Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 180850
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
350 AM CDT Mon Sep 18 2017

.SHORT TERM...(Today through Tuesday)
Issued at 350 AM CDT Mon Sep 18 2017

High pressure covered the forecast area at 08Z. Meanwhile, a
southwest flow aloft was working to bring the occasional embedded
upper level impulse across the area. Warm air advection was
beginning to affect the region with clouds on the increase. The
early morning fog is diminishing with the arrival of the cloud
cover. A batch of showers/sprinkles was just arriving over the
southern edge of the forecast area on the leading edge of the WAA
with an assist from some 700mb FGEN. Most of the short term hires
models point to this activity diminishing by 12Z and have followed.
The next batch of showers appears to be ready to develop/spread into
the southern edge of the region by mid morning. This is in response
to one of the aforementioned impulses. Another impulse will clip
Koochiching county as well and have introduced some pops. The
northern impulse quickly departs by early afternoon ending the rain
chance. A stronger vorticity maxima is progged to move over
northwest Wisconsin this afternoon. This is well advertised by the
hires as well as the deterministic models and have pops aligned
accordingly. Instability is limited and have no thunder mentioned as
seen in most models. With he cloud cover, expect max temps in the
60s.

Differences amongst the models in the handling of another impulse
moving through Wisconsin this evening. The ECMWF/NAM and GEM have
QPF over the far southeast portion of the region in the evening,
while the GFS is dry. The ARW/NMM also hint at some QPF in the early
evening. Maintained the previous forecast of pops initially, then
trended downward after 03Z, ending after 06Z. Some weak upper level
and surface ridging cover the area overnight.

This ridging persists to some extent on Tuesday. However, strong WAA
is underway by the afternoon with a 45 to 50 knot low level jet
racing into the region. Clouds will be on the increase, but no rain
is expected as the moisture is above 5K feet and mean RH is 50
percent or less on the majority of the models. Max temps a bit
warmer with 60s along the North Shore due to an onshore flow, with
70s elsewhere.

.LONG TERM...(Tuesday night through Sunday)
Issued at 350 AM CDT Mon Sep 18 2017

A fairly active period lies ahead during the long term. A
persistent upper-level trough will take up residence over the
western half of the continent and several shortwave troughs will
kick eastward into the Northern Plains and Upper Midwest from
Tuesday night through the weekend. Southerly winds near the
surface and aloft will result in warm air and moisture advection
into the region. Temperatures will generally trend above to much
above normal for late September. The first shortwave trough
arrives Tuesday night as a cool front advances eastward from the
Dakotas. Convergence along the front will encounter a modestly
unstable airmass which will support a chance of thunderstorms.
The storms will likely develop to the west and lift north-
northeast, moving into north-central Minnesota after 06Z. Shear
and instability profiles point to a threat of strong to severe
thunderstorms and the SPC has included much of the CWA within the
Marginal Risk area. Large hail and damaging wind gusts appear to
be the greatest threats.

The cool front is forecast to move out of the area on Wednesday.
Southerly flow ahead of the boundary will recharge the airmass
over northwest Wisconsin. Another round of thunderstorms is
possible Wednesday afternoon before the front exits the
Northland. Some of those storms may be strong, as well thanks to
the combination of moderate instability and deep layer shear of
30 to 40 knots.

High pressure will move across the area Wednesday night and
Thursday. A warm front is expected to lift northward across the
area Thursday afternoon with warm southerly breezes returning.
Thunderstorms are a possibility once again Thursday night thanks
to convergence and forcing for ascent over the warm frontal
surface, combined with an approaching shortwave from the
southwest. The front is forecast to loiter over the Upper Midwest
Friday through Saturday night with several rounds of showers and
thunderstorms forecast. This pattern will be similar to the one
we experienced late last week into Saturday. The potential for
heavy rainfall exists with robust moisture transport into the
frontal zone. Cloud cover and widespread rainfall is expected for
Sunday, which will keep temperatures cooler. By Sunday night the
front is forecast to move eastward, exiting the area on Monday.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1238 AM CDT Mon Sep 18 2017

High pressure will gradually move off to the east tonight, as an
area of low pressure and upper level system moves in from the west
and southwest. A few sprinkles will be possible in northwest
Wisconsin later tonight, with the chance of showers increasing
throughout the day from KDLH to KHYR. We should generally see VFR
conditions overnight and into Monday evening, although some
localized fog will be possible overnight. This could result in
spotty IFR CIG`s and VSBY`s, especially at KHIB. In addition, some
MVFR CIG`s and VSBY`s will be possible Monday evening, especially
from KDLH into KHYR.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  60  51  67  58 /  20  10   0  60
INL  64  48  70  56 /  30  10  10  70
BRD  62  51  72  59 /  20  10  10  70
HYR  62  52  72  60 /  40  20   0  50
ASX  64  50  72  58 /  30  20   0  50

&&

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

$$

SHORT TERM...GSF
LONG TERM...Huyck
AVIATION...DAP



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