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Area forecast discussion
National Weather Service Duluth Minnesota
531 PM CST Mon Nov 11 2019

Short term...(this evening through Tuesday night)
issued at 239 PM CST Mon Nov 11 2019

The Lake Superior lake effect machine will continue to generate
heavy lake effect snow over northwest Wisconsin, specifically over
Iron County, where a Winter Storm Warning continues overnight
tonight and into Tuesday morning. So far today, we have received
reports of snowfall amounts ranging from 5 to 10 inches already,
with another 3 to 11 inches possible this evening and overnight
over Iron County. The main features supporting this lake effect
are some bitterly cold temperatures aloft, with northwesterly low-
level flow. A positively-tilted upper-level trough will gradually
track eastward this evening and overnight, with 850 mb
temperatures ranging from the 20 to 24 degree c below
zero...sufficiently cold over the relatively Warm Lake to support
lake effect snow. These temperatures are actually around 2 to 3
Standard deviations below average for this time of the year! Very
cold temperatures are also expected overnight, with lows in the
single digits below zero over most of the region, which would make
tonight the coldest night so far this season. People should dress
appropriately if they plan to venture out and about tonight.

Eventually, a high pressure ridge axis will enter the region early
Tuesday morning, which will not only bring in drier air with it, but
also will back winds more southwesterly Tuesday morning. These
conditions will gradually shut down the lake effect snow over north-
central Minnesota before sunrise, and along Lake Superior later in
the morning. Southerly return flow will bring in some relatively
warmer temperatures compared to today for Tuesday, with highs in the
lower to middle teens. As winds turn more southerly, there could be
a small chance for some lake effect snow along the tip of the
Minnesota arrowhead Tuesday afternoon and early evening. If any snow
does develop, accumulation amounts should remain very light.

Attention then turns to another chance for light snow early
Wednesday as a mid-level shortwave trough along with a low-level
baroclinic zone/frontogenesis band moves across central
Minnesota. There are some timing differences among the forecast
model guidance, so it's unclear how quickly this snow will move
in. In any case, it does appear to move through the region
Wednesday morning. I have introduced some small pops around 12z
Wednesday to account for the leading edge of this system.

Long term...(wednesday through monday)
issued at 239 PM CST Mon Nov 11 2019

A gradual transition warming up to near-normal temperatures through
the work week, with above normal temperatures possible for the
weekend.

Mid to late week: a low chance for light snowfall along a cold front
Wednesday, then at least partially clearing skies into Thursday as a
broad area of high pressure builds across the Great Plains. Late-
week another strong Arctic airmass will approach from the north, but
will be on a more easterly trajectory towards New England leading to
increasing clouds and just a very low chance for some snow along the
international border on Thursday night. An area of high pressure
builds across Ontario on Friday leading to skies clearing out, with
a more zonal pattern taking hold at mid/upper levels across much of
the Great Plains and Canadian prairie. Highs in the 20s to low 30s,
with some locations reaching above freezing on Friday depending on
when the southerly flow develops at low levels as the area of high
pressure moves off to the east. Lows in the teens - warmer than
early week but still around ten degrees below normal.

Next weekend: as the high pressure builds eastward, southerly flow
develops at low levels across the Mississippi River valley causing a
warm front to approach the upper Midwest Friday night into Saturday.
Initially this warm front will just lead to increasing clouds and
warmer temps, with a chance for light precipitation developing
within the warm sector on Saturday. However, a better chance for
accumulating snow Saturday night as a cold front approaches from the
northwest. Snowfall amounts in the 1-3 inch range are most likely -
while there will be fairly good large-scale forcing from an
approaching mid-level longwave trough and good potential for low
level moisture from the Gulf advecting in ahead of the cold front,
the timing for snow falling will be along a fairly short window, and
the potential for heavy snowfall rates is low. Temperatures will be
warmer, even a few degrees above normal at times, with highs in the
mid 30s and potential for some locations to warm up to the low 40s
on Sunday/Monday. Lows in the mid to upper 20s.

Beyond next weekend there is typical variability across guidance,
with occasional chance for snow through the week and temperatures
currently leaning towards near to perhaps above normal.

&&

Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 531 PM CST Mon Nov 11 2019

Scattered to broken VFR cigs at the start of the forecast, with
some areas of MVFR, especially near hyr. The northwest wind over
Lake Superior will bring some periodic MVFR cigs near hyr until
morning, then VFR as high pressure is overhead. With the high
eventually affecting all terminals, VFR is expected. Look for
gusty surface winds to develop in the afternoon from brd and hib
to inl as southwest winds increase.

&&

Marine...
issued at 239 PM CST Mon Nov 11 2019

Northwest winds 15 to 20 knots gusting to around 25 knots will
persist through tonight across parts of Western Lake Superior, with
a brief period of even stronger winds possible around the nearshore
waters of Grand Marais to Grand Portage due to cold air sinking
along the higher terrain this evening. Overall, a diminishing
trend in winds after midnight tonight, with winds gradually
becoming southwesterly through the day Tuesday. By Tuesday
evening, winds will be south-southwest at 15 to 20 knots, causing
building waves and dangerous conditions for small craft along
parts of the North Shore. A Small Craft Advisory is currently in
effect for portions of the Western Lake Superior nearshore zones,
and after this advisory expires late tonight into Tuesday morning,
another will be needed for parts of the North Shore by Tuesday
afternoon.

&&

Preliminary point temps/pops...
dlh -1 17 10 24 / 60 0 20 30
inl -5 18 11 25 / 60 10 10 0
brd -3 19 15 28 / 10 0 30 40
hyr -4 18 10 25 / 50 0 20 50
asx 3 20 12 27 / 60 20 10 30

&&

Dlh watches/warnings/advisories...
WI...Winter Storm Warning until 9 am CST Tuesday for wiz004.

Minnesota...none.
Ls...Small Craft Advisory until 4 am CST Tuesday for lsz140>142-
146>148.

&&

$$

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