Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 120617
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1217 AM CST Fri Jan 12 2018

.UPDATE...
Issued at 1217 AM CST Fri Jan 12 2018

Updated aviation section below for 06Z TAF issuance.

Snowfall has wound down to mostly flurries this evening, with only
some lingering lake effect snow for Iron county. Snowfall rates
there have backed off to a half inch per hour or less, and the
radar is completely overshooting the convective tops. So, have
decided to back the warning off to an advisory for the rest of the
night, and end it around 12z.

UPDATE Issued at 414 PM CST Thu Jan 11 2018

A gravity wave induced narrow band of moderate to heavy snow has
developed along the North Shore into parts of Duluth to eastern
Carlton County. This band is further west than typically seen from
a gravity wave and snowfall rates around an inch per hour will be
possible under this band. The RAP continues to suggest drier air
will move in and this band of snow should weaken then dissipate
after 6 pm.

&&

.SHORT TERM...(This evening through Friday)
Issued at 151 PM CST Thu Jan 11 2018

Surface low pressure was centered near or just east of Lake
Superior as of 130 pm. A well defined shortwave was seen on water
vapor imagery moving north out of eastern Iowa. Area radars showed
moderate to heavy snow over parts of northern Wisconsin and
adjacent eastern Minnesota with more moving out of western
Wisconsin and southeast Minnesota. Snowfall rates will be around
an inch per hour at times. The snow also continued to diminish
from the west with light snow or flurries over most of Aitkin and
far western Saint Louis Counties. Most of the snow will diminish
or end around 00Z Friday, except over far northern Wisconsin.
Lake effect snow and a gravity wave induced band of snow should
continue to produce snow along much of the South Shore, all the
way west into northern Douglas County. We extended the Winter
Weather Advisory for Douglas and Bayfield County through 03Z,
after which time enough dry air should move in to shut down the
gravity wave snow. Lake effect snow will continue all night in
Iron/Ashland Counties due to northerly winds. However, the snow
intensity should diminish late tonight as inversion levels lower
and more dry air moves in. Additional accumulation tonight twill
range from 1 to 4 inches with the higher amounts in the Gile,
Montreal, and Hurley areas.

Tonight will be cold with lows 25 to 30 below zero along the
International Border to the single digits below zero over the
South Shore toward Price/Sawyer Counties. There will be enough
wind to create wind chill values from 25 below to around 40 below
over much of northern Minnesota into far northwest Wisconsin. We
will likely issue a Wind Chill Advisory for those areas. There may
be a few wind chills below 40 below but confidence in that
occurring and the need for Wind Chill Warning is low.

Friday will be cold with highs in the single digits above and
below zero. It should be mostly sunny with more lake clouds and
light snow showers in the snowbelt along the South Shore.

.LONG TERM...(Friday night through Wednesday)
Issued at 151 PM CST Thu Jan 11 2018

For the long-term forecast, no major winter storm systems look to be
on the horizon, but temperatures will be much colder compared to
what we experienced earlier this week. The best chances of
widespread snowfall will be on Sunday.

Friday night through Saturday will be dry across nearly all of the
Northland as surface high pressure builds across North Dakota. A
very dry air mass will also be place, so expecting a very cold night
over the region. Decreased overnight lows slightly to better
accommodate the radiational cooling as the consensus blends were a
bit too high. Lows look to drop to between -15 to -30, with the
coldest temperatures over north-central Minnesota. Wind Chill
Advisories will very likely be needed, with perhaps winds chills
pushing warning criteria over Koochiching county. The only
precipitation during this time might be some lake enhanced snow over
the snowbelt of Iron county in northwest Wisconsin as low-level
lapse rates remain steep and favorable northwest flow and little
shear develop.

The best chances for widespread light snow will return Sunday
morning, continuing through Monday morning as a mid-level shortwave
trough dives southeast from Manitoba and over the Northland. Pretty
good large scale lift will be associated with the wave as indicated
by the Thaler QG 850-300 mb omega progs. GFS/NAM model soundings
indicate a fairly deep layer of saturation in the dendritic snow
growth zone, but the isentropic lift within that zone looks to be
minimal, so high snow fall rates should be limited. Given the amount
of QPF from the models, total snow through Sunday night could range
between 1 to 2 inches, with possible higher amounts along the
Gogebic Range of northern Iron county due to lake enhancement. This
lake enhancement over the Lake Superior snowbelt could continue
through the early part of next week. One concern for this lake
enhancement is that the GFS model is bringing a very favorable 1000-
850 mean flow fetch along the length-wise direction of Lake
Superior, which could bring the potential for several inches of lake
effect snow. However, uncertainty still exists as the ECMWF/GEM
models don`t show this, so not putting much stock into the GFS
solution for now, but will need to be monitored.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1217 AM CST Fri Jan 12 2018

Snow has left all of the terminals as of issuace time. However,
MVFR stratus continues at KHYR as lake effect clouds stream off
Lake Superior, and would not be surprised to see some flurries out
of it. Dry air moving into the area should slowly decrease this
cloud cover, but timing is uncertain and have put in a fairly
pessimistic forecast for now. Otherwise, expect VFR conditions at
all terminals for the remainder of the TAF set.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH -13   1 -17   1 /  50   0   0   0
INL -29  -4 -28  -2 /   0   0   0   0
BRD -17   2 -22   1 /   0   0   0   0
HYR  -9   6 -18   2 /  50   0   0   0
ASX  -2   7 -10   4 /  60  20   0  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Wind Chill Advisory until noon CST today for WIZ001-006.

     Winter Weather Advisory until 6 AM CST early this morning for
     WIZ004.

MN...Wind Chill Advisory until noon CST today for MNZ010>012-018>021-
     025-026-033>038.

LS...Small Craft Advisory until 4 AM CST early this morning for
     LSZ121-140>148.

&&

$$

UPDATE...LE
SHORT TERM...Melde
LONG TERM...JTS
AVIATION...LE



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