Scientific Forecaster Discussion
fxus63 kmkx 210230
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
930 PM CDT Fri Sep 20 2019
Have seen a little light fog develop this evening, including some
coming in off of Lake Michigan. Currently don't expect this to
become dense or terribly widespread, but drivers should be alert
for localized areas of reduced visibility.
For the rest of this evening, some patchy fog has developed across
the nearshore waters, as well as parts of the northern half of the
open waters. Currently don't expect this to become too widespread,
but will continue to monitor.
Otherwise, south to southwest winds will ramp up Saturday morning,
continuing through the first half of the day on Sunday. A Small
Craft Advisory is in effect starting mid morning on Saturday for
the nearshore. For the open waters, gusts to 30 knots will be
common, and a few marginal gales are possible across the northern
reaches of the lake, especially going into tomorrow evening.
A cold front will move through the lake on Sunday, shifting winds
to the west and northwest. High pressure will then build into the
area for Monday.
Previous discussion... (issued 651 PM CDT Fri Sep 20 2019)
Despite a relatively unstable airmass, little in the way of
convection was able to develop this evening, due to an absence of
any organized source of lift. A few storms tried to develop across
extreme southern Rock County, but have since fizzled. With the
impending loss of sunlight, things should remain dry through the
rest of the evening hours.
Southerly winds will begin to increase overnight as low pressure
lifts from eastern Colorado into South Dakota. Before the winds
pick up, some fog is possible later this evening, though it should
not be terribly widespread. Any fog that does form should
dissipate before dawn as winds increase and mid and high level
clouds stream into the area.
Didn't make any significant changes to the timing of
showers/thunderstorms for tomorrow. Convection should begin to
overspread the area from the west and southwest around sunrise,
with a gradual eastward expansion through the morning. Will
probably see multiple waves of showers and thunderstorms through
the day tomorrow, so despite high pops, some breaks are likely. A
more continuous period of convection is more likely tomorrow night
as the front begins to approach.
VFR is expected through the night, with just some mid and high
level clouds streaming in toward morning. Some fog is not
entirely out of the question, but is not currently expected to be
widespread enough to have a significant impact at the terminals.
Showers and thunderstorms are then expected to push into the area
from west to east tomorrow morning, with MVFR visibility and MVFR
to IFR ceilings. This activity will persist in at least a
scattered fashion through much of the day. South to southwest
winds will also be on the increase, with gusts into the 20-25 knot
range at times.
Previous discussion... (issued 356 PM CDT Fri Sep 20 2019)
Tonight and Saturday - confidence...medium
Lingering anticyclonic flow in the low levels and aloft breaks
down this period as low pressure approaches from the plains. A
southerly flow will be on the increase and will become quite
gusty on Saturday. Moisture transport will be enhanced with the
northward pull of tropical moisture from the Southern Plains. With
extensive cloud cover cape should be somewhat limited. But have
increased pops as the day wears on Saturday to account for better
mid level forcing as well as the lower level moisture advection.
Saturday night through Sunday... forecast confidence is medium.
The upper jet will sit over the upper Midwest through the weekend,
along with the leading edge of an upper trough. A surface trough
will be the focus for repeated rounds of thunderstorms with the
focus over southern Wisconsin to northeast Wisconsin and Lake
Michigan. The trough will finally slide southeast by Sunday night.
Monday... forecast confidence is medium.
The closed upper low will side through the Great Lakes region on
Monday. Cyclonic flow will keep US in the clouds at least Monday
morning and we could see some light showers as well.
Tuesday through Friday... forecast confidence is medium.
Our next chance for showers and thunderstorms will be with the
next upper trough swinging through and an associated cold front.
Warm air advection will arrive during the day Wednesday and the
front will slide through Wednesday afternoon or evening. The European model (ecmwf)
is showing a stronger upper trough than the GFS at this time.
Yet another round of showers and storms will arrive Friday. This
surface low should focus more toward Lake Superior at this time.
Lm...Small Craft Advisory from 10 am Saturday to 1 PM CDT Sunday for