Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 130521
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1221 AM CDT Fri Apr 13 2018

.UPDATE...
Issued at 1220 AM CDT Fri Apr 13 2018

Updating Aviation section below for the 06Z TAF update.

&&

.SHORT TERM...(This afternoon and evening)
Issued at 345 PM CDT Thu Apr 12 2018

A cold front was dropping south through northern Minnesota at
19Z/2pm. Skies were clearing behind the front. Ahead of the front,
plenty of cloud cover was found over the rest of northeast Minnesota
and northwest Wisconsin. Clouds appear to be thinning as frozen
lakes are showing up via visible satellite. Mid level and surface
ridging weer also building across the forecast area. Temps were
running below normal.

The aforementioned ridging remains over the region tonight. Late
tonight, the first piece of energy associated with the large storm
system for the weekend, lifts toward the southern edge of the
forecast area. There are some minor model differences with the
handling of this energy and how it affects the region. Have some low
chance pops across the southern tier to balance the differing
solutions, especially between the short term hires and the longer
term deterministic models.

.LONG TERM...(Friday through Thursday)
Issued at 345 PM CDT Thu Apr 12 2018

The main focus for the long term is the strong spring storm
system moving through the region Friday and this weekend. A mix
of rain and snow is expected with this system, mainly across the
southern half of the Northland.

A potent storm system will move from the Rockies through the
Midwest and into New England this evening through midday Monday.
A trough of low pressure will be located along the Rockies Friday
morning with a 100 kt jet streak rounding the base of the trough
early in the day. The surface low over the Central Plains will
continue to intensify through the day. A broad area of high
pressure over the Canadian Prairies on Friday and slide eastward
into the Canadian Shield over the weekend. With high pressure to
the north and dry easterly flow wrapping into the low to the
south, precipitation will struggle to move northward into our
southern zones. Have slowed the northward progression of rain and
snow showers on Friday with this forecast. The eastward motion of
the system will slow down on Friday as the storm occludes and the
upper trough closes off. The best chance of accumulating snow
will remain focused over our southern zones, south of Minnesota
Highway 210, including the I-35 corridor, and all of northwest
Wisconsin.

The tight pressure gradient between the low to the south and the
high pressure to the north will result in strong east to
northeast winds of 15 to 30 mph with gusts as high as 45 mph
Friday through Sunday. The strongest winds are expected Saturday
into early Saturday evening. The combination of strong winds and
falling snow will result in reduced visibility wherever snow is
falling. Long fetch over western Lake Superior will support
sizable waves all along the Lake Superior shoreline, and
especially from Silver Bay to the Twin Ports and east to Saxon
Harbor. Lakeshore erosion and damage to docks and other
structures is not out of the question. Locations which are
exposed to northeast winds are at the greatest risk. The strong
winds will also pose a hazard to high-profile vehicles,
especially on bridges including the Blatnik and Bong bridges in
the Twin Ports.

The storm system will gradually weaken beginning Saturday evening
as the surface low pushes into Indiana. The ECMWF keeps
precipitation affecting the Northland through Sunday and into the
work week while the GFS and GEM taper off snow and rain showers
on Sunday. Have leaned toward the drier guidance at this time,
with lake effect snow showers possible into Monday morning in the
northwest Wisconsin snowbelt.

The long-duration snow event will bring snow accumulation of 6 to
as much as 10 inches to our southern zones over a 56-hour period.
With no 12 or 24 hour forecast period close to our warning
thresholds, have held off on any winter headlines with this
forecast package. We will likely need a long-duration winter
weather advisory, but wanted to hold off for now. Lakeshore flood
headlines may also be required.

High pressure returns for Monday and Tuesday bringing quieter
conditions to the region. Another area of low pressure may
develop in the Plains on Tuesday and migrate northeastward into
the Great Lakes by Thursday morning. That system may bring
another shot of wintry mixed precipitation to the Northland, but
confidence is low at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1220 AM CDT Fri Apr 13 2018

The Northland was between high pressure centered well northwest
of the area and low pressure centered eastern Colorado and western
Kansas. The low will move slowly northeast through the period. As
pressures fall ahead of the low and the gradient tightens winds
will be increasing especially around Lake Superior. Lingering FGEN
forcing over southern portions of the Northland may cause some
very light drizzle or possibly freezing drizzle into the early
morning hours but impacts should be minimal and miss KBRD/KHYR.
Mainly VFR conditions were occurring as of late evening and that
should continue for most areas tonight. Ceilings will gradually
lower through Friday, especially over southern areas. Most of the
guidance keeps the bulk of the precipitation on Friday south of
the TAF sites except for KHYR. Boundary layer temperatures will be
warm enough for light rain initially but as temperatures cool
more snow is expected.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  28  33  22  28 /   0  30  20  20
INL  18  35  16  37 /   0   0   0   0
BRD  31  37  24  33 /  10  40  20  30
HYR  30  36  24  31 /  10  60  40  50
ASX  26  34  23  29 /   0  40  30  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Gale Watch from this evening through late Saturday night for
     LSZ121-140>148.

     Small Craft Advisory from 4 AM early this morning to 10 PM CDT
     this evening for LSZ121-140>148.

&&

$$

UPDATE...Melde
SHORT TERM...GSF
LONG TERM...Huyck
AVIATION...Melde



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