Scientific Forecaster Discussion
fxus63 kdlh 210355
Area forecast discussion
National Weather Service Duluth Minnesota
955 PM CST Wed Nov 20 2019
issued at 955 PM CST Wed Nov 20 2019
Updated marine discussion.
Update issued at 542 PM CST Wed Nov 20 2019
Updated for the 00z aviation discussion.
Short term...(this evening through Thursday night)
issued at 400 PM CST Wed Nov 20 2019
Our first winter storm of the season is still on track to impact
the Northland this afternoon through the day Thursday, with wet,
heavy snowfall as well as a wintry mix possible for portions of
Precipitation is increasing in coverage this afternoon as a band of
850-700 mb layer frontogenetical forcing intensifies. We have
already received reports of a rain/snow mix from the Waskish, Minnesota
area east towards Cook and Ely. This fgen band is associated with
the leading edge of a positively-tilted upper-level trough that will
move through the Northland tonight through the day tomorrow. A
secondary southern stream trough will lift northeastward this
evening and overnight, which will lead to expanding chances of
precipitation. While we are expecting heavy, wet accumulating snow
across northern Minnesota, there is a transition zone of
precipitation types, with the 540 decameter 1000-500 mb layer thickness
line bisecting the Northland. Rain will be most common to the
south before colder air wraps into this system overnight and the
rain and wintry mix transitions to all snow tonight. The heaviest
snowfall accumulations are expected this evening and overnight,
with generally between 4 to 10 inches of snow possible from Grand
Rapids northeast along the Iron Range into the Minnesota arrowhead
region. There is more uncertainty on the snowfall amounts from
the Brainerd lakes region northeast towards the twin ports due to
a wintry mix of rain, snow, sleet, and freezing rain possible,
which could decrease snowfall amounts. However, if the colder air
moves through the region faster than is forecast, snowfall amounts
in these areas will need to be increased.
The system will continue to move through overnight, and chances
of snow will gradually diminish from west to east during the
daylight hours Thursday. The inverted surface trough associated
with an attendant surface low pressure moves out of the region.
Temperatures will actually decrease through the day Thursday, so
snow will largely be the main precipitation type, even into
northwest Wisconsin. The heaviest snow will shift southeastward
into northwest Wisconsin Thursday morning, where between 1 to 4
inches of snow will be possible. Snow will linger the longest over
the higher elevations of northern Iron County due to northerly
winds, which will lead to lake enhanced snow. Total accumulations
in northern Iron County could range between 3 to 5 inches. Highs
on Thursday will range from the 20s over over northeast Minnesota
to the lower 30s over northwest Wisconsin.
Long term...(friday through wednesday)
issued at 255 PM CST Wed Nov 20 2019
The upper level trof departs quickly Thursday evening as surface
high pressure builds across the region. There will be a brief
opportunity for some lake effect snow showers Thursday evening over
Ashland, Iron and price counties. Very light accumulations are
possible, but less than one half inch. Thursday night and Friday
finds high pressure in control.
Friday night finds an upper level trof reaching western Minnesota
with a cold front into the western portion of the area. Moisture is
limited with these features and no precipitation is expected. The
trof and cold front exit the area on Saturday. Models disagree on
the cold air moving across the region behind the front, with the GFS
the coldest/most moisture. Consensus is a dry forecast and will
follow. Saturday night finds a warm front moving into the region
with some ridging aloft. The GFS is once again the coldest and has
been ignored. Dry Saturday night as a result. The next cold front is
progged to move into the area Sunday afternoon. Model differences
prevail with the amount of moisture available to generate some
precipitation. Have a dry forecast as a blend leans that way.
An area of low pressure will combine with an upper short wave moving
through the region to bring the next chance of precipitation.
However, the GFS and Gem has the low in Canada, while the European model (ecmwf)
takes it right through the area. This scenario continues Monday and
will blend the models for placement of pops. Ptype issues arise due
to the amount of warm air working with this system.
A closed upper low comes into play for Monday night and Tuesday.
Models begin to agree on the upper level features, but disagree on
how it affects the surface where models are offering different
solutions. Maintained a blended approach which leads to some snow
showers, possibly mixing with rain Tuesday.
Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 542 PM CST Wed Nov 20 2019
A low pressure system moving across the region will bring an area
of snow and IFR/LIFR conditions across the terminals through the
next 18 hours. Kinl has already lowered to IFR/LIFR in snow, and
these conditions are expected to spread southeast through 06z.
Some sites are starting with rain or mixed rain and snow, and will
gradually switch over to all snow within a few hours. Conditions
will slowly improve again to at least MVFR from northwest to
southeast after 12z. Kbrd, khib and kinl may return to VFR as
early as 20z.
issued at 955 PM CST Wed Nov 20 2019
Northeast winds will develop over Lake Superior as a low pressure
system approaches the area overnight tonight. By 10 am, we should
be getting gusts in the 25 to 30 knot range, and waves should
build into the 4 to 6 foot range. During the day winds will turn
more to the northwest, then both winds and waves diminish overnight
Thursday night. We have issued a Small Craft Advisory for
Thursday and Thursday evening for a part of the South Shore. Winds
turn back out of the southwest on Friday, and pick up enough in
the afternoon and evening that we may need another Small Craft
Advisory for parts of Western Lake Superior.
Preliminary point temps/pops...
dlh 29 32 13 30 / 100 90 0 0
inl 19 23 10 32 / 100 10 0 0
brd 28 30 14 34 / 100 60 0 0
hyr 34 35 15 32 / 100 100 10 0
asx 33 35 18 33 / 100 100 10 0
WI...Winter Weather Advisory from 3 am to 6 PM CST Thursday for
Minnesota...Winter Weather Advisory until 6 am CST Thursday for mnz010-018-
Winter Storm Warning until 9 am CST Thursday for mnz011-012-
Ls...Small Craft Advisory from 4 am to 10 PM CST Thursday for