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000 
FXUS63 KDLH 062358
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
558 PM CST Fri Dec 6 2019

.UPDATE...
Issued at 558 PM CST Fri Dec 6 2019

Updated for the 00Z Aviation discussion.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 357 PM CST Fri Dec 6 2019

Another day, another clipper system moving through the Northland 
this evening, with light accumulating snow possible.

Chances of light accumulating snow will increase this afternoon, 
persisting through the evening, as a clipper system passes through 
the region. A subtle mid-level shortwave trough and southerly flow 
around a departing high pressure ridge axis will lead to increasing 
low-level warm air advection, which will support these chances of 
snow. Latest SREF and GEFS ensemble guidance depicts a mean QPF 
value of at or below 0.06 inches for this evening, which should 
yield only some small accumulation amounts. The 06.12z NAM model 
soundings indicate the heaviest snowfall should occur from near 
Bigfork, MN, southeast to Hibbing and Two Harbors, as the soundings 
show more of an enhanced isentropic lift signature within a 
saturated dendritic growth zone, so we did increase the snowfall 
amounts slightly. We are still looking at snow accumulations of no 
more than 1.5 inches, with lighter amounts to the north and south of 
this axis of heaviest snowfall. Overnight lows should remain chilly, 
with values in the lower to middle teens.

The clipper system will quickly move out of the region no later than 
sunrise Saturday, leading to a dry, but mostly cloudy day across the 
Northland. Southerly flow will continue Saturday, leading to high 
temperatures slightly warmer than average in the upper 20s to lower 
30s - warmest to the south. Another mid-level shortwave trough with 
an attendant surface low will bring more chances of precipitation 
for Saturday night and early Sunday morning. Precipitation types 
will be more of a challenge to pin down as a warm nose develops. 
This layer of warm air does appear to be unsaturated, with trapped 
moisture under a low-level inversion. This should support some 
freezing drizzle, which may mix in with snow. Accumulations from 
this precipitation should remain quite light, but the freezing 
drizzle may result in some slick road conditions in some spots.

.LONG TERM...(Sunday through Friday)
Issued at 357 PM CST Fri Dec 6 2019

The main concern of the long term is the cold temperatures with only 
a few chances for snow.

A cold front will work across the Northland Sunday and bring a first 
shot of cold Arctic air into the region. Only light snow chances 
with perhaps some freezing drizzle are expected through the day as 
drier air filters in behind the front. An upper-level longwave 
trough will then move into the Northern Plains Sunday night with a 
surface low moving from the Central Plains to the Great Lakes by 
midday Monday. An inverted trough associated with this low will 
move through the region bringing snow for Sunday night and into 
Monday. The 06.12 suite of models have nudged this system a bit 
further to the north with snow now expected to impact more of the 
Northland. Accumulations of 2 to 5 inches are expected roughly along 
and south of MN Highway 210 and through much of northwest Wisconsin 
with lesser amounts to the north.

Low pressure will become established across Hudson Bay Sunday night 
putting the Northland into northwest flow both aloft and at the 
surface. This will result in very cold Arctic air flowing into the 
region. Lake effect snows will also persist after the synoptic snow 
moves out Monday into Tuesday night with the cold air streaming in. 
Some accumulations are expected with this snowfall, but amounts 
remain in question. Wind variations may move the areas of snowfall 
around as well during this period. Additionally, the entire 
Northland will see temperatures fall well below normal, resulting in 
daytime highs in the single digits below zero for most areas Tuesday 
and Wednesday and overnight lows in the teens below zero Wednesday 
and Thursday mornings. Dangerous wind chills will also be possible 
with these very cold temperatures. 

The upper low over Hudson Bay will move east over the latter half of 
the week. A clipper system may bring some light snow during the 
Wednesday night into Thursday period with models then diverging on 
solutions heading into the weekend. A warmup is expected during this 
time, however, as surface winds turn more westerly then 
southwesterly as the upper low pulls away allowing warm air 
advection to set up.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 558 PM CST Fri Dec 6 2019

A fast moving shortwave will bring a period of MVFR visibilities
in light snow and deteriorating ceilings. Ceilings will start out
VFR, but then deteriorate to MVFR, which will then linger through
the remainder of the TAF period. KINL, KHIB and KBRD are likely 
to drop into IFR as well, but not until well after the snow ends.
Have some concerns for this stratus as models are well known for
overdoing the amount of low level moisture and whether it will
create clouds or not. Would not be surprised to see a few hours of
VFR at the terminals generally between 12z and 18z before the next
period of snow begins to move toward the area and increases the
potential for lower cloud bases. 

&&

.MARINE...
Issued at 357 PM CST Fri Dec 6 2019

Winds will be southwesterly at 5 to 10 knots tonight with gusts to 
15 knots as high pressure passes to the south of western Lake 
Superior. South-southwesterly winds will then be in place for 
Saturday at 6 to 12 knots with gusts to 20 knots. A trough of low 
pressure will approach the Northland and lead to increasing 
southwest winds for Saturday night before diminishing and turning 
northerly in the wake of a cold front. Winds of 10 to 20 knots will 
be seen Saturday night into Sunday morning with gusts to 25 to 30 
knots, especially east of Chequamegon Bay on the South Shore and 
Taconite Harbor on the North Shore. A Small Craft Advisory will 
likely be needed during this time period. Waves will generally be 
around 2 feet or less through through Saturday afternoon before 
increasing along the North Shore east of Taconite Harbor to 3 to 6 
feet.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  14  29  26  31 /  60  10  30  20 
INL  15  29  18  24 /  50  20  30  30 
BRD  15  31  26  29 /  10   0  10  20 
HYR  14  33  28  34 /  20  10  20  20 
ASX  15  32  29  35 /  60  10  20  40 

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

UPDATE...LE

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