Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 201226 AAA
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
726 AM CDT Sun Aug 20 2017

.UPDATE...
Issued at 726 AM CDT Sun Aug 20 2017

Update for new 12Z Aviation Discussion below.

&&

.SHORT TERM...(Today through Monday)
Issued at 326 AM CDT Sun Aug 20 2017

Upper level and surface ridging covered the forecast area at
07Z/2am. However, a cold front was just moving into northwest
Minnesota and extended southwest into southeast North Dakota.
Mainly cirrus was found over the area. A mid level deck of clouds
was beginning to develop just to the west of the forecast area
ahead of the front. Patchy fog has developed over the central and
eastern portions of the region. This fog is fairly shallow as
denoted by the rapid changes in visibility in the observations.
With the anticipated cloud cover spreading into the region, this
should preclude further fog development. The deepest surface
moisture convergence is located ahead of the cold front and just
ahead of the stratus. This is the case during the morning as the
cold front moves through northeast Minnesota. This is confirmed by
the various models, including the short term hires models and
have a rain free morning forecast. In the afternoon, the models
disagree on where to develop showers and thunderstorms as the
front continues its march eastward through northwest Wisconsin.
The ECMWF is the most robust with QPF over the entire area. The
GEM/NAM only have QPF over the tip of the Arrowhead. The GFS has
QPF over the Arrowhead, but also in the southeast corner of the
region. The ARW/NMM split the difference of the aforementioned
models. Have some small pops over the Arrowhead early in the
afternoon, and in northwest Wisconsin. Behind the front, high
pressure is building into the rest of the region.

The ECMWF appears overdone with additional activity across the
southeast portion of the region this evening. The NAM/ARW/NMM/GFS
are rain free. The GEM is hinting at some activity near Price
county. Used a blend and have small pops to account for any
lingering storms behind the departing cold front. Late tonight,
high pressure covers the region. Added some fog late tonight with
a mainly clear sky expected.

Monday morning will be rain free with the high pressure nearby.
By afternoon, a digging upper level trof approaches northwest
Minnesota from Canada. Meanwhile, an embedded impulse ahead of
this trof moves through southern Minnesota into Wisconsin. Varying
degrees of strength of the trof and the impulse affects the
amount of QPF and thus the pops. Used a blended approach to pops
to resolve these differences. Have thunder mentioned over the
southeast corner of the region. Not expecting thunder over the
northwest zones as instability is lacking with all models having
850mb LI`s above 0C with marginal CAPE, less than 200 J/kg.

.LONG TERM...(Monday night through Saturday)
Issued at 326 AM CDT Sun Aug 20 2017

A few showers and thunderstorms are possible Monday night into
Tuesday, then a quieter pattern emerges for much of the upcoming
week.

A high amplitude mid-level trough of low pressure is forecast
from northern Quebec southwestward into the Upper Midwest Monday
night. A few shortwave troughs will round the base of the
planetary wave and move into the Upper Midwest overnight. An area
of thunderstorms is expected over southern Minnesota into central
and southern Wisconsin and should move away from the Northland
Monday night. The approaching shortwave troughs may provide enough
lift for scattered to isolated thunderstorms spreading southeast
across the Northland. Portions of northwest Wisconsin may be
clipped by the southern storms. Cyclonic flow aloft will continue
through Tuesday afternoon and may trigger a few diurnal showers or
storms, mainly across northern and northeast Minnesota.
Deterministic solutions diverge around midweek with the GFS
bringing another shortwave trough diving into the region while the
other models have a subtler feature or nothing at all. Leaned on
the non-GFS members for sensible weather until late in the week. A
high amplitude ridge will build into the center of the continent
Thursday and Friday keeping weather fairly quiet. By Friday
afternoon, a convectively generated shortwave is forecast to push
into the Northland from the Plains. Since this feature is
dependent on the placement and intensity of thunderstorms upstream
Thursday night, confidence is somewhat low. However, by Friday
night 17 of the 42 GEFS members from the 00Z and 12Z runs feature
precipitation in the Northland, along with all of the
deterministic models. Have raised POPs above the consensus blend
and broad-brushed slight chance and low-end chance POPs across the
Northland Friday night through Saturday. It seems a more
organized rain and thunderstorm threat will arrive Saturday
afternoon and evening as a more robust shortwave trough moves out
of the Dakotas and Canadian Prairies and into the Upper Midwest.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 726 AM CDT Sun Aug 20 2017

A cool front will move eastward across the Northland today,
pushing across Minnesota this morning and over northwest Wisconsin
this afternoon. Moisture pooling along the front has lead to a
ribbon of MVFR stratus this morning which is forecast to drift
over INL/HIB/DLH before the noon hour. VLIFR visibility and
ceilings at HIB are expected to improve with the arrival of the
slightly higher stratus over the next few hours. After the stratus
moves through, look for VFR conditions through the rest of the
day. Winds will turn westerly behind the front and wind speeds
will increase after frontal passage. There is a potential for fog
development once again tonight, but think HYR is the most likely
candidate with drier air moving into the remain forecast sites.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  80  56  76  54 /  10   0  10  20
INL  77  49  75  49 /   0   0  20  20
BRD  77  53  76  53 /  10   0  10  20
HYR  82  54  79  54 /  10  10  10  30
ASX  84  56  79  56 /  10  10  10  20

&&

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

$$

UPDATE...Huyck
SHORT TERM...GSF
LONG TERM...Huyck
AVIATION...Huyck



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