Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 271654 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1054 AM CST Fri Jan 27 2023

.UPDATE...
(Issued 1054 AM CST Fri Jan 27 2023)

Bands of snow showers continue to shift east through the area,
with warm air advection and differential CVA. Watching these bands
for some heavier snow showers, as there is some saturation within
the dendrite growth zone with the upward vertical motion fields.
May see reduced visibility below 1 mile for a brief period of time
with these heavier snow showers, and a quick few tenths of an inch
of snowfall.

Forecast soundings are showing this saturation in the low
levels/dendrite growth zone lingering this afternoon, with steep
low level lapse rates developing. The main 500 mb shortwave
trough will shift east through the area this afternoon, exiting by
early evening. Thus, will continue off and on snow showers in
forecast. Will continue to monitor the heavier snow shower
potential, though still uncertain how much low level instability
may develop this afternoon, with the NAM the only model showing
any appreciable values. Thus, not expecting squalls to be a big
concern, despite the cold front moving through with the decent
frontogenesis response.

Travel into early this evening may be slippery on untreated roads,
especially where the heavier snow showers occur. Could see up to
an inch of accumulation in these localized areas.

Still looking over models and what to do for winter weather
headlines for the snow event for Saturday into early Sunday. Looks
like the main issue will be where the strong frontogenesis band
sets up and the heaviest snowfall rates/accumulation will be. It
could be in the southern parts of the area, or further to the
north across the area. This uncertainty will likely linger until
it starts occurring on Saturday, so will take this into account
when adjusting snowfall amounts and deciding on headlines.

Wood

&&

.SHORT TERM...
(Issued 411 PM CST Fri Jan 27 2023)

Today and Tonight:

A couple shortwave troughs will move across S WI today, while well
organized low pressure deepens slightly across Ontario. A surge of
sfc-850 mb warm advection is expected into the early afternoon
with sfc temps warming into the lower to middle 30s, followed by
the cold front with falling temps late. Only light snow expected
with these features with around an inch expected. Sswly winds will
gust to 30 to 35 mph ahead of the cold front with wly winds after
fropa then weakening. Low temps tnt falling into the teens but
single digits will be possible depending on sky conditions.

Gehring

&&

.LONG TERM...
(Issued 411 PM CST Fri Jan 27 2023)

Saturday through Thursday:

After a month long hiatus, sustained cold weather will settle over
the region this weekend and linger into at least the first half of
next week. The upper level wave train has another snow maker for
us this weekend. Lift enters from the west on Saturday and there
will be a good period of light to moderate snow for much of
southern Wisconsin from midday Saturday through Saturday evening.

As opposed to our small snowfall events over the past week, there
is a stronger, more deep frontogenetical signal with this system.
And with a colder temperature profile, there is better opportunity
for more sustained lift in the dendritic growth zone. The GEFS,
GEPS and ECMWF ENS all continue to focus the best accumulation
potential either side of the WI/IL state line. Each ensemble
system has increased QPF a little and shifted northward a bit
with the probabilities of greater than 1 and 3 inches of snow.
With snow to liquid ratios at or just above climo, this results in
a swath of decent accumulation (generally 2-5 inches) along and
south of the I-94 corridor. In addition, all guidance exhibits
decent warm advection signal with 40-50 kt of southwest flow at
700mb. The NAM is the most bullish with this, which is
contributing to its more northward band of snow and bullish QPF
output. The moral of this story is that an embedded narrow swath
of higher amounts (approaching 6 inches) is plausible somewhere
within this larger band of light to moderate snow. Current
guidance suggests placement anywhere across northern IL and
southern WI. This is a mesoscale forecast problem and not one we
can pinpoint (likely) until hours before the system arrives.

Snow will gradually end from west to east overnight Saturday night
into early Sunday morning and the cold settles in from there
onward. For the first time in nearly a month we will observed
sustained below average temperatures. Wind chill values below zero
will begin Sunday and persist through at least Tuesday. The period
of coldest wind chills (approaching 20 below zero) is Monday night
and Tuesday morning.

Gagan

&&

.AVIATION...
(Issued 1054 AM CST Fri Jan 27 2023)

Look for on and off snow showers to continue across the area this
afternoon, before ending early this evening. May see brief heavier
snow showers occur with visibility below 1 mile and a few tenths
of an inch of snow accumulation. Otherwise, visibility should
bounce around between 2 and 6 miles with light snow showers and
perhaps some blowing snow. Ceilings will be dropping to 800 to
1300 feet AGL this afternoon, before slowly rising above 2000 feet
AGL early this evening. Gusty south winds will become southwest
this afternoon, with a cold front moving east through the area.

Gusty southwest winds will shift to the west behind the front
later this afternoon and evening, gradually weakening later
tonight. Ceilings should rise to VFR category by middle evening
and remain so later tonight into early Saturday morning.

Snow will push east into the area Saturday morning, lingering
Saturday night into early Sunday morning. Visibility should
generally be 1 to 2 miles, with ceilings of 500 to 1000 feet AGL
over most of the area. Reduced visibility of 1/2 mile or less and
ceilings below 500 feet AGL are possible where heavier snow bands
set up, which remains uncertain at this time. Snowfall rates of
1/4 to 1/2 inch per hour are possible, again higher where the
heavier snow bands set up.

Wood

&&

.MARINE...
(Issued 411 PM CST Fri Jan 27 2023)

Low pressure around 29.3 inches over northern Minnesota will
track just north of Lake Superior today, and just east of James
Bay, Canada by late tonight. South to southwest gales and high
waves will develop this morning and last through the day. A cold
front will then pass across the lake late this afternoon and early
evening. The winds will become west to northwest after the
frontal passage and gradually weaken.

Another low pressure system around 29.9 inches should remain south
of Lake Michigan Saturday night into Sunday. This will favor
winds becoming north to northeast. As high pressure around 30.6
inches builds into the region from the northwest Monday and Monday
night, winds will become northwest.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 until 6 PM Friday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until
     midnight Saturday.

&&

$$

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