109
FXUS63 KMKX 121651
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1051 AM CST Wed Feb 12 2025

.KEY MESSAGES...

- Widespread accumulating snowfall is expected today through
  tonight night. Accumulations of 3 to 6 inches are expected in
  most regions, with areas along Lake Michigan and the Kettle
  Moraine seeing accumulations of 5 to 9 inches, locally higher
  in regions where lake effect banding is able to set up. The
  highest rates are expected today through the mid evening,
  leading to hazardous travel.

- Increased precipitation chances return Friday
  afternoon/evening into Saturday bringing another bout of
  accumulating snow and potentially a wintry mix.


&&

.UPDATE...
Issued 1050 AM CST Wed Feb 12 2025

Snowfall rates (0.5-0.75/hour) have picked up nicely over far
srn WI into se WI late this morning. The right entrance region
of the upper jet and attendant mid to upper level warm advection
has set up over srn WI, with PVA from a vorticity maximum
also streaming into the region from IAw today and tonight. Cigs mainly 1-1.9 kft
with vsbys ranging from. In the lower levels, weak warm
advection is present. The deep lift with this initial round will
shift east by mid afternoon so there probably will be a few
hours or so of lesser snowfall rates, although lake enhancement
will continue better snowfall rates at times over the Winter
Storm warned area in far ern WI.

The slow moving shortwave trough will then approach for early
evening and slowly pass from late evening into the overnight.
This will maintain widespread light snow with higher rates in
the warned area via lake enhancement. The 1000-850 mb flow will
be ely today through 03Z then will quickly back to nly from
03-07Z. Thus do not expect a dominant lake band to develop but
still some lake enhanced snow until 07-08Z.

Overall will maintain the 5-9 inches of powdery snow over the
warned area, and 3-6 inches, locally more elsewhere across srn
WI.


Gehring

&&

.SHORT TERM...0 mb flow will
be ely today through 03Z then will quickly back
Issued 320 AM CST Tue Feb 11 2025

Today through Thursday:

Early this morning we see snow showers trying to push in from
the southwest but very dry air is prevent much of anything from
falling though we could see a few flakes in spots over the next
few hours. By daybreak we should start to see the region moisten
up enough to start allowing snow to fall gradually from
southwest to northeast across the CWA. The lake may help snow
fall a bit earlier along the shoreline.

This system remains a fairly weakly forced system with broad
regions of relatively weak PVA, fairly strong WAA (at least
across the southeast half of the CWA), and some mid to upper
level Fgen across parts of the CWA. Lake Michigan will play a
rather large role with this system, however. With modest east
to northeast winds off the lake and surface to 850mb temp
differences around 12-14 degrees there will be lake enhancement
with this system. This will give areas near the lake and more
specifically the far southeast the best potential for increased
snowfall. The system itself only bringing around 0.2-0.3 inches
of precip with the another 0.1-0.2 inches of precip coming from
the lake influence. Latest model trends have pushed down the
latest QPF likely in accordance with the relatively lack of
fantastic forcing.

Normally the QPF expected 0 mb flow will
be ely today through 03Z then will quickly back  would not be anticipated to bring
that much snow (more in the 2-4 inch range, 4-6 near the lake)
but one of the main concerns with this system is the very deep
DGZ shown in model soundings for prolonged periods due to the
strong WAA that suggests unusually high SLRs. While the forcing
within the DGZ may not be huge it has improved quite a bit in
the latest model runs. Previously forcing was located further
aloft but has shifted down the column a bit which increases the
concern for SLRs. In addition, a moist column and light winds
within the DGZ will help facilitate and maintain higher ratio
snowfall. This all suggests SLRs should be well above
climatology, probably in the range of 16-20:1, maybe higher in
spots. These SLRs have pushed the snowfall amounts considerably
from what a typical system would bring.

There are still some uncertainties with this system especially
as it relates to the snow ratios but improved forcing in the DGZ
has quelled some of that concern in the latest models. Dry air
is the main question regarding onset of snow in the CWA but
generally models have kept us dry until after daybreak. Increasing
confidence in the main impact coming near the lake with
enhancement with the entire area seeing a low QPF/high SLR
system pushing through today into tonight.

