Area Forecast Discussion
Issued by NWS Duluth, MN

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993
FXUS63 KDLH 201527
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1027 AM CDT Thu Jul 20 2017

.UPDATE...
Issued at 1027 AM CDT Thu Jul 20 2017

Made adjustments to temperatures, sky cover and wind gusts.
Bumped up temperatures and wind gusts across northeast Minnesota,
especially along the north shore as katabatic warming is expected
due to westerly flow. Increased cloud cover across southern
portions of the CWA to based on current satellite data.

&&

.SHORT TERM...(Today through Friday)
Issued at 328 AM CDT Thu Jul 20 2017

An area of high pressure near the border between North Dakota and
Canada will shift into Minnesota today. The surface ridge axis
will be just to the west and south of the Northland, so light to
breezy northwest flow will develop by this afternoon. Despite the
flow, the lack of cool air advection and relatively dry air will
mean it will even be difficult to produce any cumulus. It should
be a truly sunny day. Highs will be in the upper 70s to middle
80s. Some of the warmest areas in the forecast include the lower
elevation areas of Duluth and along the North Shore because of
the typical downslope warming from the northwest flow.

The surface ridge will move through the Northland tonight,
promoting clear skies and calm conditions. Winds and cloud cover
will begin to increase from the west late tonight as the surface
ridge departs and lower pressure approaches from the west. This
means the coolest overnight temperatures will be across the
eastern forecast area. Leaned on the cooler model guidance, such
as the consensus of the GFS MOS and NAM MOS. Lows should range
from the low 50s in the Arrowhead, to the middle 50s in northwest
Wisconsin, and to upper 50s to low 60s from central to north-
central Minnesota. There is a low chance of showers and very weak
storms (as suggested by the 00Z GFS) across the far northwest
forecast area, west of Bigfork and International Falls, due to a
potential mid- level frontogenetical band and passing weak
shortwaves.

An area of low pressure lee of the Rocky Mountains in the Northern
High Plains will advance east into the Dakotas Friday. The
associated warm front will be well south and west of the
Northland, but south-southeast flow will bring an influx of
humidity northwards into the Northland. However, the approaching
low pressure will stimulate the typical easterly, cool outflow
from Lake Superior. This will set up a stationary boundary across
the southern forecast area. Daytime heating will build up
instability from the west, with as much as 500 to 1500 J/kg of
MUCAPE across the southern and western forecast area. Passing
shortwaves and the stationary boundary across the southern
forecast area may provide enough forcing to generate some showers
and storms. If storms develop, they may become organized and
strong thanks to plenty of deep layer wind shear. There will
likely be at least 35 to 45 knots of 0-6 km wind shear. Highs
should range from the middle 70s near Lake Superior to the upper
70s and low 80s inland.

.LONG TERM...(Friday night through Wednesday)
Issued at 328 AM CDT Thu Jul 20 2017

A stronger shortwave will continue to move from southern
Saskatchewan Friday evening to the Manitoba, northwest Ontario,
northern Minnesota region by Saturday evening. A surface low and
frontal boundary will be over the Northern Plains to the shortwave
Friday evening and will move into southeast Minnesota but extend
northwest into Manitoba by 12Z Saturday. It will continue east
Saturday into Saturday night with much of the region in a cooler
northwest flow by 12Z Sunday per both the GFS and ECMWF. The NAM
is slower.

There will be plenty of moisture across the region Friday night
into Saturday evening as PWAT values rise to 1 to around 1.5
inches...a bit higher from the NAM. The instability will be on the
increase as well. Showers and storms will be possible Friday
night becoming more likely overnight into Saturday as the
shortwave and low approach the region. The NAM and GFS also show
some areas of low level FGEN which would enhance lift. There isn`t
great agreement between the models on the exact location of the
FGEN and we may have to wait another 24 hours or so to get a
better handle on where it will set up for Friday night. There will
be a chance for strong to severe storms over much of the area
Friday night into Saturday evening. Heavy rain will be an
additional threat, especially near the stronger low level FGEN.

As the low and front pass through the region Saturday night into
Sunday, cooler air will be moving in and the severe threat will be
low. Showers and a few storms will remain possible Sunday but it
will then dry out Sunday night into Monday as high pressure
temporarily builds in.

There will be chances for showers/storms Tuesday/Wednesday. Both
the GFS and ECMWF show a front and shortwave moving through the
area but have some timing differences.

High temperatures Saturday will range from around 70 in the
Arrowhead to around 80 in the Brainerd Lakes region east toward
Siren. Highs Sunday will be in the lower to middle seventies with
temperatures warming to the mid to upper seventies by next
Wednesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 636 AM CDT Thu Jul 20 2017

High pressure has led to mostly clear skies, calm winds, and fog
over the Northland early this morning. The fog will quickly lift
over the next 1 to 2 hours leading to VFR conditions into this
evening. More fog will be possible later tonight dropping the
visibility to IFR or MVFR in spots. In addition to the fog later
tonight, some showers and storms may form as well. We left the
mention out of the TAF sites for now and KINL would be most likely
to see a shower/storm late in the period and it may need to be
added with later updates.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  84  59  78  59 /   0   0  20  20
INL  79  54  80  59 /   0  10  20  40
BRD  84  62  81  63 /   0   0  40  30
HYR  85  55  81  62 /   0   0  30  30
ASX  85  55  80  58 /   0   0  20  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

UPDATE...WL
SHORT TERM...Grochocinski
LONG TERM...Melde
AVIATION...Melde



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