Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 301742
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1142 AM CST Wed Nov 30 2016

.SHORT TERM...(Today through Thursday)
Issued at 351 AM CST Wed Nov 30 2016

The slow-moving low pressure system across central Minnesota will
gradually exit to the east today leading to cyclonic flow across
the upper Midwest today into tomorrow. Light precipitation - a mix
of rain, snow, and drizzle - will be possible much of the time, with
lake effect snow showers producing a few inches of snow along the
snow belt region in northern Iron and Ashland counties. Elsewhere,
though, snow amounts will be less than an inch. Not great news for
snow-lovers given the deep snowpack from the mid-November winter
storm has been all but reduced to a few inches due to the recent
warmth and rain. (Our observer near Orr went from receiving 24.8" of
snowfall and a snow depth of 18" to just 4" as of yesterday morning.)

On the synoptic scale not much new to say as this weak low slowly
exits. Through the next 36 hours low level moisture will stick
around, but the mid and high level moisture will begin to give way
to drier air moving in aloft. The drying aloft will result in at
least some loss of ice aloft, opening up the window for freezing
drizzle late tonight into Thursday, mainly across northern
Minnesota. However, the upstream airmass in northern Ontario should
have plenty of ice aloft, so even though there will be a loss of
moisture through the typical snow growth layer, the low level
moisture should have enough to to produce more snow than, say, if
the airmass had a more tropical origin. Stratiform rain/snow will
give way to more of a showery nature Thursday, with low level lapse
rates steepening which will continue the chance for snow showers
until drier air moves in from the west Thursday.

Along the south shore conditions will be very favorable for a period
of lake effect snow showers tonight into Thursday. Low level winds
turn northerly by midnight tonight, slowly becoming north-
northwesterly towards daybreak Thursday. The already moist
environment will only be enhanced as the colder air aloft (850mb
temps around -5C to -10C) travels over the relatively warm water (40
to 45F, or +4 to +7C) which will lead to water-air temp differences
of 9 to 17 C, favorable to lake effect snow processes. Low level
wind profiles are very favorable for lake effect bands to set up to
the lack of directional shear and not-too-strong speeds in the low
levels. Overnight tonight will be the prime time for a few inches to
fall across the snow belt region, with the chance for snow
continuing on Thursday dependent on moisture availability and wind
directions. Winds will gradually becoming northwesterly through the
day, but if open lakes in northern Ontario can help to introduce
moisture into the upstream airmass, lake effect snow could continue
through the day. Lake effect snowfall may also be possible on our
larger inland lakes tonight due to their warm temperatures, with the
concern for loss of ice aloft even more relevant because of the
limited parcel transit times compared to Lake Superior. Did not add
any inland lake snow to the forecast for now, but some local snow
bands could produce a small swath of snowfall accumulation if
conditions are just right.

In addition to lake effect snowfall, as winds turn northwesterly
conditions appear favorable for the terrain-induced gravity wave to
develop across northern Douglas and Bayfield counties as often
happens in northwest flow. Best timing for this looks to be late
tonight into Thursday, dependent on upstream moisture. Added around
an inch or so of snowfall to the favored region for this phenomena.

Temperatures gradually falling through the rest of the work weeks.
Highs not budging by much today in the mid 30s. Lows tonight in the
mid 20s to low 30s tonight, then highs cooler in the low to mid 30s
Thursday. At DLH the normal high is 28, low 14, continuing the very
warm November trend into the start of December.

.LONG TERM...(Thursday night through Tuesday)
Issued at 351 AM CST Wed Nov 30 2016

The extended period will start out with a broad upper level trough
over the northern CONUS. The Northland will be under northwest flow
aloft Thursday night into Friday with a shortwave moving through far
northeast Minnesota Thursday night. The surface flow will also be
northwest with deeper low pressure well off to the east. We have a
chance for snow showers over the snowbelt region of northern
Wisconsin and a chance in the Arrowhead as well as the shortwave
moves through that area.  There should be enough low level moisture
present in the cyclonic flow for some flurries over portions of the
rest of the Northland. Forecast soundings suggest enough drying
above the low level moisture to support freezing drizzle, mainly
Thursday night. Confidence in how widespread or significant this
will be is low. We think the models are underdoing the depth of the
moisture into the colder air aloft. There may be some freezing
drizzle as well Thursday night along the South Shore but we do
expect mainly snow showers as the cloud depth will be deeper given
the convective nature of the snow showers. At this time, we only
expect light snow accumulation Thursday night into Friday.

There isn`t really any significant forcing for precipitation Friday
night into Saturday and we have mainly low pops at times for some
light snow showers. There could be some light accumulation along
the snowbelt of the South Shore due to lake effect processes.

Both the GFS and ECMWF are in decent agreement bringing a stronger
shortwave through the region late Saturday night into Sunday. There
will be a chance for mainly snow with mostly light accumulation
expected. There is a chance for some higher amounts along portions
of the North Shore with lake and terrain enhancement there.

Another shortwave will bring a chance for light snow late Monday
into Tuesday. Mostly snow is expected with this system as well and
it does not look strong enough for heavy snow.

The period will feature temperatures near or a few degrees above
normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1142 AM CST Wed Nov 30 2016

The surface low center had moved into west central Wisconsin at
the start of the forecast. It will trek east northeastward and
reach southern Ontario by the end of the forecast. This will keep
the ceilings/visibilities in the IFR/LIFR, and occasionally VLIFR
range through the forecast. A variety of precipitation types will
affect the terminals through the forecast. Visibilities look to
improve to VFR late tonight into Wednesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  36  29  32  25 /  70  50  10  10
INL  34  27  30  24 /  60  50  20  10
BRD  36  30  33  25 /  60  40  10  10
HYR  37  31  34  25 /  60  60  30  10
ASX  39  32  35  29 /  70  70  50  30

&&

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

$$

SHORT TERM...JJM
LONG TERM...Melde
AVIATION...GSF



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