Overall we will maintain the Winter Storm Warning for the
counties near and along the lake with a Winter Weather Advisory
across the rest of the CWA0 mb flow will
be ely today through 03Z then will quickly back  . Rates with this will likely be
generally in the 0.5 in/hr range, but closer to the lake having
the potential to see period of the higher end rates to 1.0
in/hr, given lake enhancement. The best accumulation and rates
are expected Wednesday afternoon and early evening. However, one
thing we have noticed in the latest models is that once we
moisten up we could see a period of fast and heavy snow for
just a few hours before it lightens up in the late morning into
the early afternoon before picking back up by mid afternoon.
Accumulating snow of 6-9 inches is currently expected in the
Warning area with 3-6 inches in the Advisory area, through
gradually decrease the further northwest you go. This system
will push out overnight early Thursday morning with chilly
temperatures pushing in behind this system.

Thursday will feature high pressure pushing through the central
US bringing clear skies back to the region.

Kuroski

&&

.LONG TERM...
Issued 320 AM CST Tue Feb 11 2025

Thursday night through Monday:

Strong high pressure will take a flat west to east path across the
Corn Belt Thursday night into the first half of Friday. As the
center of the arctic high passes close by Thursday night,
overnight lows are expected to dip to near zero and a few degrees
below zero inland, as we cool efficiently beneath clear skies and
light winds. Strong lee troughing is expected to begin along the
Colorado Rockies during the pre-dawn hours on Friday, and by noon,
models expect a weak low pressure center over central Colorado
with a warm front extending northeast into Minnesota. By Friday
afternoon, this feature is expect to move toward southern WI,
bringing a very strong push of 850-700mb warm advection,
overlapping with strong frontogenesis. Snow is anticipated to be
the main precip type with the advancing mid lvl forcing, as
surface temperatures will remain below freezing. The strong lift
may also support high rates during the afternoon commute on
Friday, especially along the lakeshore.

Snow rates then taper off Friday night as the main WAA/fgen
pushes east and models hint toward the brief passing of a dry
slot aloft. The sfc low is expected to track through the middle
Mississippi Valley potentially bringing a second period of light
snow early Saturday morning into early Saturday afternoon as we
experience the northern edge of a deformation band aloft. Models
disagree on the track of this secondary round of snow however, as
the GFS favors this snow south of Wisconsin, while the ECMWF is a
bit further north and favors us for more flakes. We`ll continue to
iron out the details with successive model runs over the next few
days.

Beyond, models point toward a mid February arctic blast, as arctic
high pressure builds in from Saskatchewan, Canada to the Upper
Mississippi Valley. There is some ensemble spread at the moment,
but the overall consensus is for single digit highs by Monday of
next week.

CMiller

&&

.AVIATION...
Issued 1050 AM CST Wed Feb 12 2025

Widespread lgt-mdt snow today and tonight. Cigs mainly 1-1.9 kft
with vsbys ranging from 1/2-1 mile. Areas of Cigs under 1 kft
today and tonight. Brief 1/4SM +SN over far ern WI at times.
Cigs scattering out from west to east during the Thu AM daylight
hours.

Gehring

&&

.MARINE...
Issued 320 AM CST Tue Feb 11 2025

We will see winds increase a bit and turn east to northeasterly
today as low pressure moves from the southern Plains into the
eastern Great Lakes through the day today. Will see snow showers
accompanying this low as it pushes through the region. Brisk
winds turn more northwesterly overnight into Thursday as the low
lifts into the eastern Great Lakes and filled in behind by high
pressure. Given the cold air and lingering winds, Thursday may
result in some moderate to freezing spray concerns through
Thursday afternoon. Then will see the high pressure skirt across
the Midwest and south of Lake Michigan Thursday evening into
Friday and bringing lighter winds.

Small Craft Advisory is in effect for mainly waves of 4-6 feet
this afternoon through the evening. A brief lull in waves
expected later tonight but northwest winds will pick up and
bring another period of Small craft conditions early Thursday
morning through the day.

Kuroski

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning...WIZ052-WIZ059-WIZ060-WIZ065-WIZ066-
     WIZ071-WIZ072 until 3 AM Thursday.

     Winter Weather Advisory...WIZ046-WIZ047-WIZ051-WIZ056-WIZ057-
     WIZ058-WIZ062-WIZ063-WIZ064-WIZ067-WIZ068-WIZ069-WIZ070
     until 3 AM Thursday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 6 PM
     Thursday.

&&

$$

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