Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 132212

Area Forecast Discussion
National Weather Service Duluth MN
412 PM CST Mon Feb 13 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 412 PM CST Mon Feb 13 2017

A mid-level shortwave trough, with an associated surface cold
front will support chances of precipitation this evening and
overnight for the northern portions of our forecast area. As of
2:30 PM CST this afternoon, some light returns can be seen on the
regional radar mosaic. However, analysis of the model soundings
indicate a layer of dry air near the surface, which should
suppress precipitation from reaching the surface. Thus, reduced
the chances of precipitation from the morning package. The only
ground truth received from the west was one ASOS site that
reported only a trace of precipitation. For now, kept only slight
chance POPs through this evening and most of the overnight period.
The latest RAP model soundings are indicating a lack of deep
saturation through the column, with some low-level saturation
present, indicating more of a drizzle/freezing drizzle
precipitation type tonight and Tuesday morning, eventually
transitioning to more snow as cold air advection enhances behind
the front late Tuesday morning. Where freezing drizzle occurs is
where some slick roads are more likely to develop. The low-level
cold air advection will bring colder 925 mb air during the day
Tuesday with values between -2 to -4 degrees C Tuesday morning
dropping to -7 to -9 degrees C by Tuesday evening for DLH.

Northwesterly winds will become gusty again Tuesday as surface
pressure gradient tightens and up to 50 knots of 850 mb level
winds advances, with winds possibly reaching up to 25 MPH at the
surface, with some isolated higher gusts. As the winds veer from
the northwest after FROPA, 1000-850 mb will become more supportive
for lake-effect snow along the Lake Superior snow belt region.
The heaviest snow amounts are expected to be from the Bayfield
Peninsula, southeast to Iron county. Total snowfall through 00Z
Wednesday could be up to one inch for portions of the MN Arrowhead
and the Gogebic Range.

.LONG TERM...(Tuesday night through Monday)
Issued at 412 PM CST Mon Feb 13 2017

High-amplitude blocking pattern expected to develop Tuesday night
and Wednesday with continued above to much above normal
temperatures a low precipitation chances through the long term.

An impressive shortwave trough will be centered over the western
Great Lakes Tuesday evening with high amplitude ridging building
over the western CONUS and western Canada. As the trough pivots
eastward toward New England by Wednesday morning, it will deepen
and close off. Lake-effect snow showers are possible in the
northwest Wisconsin snow belt through Tuesday evening, but should
taper off early Wednesday morning as upstream moisture shifts

The closed upper low will anchor the eastern side of an Omega
Block over the western two-thirds of North America. By late
Wednesday afternoon the high amplitude, nearly meridional, arm of
the block will be positioned over the Northland. A meager stream
of moisture will support stratus, but otherwise conditions should
remain dry. Temperatures will trend cooler for Wednesday with the
cold airmass pouring into the area.

The closed upper low is forecast to drift farther eastward
Wednesday night to near Nova Scotia by late Friday night. The high
amplitude ridge will result in continued warm conditions across
the Northland and dry weather through Friday. By Friday night a
northern stream shortwave trough will move across the Canadian
Prairies, further flattening the ridge. The passing low will bring
an uptick in cloud cover, but dry conditions should continue in
the Northland. Behind that system, a return to a quasi-zonal
pattern is expected with quiet weather continuing through Sunday.
Deterministic and ensemble guidance is split on the potential for
precipitation late Sunday night and Monday. For now kept a mix of
rain and snow in the forecast with chance POPs.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1156 AM CST Mon Feb 13 2017

VFR conditions continue this afternoon ahead of an approaching
trough of low pressure and cool front expected to arrive tonight.
Wind speeds will increase this afternoon and remain breezy
overnight. There is a potential for LLWS behind the front, but
think mixing will be sufficient to support wind gusts into the
mid-20 kt range, so opted to leave explicit LLWS mentions out of
this package. Upstream observations indicated a VFR broken deck
moving across southern Manitoba and eastern North Dakota late this
morning. Continued the trend of introducing a high broken ceiling
at all sites through the afternoon and evening. Radiative cooling
and cold air advection tonight should result in MVFR stratus
development. Moisture depth is quite limited and there is a
potential for all sites to remain VFR overnight. Should the lower
CIGS develop, there will be a potential for light snow showers or
possibly freezing drizzle. Continued the VCSH mentions until mid-
morning Tuesday when -SHSN is introduced. Confidence in this
forecast package is average.


DLH  27  31   9  25 /  10  10   0   0
INL  25  28   2  23 /  20  20   0   0
BRD  27  33  10  30 /  10  10   0   0
HYR  27  34  11  26 /  20  20  10   0
ASX  29  35  14  26 /  20  30  20  10




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