Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
309 am CDT Monday Apr 27 2015
Today and tonight...forecast confidence is high.
An upper level trough across the northeast U.S. Extends back across
the Great Lakes. This trough drops a little more south today before
weakening and pushing east as a weak ridge extends over the upper
Mississippi Valley. Little in the way of upper divergence. At 500 mb
one more shortwave drops south/southwest across the Great Lakes...
with the trough axis brushing southeast Wisconsin around noon. Weak
700 mb upward motion with this...otherwise generally downward motion
today and weak upward motion starting tonight.
There is some increase in 700 mb relative humidity dropping south towards Lake
Michigan this morning...but dries by the time it reaches the
southeast. Another areas of increasing 700 mb relative humidity reaches the far
east tonight. 850 mb relative humidity increases this morning before drying late
tonight. Expect the southeast to see a little more clouds...
especially towards Lake Michigan.
The 700 mb winds are near 30 knots this morning today then weakening
tonight. The 850 mb winds are 20 to 25 knots...especially southeast
and over Lake Michigan. With surface heating wind gusts...while not
strong...will likely be stronger than the weak surface pressure
gradient suggests again today.
With the northeast winds off Lake Michigan...expect typical
springtime cooling near Lake Michigan...with mild temperatures well
Tuesday through Friday... forecast confidence high.
Overall... dry surface high pressure will dominate the region and
bring a pleasant stretch of weather to southern WI. There will be a
steady breeze out of the north through this period... but the weak
pressure gradient will allow for a lake breeze to develop each day.
Diurnal cumulus clouds are expected as well. Inland temperatures will be in
the 60s for this period while Lakeshore temperatures will be stuck in the
A shortwave will cross the northern plains Tuesday and Lake Superior
Tuesday night. It should bring a period of middle and high clouds to
southern WI... but no precipitation. Another shortwave trough will
drop down through the Great Lakes on Wednesday night. Cooler air
will slide Down Lake Michigan and overspread southern WI in the wake
of this trough on Thursday.
Yet another shortwave will zip through the upper Great Lakes as it
weakens on Friday. It should again bring a round of clouds... but
precipitation chances are minimal.
Saturday through Monday... forecast confidence medium.
Saturday weather is now looking quiet for southern WI with no real
strong forcing or feed of moisture in this fairly zonal flow across
the northern part of the country.
The GFS and European model (ecmwf) are in general agreement for a weak shortwave
crossing WI sometime later Sunday into Monday that would bring a
chance of showers and thunderstorms as some Gulf moisture could
reach up into the region. The 00z runs are leaning toward the better
chance being Monday now with stronger upper level support.
The warming trend will continue through early next week. Highs are
expected in the Lower/Middle 70s inland and 60s near the Lakeshore.
VFR conditions expected through the forecast. A few clouds around 3
thousand feet expected this morning with heating...especially southeast.
Cloud area moving south southwest from Northern Lake
Michigan/northern lower Michigan with a middle level trough axis
expected to just brush the eastern third of the forecast area and
remain at VFR levels in the 5 thousand feet range. Then lingering
scattered middle clouds far east into the evening.
High pressure near Western Lake Superior with a persistent
north/northeast flow over Lake Michigan. Winds and waves
approaching small craft criteria...especially south of Milwaukee
High pressure near Western Lake Superior will help keep very low
relative humidity values around 25 percent in the afternoon hours
Monday and Tuesday...away from Lake Michigan. North winds will be in
the 7 to 12 miles per hour range...with higher gusts to near 20 miles per hour this
afternoon. Winds a bit higher near Lake Michigan. Temperatures will
top out in the lower to middle 60s well inland...cooler near the lake.
Today/tonight and aviation/marine...hentz
Tuesday through Sunday...mrc