Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Duluth Minnesota
332 am CST Tuesday Jan 27 2015
Short term...(today and tonight)
issued at 331 am CST Tuesday Jan 27 2015
High pressure was settling over the forecast area at 08z. Plenty of
low clouds covered the area trapped under the low level inversion
from the high. There are a few holes that open near Lake
Superior...but not anticipating any of them making it inland. If
they do...they will fill in rather quickly. The high will drift
over the central Great Lakes by 00z Wednesday resulting in a SW flow
affecting the area. Models are trying to clear out the cloud cover
somewhat during the day...but have opted to hang onto the cloud
cover through the day as 1000-850mb relative humidity remains above 65 percent.
Model differences begin to creep into the forecast process tonight.
By 06z...the European model (ecmwf) is bringing some light quantitative precipitation forecast from inl to The
Arrowhead. Other models keep the precipitation north of the Canadian
border. However...the hires nmm/arw east and west are hinting at
some light precipitation...but just over The Arrowhead. Will use a
blended approach and have no quantitative precipitation forecast prior to 06z. After 06z...have
introduced some probability of precipitation to the tip of The Arrowhead. This is when some
weak frontogenesis is found from 700mb to 850mb. Ptype should be all
snow as suggested by thermal profiles. Snow amounts will only be
about a trace.
Long term...(wednesday through monday)
issued at 331 am CST Tuesday Jan 27 2015
Our next weather maker is projected to move through the area on
Wednesday and Wednesday night. There are still lots of differences
in the models...but the consensus seems to point to a pair of
shortwaves moving through the west-northwest upper level flow. One
in the northern stream that tracks across the US/Canadian border to
Lake Superior...and another that tracks from Colorado east to
southern Illinois by Thursday morning. The better dynamics are
focused along these corridors...despite the waves being phased
enough for a single 850mb low moving across the plains. The surface
low tracks from western South Dakota east across Iowa...but the
models have lots of differences here...with some placing more energy
in the northern stream and placing a low farther north in addition
to this more southerly one. Either way...the better dynamics stay
just north of the area and skim the northern County Warning Area with precipitation
Wednesday and Wednesday night...mainly associated with the northern
stream wave. Still lots to sort out with this system...but for now
have kept probability of precipitation in the likely category Wednesday night across the
north...with lower probability of precipitation to the south. Middle level temperatures get
warm once again with this system...and we have a very real threat of
mixed precipitation including freezing rain Wednesday and Wednesday
evening before the low passes the area and strong cold air advection
switches all to snow. Snowfall amounts with this system will not be
very large...but the mixed precipitation may cause travel problems.
A strong high pressure builds into the area for Thursday night and
Friday...bringing colder temperatures to the region. We may be
looking at some below zero temperatures by Friday morning. Another
cold front brings another chance of snow to the area on
Saturday...before another surge of cold air moves into the area.
Saturday night and Sunday night will be colder yet...with
temperatures in the negative double digits by Monday morning.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1134 PM CST Monday Jan 26 2015
MVFR with a few IFR ceilings covered the Northland late this
evening...and are expected to continue for most areas into at
least Tuesday morning. Observations and radar indicate little
precipitation left across the area and we expect that through the rest of
the period as well.
The main challenge continues to be when and if these low clouds
will become scattered. The latest NAM and rap guidance continues
to push off the change from MVFR/IFR to VFR. We will delay this
for several more hours with the 06z tafs.
Preliminary point temps/pops...
dlh 32 21 32 22 / 0 10 20 50
inl 32 24 31 14 / 0 10 50 60
brd 34 25 34 23 / 0 10 10 40
hyr 32 20 33 24 / 0 0 10 50
asx 33 21 34 25 / 10 0 20 50