Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 170520

Area Forecast Discussion
National Weather Service Duluth MN
1220 AM CDT Mon Jul 17 2017

Issued at 1220 AM CDT Mon Jul 17 2017

Updated for the new 06Z Aviation Discussion below.


.SHORT TERM...(This evening through Monday)
Issued at 335 PM CDT Sun Jul 16 2017

At 330 PM, skies were sunny across the northland. There was some
scattered cumulus in spots, and there was a swath of smoke
associated with Canadian forest fires bisecting the CWA.
Temperatures ranged from near 60 along the Lake Superior
shoreline, to the 70s inland. Gusty northeast winds continued in
the Twin Ports area, with rip currents expected to last into the
evening on Minnesota and Wisconsin Point.

The main focus overnight will be on low temperatures and cloud
trends. High pressure will bring a cool night to much of the
region, as dewpoints had fallen into the upper 40s to lower 50s in
spots. Looking for overnight lows in the 40s across portions of
northeast Minnesota, as well as in northwest Wisconsin. Winds were
from the southeast, other than near Lake Superior, where winds are
from the east to northeast. Cloud cover will be minimal, although
the persistent band of smoke from Canadian forest fires may have
somewhat of an impact on northern lights observation.

The focus will then shift to Monday, as a frontal boundary
approaches the area from the west. A few showers and thunderstorms
are expected to migrate eastward into the CWA by late morning, but
probably not reaching as far east as the Twin Ports until later in
the day. Moisture and heat build considerably on Monday, driven by
a strong southerly push of air into the western Great Lakes.
Favorable upper levels winds are also expected to develop on
Monday or Monday evening. As a result, we could see some strong to
severe storms, especially later in the day Monday, and Monday
night. Temperatures are expected to be well into the 80s.

.LONG TERM...(Monday night through Sunday)
Issued at 335 PM CDT Sun Jul 16 2017

A 500 hPa trough will lift from central Saskatchewan Monday evening
into Ontario by Tuesday evening. At the surface a cold front will
slide southeastward through northern Minnesota into northern
Wisconsin. This will bring showers and storms to the Northland.
MUCAPE values are on the order of 1000-3500 J/kg Monday evening and
decreasing overnight. This will combine with 0-6 km bulk shear on
the order of 30-50 kts, and PWAT values of 1.5 to 2.0 inches. PWAT
values in this range are near to above the 90th percentile based on
the SPC sounding climatology for KINL/KMPX. Ahead of the front,
dewpoint temperatures will range from the mid 60s to near 70. With
the widespread forcing from the front and the environmental
parameters in mind, expect strong to severe storms to develop. Based
on the latest NAMNEST storms could initially start out as discrete
supercells before becoming linear. The strongest storms will be
capable of very large hail, damaging wind gusts, and heavy rainfall.
As highlighted in the current SPC Day 2 Outlook. Expect this
activity to spread southeastward as the night progresses. Lows
heading into Tuesday will be in the 60s.

The cold front movement will slow down on Tuesday and Tuesday night,
possibly becoming stationary across southern portions of the CWA.
Expect shower and thunderstorms to redevelop late in the afternoon
and into the evening per the GFS/CMC/ECMWF. Still cannot rule out
strong to severe storms with MUCAPE values around 1000-2500 J/kg,
and 0-6 km bulk shear around 35-45 kts. Instability will be the main
question as the previous days convection will impact how things
develop on Tuesday. Nonetheless, strong to severe storms cannot be
ruled out and this is highlighted by the latest Day 3 Outlook from
SPC. Highs will generally be in the low to mid 80s.

Behind the front, a weak 850 hPa ridge will build into Minnesota
from the northern Plains Tuesday evening into Wednesday. This will
provide a period of quiet weather. Wednesday afternoon into Thursday
a subtle shortwave trough will dig into the region from the northern
Plains bringing additional chances of showers and storms.

The forecast becomes more uncertain for Thursday through the
weekend. Flow will remain cyclonic Thursday through Friday, with
subtle shortwaves moving through Ontario. These combined with
heating may be enough for showers/storms to develop. Late in the
week and into the weekend a ridge will build in from the northern
Plains, while a trough digs in behind it. The GFS is much slower
with the breakdown of the of ridge, while the ECMWF/CMC break the
ridge down quickly. The ECMWF/CMC solution would keep the Northland
stormy through the weekend, while the GFS would bring shower/storm
chances on Sunday.

Highs through the extended will be seasonable with readings in the
70s and 80s. Besides Tuesday night, lows will generally range from
the 50s to low 60s throughout the region.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1220 AM CDT Mon Jul 17 2017

High pressure has moved east of the forecast area early this
morning while low pressure was slowly advancing over the Dakotas.
Winds will be from the south and gradually increase by morning and
become a bit gusty to around 20 to 25 knots Tuesday morning.
Thunderstorms will move into northeast MN late today and gradually
spread east as a cold front slowly moves through. By 06z the
front will likely be nearing the MN Arrowhead to the KBRD area.


DLH  48  80  64  81 /   0  40  60  40
INL  51  82  60  81 /  30  50  60  10
BRD  57  89  68  83 /  10  40  50  40
HYR  52  83  66  82 /   0  10  40  60
ASX  49  82  64  83 /   0  10  60  50




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