Scientific Forecaster Discussion
fxus63 kmkx 120554
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
1154 PM CST Wed Dec 11 2019
Update...mid to high clouds continue to increase across srn WI.
No snow is expected until late Thu am NW of Madison. The forecast
is on track for mixed pcpn Thu afternoon followed by drizzle or
freezing drizzle Thu nt.
Aviation(06z tafs)...VFR conditions for most of Thu am. Low cigs
of 600-1900 feet will then slowly overspread srn WI from the NW
late Thu morning into Thu evening. Mixed precipitation will
accompany the low cigs. Vsbys will range from 1-3sm with the
precipitation north of Madison and Milwaukee with vsbys of 3-6sm
south of Madison and Milwaukee. Minor snow accum expected mainly
north and west of the Milwaukee Metro area. Some minor ice accum
also expected due to freezing drizzle mainly north and west of
Milwaukee late in the day and night. Patchy fog may form Thu eve
as well. Low level wind shear will be possible from 11z-15z Thu due to a sly low
level jet overspreading the area.
Previous discussion... (issued 905 PM CST Wed Dec 11 2019)
Update...mid level clouds have been scattered but thicker mid
level clouds will increase from the west for late this evening
into the overnight. The coldest temps will occur btwn now and
midnight then gradually warm on increasing sely winds and warm
Marine...a Gale Warning is in effect from 9 am to 9 PM Thu for
all of Lake Michigan with the exception of the far nrn portion of the
Lake. A Small Craft Advisory is in effect from Sheboygan to
Winthrop Harbor from 7 am to 9 PM Thu for breezy sswly winds and
High pressure of 30.4 inches will shift east across Lake Michigan
tonight. Modest wly winds will back to sly during the overnight
hours. Stronger sly winds will then develop for Thu as low
pressure of 30.0 inches moves from the Great Plains to nrn Lake
Michigan by Thu eve. Gale force gusts are likely for all but the far
nrn portion of the lake for Thu-Thu eve. The low will then weaken
over Northern Lake Michigan or the northern portion of lower Michigan
Thu nt. Much lighter winds are expected for late Thu nt-Fri.
Nwly winds are then expected to develop by the weekend.
Previous discussion... (issued 601 PM CST Wed Dec 11 2019)
Update...low temps will occur this evening as polar high pressure
moves across the region. Clouds will then increase later this
evening along with sely winds and warm advection. Temps will warm
into the lower 20s by sunrise Thu. The forecast is on track for
Thu-Thu nt with mixed pcpn and light snow and ice accums
expected, with possibly the exception of far se WI which will
remain above freezing during the pcpn.
Aviation(00z tafs)...VFR conditions tonight then low cigs of
600-1900 feet slowly overspreading srn WI from the NW on Thu.
Mixed precipitation will accompany the low cigs. Vsbys will range
from 1-3sm with the precipitation north of Madison and Milwaukee
with vsbys of 3-6sm south of Madison and Milwaukee. Some minor
ice accum expected due to freezing drizzle mainly north and west
of Milwaukee late in the day. Patchy fog may form Thu eve as well.
Low level wind shear will be possible from 11z-18z Thu due to a sly low level
Previous discussion... (issued 313 PM CST Wed Dec 11 2019)
Rest of this afternoon through tomorrow night...forecast
confidence medium to high...
Quiet conditions will persist this evening, as high pressure
continues to push southeast through the region. Low pressure
taking shape over the High Plains will lift into the lower Great
Lakes tomorrow morning. Precipitation will begin to overspread
the area from the northwest during the mid day hours, and will
initially be in the form of snow. Temperatures will be right
around freezing, and the best lift will be focused to our north,
so only light accumulations are expected. Right now, it appears
that snow will be mostly confined to areas north of I-94, with a
dusting to up to 1-2 inches possible.
Heading into the late afternoon and evening hours, cloud ice will
be lost, with precip changing to a mix of drizzle and freezing
drizzle, depending on exact surface temperature. A glaze of ice
will be possible from this activity late tomorrow afternoon and
evening, which could cause some travel impacts across the region.
Friday through Saturday...forecast confidence: medium...
There is a deepening trough that will be moving through the
Southern Plains out into the eastern Continental U.S. Over the weekend. There
is a weaker shortwave that will begin to descend into the Great
Lakes region Friday night into Saturday that could bring some
light precipitation to the area. During this period, there is
expected to be sufficient moisture and temperatures at the
surface will be dropping. As the weak shortwave moves into the
region, the GFS and European model (ecmwf) are showing the initial surface
temperatures in the mid 30s and a larger warm layer near the
surface, so precip type would start as liquid. Middle level dry
air will introduce a chance of freezing drizzle from Friday night
through mid Saturday. Right now there is a lot of uncertainty
about sufficient moisture and timing for freezing drizzle. Precip
should transition to snow during the day Saturday. Any snow
accumulations would be light.
Sunday through Tuesday...forecast confidence: low...
As the system moves out of the region on Saturday, high pressure
and cold air return to southern Wisconsin. The high pressure system
will linger in southern Wisconsin Sunday into Monday morning.
During this time there is a low pressure system that will be
forming in the Southern Plains. This is where the models start to
disagree and lots of uncertainty is introduced. The mid level
trough will be digging further south and strengthening for the
European model (ecmwf) solution, while the GFS solution has the mid level trough
moving through the central Continental U.S.. when looking at the moisture
transport and associated surface low pressure systems, the European model (ecmwf)
solution has the track of the low much farther south and little to
no moisture present. This would give southern Wisconsin no
precipitation accumulations. While the GFS solution has the
moisture transport and track of the low moving through Illinois. This
track would give southern Wisconsin a far greater chance of
precipitation. The GFS and European model (ecmwf) model solutions best represented
the spread of all of the models available, which demonstrated a
spread where southern Wisconsin could either get no precipitation
or had increasing chances for precipitation.
Winds settle down this evening, and will likely become light and
variable for a time. South to southeast flow will develop late
tonight, as low pressure develops and pushes toward central
On Thursday, expect to see an area of mainly light snow begin to
affect the region during the late morning hours. Madison has the
best chance of seeing this activity, but for the most part, the
more impactful snow will remain north of the terminals. Snow is
then expected to transition to light drizzle and/or freezing
drizzle tomorrow afternoon and evening, which will likely impact
most of the area.
Southerly winds will increase on Thursday, with gales expected
across all but the far northern-most portions of the open waters.
A Gale Warning is in effect starting mid morning, continuing into
For the nearshore, winds should remain just below gale force, but
will be quite gusty with high waves. A Small Craft Advisory is in
effect from tomorrow morning through tomorrow evening.
Another front will pass through the lake on Saturday night, with a
return of gusty northwest winds.
Lm...Gale Warning from 9 am to 9 PM CST Thursday for lmz080-364-366-
Small Craft Advisory from 7 am to 9 PM CST Thursday for