Area Forecast Discussion
Issued by NWS Duluth, MN

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382
FXUS63 KDLH 190949
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
349 AM CST Thu Jan 19 2017

.SHORT TERM...(Today through Friday)
Issued at 345 AM CST Thu Jan 19 2017

Fog has developed across portions of the Northland this morning as a
warmer and more moist airmass has made its way into the region. The
warmer air has lead to some snow melt, lending further moisture for
fog. Some fog this morning is expected to become dense in some
locations, so decided to issue a Dense Fog Advisory for the southern
half of our forecast area through 15z this morning. Some fog may
linger later in the morning, but shouldn`t be as dense.

Most of today will remain dry, except for some developing areas of
drizzle/freezing drizzle/fog this evening and overnight as a push of
mid-level positive vorticity advection and weak 700-500 mb layer
frontogenetical forcing translates from the south. Another day of
above freezing temperatures is expected again today across the area,
with highs in the upper 30s and lower 40s.

A better push of FGEN and 500 mb isentropic lift moves into the
forecast area Thursday night and Friday morning, which will bring
increasing chances of a wintry mix to the area through the day
Friday. Freezing rain, sleet, and snow are all possible, depending
on the thermal profile. Any snow and ice accumulations that
occur will be very light in nature. However, there may be some
slick spots on untreated roadways during this time. Precipitation
type should be mostly light rain by Friday afternoon,
transitioning back to brief wintry mix, and then all snow by
Friday night.

.LONG TERM...(Friday night through Wednesday)
Issued at 345 AM CST Thu Jan 19 2017

A mild and wet period through the weekend into early next week, with
a chance for a more substantial storm and a return to slightly
colder temperatures by mid-week.

On the synoptic scale a somewhat active pattern across North America
with a broad upper low lifting into the upper Midwest over the
weekend, getting stuck and slowly dissipating as a stronger upper
low ejects out of the southern High Plains into the southeast US. To
the north, a broad ridge builds over Hudson Bay with little in the
way of arctic air even as north as the northwest Territories. With
the upper low getting essentially stuck in the flow over the upper
Midwest, a period of mild temperatures and light precipitation is
expected through early next week. Temperatures at the surface and
aloft will be very warm, with surface temperatures likely driving
the precipitation type much of the time. Ice loss aloft may be an
issue, and with a thin warm layer between 800mb and 925mb depicted
on the NAM, a period of freezing rain is possible. However, most
guidance is a bit cooler and thus, when precipitation is ongoing and
temperatures at the surface are below freezing, precip type should
be snow. Occasional freezing drizzle is still possible at times,
which could result in minor ice accumulations, but through the
weekend  generally little snow/ice is expected. Highs in the upper
30s to low 40s Saturday through Monday, lows upper 20s to low 30s.

Late Monday into Tuesday a mid-level longwave ridge builds across
the central and southern Plains east into the lower Mississippi
River Valley. Then another upper low lifts from the central Great
Plains towards the Great Lakes region. The latest guidance keeps the
bulk of the large-scale lift and precip focused south of the
Northland, but there is still enough uncertainty across ensemble
guidance to suggest a more northerly track is at least possible.
However, because of the deepening low to the south, colder air will
advect south across the region leading to at least some light
precipitation and colder temperatures, especially as the low lifts
east towards the lower Great Lakes on Wednesday. Temperatures will
be colder aloft but at the surface temperatures will remain mild
with highs in the 30s Tuesday and Wednesday, lows in the 20s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1147 PM CST Wed Jan 18 2017

Will see fog and low level stratus impact all terminals overnight
into Thursday as a ridge axis slides through the region. Still
uncertain how widespread the stratus will be as the NAM/GFS are
more pessimistic than the current forecast. Think that the latest
RAP/HRRR have the best handle on the current situation, so leaned
heavily on this guidance for the forecast.

Southwesterly warm air advection will bring an influx of low
level moisture and warmer temperatures through the period. This
will aid in melting snowfall, which will bring additional low
level moisture. Based on this, was pessimistic in the latest TAF
set with IFR ceilings through much of the forecast with
visibilities ranging from MVFR to LIFR. Late in the TAF period a
cutoff low will lift northward into southern MN. The additional
lift from the cutoff will bring freezing drizzle/drizzle to all
sites. Think it may not be until after 06Z where freezing
drizzle/drizzle begins to impact KHYR, as the best lift is further
to the west.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  38  33  37  31 /  10  40  60  50
INL  39  28  39  28 /   0  10  40  70
BRD  38  31  38  31 /  10  30  50  40
HYR  42  32  40  34 /   0  60  60  30
ASX  43  32  40  32 /   0  50  70  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Dense Fog Advisory until 9 AM CST this morning for WIZ001>004-
     006>009.

MN...Dense Fog Advisory until 9 AM CST this morning for MNZ025-
     033>038.

LS...None.
&&

$$

SHORT TERM...JTS
LONG TERM...JJM
AVIATION...WL



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