Area Forecast Discussion
Issued by NWS Duluth, MN

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401
FXUS63 KDLH 152342
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
542 PM CST Thu Feb 15 2018

.UPDATE...
Issued at 532 PM CST Thu Feb 15 2018

Updating Aviation section below for the 00Z TAF update.

&&

.SHORT TERM...(This evening through Friday)
Issued at 341 PM CST Thu Feb 15 2018

High pressure was building across the Northland in the wake of
this morning`s cold front. Shortwave trough was found upstream
and stretched from central Manitoba to the southwest through
northern North Dakota and into Montana and Wyoming. The trough
will swing through the Northland this evening with a brief
increase in cloud cover expected. Clouds will depart as another
shot of Arctic air settles into the region. Nudged overnight lows
a little colder with readings in the -5 to -15 degree range for
most locales, but a little warmer near Lake Superior in northwest
Wisconsin. The surge of Arctic air will keep the boundary layer
mixed overnight and preventing winds from diminishing. Wind chill
values will dip into the -25 to -35 range across our northern
tier of zones overnight warranting another Wind Chill Advisory.
Friday appears sunny with cooler temperatures in the teens and
20s above zero.

.LONG TERM...(Friday night through Thursday)
Issued at 341 PM CST Thu Feb 15 2018

A much more active weather pattern is expected to be in place
across the Upper Midwest and western Great Lakes region for much
of the extended period. As the long wave trof retrogrades
slightly, this will allow for more wave amplification in the part
of the stream originating in the Pacific NW and northern Rockies.

A few snow showers, areas of light snow, or perhaps some freezing
drizzle will be possible Friday night/Saturday as warm advection
and a slow erosion of the latest arctic airmass commences.
However, this is not expected to have significant impacts.

A more potent, rapidly moving confluent flow wave is forecast by
all the various model guidance to traverse the region Saturday
night/Sunday, and chances for accumulating snow appear to be
rather high with this disturbance. While it is expected to be
moving quite rapidly, this wave should be rather strongly
frontogenetical, resulting in rather high snowfall rates for a
short period of time. Most model guidance is in a pretty tight
spread regarding both timing and placement, so confidence is
rather high that a good portion of the Duluth CWA will see enough
snow to shovel and plow. A rough first guess on amounts would be
2-5 inches - with the potential for a bit more where ever the
narrow band of max accumulation eventually sets up.

The forecast then becomes significantly more muddled from later
Sunday into Tuesday. While most available guidance brings another
significant short wave out of the central Plains into the lower
Great Lakes, confidence that the models have the correct solution
on the placement of precip/snow is not necessarily that high just
yet for a couple of reasons. First, there will be significant
convection breaking out in the mid MS Valley region, which could
have a major effect on the various models` handling of this
system. Second, the wave is moving rather rapidly and also de-
amplifying as it moves from the Plains into the Great Lakes,
casting doubt as to the extent of precip placement and duration,
and finally, the primary baroclinic zone and surface low is
detached quite far south for northern MN/WI to receive significant
precip - at least in a climatological sense. It`s certainly
within the realm of possibility that somewhere in the Duluth CWA
(likely the southeast third to half) could receive a second round
of accumulating snow during this time period, but we are not ready
to sound the alarm bells on a high impact event just yet due to
these uncertainties.

For the remainder of next week, we appear to descend into a
colder arctic airmass yet again, although this may be tempered
somewhat as 925/850 temps are not out-of-bounds cold, and getting
into late Feb, days are long enough and the sun angle high enough
to allow for more significant daytime recovery in temps, even if
we get quite cold at night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 532 PM CST Thu Feb 15 2018

VFR conditions as a cold front moves through with some isolated
MVFR stratus though the main concern will be wind shift timing.
Another VFR day for Friday under arctic air.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  -7  19  11  27 /   0   0  40  20
INL -14  19  10  20 /   0  10  30  10
BRD  -5  21  13  27 /   0   0  30  10
HYR  -7  20   9  31 /   0   0  20  30
ASX  -2  22  11  32 /  10   0  20  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Wind Chill Advisory from 9 PM this evening to 9 AM CST Friday
     for MNZ010>012-018>021-025-026.

LS...None.
&&

$$

UPDATE...Wolfe
SHORT TERM...Huyck
LONG TERM...Miller/WFO DLH
AVIATION...Wolfe



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