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fxus63 kdlh 200640 

Area forecast discussion
National Weather Service Duluth Minnesota
1240 am CST Wed Nov 20 2019

issued at 1240 am CST Wed Nov 20 2019

Updated for the 06z aviation discussion.


Short term...(this evening through wednesday)
issued at 325 PM CST Tue Nov 19 2019

An upper level short wave was moving over the forecast area this
afternoon with a good sized vorticity maxima. Meanwhile, a warm
front was over the western portion of the region, moving east. These
features were combing to keep some fog, drizzle, flurries and plenty
of clouds around. The short wave and front depart this evening
allowing for some upper level/surface ridging to cover the area
tonight. Some low and mid level drying is seen from area
soundings/models, but will see the clouds stick around with some
pockets of fog underneath the inversion.

The ridging begins to move off to the east Wednesday while a
positively tilted upper trof sharpens up as it moves through the
Canadian prairies and the northern plains. In response, a surface low
begins to deepen over eastern Colorado before moving out into
western Nebraska. After a cool start, warm air advection gets
underway providing some isentropic lift across northeast Minnesota.
As temps warm, will see a drizzle/rain/snow mix in the morning,
before becoming all snow over the Borderland in the afternoon.
Mainly rain is expected south of U.S. Highway 2 in Minnesota and
Wisconsin, with a rain/snow mix in between. North central Wisconsin
sits under a dry tongue and looks to be precipitation free. The
precipitation will intensify in the mid afternoon along the
Borderland as a deformation zone sets up. A quick one to two inches
of wet snow is possible over Koochiching and northern St. Louis
counties as precipitable waters are around 0.6 inches.

Long term...(wednesday night through tuesday)
issued at 325 PM CST Tue Nov 19 2019

The main focus for the long-term forecast continues to be on the
Wednesday night/Thursday wintry system that should bring some
accumulating snow, along with rain and possibly freezing rain in
some locations.

Wednesday night finds an area of precipitation, mainly across
northern Minnesota, as a positively-tilted upper-level trough makes
its way into the region. Meanwhile, a secondary southern stream mid-
level shortwave trough will lift northeastward, along with the
attendant surface low. The strongest lift with this event will be
associated with the southern stream shortwave. The biggest area of
uncertainty with this event will be where the corridor of a wintry
mix will be as the 540 thickness line bisects the region. The models
are generally in good consensus, but any wiggle in the track of the
surface low or change in the thermal profile will change
precipitation types quite a bit. The models have trended toward
higher qpf, and in turn, higher snowfall totals across northern
Minnesota. Generally, we now have an area of 3 to 7 inches of snow
accumulations from Wednesday afternoon through Thursday afternoon,
with the heaviest totals across the tip of The Arrowhead region.
These snowfall amounts appear to reach criteria for a Winter Weather
Advisory, but will hold off on issuing one for now due to the
uncertainty with the precipitation types. The Thursday morning
commute looks to be when the most impacts from this system will be
due to the accumulating snowfall and wintry mix potential.

As the surface low moves off to the east, there should be a
diminishing trend in precipitation chances through Thursday evening.
There will be some lingering lake effect snow as winds turn more
northwesterly behind the departing system, with colder air filtering
in. A surface high pressure ridge will build into the region
Thursday night into Friday morning, which should help temperatures
plummet Friday morning. Low temperatures will range from the upper
single digits to the teens above zero. Drier conditions, with a
gradual warming trend is expected through the upcoming weekend.
Highs Saturday and Sunday will warm back up into the 30s. There will
be some weak mid-level shortwaves that could move through the
region, but the air mass in place appears to be too dry to support
much precipitation. Our next potential for widespread precipitation
appears to be sometime in the middle of next week.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1240 am CST Wed Nov 20 2019

A warm front that has been moving across the area has weakend this
evening, and while conditions remain LIFR for khyr, sites to the
west of the front have improved to MVFR or even VFR. I curently expect
the poor conditions to linger at khyr for several more hours, but
higher ceilngs are not very far west of there and we may get an
abrupt improvement earlier than currently forecast. The other
sites should continue to fluctuate around the MVFR/VFR boundary
through at least 15z. After 15, a new round of snow will move into
the area ahead of a low pressure system, causing conditions to
drop to IFR in a rain/snow mixture at kdlh, khib and kinl by 21z,
which then gradually turns to all snow and visibilities become IFR
as well. These conditions to not spread into kbrd until after 00z,
or khyr until 03z. All sites to remain at least IFR if not LIFR
through the remainder of the taf period.


issued at 307 PM CST Tue Nov 19 2019

No hazardous weather conditions are expected through Wednesday
night. Light southwest winds will turn more westerly this evening
and overnight, but should remain between 5 to 10 knots through the
overnight hours. Wave heights will remain 2 feet or less through
Wednesday evening. However, an approaching area of low pressure from
the south will help turn winds more east to northeasterly late
Wednesday night and Thursday morning, which will gradually
strengthen as the low nears. Conditions hazardous to smaller vessels
will become likely, with winds between 15-20 knots and gusts of 20-
30 knots. This will also lead to building waves along the South
Shore of Western Lake Superior, with wave heights between 2 to 5
feet possible. A Small Craft Advisory will likely be needed.


Preliminary point temps/pops...
dlh 28 37 31 31 / 10 50 100 90
inl 27 34 23 24 / 10 100 100 40
brd 30 38 29 30 / 10 50 100 60
hyr 30 39 33 35 / 10 20 100 100
asx 30 40 33 36 / 10 20 100 100


Dlh watches/warnings/advisories...
WI...dense fog advisory until 4 am CST early this morning for wiz001-

Dense fog advisory until 9 am CST this morning for wiz002>004-

Minnesota...dense fog advisory until 4 am CST early this morning for mnz011-

Dense fog advisory until 9 am CST this morning for mnz012-020-




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