Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 111134
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
634 AM CDT Fri Aug 11 2017

.UPDATE...
Issued at 634 AM CDT Fri Aug 11 2017

Please see the 12Z Aviation Discussion below.

&&

.SHORT TERM...(Today through Saturday)
Issued at 324 AM CDT Fri Aug 11 2017

An area of low pressure over the north-central Great Lakes region
will continue lifting into Quebec early this morning. Meanwhile,
surface high pressure across the Northern and Central Plains, and
south-central Canada, will continue to build into the Northland
from the west. This area of high pressure will dominate the
Northland by this afternoon and through Saturday. The high will
promote fairly clear skies for much of the day, and clear and calm
conditions overnight. Expect light northerly flow and near-
seasonal temperatures. Today will be a bit cooler because of a bit
more northerly flow than Saturday. Highs should in the lower to
middle 70s today, followed middle to upper 70s Saturday.

There is a good setup for fog early this morning. We had a couple
days of cloud cover and rain, so soil moisture is rather wet. The
surface high and resulting calm wind and clear skies is promoting
strong radiational cooling, trapping low-level moisture. We
already see some fog and low-level stratus across parts of the
Northland as of around 3 am, and it will likely become more
widespread and denser by around dawn. May need a dense fog
advisory at some point, but waiting to see greater indications of
the development of widespread dense fog.

Some fog is also possible tonight, but it will not likely be as
widespread as early this morning. Sunshine today will help dry out
the soil moisture from the recent rain. Added some fog to parts of
northeast Minnesota for late tonight.

.LONG TERM...(Saturday night through Thursday)
Issued at 324 AM CDT Fri Aug 11 2017

Cyclonic flow initially in the long term will be followed by a
pattern change mid to late this upcoming week with zonal flow
aloft. Initially, a trough will dig southeastward across the
Northern Plains into the Upper Mississippi River Valley on Sunday.
Despite the 500 hPa trough aloft, 850 hPa ridging will hold
strong across the Northland. Due to the high, skies will be mostly
clear with light winds. So, expect patchy fog development across
the region late Saturday night into early Sunday morning. There
will be chances of rain showers and thunderstorms from the
Brainerd Lakes southeast to the Spooner area. Elsewhere across the
Northland skies will be partly to mostly sunny.

The 850 hPa ridge will remain in place over the Upper Midwest
until late on Tuesday/early Wednesday once it builds into the
central Great Lakes. This will bring dry and quiet conditions to
the Northland. By Tuesday afternoon much of the region will be
located on the western side of the high/850 hPa ridging, which
will bring the region southwesterly warm air advection and milder
temperatures. Higher aloft, the 500 hPa ridge axis will slide
eastward from eastern Montana late on Sunday into Minnesota by
Tuesday afternoon. This ridge will build eastward into Upper
Michigan/Wisconsin Tuesday night, while a shortwave lifts across
the Northern Plains into western Minnesota. Ahead of the
shortwave, a broad area of lower pressure will develop, bringing
chances of showers and storms across the region late Tuesday night
through Wednesday. There will be a few hundred to 1500 J/kg of
MUCAPE Wednesday afternoon/evening with increasing 0-6 km shear,
with values around 20-30 kts. So, cannot rule out a few strong
thunderstorms.

A weak 850 hPa ridge will slide in on Thursday bringing another
period of quiet weather. However, the precipitation chances will
return on Friday as a shortwave slides through the Northern Plains
into the Upper Midwest.

High temperatures will remain in the 70s across the Northland
through the extended, with a few 80 degree readings possible on
Tuesday. Low temperatures will generally be in the 50s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 634 AM CDT Fri Aug 11 2017

Main concern in the aviation is VLIFR to IFR fog early Friday
morning. Fog should dissipate at all terminals around 14Z, once
the mixed layer begins developing per NAM/RAP and DLHWRF.
Afterwards, expect VFR conditions as an 850 hPa ridge axis
builds over the region. Will see a fair weather cumulus deck
develop around 4000 to 7000 feet late this morning and persist
into the afternoon hours.

The mixed layer will decouple around 23Z to 01Z per forecast
soundings. With the high overhead, skies will be clear and winds
will remain light tonight. This will provide another opportunity
for radiation fog development. Uncertain how widespread fog will
be at this point as there will be some drying out today, but have
hinted at development at HIB/BRD as suggested by the GLAMP.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  73  53  77  54 /   0   0  10   0
INL  76  49  77  50 /   0   0  10   0
BRD  76  52  77  54 /   0   0   0  10
HYR  73  48  78  51 /   0   0   0   0
ASX  72  51  79  53 /   0   0   0   0

&&

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

$$

UPDATE...WL
SHORT TERM...Grochocinski
LONG TERM...WL
AVIATION...WL



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