Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 301408

Area Forecast Discussion
National Weather Service Duluth MN
908 AM CDT FRI SEP 30 2016

Issued at 908 AM CDT Fri Sep 30 2016

Updated the cloud cover forecast through tonight. It appears the
HRRR to be among the models best depicting the current low-level
stratus covering most of the Northland. The HRRR, and some other
models (such as the local WRF and 950 hpa RAP13 RH), are
indicating it will take longer to dissipate the stratus than the
previous forecast. Therefore, delayed its dissipation with the
latest update. Also, the HRRR, RAP, local WRF, and 4 km NAM
suggest the marine stratus, from the cool and humid easterly flow
from Lake Superior, will linger near the Twin Ports and Ashland
areas, so increased afternoon cloud cover for those areas. It then
looks like the marine stratus will surge back inland this evening,
so increased cloud cover into tonight, using the HRRR cloud cover
as a guide.


.SHORT TERM...(Today through Saturday)
Issued at 344 AM CDT Fri Sep 30 2016

Stratus is continuing to be the major concern this morning.  It is
developing over relatively warmer Lake Superior, where the average
surface water temperature is about 53 degrees, with the air
temperature now in the 40s where clouds have not formed.  A lake
effect of sorts, with enough moisture and temperature differential
for clouds but not precipitation.  The stratus downstream of Lake
Superior should continue early this morning, then gradually
dissipate late this morning as the airmass warms and mixing helps
get rid of it.

On the larger scale, the upper level low that we have been dealing
with for several days now is currently over the lower Ohio river
valley.  This feature is expected to ease slowly north tonight and
Saturday, slowly pushing additional clouds and some chances for
precipitation into the southeastern portions of the forecast area
later tonight and Saturday.  Otherwise, the ridge axis is expected
to linger over the northern portions of the area.  Stratus may form
once again tonight, though the models are not picking up on it as
well as they did last night and have backed off on the cloud cover.
Higher clouds from the upper low may keep temperatures warm enough
to diminish the potential for stratus formation.

Temperatures today to be warmer than yesterday with the clouds
expected to clear, so have brought highs up into the mid-upper 60s
most locations.  Tonight have kept things milder with lows in the
upper 40s south, and lower 40s north where there should be less
cloud cover.  Saturday to be slightly cooler than today, depending
on exact cloud cover.

.LONG TERM...(Saturday night through Thursday)
Issued at 344 AM CDT Fri Sep 30 2016

The main focus on the extended initially will be a cutoff system
located in the central Great Lakes. The latest GFS/GEM/ECMWF
continues to be in excellent agreement for the weekend and early
next week bringing this feature northeastward into the eastern Great
Lakes/New England. Behind the cutoff, high pressure will nudge into
the Northland from north on Sunday. This will keep light winds out
of the east/northeast. Highs will be in the 60s throughout the

The ridge axis will move east of the forecast area on Monday and
Tuesday, which will bring southerly warm air advection at 850 hPa
and result in a warming trend early in the week. Highs will be in
the mid to upper 60s on Monday and around 70 on Tuesday. As the
ridge departs, a trough will dig and deepen across the Western US
into the Plains. Ahead of the trough and area of low pressure will
develop in the Northern Plains and this feature will bring the
Northland the next chance of precipitation. This system will
gradually slide northeastward across the Northern Plains into
Ontario by late in the week. This will spread shower and
thunderstorm chances from southwest to northeast on Monday evening
through Wednesday. Removed thunderstorm mention for Thursday/Friday
as the system will be northeast of the CWA and instability will be
limited. Expect rain showers to linger around the backside of the
mature system. Still expect temperatures in the 60s on Wednesday,
but it will be cooler than Tuesday due to cloud cover.

Late in the week and heading into the weekend guidance continues to
show a cooling trend as northwest/westerly flow develops around the
back side of the system. This will bring near to below 0 degrees
Celsius 850 hPa temperatures for late on Thursday/Friday, which will
bring the coolest airmass of the Fall season to this point. Still
some run to run and model to model discrepancies with how cold of an
airmass will move in, with the latest ECMWF being the coldest and
farthest south at this point in time.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 704 AM CDT Fri Sep 30 2016

Will gradually see the IFR/LIFR stratus deck lift and scatter out
as the morning progresses per the latest NAM/RAP/HRRR guidance.
Expect VFR conditions at all terminals between 17Z to 20Z as the
stratus deck scatters out. Will see visibilities improve this
morning to VFR as fog lifts due to the mixed layer developing.

Guidance continues to hint at a stratus layer redeveloping late
tonight. Tried to account for this by hinting at IFR ceilings at
all terminals except for KDLH, where am fairly confident a stratus
deck will move in. Along with the stratus expect fog to develop
due to light winds.


DLH  59  48  61  47 /   0   0   0   0
INL  63  45  64  45 /   0   0   0   0
BRD  67  48  67  47 /   0   0   0   0
HYR  64  48  64  46 /   0   0   0   0
ASX  58  51  59  49 /  10   0   0  10


.DLH Watches/Warnings/Advisories...


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