Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 131802

Area Forecast Discussion
National Weather Service Duluth MN
102 PM CDT Wed Sep 13 2017

Issued at 102 PM CDT Wed Sep 13 2017

Updated aviation section below for 18Z TAF TAF issuance.


.SHORT TERM...(Today through Thursday)
Issued at 404 AM CDT Wed Sep 13 2017

The combination of weak winds, nearly clear skies, and longer
night time radiational cooling hours have resulted in the
formation of patchy dense fog again this morning. However, in
contrast to yesterday morning, fog is much more localized, and
mostly confined to valleys, low lying areas, and other favored
locations. Still, some visibilities are down to a quarter to half
mile in a few spots (Moose Lake/Hibbing). Similar to yesterday,
the fog should rapidly dissipate by between 7 and 9 AM in most
locations, if not earlier. For the rest of the day, clouds will
gradually increase from southwest to northeast, but there still
should be enough filtered sunshine to allow temps to warm into the
80s in most locations, along with a continued slow increase in

A front will slowly sag southeastward from northwest Minnesota and
Ontario this afternoon and tonight. As forced ascent slowly
increases with time along and north of the surface front, small chances
for showers will begin this afternoon, and then continue to
increase tonight and Thursday and expand south/east with time as
deep layer moisture flux persists into the frontal zone across
northern Minnesota and the first of several disturbances to
interact with the front traverses the area. The best chance for
showers and thunderstorms and the greatest areal coverage is
expected across far northern Minnesota tonight and Thursday within
the zone of most persistent and deepest forced ascent, but at
least some small risk for precip will exist as far south/east as
the Lake Mille Lacs to Twin Ports corridor by midday Thursday.

.LONG TERM...(Thursday night through Tuesday)
Issued at 404 AM CDT Wed Sep 13 2017

Much of the long term period will be dominated by the development of
a frontal boundary across the Upper Midwest and into Canada. The
front will develop in response to a developing long wave trough in
the western states, as a blocking upper level ridge develops to
our east. On Thursday night, we will see a frontal boundary
stretching from northeast Colorado into the Lake Superior basin,
and into Ontario. This front will be the focus for showers and
thunderstorms, with the most numerous showers and storms across
the northwest half of the CWA.

Timing the various opportunities for precipitation will generally
coincide with shortwave energy moving along the frontal boundary
from Thursday night into Saturday. Surface low pressure and an
upper level shortwave will bring a fairly high chance of POP`s to
the CWA on Thursday night, especially in the Lake Superior region.
SPC has much of our CWA in a marginal risk of severe
thunderstorms from Friday into Friday night, as the cold front
associated with another surface low in northern Minnesota moves
slowly eastward. An upper level shortwave will then kick the
frontal boundary and surface low eastward from Saturday into
Sunday, bringing cooler air for the remainder of the weekend and
into early next week. Heights build considerably from early to mid
next week, resulting in warmer air building back into the region.

There are generally small opportunities for precipitation from
Sunday into Tuesday of next week, but building heat and humidity
ahead of another frontal boundary to our west should help to bring
a return of thunderstorms toward the middle of next week. While
highs will generally be in the 60s and 70s, they will range from
the mid 50s to mid 60s on Sunday, as cool high pressure builds in
behind the departing cold front. Sunday night could feature
overnight lows in the upper 30s to lower 40s.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 102 PM CDT Wed Sep 13 2017

VFR conditions are across the terminals as of issuance time. A
warm front extends from near KINL southwest to around Fargo, and
on towards Aberdeen. A warm and unstable airmass is along and east
of this front, where a few isolated showers and thunderstorms have
developed. for now these should stay away from the terminals, and
have left out of the forecast for now. Tonight the front remains
nearly stationary, and we should see more storms bloom along the
boundary, which may affect KINL. Conditions east of the front will
also be good for fog formation, and have included fog and stratus
for several sites after 05z, especially where the east flow off
Lake Superior will supply extra low level moisture and IFR/LIFR
conditions are possible. Fog and stratus should dissipate in the
13-15z time range. The front is expected to serve as the focus for
shower development after 15z for several locations, but due to
uncertainty have kept to VCSH or VCTS for now.


DLH  82  59  73  58 /  20  30  40  60
INL  80  59  71  53 /  20  40  40  40
BRD  85  61  81  61 /  10  30  40  40
HYR  83  59  85  61 /  10  10  10  40
ASX  85  58  79  59 /  10  20  30  60




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