Area Forecast Discussion
Issued by NWS Duluth, MN

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064
FXUS63 KDLH 212143
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
343 PM CST Wed Feb 21 2018

.SHORT TERM...(This evening through Thursday)
Issued at 342 PM CST Wed Feb 21 2018

An area of high pressure over the Upper Midwest this afternoon
will shift into eastern Canada by Thursday afternoon. Expect a
clear, calm, cold night across the Northland. Leaned on the colder
model guidance considering the ripe conditions for radiational
cooling overnight. The fresh snowpack also helps. Overnight lows
will be anywhere from several degrees below zero to approaching 15
below zero.

The Northland will get southerly return flow Thursday in the wake
of the departing high. There will be increasing cloud cover from
the south because of our next approaching snow system. Highs
should reach the middle to upper 20s. Snow will begin to spread
into areas from central MN into northwest WI during the middle to
late afternoon. The snow should be very light until the evening
when deeper forcing and saturation kicks in.

.LONG TERM...(Thursday night through Wednesday)
Issued at 342 PM CST Wed Feb 21 2018

A fast-moving inverted trough Thursday night and Friday and a
potential winter storm Saturday night through Sunday are the main
concerns for the long term.

A potent and fast-moving shortwave trough and associated inverted
surface trough will move through the Upper Midwest Thursday night
and Friday. The past several runs of the deterministic models and
SREF plumes have incrementally raised precip amounts with this
wave. A trend which has continued with the 12Z runs. Strong
frontogenesis will accompany the trough, which will likely result
in a band of 1 inch per hour snowfall. The NAM, GFS, and GEM all
feature different orientations of the best forcing and speed of
translation across the forecast area. While we have high
confidence in mesoscale banding and enhancement, the location and
duration are uncertain. Thermal profiles from the I-35 Corridor
east across northwest Wisconsin suggest loss of ice crystals from
the pre-dawn hours Friday morning through the afternoon. Have
continued the earlier forecast trend of including a mix of snow
and freezing drizzle where temperatures warm above ice nuclei
activation. A glaze up to a few hundredths of icing is possible.
Given the lingering questions, but high confidence a band of heavy
snow, mixed with icing potential, we issued a combination of
Winter Weather Advisory and Winter Storm Watch. The watch area
highlights the best potential for more than 6 inches of snow in a
12 hour period, with lower amounts in the advisory areas.

Attention then shifts to this weekend and a potential winter
storm. The GFS has been fairly consistent in handling this system
during the past 4 runs and the ECMWF features a Colorado Low
lifting through Wisconsin into northeast Ontario Friday night
through Sunday night. With continuing dissemination issues at NCEP
today, we were unable to dig into the particulars of the ECMWF
for this forecast and relied on MSLP ensemble mean, spread, and
standard deviation plots to compare with the GFS and GEM. The GEM
is less organized with the storm system and shunts the main
moisture stream eastward into the Ohio Valley with a weaker low.
The GFS, however, brings the Colorado Low through Wisconsin with a
robust precipitation shield moving through eastern Minnesota and
Wisconsin. The ECMWF solution seems to lean toward the more
organized side, but a little farther east than the GFS. If the
GFS/ECMWF type solution comes to pass, we will be looking at
another 6 or more inch snow event this weekend, while the GEM only
brings a few to several inches. There is also a question of
precipitation types with that system. Warm air is forecast to wrap
into the low, which may lead to a period of mixed precipitation
over northwest Wisconsin. Anyone with travel plans this weekend is
encouraged to keep up with the forecast through the rest of the
week.

The active pattern continues into next week with a weak wave
moving through the region Monday night through Wednesday. The GFS
brings a more organized clipper across the Canadian Prairies and
into northwest Ontario Monday night and Tuesday while the GEM
features a slower progression. With the weak wave moving through
the region, another round of light snow is possible Tuesday and
Wednesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1143 AM CST Wed Feb 21 2018

High pressure will continue to be the main story during this
period. VFR conditions will continue this afternoon into tonight.
Visibility may drop into the MVFR range overnight at INL and HIB
as patchy fog develops. Look for conditions to return to VFR and
continue through 18Z Thursday. An area of low pressure will
approach later in the afternoon which will bring in lower ceilings
and light snow to BRD and HYR after 18Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  -3  24  18  30 /   0  30  90  40
INL -11  28  12  28 /   0   0  70  40
BRD  -5  24  17  30 /   0  80  90  20
HYR  -7  29  22  33 /   0  50  90  40
ASX  -2  30  22  34 /   0  20  90  50

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 3 PM Thursday to noon CST Friday
     for WIZ006>008.

     Winter Weather Advisory from 6 PM Thursday to 3 PM CST Friday
     for WIZ002-003.

     Winter Storm Watch from Thursday evening through Friday
     afternoon for WIZ001.

MN...Winter Weather Advisory from 3 PM Thursday to noon CST Friday
     for MNZ025-033>036-038.

     Winter Weather Advisory from 6 PM Thursday to 3 PM CST Friday
     for MNZ011-018-026.

     Winter Storm Watch from Thursday evening through Friday
     afternoon for MNZ012-019>021-037.

LS...None.
&&

$$

SHORT TERM...Grochocinski
LONG TERM...Huyck
AVIATION...Huyck



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