Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 212020

Area Forecast Discussion
National Weather Service Duluth MN
220 PM CST Sun Jan 21 2018

.SHORT TERM...(This evening through Monday night)
Issued at 152 PM CST Sun Jan 21 2018

The main story continues to be the heavy snow potential over our
northwest Wisconsin counties in addition to icing potential along
the south shore and head of the lakes area of Lake Superior.

Current conditions show strong reflectivities on radar to our
south along an fgen band, but a thick layer of dry air seems to be
absorbing the precip before it hits the ground. It wouldn`t be
surprising if a few raindrops started falling out of that.

Patchy freezing drizzle is possible along the head of the lakes
area tonight, but significant precipitation shouldn`t begin until
the main system gets closer.

The well-advertised winter storm continues to be well modeled
with the 12Z euro jogging the storm a little back to the
northwest. Due to the tight gradient in expected snowfalls a
slight shift in track is very important in the ultimate snowfall
accumulations from this system. Right now, the heaviest snow
appears to pile up southeast of a line extending from Hayward, WI
to Ironwood, MI where 6 to 10 inches are possible. Another
potential impactful weather event form this storm will be the
potential for freezing drizzle along the south shore of Lake
Superior. Strong northeast winds circling into the low pressure
center will bring moisture rich air into a saturated, albeit thin,
boundary layer. It appears the depth of the layer will be
sufficient enough to produce icing, but the main question is to
how much. Opted to issue a winter storm warning for the icing
potential in the counties adjacent to Lake Superior east of
Douglas County. This will be something to keep an eye on in
subsequent model runs. Despite not meeting ice storm warning
criteria or winter storm warning for snow criteria - the
combination of ice followed by snow could be quite impactful, so
opted to raise the warning flag on this potential hazard.

.LONG TERM...(Tuesday through Sunday)
Issued at 152 PM CST Sun Jan 21 2018

Quiet through much of the extended with lake effect snow chances
early on Tuesday, and Wednesday. Late in the week low pressure
will move in from the Central/Northern Plains bringing widespread
chances of precipitation to the CWA.

Initially in the extended low pressure will lift northeastward from
the central Great Lakes into the eastern Great Lakes on Tuesday.
Flow aloft will remain favorable early on Tuesday, which will allow
lake effect snow showers to persist during the morning hours. During
the afternoon and evening drier air will move in from the northwest
as high pressure nudges in from Hudson Bay. Expect dry conditions
Tuesday afternoon and evening. Temperatures will be cooler on
Tuesday due to northwesterly cold air advection. Highs range from
the teens along the International Border, to the mid 20s in southern
portions of the area. Tuesday night lows will generally be in the
single digits above zero.

A shortwave trough will dig southeastward from central Saskatchewan
late Tuesday night into northern Wisconsin by Wednesday evening.
Flow aloft will shift to a southeasterly direction, this combined
with the trough digging in and orographic lift will bring chances of
snow along the north Shore of Lake Superior. Increased precipitation
chances as the latest GFS/NAM seem to have the best handle on the
situation. This may bring some light snowfall accumulations. Highs
will generally be in the 20s on Wednesday.

High pressure will build eastward from the the Pacific Northwest on
Wednesday into the Northern Plains on Thursday. This will bring a
period of dry weather Wednesday night through early Friday.
Temperatures will be on the rise as warm air advects in aloft as 850
hPa flow becomes southwesterly. Expect the warmest readings of the
extended on Friday with highs ranging from the mid 30s to the mid
40s. Precipitation chances return late on Friday into Saturday as a
trough digs into the Central/Northern Plains, which will develop
another Colorado low. At this point in time precipitation will
initially begin as rain before changing over to snow on Saturday.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1202 PM CST Sun Jan 21 2018

The main concerns over the next 6 hours is IFR/MVFR stratus
slowly moving southward across northern Minnesota as a front moves
south. This is fairly well depicted by the latest NAM/RAP, so
have heavily leaned on this guidance in the TAFs.

Tonight through Monday morning, the front will slide southward and
move IFR/MVFR stratus into other terminal sites. In addition,
winds will shift to a northeasterly direction ahead of the
incoming system, which will advect moisture inland from Lake
Superior. This will aid in lowering ceilings to LIFR levels at
DLH and HYR. In addition, expect a prolonged period of freezing
drizzle with some snow mixing in at DLH, as forecast soundings
keep a saturated supercooled liquid layer in the lowest 2000 ft.
Guidance has continued to shift the incoming system further
southeast and slower, so HYR may remain on the periphery of the
snowfall. Future TAFs may need to remove the mention of snow
altogether at HYR. Regardless of the system track, expect
MVFR/IFR conditions Monday morning with ceilings between 500-2000
ft with increasing winds as the pressure gradient tightens.


DLH  22  25   9  21 /  20  30  20   0
INL  12  22   0  17 /   0   0   0   0
BRD  23  29  12  24 /  10  10   0   0
HYR  26  30  15  25 /  30  80  70  10
ASX  25  28  17  23 /  30  70  70  20


WI...Winter Storm Warning from 6 AM Monday to midnight CST Monday
     night for WIZ002>004-008-009.

     Winter Weather Advisory from 6 AM Monday to midnight CST Monday
     night for WIZ001-006-007.



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