Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 010221

Area Forecast Discussion
National Weather Service Duluth MN
921 PM CDT Sun Apr 30 2017

Issued at 907 PM CDT Sun Apr 30 2017

There was an area of low pressure with centers in northeast
Kansas and along the southeast Iowa/Northern Missouri border as of
01Z similar to what the models have shown. Rain was falling over
central and southern Minnesota into northern Wisconsin due to
increasing isentropic lift and increasing FGEN. Forcing and
moisture will continue to be on the increase tonight and we will
see the precipitation expand and the current forecast has that
handled well. Temperatures have been cooling this evening and
dewpoints remain rather low with teens and single digits over far
northern Minnesota and lower to mid twenties over our southern
zones. Boundary layer temperatures remain critical in determining
precipitation types and amounts. The new NAM is just coming in now
and we do not have reason to make significant changes to the
forecast at this time. We did lower QPF some over northern
portions of the Iron Range between 06Z-12Z as much of the short
term guidance was in agreement with that. That lowered expected
snowfall tonight a bit...but not real significant.

The precipitation will increase in coverage and intensity around
or shortly after midnight.

UPDATE Issued at 703 PM CDT Sun Apr 30 2017

Please see the 00Z Aviation Discussion below.


.SHORT TERM...(This evening through Monday night)
Issued at 512 PM CDT Sun Apr 30 2017

Significant late-season winter storm is on tap for the next
several days. Low pressure over northeast Kansas this afternoon
will lift northeastward to northeast Ontario by Tuesday morning.
Frontogenetic forcing to the northwest of the low track, along
with steep Theta-E contours and a ribbon of CAPE advecting up the
frontal surface brings the potential for deep convective snow
bands to develop. GFS and NAM cross-sections feature a bullseye of
QG Omega greater than 50 ubar/sec (~185 mb/hr) coincident with
the strong instability. The axis of the strongest vertical motion
and instability will lift from central Nebraska and eastern South
Dakota into the Brainerd Lakes area tonight, and farther northeast
into the Arrowhead by 15Z Monday morning. Several hours of
snowfall rates greater than 1 inch per hour are expected between
09Z in central Minnesota and 18Z in the Arrowhead. Locations along
US Highway 2 and MN Highway 210 from the Brainerd Lakes and Grand
Rapids vicinity to the western portions of the Twin Ports may
experience the highest snow rates and lowest visibility during the
Monday morning commute.

With this forecast package, snowfall amounts have increased once
again due to favorable mesoscale forcing indications. We have
replaced the Winter Weather Advisory with a Winter Storm Warning
for southern Itasca and northern Aitkin Counties to the interior
of the Arrowhead. We have also expanded the Winter Weather
Advisory into the lakeshore zones of southern Lake and Cook
Counties. Areas to the northwest and southeast of the heaviest
snow should pick up more rain than snow, as considerably less
diabatic cooling is expected in those areas. Portions of northern
Douglas and Pine Counties, while not under headlines at this time,
should see an inch or two of snow accumulation.

Snow accumulation may wane Monday morning as snowfall rates
gradually decrease. Given the time of year and high sun angle,
some diurnal heating seems likely. Snow may change back to rain
during the daylight hours and the warmer and stickier snowflakes
should compact and partially melt on all surfaces. Visibility will
likely remain low until snow rates ease during the late morning
and afternoon hours. As the storm system departs the region Monday
night and early Tuesday morning, precipitation will taper off to
showers, all but ending by sunrise.

.LONG TERM...(Tuesday through Sunday)
Issued at 512 AM CDT Sun Apr 30 2017

The large low pressure system that will impact the Northland over
the next couple days, will finally start to pull out of the
region on Tuesday. Some rain and snow showers will linger
throughout the day, especially in the eastern CWA, before high
pressure and a short wave upper level ridge builds across the
western Great Lakes. A weak short wave will then move across
Minnesota on Wednesday, bringing another small chance for light
rain or snow showers from Wednesday into Thursday. Not looking for
much in the way of precipitation, but should be at least some
spotty showers. A massive upper level ridge will continue to build
across the western third of the country on Friday, with generally
dry weather expected across the Northland from Friday into
Saturday. Have added a slight chance of precipitation from Friday
afternoon into Friday evening, as a weak shortwave is expected to
drop southeast across Lake Superior during that time. Temperatures
will climb from Tuesday`s highs in the mid 40s to mid 50s, to the
60s by the weekend. As is climatologically typical this time of
year, we will continue to see colder temperatures near Lake
Superior, with easterly winds prevailing. Temperatures there
should be limited to the 40s.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 703 PM CDT Sun Apr 30 2017

A strong low pressure will lift northeastward from the Mid
Mississippi River Valley tonight, into eastern Wisconsin by Monday
afternoon. This will gradually spread precipitation into all
terminals tonight, with the only exception being KINL. KINL should
remain on the northwestern fringe of the precipitation shield.
Winds will remain gusty through the forecast due to the tightening
pressure gradient from the incoming low per the latest forecast
guidance. As the lower levels moisten, expect ceilings to lower
from VFR to IFR eventually. There are some hints of LIFR ceilings,
but have held off for now as confidence is low in that occurring
at this point. Expect visibilities to drop to MVFR/IFR with some
periods of LIFR. Uncertain on the exact timing of LIFR at this
point, so have held off from including in the latest TAF set.


DLH  33  35  32  51 / 100 100  70  20
INL  33  42  34  55 /  20  40  30   0
BRD  33  39  35  56 / 100 100  50  10
HYR  37  37  32  49 / 100  90  80  30
ASX  36  38  32  49 / 100 100  80  40


MN...Winter Weather Advisory until noon CDT Monday for MNZ018-025-033-

     Winter Storm Warning until 7 PM CDT Monday for MNZ019-026-035-

     Winter Weather Advisory from 4 AM Monday to midnight CDT Monday
     night for MNZ011-020-021.

     Winter Storm Warning from 4 AM Monday to midnight CDT Monday
     night for MNZ012.

LS...Small Craft Advisory until 11 AM CDT Tuesday for LSZ121-140>148.



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