Area Forecast Discussion
Issued by NWS Duluth, MN

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123
FXUS63 KDLH 240359
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
959 PM CST Fri Feb 23 2018

.UPDATE...
Issued at 959 PM CST Fri Feb 23 2018

Clouds continue to exit the eastern third of the forecast area at
this hour. Latest short term models all point to some fog
developing tonight, especially in north central Wisconsin. Have
adjusted the sky and weather grids for these trends. Rest of the
forecast in the ballpark.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 304 PM CST Fri Feb 23 2018

Tonight through Saturday morning will feature quiet and dry
conditions before another impactful winter storm arrives Saturday
evening, persisting through Sunday morning. The area of low pressure
that brought the snow this morning will continue to shift eastward
this afternoon and evening, making way for surface high pressure,
currently located over South Dakota. The surface high will keep
conditions dry through Saturday morning, with another chilly night
expected. Overnight lows will range from the single digits below
zero over the west to the upper single digits above zero and lower
teens over northwest Wisconsin where clouds will linger the longest.
A low-level inversion may trap enough moisture for some patchy fog
to develop over northwest Wisconsin, and into adjacent areas of
northeast Minnesota, but confidence in wider areas of fog is quite
low.

After sunrise Saturday, clouds will increase from the south ahead of
the next winter storm to bring accumulating snow to the region. More
details on this storm can be found below in the long-term forecast
section.

.LONG TERM...(Saturday night through Friday)
Issued at 304 PM CST Fri Feb 23 2018

The focus remains on what looks like a major winter storm for the
Northland and WI/MN region this weekend. An impressive looking
Colorado Low is still projected to lift from the Central Plains into
the western Great Lakes region Sunday into Sunday night. This is the
type of system that can pack a lot of Gulf moisture with it and
transform it into heavy snow for our region, and this storm is
one of them. There is high confidence that a large area in the MN
and WI region is going to get a swath of heavy snow, of 6 to 10
inches, it is just a matter of where this low tracks. The heaviest
snow can be expected on the northern and western side of the low.
The likely track is through central WI into Upper Michigan, so
areas of northwest WI and east-central into northeast MN have a
really good chance of getting this heavy snow. The highest
confidence is for northwest WI, the Twin Ports, and the MN
Arrowhead, which most models have been hitting hard for days. The
latest European model continued this trend, so leaning on that
track. However, there is still enough spread in the modeled track
of the low with the latest 12Z model runs to believe we may need
to shift our snowfall totals a little west or east with our next
forecast early Saturday as we narrow down that track. The models
should come into better agreement tonight, so we should have a
better idea on the track in the morning.

This low will be deepening (intensifying) as it lifts into the Great
Lakes, bringing a period of very strong large-scale forcing for
ascent. Its inverted trough will swing through the Northland,
another feature of forcing for snow across the Northland, as well as
banding of more intense snowfall rates. There will be deep
saturation of the atmosphere, with models having ample moisture to
work with. The precipitable water values will be about 0.25 inches
in central and north-central MN, and 0.5 inches in northwest WI.
There will also be a period of good dendritic growth, so large
snowflakes, overnight because of strong lift near the -15 degrees
Celsius ideal dendritic growth zone layer. The best dendritic growth
appears to be for the MN/WI border region and into the Arrowhead.
There could be intense snowfall rates of 1 to 2 inches overnight,
and resulting low visibility. Strong east-northeast flow from Lake
Superior will not only provide some lake moisture enhancement and
terrain enhancement to bump up totals near Lake Superior, but those
winds will cause even lower visibility. The strongest winds will be
from about Duluth to Silver Bay. The North Shore could get up to 12
inches of snow, especially in the higher terrain, because of the
lake and terrain enhancement. The winds across the rest of the
Northland look fairly light, so it`s mostly the shoreline areas that
are affected by strong winds.

Most of the snow will fall overnight, but there will be lingering
snow Sunday morning from south to north. It will certainly take
some time for road maintenance crews to do their fine work on the
roads, so not only expecting poor travel Saturday night, but also
Sunday morning until the roads are in better shape. However,
gusty westerly winds will set Sunday afternoon. Gusts of 20 to 25
mph will cause drifting of the fresh and fluffy snow back on to
the roads, so slippery stretches on roads are anticipated through
the afternoon.

High temperatures will be in the upper 20s to lower 30s Saturday
before the onset of the storm. Temperatures dip back into the upper
teens and lower 20s Saturday night, then rebound back to the upper
20s and low 30s Sunday afternoon. Those winds will make it feel
colder than that.

The weather looks fairly quiet after Sunday through the middle of
the week. Daytime highs will likely be in the 30s, so we should see
slow melting of the snow and ice on the roads. Some models are
showing a storm system affecting the southern Great Lakes region
around Thursday. We will keep an eye on this more in coming
forecasts.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 548 PM CST Fri Feb 23 2018

A batch of MVFR cigs covered HIB/DLH/HYR terminals at the start of
the forecast. Expect the MVFR cigs to improve to VFR by 02Z. VFR
at INL/BRD at the outset. The VFR cigs will last through much of
the forecast. However, some BR is expected to form late tonight
and affect HIB/HYR/BRD through late morning with MVFR vsbys. Isold
IFR vsbys at HYR until 17Z. MVFR cigs and IFR vsbys at BRD
beginning at 22Z with the arrival of the next round of snow.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH   4  29  21  29 /   0  20  90  20
INL  -4  29  18  30 /   0  10  90  40
BRD  -3  28  18  28 /   0  60 100  10
HYR   4  34  23  31 /   0  30 100  20
ASX  11  32  25  33 /   0  20 100  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning from 6 PM Saturday to 9 AM CST Sunday for
     WIZ001>004-006>009.

MN...Winter Storm Warning from 9 PM Saturday to noon CST Sunday for
     MNZ011-012-019>021-026.

     Winter Weather Advisory from 6 PM Saturday to 9 AM CST Sunday
     for MNZ025-033-034.

     Winter Storm Warning from 6 PM Saturday to 9 AM CST Sunday for
     MNZ035>038.

     Winter Weather Advisory from 9 PM Saturday to noon CST Sunday
     for MNZ010-018.

LS...None.
&&

$$

UPDATE...GSF
SHORT TERM...JTS
LONG TERM...Grochocinski
AVIATION...GSF



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