Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 142354
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
654 PM CDT Sat Apr 14 2018

.UPDATE...
Issued at 654 PM CDT Sat Apr 14 2018

Snow has been lifting north through northern Wisconsin and parts
of central and northern Minnesota. Calls to spotters reveal
anywhere from 1 to 4 inches has fallen across southern portions of
Washburn and Sawyer Counties. Strong lift was moving into that
area and is forecast to continue into this evening. We increased
snowfall totals through this evening to account for the latest
radar and observations.

The lake effect snow band that was affecting the Twin Ports has
temporarily diminished but as increasing lift and moisture advect
north, it should redevelop in some form overnight. We`ll continue
to monitor trends through the night and adjust snow totals as
needed.

The Wind Advisory will expire at 7 pm but that is when the Winter
Storm and Blizzard Warnings will go into affect. The wind will
remain strong into tonight and details on the wind will be in the
Winter Storm/Blizzard Warnings.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 259 PM CDT Sat Apr 14 2018

While the wind begins to gradually decrease tonight the snow will
begin from south to north. We have made adjustments to the snowfall
forecast to generally increase snowfall amounts, and even when using
what might be a too low (too "wet") of a snow-to-liquid ratio and a
very middle-of-the-road QPF forecast (not much above the median of
available guidance, both inclusive or exclusive of the outlier ECMWF
with its high values) this looks to be a historic storm for
northwest Wisconsin. Specifically, for Bayfield and Ashland counties
this storm could produce blizzard-like conditions for a period of 8-
12+ hours causing travel to be nearly impossible.

Blizzards are extremely rare in the Northland and especially so in
northwest Wisconsin. There has only been one instance of observed
blizzard conditions in Ashland and Bayfield counties since 2000 -
April 10, 2008. However, there is such a strong signal for both a
prolonged period of heavy snow and very strong northeast winds that
we have high enough confidence to issue a blizzard warning. We have
kept the initial issuance limited in area to where conditions will
be worst, but elsewhere across the south shore and even in the Twin
Ports conditions could be blizzard-like. (As a reminder, a blizzard
is defined as 3+ hours of 35+ mph winds and falling or blowing snow
causing < 1/4 visibility. Technically there is no requirement for
falling snow, but in this case... there will be plenty of falling
snow for this blizzard.)

Confidence in snowfall amounts on the western edge of the storm is
below normal, especially with possible lake enhancement with the
strong northeast winds and colder air aloft. Looking at winds in the
low levels this would typically be too much shear to cause lake
effect bands, but given low level convergence has produced light
lake effect snow all day today at the head of the lake, confidence
is higher that the winds and lake will help to produce narrow
locally heavy bands of snowfall. This is a challenge to communicate
since parts of Duluth might see over a foot while other areas barely
reach six inches, but we decided to expand the warning into
Carlton/Southern St Louis county because of this possibility. We
also added a winter weather advisory to the MN Arrowhead, with the
highest snowfall amounts expected along the north shore and
decreasing westward.

In addition to increased snowfall amounts the timing of this
forecast has also slowed just a tad, which means snow may not get
going until the morning for the Twin Ports and across the MN
Arrowhead. Snowfall will linger into Sunday night, but come quickly
to an end in most locations late Sunday night. Thus, there will
probably be limited impacts to travel come Monday morning. The
exception will be along the south shore where the blizzard
conditions may cause a longer recovery time due to the blowing and
drifting snow.

.LONG TERM...(Sunday night through Saturday)
Issued at 259 PM CDT Sat Apr 14 2018

The historic Spring snow storm will continue to impact the Northland
into Sunday night and Monday, but little accumulation is expected
after 12Z Monday. The exception will be along the south shore of
Lake Superior, where another 1 to 3 inches of snow will be possible
on Monday. The surface low will move into Quebec by 00Z Wednesday,
while high pressure moves in behind the departing storm system on
Tuesday. Clouds will gradually decrease in the west on Monday, but
most of the CWA will need to wait for sunshine until Tuesday. Highs
will range from the 30s to around 40 on Monday, with widespread
lower to middle 40s by Tuesday. This should lead to some pretty
decent melting across the CWA. The ECMWF and GFS both agree that a
low pressure system will move through the central Plains on
Wednesday, but the GFS is further north and east with the system by
00Z Thursday. The GFS solution would bring a bit more precipitation
to the CWA than the ECMWF, with the most precipitation expected in
our southern tier of counties. At this point, we will have chance
pops across the area on Wednesday, with likely pops just south of
the CWA. As the system pulls east of the region on Thursday and
Friday, we will see a return to some sunshine for Friday. The
warmest temperatures of the week are expected on Friday and
Saturday, with temperatures ranging from the mid 40s to lower 50s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 654 PM CDT Sat Apr 14 2018

Moderate to heavy snow was moving north into southern parts of the
Northland and it will gradually work its way north overcoming
drier air in place. Heavy snow will affect KHYR and snow will
develop in KDLH/KBRD later tonight but will likely hold off until
late tonight at KHIB. Conditions will deteriorate as the snow
develops with IFR/MVFR over southern areas with a period of LIFR.
VFR conditions will continue far north. Strong winds will
continue, especially around Lake Superior. &&

.PRELIMINARY POINT TEMPS/POPS...
DLH  22  26  20  35 /  70  90  60  20
INL  17  34  20  39 /   0  30  30  20
BRD  22  32  20  40 /  60  60  40  10
HYR  22  27  22  34 / 100 100  60  30
ASX  22  27  23  34 / 100 100  70  50

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Lakeshore Flood Warning until 10 AM CDT Sunday for WIZ001>004.

     Wind Advisory until 7 PM CDT this evening for WIZ001>003.

     Winter Storm Warning until 7 AM CDT Monday for WIZ001-004.

     Winter Storm Warning until 7 PM CDT Sunday for WIZ006>009.

     Blizzard Warning until 7 AM CDT Monday for WIZ002-003.

MN...Winter Weather Advisory from 7 AM Sunday to 7 AM CDT Monday for
     MNZ011-012-019>021.

     Lakeshore Flood Warning until 10 AM CDT Sunday for MNZ020-037.

     Wind Advisory until 7 PM CDT this evening for MNZ020-037.

     Winter Storm Warning until 7 AM CDT Monday for MNZ037.

     Winter Storm Warning until 7 PM CDT Sunday for MNZ038.

     Winter Weather Advisory until 7 PM CDT Sunday for MNZ036.

LS...Gale Warning until 10 PM CDT Sunday for LSZ121-140>148.

&&

$$

UPDATE...Melde
SHORT TERM...JJM
LONG TERM...DAP
AVIATION...Melde



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