
1SM and dropping 2-3 inches of snow.

Thu...VFR. Wind NW 5-10 kt.
Fri...VFR. Wind variable 5 kt or less.
Sat...VFR. Wind S 5-10 kt.


WI...Winter Weather Advisory until noon CST today for WIZ014>016-

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



AVIATION...CLF is the U.S. government's official web portal to all federal, state and local government web resources and services.