Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Duluth Minnesota
1241 am CDT Tuesday Apr 21 2015
issued at 637 PM CDT Monday Apr 20 2015
We expanded probability of precipitation this evening to account for observations/radar.
Much of the precipitation is light...so not much accumulation is
expected this evening.
Short term...(this evening through Tuesday night)
issued at 328 PM CDT Monday Apr 20 2015
The closed upper low was meandering around northwest Minnesota at 19z with
embedded pieces of short wave energy rotating through the forecast
area. This was resulting in precipitation over the far eastern edge of the
area from Cook County southward to Iron and Price County WI. Most of the
snow has been a trace to a couple tenths. Did get a report from Gile
WI of 1 inch as of 1830z. Snow had ended at Gile as of the report.
Next piece of energy will push rain/snow showers into the western
third of the region. Snow amounts through 00z will be light.
After 00z...expect more pieces of short wave energy to move through
the forecast area as the upper low travels to the western edge of
Upper Michigan. Highest probability of precipitation will be found over the northern half of the
forecast area north of the Iron Range. The precipitation will begin as
primarily rain early...then a mix of rain/snow until near 06z before
changing to all snow. Around one inch of snow is possible from the
Iron Range north to the Canadian border. Up to one inch is possible over
Iron County WI as a weak band of low level fgen moves nearby.
The upper low drifts over to Eastern Lake Superior by 00z Wednesday.
More short wave energy will continue to be pulled into the region
along with colder air. Ptype will be snow in the morning with some
accumulations anticipated...especially over The Arrowhead and into
northwest WI. By afternoon...the precipitation becomes mixed due to diurnal heating
processes. Some areas may change over completely to rain in the late
afternoon. Up to an inch is possible in the afternoon along the
Long term...(wednesday through monday)
issued at 328 PM CDT Monday Apr 20 2015
The cut off low situated over the northern Great Lakes/Ontario
Tuesday night...will gradually fill as it slowly pushes east through
the end of the week. The continued cyclonic flow with unstable lapse
rates will keep clouds...gusty winds and rain/snow showers across
much of the Northland Wednesday. Have lowered dew points and relative humidity
values Wednesday as latest NAM bufr soundings suggest deep mixing of 5000
feet or higher brings down much drier dry air from aloft.
The low clouds/showers will depart to the east Wednesday night/Thursday as
a ridge of high pressure and drier air works into western Minnesota.
Although there remains some model disagreement in the eastward
extend of the ridge axis/driest air over Minnesota...at this time
conditions are expected to be mostly sunny and dry across the dlh
forecast area Thursday/Friday.
Long range models are struggling to resolve a series of short waves
that track across The Rockies and into the upper plains through the
weekend. At this time have kept forecast dry...but probability of precipitation may need to be
added later as details become worked out.
Temperatures will run about 5 to 10 degrees below normal through the
end of the week...warming to near normal readings with highs in the
50s and lows around 30 this weekend.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1240 am CDT Tuesday Apr 21 2015
An upper level low over far northern Minnesota will move east and
continue to cause periods of light snow or flurries across much of
the Northland. The snow may diminish in spots overnight...but steep
lapse rates should cause more snow showers...possibly mixed with
rain Tuesday afternoon...to develop on Tuesday. Mainly MVFR ceilings
will occur and widespread IFR is looking less likely. Ceilings may
increase to low VFR in spots on Tuesday...and more so Tuesday
Gusty west/northwest winds will occur through much of the
period...and increase by late Tuesday morning for all areas before
diminishing Tuesday evening.
Preliminary point temps/pops...
dlh 27 42 26 43 / 20 10 10 10
inl 24 39 22 40 / 30 10 10 10
brd 27 44 25 46 / 10 10 10 0
hyr 27 43 25 44 / 30 20 10 10
asx 28 43 27 42 / 40 40 30 20
Ls...Small Craft Advisory until 5 am CDT Wednesday for lsz121-140>148.