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Area forecast discussion 
National Weather Service Green Bay WI
621 PM CDT sun Apr 19 2015

Updated aviation portion for 00z taf issuance

Short term...tonight and Monday
issued at 243 PM CDT sun Apr 19 2015

Weather pattern becomes more active starting tonight...with the
first chance of widespread rain arriving this evening and
continuing Monday.

Current surface analysis showed a deepening low pressure spinning in
southern Illinois and slowly drifting north. Rain became more
widespread as the low drifted north...with observation occasionally
showing moderate to heavy rain in Illinois and in. Meanwhile...water
vapor imagery showed another disturbance shifting into the northern
jet stream...with a noted stronger area of forcing associated with
it on mesoanalysis. The reflection of this was seen at the surface
with a developing low and trailing cold front over NE Minnesota. How
all these features interact as they merge and shift through the
Great Lakes region will determine how precipitation trend pan out tonight.

Through this evening...todays precipitation was scattered at best and
eastern Wisconsin even cleared out and warmed up through the
afternoon. Given the drier trend today...slowed down precipitation
arrival this evening. Better lift doesnt really overtake the County Warning Area
until after 03z wouldnt be surprised if many locations
make it until sunset without seeing much if anything in the way of

Tonight and Monday...the low pressure system in Illinois will shift
north and east through the night towards lower Michigan.
Meanwhile...the disturbance over Minnesota will swing east and
strengthen as it interacts with better forcing. The two system
will interact and widespread precipitation is expected. Introduced higher
end probability of precipitation after 06z Monday as the stronger forcing shifts over
northeast Wisconsin. Couldnt add much detail from
models differ on how these weather features interact and where the
better forcing will be. Leaned towards a solution that showed the
better lift and higher quantitative precipitation forecast in central and eastern Wisconsin...but
certainly not the only solution. Heaviest rainfall should be
between midnight and early Monday morning.

Latest models have trended towards a stronger low in lower
Michigan Monday morning with a more easterly track through Monday.
This would result in precipitation taking longer to exit the area. In
addition...a cold front will swing through the state through
Monday morning and give any lingering rainfall a quick shot of
extra lift. Increased probability of precipitation Monday morning and slowed the exit of
rainfall Monday afternoon to mirror these trends. Colder air will
filter in behind the front Monday afternoon...and will usher out
the nice Spring weather we have seen this past week. Below normal
temperatures will be reintroduced starting Monday and wont do anywhere
quickly. Winds will shift northeast and increase Monday
afternoon...making it feel a bit cooler than actual high temperatures

Long term...Monday night through Sunday
issued at 243 PM CDT sun Apr 19 2015

Cooler than normal weather will prevail this week as
an upper low sits over the northern lakes. The upper low will be
closest to northern Wisconsin Monday night and Tuesday and should
have enough upper dynamics to produce snow and rain showers over
all of the area Tuesday. Should be cold enough for snow showers in
the north and either rain or snow showers in the south. Increasingly
drier weather should follow for the middle and end of the week
though there still could be scattered snow or rain showers Wednesday.
Lake effect potential is small Monday night through Tuesday night
due to unfavorable wind direction. Winds and instability are more
favorable Wednesday and Wednesday night though drier air is arriving
from the north as well. So do not expect much in the way of lake
effect snow.

Aviation...for 00z taf issuance
issued at 617 PM CDT sun Apr 19 2015

Clouds will continue to thicken and lower this evening
as a low pressure system moves through the area tonight. Although
some spotty shower activity is possible early this
evening...especially out to the west...steady rain will arrive
later tonight. This steady rain will continue for much of the
night...and well into Monday for the eastern taf sites. IFR ceilings
look likely...and some threat of LIFR ceilings based on upstream observation
over the northern plains and MOS guidance.

Grb watches/warnings/advisories...


Short term.....Allen
long term......rdm

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