Scientific Forecaster Discussion
fxus63 kmkx 110539
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
1139 PM CST Tue Dec 10 2019
Update...mid level clouds will overspread srn WI during the early
morning. Very light snow or flurries may still occur over far srn
WI from 10-14z as a band of light snow tracks from Iowa to Illinois. Skies
will then clear shortly afterward with another cold day expected.
Aviation(06z tafs)...few-sct025 stratocumulus and flurries will
exit ern WI by 07z. Brief periods of bkn025 will be possible. Mid
level clouds will overspread srn WI from the west during the early
morning hours. Flurries or very light snow may occur for a few
hours over far srn WI from 10-14z. Skies will then clear from
NW to se.
Previous discussion... (issued 922 PM CST Tue Dec 10 2019)
Update...the forecast is on track for tnt-Wed.
Marine...low pressure of 30.0 inches over the northern Great
Lakes will move into Quebec on Wednesday. High pressure of 30.6
inches over the northern Great Plains early Wednesday morning will
move across Lake Michigan Wednesday night. Brisk westerly winds
will continue tonight into Wednesday but diminish late Wednesday.
Westerly wind gusts will approach Small Craft Advisory conditions
from Sheboygan to Winthrop Harbor for the early morning hours of
Wed. The modest west winds will then back to southerly early
Thursday morning as the high passes by. The colder airmass in
place will lead to freezing spray at times.
South winds will increase Thursday as a weak low pressure system
around 30.0 inches pushes in. A few gale force gusts are possible
in the afternoon, especially over the center and south half of the
Lake. A gale watch may be needed. The low will move across the
lake Thursday night. Lighter winds are expected on Friday.
Previous discussion... (issued 603 PM CST Tue Dec 10 2019)
Update...an upper trough extending from Ontario to srn Manitoba
will quickly dig sewd to Lake Michigan by 12z Wed. This will help
maintain a sfc trough over srn WI with sct stratocumulus west and
south of Madison continuing slowly ewd this evening. Ahead of the
upper trough a surge of warm advection and 850 mb frontogenesis
will bring a narrow band of light snow across Iowa and nrn Illinois. Far
SW WI may get clipped by a brief period of very light snow or
flurries from 10-14z Wed. Afterward, skies will clear with high
temps in the teens. A sfc ridge will then shift ewd across srn WI
for the late afternoon and evening.
Aviation(00z tafs)...few-sct025 stratocumulus are expected tnt.
Brief periods of bkn025 will be possible mainly south of a line
from Baraboo to Milwaukee. Skies will clear during the morning
daylight hours with VFR conditions continuing into Wed nt.
Previous discussion... (issued 256 PM CST Tue Dec 10 2019)
Rest of this afternoon through Wednesday afternoon...forecast
Light flurries associated with a lingering stratocu deck continue
across eastern Wisconsin early this afternoon. This activity will
slowly diminish in coverage this afternoon, with skies clearing
out by mid to late afternoon. Temperatures will remain in the
teens and low 20s this afternoon.
Temperatures will quickly fall with sunset, reaching the single
digits by mid evening. Overnight lows will be in the low to mid
single digits above zero. A steady west breeze will bring wind
chill values into the -5 to -15 range by morning.
A passing wave will bring the potential for some very light snow
to the southwest of the area late tonight and early tomorrow, but
for US, mid level cloud cover should be the only real impact.
Skies should again clear by tomorrow afternoon, with afternoon
highs ranging from the low teens north to around 20 across the far
Wednesday night through Friday...forecast confidence: medium...
A short wave will advance into the region Thursday. There is a
swath of warm air advection at 850 mb and frontogenesis around 700mb that should
support some precipitation for central and northern Wisconsin. The
freezing line will bisect southern Wisconsin on Thursday,bringing
the best chance for snow to counties north of I-94. Any
accumulating snowfall is expected to remain light for all of
southern Wisconsin. The areas south of I-94 could see little to no
precipitation accumulations given the current model trends.This
system will move out by Thursday night and there is expected to be
a rather short break in the precipitation Friday.
Friday night through Monday...forecast confidence: medium...
There is a trough that is expected to dig into the center Continental U.S.
Late Friday into Saturday. As this trough digs into the region, a
surface low is expected to develop across the Central Plains late
Friday. As the system moves eastward toward the Great Lakes
region, it is expected to deepen. With the latest model updates
the track of the surface low pressure system has a little bit more
uncertainty. The GFS has a track over the northern half of IL,
while the European model (ecmwf) has the track further south. Despite the
uncertainty in track, southern Wisconsin is expected to get some
snow/wintry precipitation Saturday. After the system move through
on Saturday, high pressure will build into the area and colder
temperatures are expected to return. Another trough is expected to
move though the area early next week for the start of the work
week. There is still moderate uncertainty in the timing of this
MVFR ceilings and a few flurries will continue to persist across
the area early this afternoon. This activity will slowly diminish
with time, with ceilings scattering out by late afternoon, and
eventually clearing. Late tonight into tomorrow, a passing wave
to our south will bring mid and high level cloud cover to the
area, but no precipitation is expected.
Winds through the period will remain westerly.
West winds will continue across the lake today and tonight. High
pressure will build into the region on Wednesday, with lighter
Winds will become southerly on Thursday, with gusts approaching
gale force across the southern half of the open waters. For the
nearshore, a Small Craft Advisory will likely be needed.