Area Forecast Discussion
Issued by NWS Duluth, MN

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469
FXUS63 KDLH 172343
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
543 PM CST Tue Jan 17 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 327 PM CST Tue Jan 17 2017

Surface ridge axis over the forecast area this afternoon has kept
the sensible weather relatively quiet this afternoon, with quite a
bit of sunshine and increasing south winds across the forecast
area. All but the western quarter of the forecast area have gotten
above freezing today, producing some more snow melt, thus adding
some low level moisture to the atmosphere. This morning that
contribution produced dense fog from the Twin Ports up the north
shore and into the Iron range somewhat as well. These areas were
also under the surface ridge axis, with calm or light winds. Fog
is possible once again tonight, and with the second day of melting
expect the fog to develop earlier than it did this morning. The
ridge axis will have shifted to east of the forecast area, and
normally would say that this increases the potential for fog
tonight. However, the upstream air is coming from a colder and
drier airmass, and very little melting occurred upstream over
central and southern Minnesota today. It`s actually warmer in the
Arrowhead (mid 30s-low 40s) than it is southwestern Minnesota as
of 3 pm this afternoon (upper 20s-low 30s). This is going to make
it harder to develop fog tonight. Thus, have focused on northwest
Wisconsin for the greatest potential for fog tonight, developing
sometime from mid evening to early morning and lingering through
to mid morning. The fog and associated cloud cover should keep
temperatures from dropping off too badly overnight and have kept
lows around 20, with colder values farther northwest where skies
should be clearer. Wednesday high temperatures to get well above
freezing, with sunshine and warm air advection going on that
started this afternoon. Depending on the fog trends this may need
to be reduced, but anticipate the south flow should clear things
out and allow the sunshine in.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 327 PM CST Tue Jan 17 2017

Summary: The Northland can expect a prolonged period of
substantially warmer than normal weather through at least early next
week, with temperatures about 15 to 20 degrees above seasonal
normals. This will bring a slow January thaw, with daytime highs in
the 30s to near 40 degrees, and generally freezing temperatures at
night and the early mornings. Cloud cover will be somewhat limited
though because the melting snowpack will add abundant moisture to
the air, as well as the general influx of more humid air into the
region over the period. There is a risk of drizzle and freezing
drizzle Thursday night and early Friday, followed by the potential
for a round of rain/snow Friday afternoon into Friday night. Periods
of light rain and snow are possible over the rest of the weekend
into early next week.

Wednesday night and Thursday...An upper level ridge will build into
the region from the west, which should help promote clear skies.
However, both the GFS and NAM are indicating abundant low level
moisture advecting into the Northland from the south overnight into
Thursday. Trended the cloud cover up a bit to reflect this cloud
cover potential, and we may need to increase cloud cover quite a bit
more. This might have consequences on the Wednesday night low
temperature forecast, because the extra cloud cover could bolster
the temperatures significantly more than current forecast of lows in
the lower 20s. Did not forecast fog for this period because it looks
like there would be enough southerly flow to just result in
widespread stratus and lower visibilities in the 2 to 4 mile per
range, if the extensive stratus layer indeed happens. There would
likely be some clearing Thursday afternoon, especially over northern
Minnesota, before even more moisture advects into the region late
Thursday.

Thursday night and Friday morning...There will likely be another
surge of moisture into the Northland as an upper-level trough,
associated with an upper-low lifting to the north-northwest through
the Great Plains, swings into the Northland. The upper-trough will
provide some modest synoptic lift to possibly help squeeze out some
light drizzle and freezing drizzle for areas near and south of
Highway 2.

Friday afternoon and night...Another upper-trough associated with
the Great Plains wave will swing through the Northland, from south
to north, late Friday afternoon through Friday night. This wave
should have deeper moisture, and likely result in a period of wet
and sloppy snow. Snowfall amounts are a little difficult to
determine at this time, but even if there is significant melting due
to relatively warm surface temperatures, it might come down fast
enough to warrant a winter weather advisory. There could be some
back-end freezing drizzle in the wave`s wake late Friday night into
Friday morning. The GFS and ECMWF are in pretty good agreement for
this period, but the Canadian is about 12 hours slower. Leaned on
the GFS and ECMWF.

Saturday and Saturday night...A weak upper-low may move through the
Northern Plains and Upper Midwest, potentially helping to maintain
cloud cover over the Northland and some light rain and/or snow.

Sunday into Monday...A Southern Plains low will lift into the
Eastern US, and its inverted trough over the western Great Lakes
could bring additional light rain and snow to the Northland.
Considering its inverted trough, there could be some banding of the
rain and snow, but those details will be forthcoming once we get a
better idea of even where the inverted trough would set up.

Tuesday...There doesn`t look like any significant weather for the
Northland at this time...but...there are early signs of a potential
winter storm system heading into the middle of the week. Both the
GFS and ECMWF continue to indicate, similar to their 00Z runs, a
Colorado or New Mexico low developing early in the week and then
ejecting and lifting towards the western Great Lakes by the middle
of next week. This track could bring significant snow to parts of
the Northland. Stay tuned as we keep an eye on this potential storm
system.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 543 PM CST Tue Jan 17 2017

A weak ridge of high pressure will move through the Northland
tonight. Stratus and fog was forming along portions of the North
Shore/Arrowhead already and stratus was seen moving slowly north
into Pine/Burnett counties and should continue through the night.
Increasing warmth and moisture today will lead to fog and this
will be most likely over northwest Wisconsin where the surface
ridge will be for much of the night creating light winds. Further
northwest, increasing low level flow should keep the fog from
becoming widespread. The stratus and fog along the North
Shore/Arrowhead region may diminish later this evening as those
winds increase. LLWS will occur across much of the region tonight
then diminish late tonight or Wednesday morning. VFR conditions
are then expected after the stratus/fog lift.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  19  35  24  38 /   0   0   0  10
INL  19  36  20  40 /   0   0   0   0
BRD  15  37  22  39 /   0   0   0  10
HYR  19  38  24  40 /   0   0   0  10
ASX  23  39  26  41 /   0   0   0  10

&&

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

$$

SHORT TERM...LE
LONG TERM...Grochocinski
AVIATION...Melde



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