Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kmkx 202351 

Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
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.


Aviation(00z tafs)...

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)

Short term...

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.

Long term...

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.

Marine...lingering influence of high pressure tonight though the
high shifts east with an evolving southerly flow. Some fog out on
the lake so an advisory may eventually be needed should overall
coverage increase. Southerly flow increases on Saturday. As a
surface low approaches on Saturday expect winds up to 30 knots
across the Lake. A Small Craft Advisory will likely be needed for
Saturday afternoon and night. Rounds of rain and thunderstorms are
also expected before the front pushes through Sunday afternoon
and evening. Winds will also decrease and shift to the west to
northwest into Monday.


Mkx watches/warnings/advisories...


National Weather Service Glossary of Abbreviations