Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 281203

Area Forecast Discussion
National Weather Service Duluth MN
603 AM CST Tue Feb 28 2017

.SHORT TERM...(Today through Wednesday)
Issued at 501 AM CST Tue Feb 28 2017

Tough forecast this morning with a variety of precipitation types
possible today. Surface low pressure was centered over southeast
Nebraska with an inverted trough and baroclinic zone extending
northeastward across central Minnesota and into Northwest
Wisconsin. A cool front arced from southern South Dakota across
the Twin Cities Metro to near Pine City, where an inflection point
in the flow was located, and a warm front continuing northeast
across northern Wisconsin and southern Lake Superior. A wintry mix
of rain and snow was located portions of central and northeast
Minnesota and northwest Wisconsin at 4 AM. Road temperatures may
be below freezing in some spots, which could result in ice
accretion in areas receiving rain. The wintry mix is expected to
change to all snow within a few hours of onset at any one location
north of the front as diabatic cooling brings the low-level
thermal profile below freezing. Along and south of the front, a
wintry mix will likely continue through 6 AM.

Isentropic upglide over the frontal surface and a ribbon of
impressive mid-level FGEN seems to match well with radar returns
and surface observations this morning. The high resolution models
and the RAP seem to have the best inter-model agreement with the
GFS/GEM/NAM12 close behind. The best forcing for ascent is
forecast to drift southeastward this morning and strengthen from
Pine County across Burnett, Douglas, and Bayfield Counties by mid-
morning. Even with limited moisture, expect precipitation rates to
increase through the morning along the I-35 corridor into the
Twin Ports and up the North Shore. Modest warm air advection
between 850 mb and the surface will support a rain/snow mix
eventually changing to rain over portions of northwest Wisconsin
today. The surface warm front will lift northward through the Twin
Ports with the potential for mixed precipitation expanding north
by noon. Surface temperatures upstream over east-central Wisconsin
are above freezing, as are temps along our southern Wisconsin
zones. Think the potential for freezing rain is limited to a short
window of an hour or so after precipitation begins. The
temperature profile supports a rain/snow mix, but pavement
temperatures in northwest Wisconsin are still below freezing.
Think those pavement temperatures will rise above freezing pretty
quickly, ending the freezing rain threat.

The surface low will advance northeastward into southern
Wisconsin by tonight pulling the baroclinic zone/inverted trough
east of the forecast area. The strongest forcing for ascent will
push eastward, as well, but a convergence zone may set up over
northern Wisconsin with winds over Lake Superior strengthening. A
combination of lake-effect processes and convergences will keep a
chance of light snow in the picture through this evening. Several
models point to a trough of warm air aloft developing from the
Twin Ports to Mora and arcing northeast over northern Wisconsin. A
second area of isentropic upglide may develop over north-central
Minnesota. Deterministic and ensemble models all carry a potential
for a short burst of light snow overnight. With the departing
moisture and partial clearing, think any precip will sublimate
before reaching the ground. Trended toward a dry forecast
overnight for north-central Minnesota and Slight/Chance POPs for
the North Shore through Brainerd and northwest Wisconsin.

A fast-moving shortwave is forecast to advance across northern
Minnesota Wednesday afternoon. Moisture and lift will be limited,
but there is another slight chance of snow showers entering our
west after the noon hour.

.LONG TERM...(Wednesday night through Monday)
Issued at 501 AM CST Tue Feb 28 2017

No strong storm systems are expected through the extended period
but there will be several disturbances that bring a chance for
light precipitation at times.

The period will start out with northwest flow and a shortwave
will continue through the area Wednesday night, with another
stronger wave diving through the Northern Plains Wednesday night
into Thursday. There may be some light snow or flurries in spots
Wednesday night with a better chance for lake effect snow showers
along the snowbelt of Ashland and Iron Counties. Conditions look
most favorable for snow accumulation along portions of the South
Shore Wednesday night into Thursday morning with the best
combination of fetch, low-level instability, and deeper moisture
present. Colder air moves over the region later Wednesday night
through Thursday leading to even greater low-level instability.
However, this is offset by drier air and low-level flow that backs
some to more northwest during the day Thursday. Some additional
snow accumulation will be possible but significant snowfall looks
unlikely Thursday afternoon into Friday. A surface high will move
into the Red River Valley by early Thursday evening then continue
east Thursday night to eastern Minnesota/western Wisconsin by 12Z
Friday. This high will keep most other areas dry through Friday.
Highs Thursday will range from around 20 along the International
Border to 25 to 30 from the Brainerd Lakes into northwest
Wisconsin. We lowered temperatures Thursday night with the high
moving through and light winds expected. Lows will be from 5 below
to 10 below in far northern Minnesota to 5 to 10 above in the
Brainerd Lakes region into northwest Wisconsin. Locally colder
temperatures will be possible.

As the high shifts east of the region on Friday, warm air
advection will commence and then strengthen Friday night. An area
of light snow will be possible Friday night due to the warm air
advection but any accumulation will be light.

Most areas will be dry and mild on Saturday with highs from 35 to
40 in the Arrowhead to 45 to 50 in our southern counties. An area
of low pressure tracking well north of the International Border
will drag a weak front through the Northland Saturday night. There
may be some mixed precipitation as a result but both the
GFS/ECMWF suggest any precipitation will be quite light and
spotty. Any lingering precipitation will come to an end on Sunday
as an upper level ridge moves in. Highs will again be from 35 to
40 in the Arrowhead to 45 to 50 south.

A stronger shortwave will affect the region on Monday and
temperatures will remain high enough for a wintry mix or just rain
in southern areas. A surface low will deepen Sunday night into
Monday but is forecast to track along or north of the
International Border keeping the higher precipitation amounts
north of the Borderland.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 603 AM CST Tue Feb 28 2017

Low pressure was centered along the Iowa and Nebraska border early
this morning with in inverted trough and frontal boundary
extending well north into far eastern Minnesota and far western
Wisconsin. Areas of light snow will be possible north and west of
the frontal boundary over northeast Minnesota with rain or a mix
rain, snow, or light freezing rain over northwest Wisconsin. The
precipitation will decrease in coverage this afternoon into
tonight from west to east as the low and front move further north
and east. Much of the guidance suggests MVFR and IFR ceilings
will increase over most of the area. However, VFR conditions will
become more widespread over far northern Minnesota later this
afternoon into tonight.


DLH  35  15  26  10 /  80  30  10  20
INL  27   4  23   4 /  10   0  20  10
BRD  36  19  32  13 /  80  10  20  20
HYR  41  21  29  14 /  60  40  20  10
ASX  37  21  26  14 /  80  60  30  30




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