Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 200826

Area Forecast Discussion
National Weather Service Duluth MN
326 AM CDT Sun Aug 20 2017

.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

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 06Z TAFS through 06Z Sunday night)
Issued at 1236 AM CDT Sun Aug 20 2017

Fog is expected to develop and affect the terminals through 13Z
this morning. Several sites may experience IFR/LIFR visibilities
due to lingering low level moisture and light winds. Conditions
should return to VFR by 13Z. A cold front is advancing towards
the area, and I do not expect anything along the front until after
15Z due to the lack of lift along the boundary itself. Some
models are hinting at some low clouds with MVFR bases in the 15Z-
18Z time range, but am not at all confident of this and have left
out for now. Have included some VFR cloud bases and VCSH groups
for the 19Z to 01Z time range for KHYR for the chances for


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




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