Area Forecast Discussion
Issued by NWS Duluth, MN

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508
FXUS63 KDLH 172016
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
316 PM CDT Thu Aug 17 2017

.SHORT TERM...(This evening through Friday)
Issued at 316 PM CDT Thu Aug 17 2017

Light rain showers will gradually diminish and pull out of the
Northland through this evening with a departing area of low
pressure. This low over northern Wisconsin will lift into Upper
Peninsula Michigan this evening and into Ontario Friday morning.
Meanwhile, a weak surface ridge will move in from the west,
helping to clear out the forecast area. Think much of the forecast
area, especially across northeast Minnesota, will see good
clearing and light winds speeds develop with the resulting
boundary layer from the radiational cooling. Northeast Minnesota
is where the heaviest rains fell yesterday through today, so soil
moisture is very rich. Think tonight will be a very good setup for
fog. The model consensus of visibility guidance is suggesting a
good chance of widespread and dense fog across a large portion of
central and northeast Minnesota. Ramped up the fog wording added
earlier in the day. The one threat to the formation of the fog
will be associated cloud cover approaching from the west with
a weak/moderate mid-level trough. However, its cloud cover should
hold off just to the west and south of the forecast area by dawn,
so not much impact on the development of the fog. If anything,
think the cloud cover will only make it more difficult for any fog
in central and northeast Minnesota to dissipate Friday morning
considering the wind flow will be pretty light. The trough`s cloud
cover would limit solar heating on the fog layer, and it may take
an extra couple hours than usual for this time of the year to
lift and dissipate the fog/stratus. Overnight lows should be in
the lower and middle 50s, but some upper 40s in the bog country of
the northwest forecast area.

The trough will provide weak large-scale forcing for ascent
Friday. Once the morning fog and stratus dissipates, and
temperatures climb into the 70s, we will likely see the
development of scattered/broken cumulus across the Northland with
the help from the forcing. There may be some light showers and
weak storms. The lack of wind flow in the column and lack of wind
shear though should keep those storms relatively weak. The best
chances of showers and storms should be in the southwest forecast
area closer. Highs should be in the middle to upper 70s.

.LONG TERM...(Friday night through Thursday)
Issued at 316 PM CDT Thu Aug 17 2017

Friday night could have some lingering showers and storms over
the Iron Range, southeast over the Twin Ports and into northwest
Wisconsin as the remnants of a mid-level shortwave impulse moves
off to the east. Bumped up the POPs over the tip of Lake Superior
over the consensus blends to better capture this wave. Any storms
that develop at this time should stay sub-severe as sufficient
instability and deep layer shear appears to be absent. MLCAPE
values are progged to be between 500 to 1000 J/kg, with 0-6 km
shear between 20 to 25 kts, per the 17.12z GFS and NAM models
during this time.

After the shortwave departs, sfc high pressure will build over
southern Minnesota/northern Iowa for Saturday, which will bring
mostly sunny conditions to the region. High temperatures Saturday
will be slightly above seasonal averages, with highs in the upper
70s and lower 80s. There might be a small chance of showers and
thunderstorms from the Brainerd Lakes area north towards
International Falls as another weak shortwave moves into the
region. However, this appears to be a brief chance.

The best chances of precipitation don`t arrive until Sunday
night, and continue through Monday night, particularly over
northwest Wisconsin as a warm frontal boundary associated with a
sfc low moves into the region. The baroclinic zone stays
relatively stationary over this area, causing the persistent
chances of precipitation.

Tuesday and beyond: another area of high pressure moves into the
region, once again bringing drier conditions to the Northland.
Temperatures will cool down gradually through the early part of
next week, which will be slightly below normal. Highs Wednesday
and Thursday next week could drop to the lower to mid 70s.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1237 PM CDT Thu Aug 17 2017

MVFR to LIFR conditions will gradually improve through the
afternoon as an area of low pressure, currently located over west-
central Wisconsin, will continue to move northeast. Winds will
continue to turn more north to northwesterly as the low pressure
advances northeastward. A tightening sfc pressure gradient on the
backside of the low will support gusty conditions over KDLH, KHIB,
KBRD, and KHYR TAF terminals, with gusts between 15 to 25 kts
possible. Ceiling heights will remain in the MVFR/IFR range this
evening, with some improvement overnight.

An area of high pressure will then move into the region for early
Friday, which will cause the winds to go light. This, coupled
with saturated soil conditions, will lead to the development of
fog in some locations. Some of the model guidance is indicating
fog to drop to IFR categories, but confidence isn`t high enough at
this point to go with this solution. Instead, went with more MVFR
vsby reductions.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  54  75  56  79 /  10  20  30   0
INL  51  78  52  81 /  10  20  10   0
BRD  54  76  54  79 /   0  30  10   0
HYR  55  74  53  80 /  10  10  30   0
ASX  57  76  57  81 /  40  10  40   0

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.

MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.

LS...Small Craft Advisory until 10 PM CDT this evening for LSZ141>143-
     146-147.

     Small Craft Advisory until 4 PM CDT this afternoon for LSZ144-
     145.

     Small Craft Advisory until 4 AM CDT Friday for LSZ121-140-148.

&&

$$

SHORT TERM...Grochocinski
LONG TERM...JTS
AVIATION...JTS



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