Area Forecast Discussion
Issued by NWS Duluth, MN

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857
FXUS63 KDLH 232335
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
635 PM CDT Sat Sep 23 2017

.SHORT TERM...(This evening through Sunday)
Issued at 331 PM CDT Sat Sep 23 2017

The large upper level trof that has been over the West Coast will
develop a closed low in the base of the trof as it begins to move
into the Rockies. Meanwhile, the blocking upper level high remains
over the East Coast. With the forecast area in between, warm, moist
air will continue to be pumped into the region on the southwest flow
aloft. This is Gulf of Mexico based moisture and is resulting in
dewpoints into the upper 50s over the northwest corner of the
region, with 60s and low 70s elsewhere. 850mb temps in the teens are
also in play across the area which is resulting in minimum temps
tonight in the 50s north, to the upper 60s south. Max temps on
Sunday will be in the upper 60s over northwest Koochiching county,
to the middle 80s in northwest Wisconsin.

At the surface, a cold front was reaching the Twin Ports at 20Z.
Showers and a few storms will occur along and ahead of the front. As
the evening progresses, the cold front is expected to become a warm
front and lift north to the Canadian border later tonight. It will
be pushed along by a low level jet. The showers and storms will also
lift north later tonight with the he storms diminishing as the low
level jet weakens. A front will remain over the western portion of
the forecast area through Sunday. Showers and storms will persist
along and ahead of this front and drift a bit east in the afternoon.
Brief heavy rains will be found near the stronger storms, but no
severe weather is expected.

.LONG TERM...(Sunday night through Saturday)
Issued at 331 PM CDT Sat Sep 23 2017

The Northland`s warm weather pattern will soon come to an end. A
cold front will move through the Northland Sunday night and Monday,
then the Northland can expect cooler northwest flow through much of
the week, with temperatures returning to near or slightly cooler
than normal.

There will be dominant area of high pressure over the eastern US and
southeast Canada Sunday evening. The high will be somewhat blocked
from moving eastward because of Hurricane Maria lifting northward in
the Atlantic Ocean. This will cause a cold front in western
Minnesota and far northwest Ontario to slowly advance eastward
through the Northland Sunday night and Monday. Passing shortwaves in
the warm, humid, strong south-southwest flow aloft could provide
enough forcing to trigger some thunderstorms in the warm sector
ahead of and near the front. The models suggest only up to several
hundred J/kg of most-unstable CAPE, so the environment does not look
particularly favorable for strong storms. However, given the deep
moisture, with precipitable water values of 1.5 to nearly 2 inches,
any storms could drop heavy rain rates. The slow movement of the
front could lead to training and contribute to some locally heavy
rainfall. There could be additional storm development in northwest
Wisconsin and nearby areas of Minnesota Monday afternoon and early
evening, before the front finally exits the Northland later that
night or early Tuesday.

An upper-level low will lift out of the Rocky Mountains into the
Northern Plains and south-central Canada Monday into Tuesday. This
could lift multiple shortwaves through the Northland, providing the
forcing to possibly generate more showers Monday night and Tuesday.
The cool northwest flow on Tuesday will widespread cumulus
and showers.

The upper low will lift off to Hudson Bay and eastern Canada
Wednesday and Wednesday night. The Northland should get a break from
showers with breezy westerly flow and some partly cloudy skies.
Another upper low, though, looks like will drop out of northern
Canada Thursday and/or into Friday. This will likely bring the
coldest air the Northland has yet seen. The GFS and European have
850 hpa temperatures dropping to near or a bit below 0 to -2 degrees
Celsius. We are forecasting highs in the middle to upper 50s at this
time for late in the week. However, this forecast is somewhat skewed
towards climatology. We will likely trend the forecast temperatures
down and sky cover up if the models continue to show this cold air
coming down. That kind of cold air would likely generate plenty of
cumulus, which would limit solar heating, and further contribute to
cool temperatures. It is not out of the questions that highs could
be in the 40s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 632 PM CDT Sat Sep 23 2017

The frontal boundary that has remained quasi-stationary over the
past few days, will continue to impact the Northland TAF sites
throughout the period. The front will continue to bisect the
region, with the best chance of showers and storms in the western
TAF sites, and much less of a chance to the east. The atmosphere
ahead of the front will continue to be warm and humid, and
relatively unstable. A sizable cap is in place across much of the
western Great Lakes states. As a result, expect showers and
thunderstorms tonight, with a bit of a decrease overnight and on
the day Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  63  79  60  63 /  40  10  50  50
INL  54  68  51  56 /  80  70  80  30
BRD  62  80  56  60 /  50  40  70  40
HYR  67  84  63  73 /  20  10  30  60
ASX  64  86  62  73 /  30  10  30  60

&&

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

$$

SHORT TERM...GSF
LONG TERM...Grochocinski
AVIATION...DAP



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