Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 180449
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1049 PM CST Sun Dec 17 2017

.UPDATE...

The HRRR continues to show a rather quick wave of light rain
clipping across the area between midnight and 6 am tonight. There
is potential on the northwest edge of the rain, where surface
temps are at or below freezing, we might see a little freezing
rain.  It looks like at this point, so impact should be limited.
We should then see improving skies by afternoon.

&&

.AVIATION(06Z TAFS)...

Overall, IFR conditions are expected across the area through the
morning on Monday. Conditions did lift to VFR levels at KMKE/KENW
this evening, but lower clouds are spreading in quickly. We are
still looking at a 3-5 hour period of light rain across the
southeast before sunrise on Monday. Surface/pavement temps should
remain above freezing to limit the risk of freezing rain. But, it
will be close. Look for VFR CIGS to quickly return from west to
east across the area by late morning and early afternoon on
Monday. Light winds early in the TAF period will swing to the
southwest and increase steadily through the day.

&&

.PREV DISCUSSION... (Issued 842 PM CST Sun Dec 17 2017)

UPDATE...

Not much change to the current forecast. Temperatures are fairly
stable and will continue to hold steady, or rise slightly
overnight. The rain that was over northwest Illinois earlier this
evening looked better, but it mostly dried up very quickly.
However, soundings are all showing the better saturation and
potential for some light rain moving through southeast Wisconsin
later tonight, between about 2-6am. The light returns currently on
radar are not yet showing any confirmation at ground level.

We do have some areas of more significant fog with visibilities at
times to 1/2 mile developing over Washington and Fond du Lac
counties. Will continue to watch trends, but will hold off on any
dense fog advisories for now.

MARINE...

Brisk swly winds will develop Mon aft and become wly for
Tue. The wind gusts may reach Small Craft Advisory criteria. Waves
of 1 to 3 feet are expected.

PREV DISCUSSION... (Issued 509 PM CST Sun Dec 17 2017)

UPDATE...

Light rain is beginning to expand across eastern Iowa and
northwest Illinois. I`ll probably be raising POPs into the likely
category for the southeast and depending on trends, may have to
expand it spatially. Temperatures should hold pretty steady or
even rise slightly, remaining above freezing where it`s raining.
It could get iffy north of Milwaukee and Madison if the rain
expands too far into this area. Then we could have some light
freezing rain concerns.

AVIATION(00Z TAFS)...

Look for IFR conditions to persist through the night. Conditions
don`t look like they`ll improve until we get into a southwest flow
on Monday. We should see rapidly improving CIGS during the early
afternoon on Monday, improving from west to east across the area.
Light rain is expected to spread across the southeast, primarily
along and south of Milwaukee and Madison. Temperatures should
remain above freezing at the TAF sites while the rain falls.

PREV DISCUSSION... (Issued 324 PM CST Sun Dec 17 2017)

SHORT TERM...

Tonight through Wednesday night...Forecast confidence medium.

There has been a dissipating trend with light rain over srn IA
this afternoon with some very light rain remaining over far ern
IA. Will still maintain chances for light rain or drizzle over far
srn WI and se WI this evening into the overnight as fcst
soundings show good moistening up to 700 mb. Expect temps to stay
above freezing as the pcpn arrives. Light freezing fog may occur
over the nrn and wrn forecast area where temps will be below
freezing.

Strong low pressure moving ewd across Canada will lead to brisk
swly winds Mon aft-nt becoming wly on Tue with the passage of a
weak and dry cold front. The swly winds should bring drier air to
the region Mon aft with a dissipation of the stratus expected.
Warm advection and some sunshine should lead to high temps in the
lower 40s with milder temps for Tue. High pressure will then move
into srn WI Tue nt-Wed with cooler temps expected. Middle to high
clouds will increase on Wed with slight chances of light snow
late Wed nt toward central WI as mid level frontogenesis begins.

LONG TERM...Thursday through Sunday...Forecast confidence low to
medium.

The ECMWF and GFS agree on taking a low pressure area newd through
srn WI but with timing differences. Thu-Fri will be the primary
days for pcpn with the likely outcome of rain changing to snow
although confidence is still fairly low in the overall evolution
of this system. Afterward, the latest models delay the arrival of
arctic air while producing a mid level frontogenesis band of
light snow for Christmas Eve. Overall confidence in this snow band
is low at this time.

AVIATION(21Z TAFS)...Cigs of 600-1500 feet late this afternoon
and early evening will lower to less than 1 kft for later this
evening into Mon AM. MVFR vsbys from light fog will continue with
with pockets of 2SM BR. Some of the light fog may become freezing
fog especially north of the Milwaukee and Madison areas late this
evening and overnight. Areas of very light rain or drizzle is
forecast across se WI from late evening into the overnight. The
pcpn will move out by 12z Mon with wly winds bringing drier air
and scattering out the ovc stratus from late morning into the
afternoon.

MARINE...Brisk swly winds will develop Mon aft and become wly for
Tue. The wind gusts may reach Small Craft Advisory criteria. Waves
of 1 to 3 feet are expected.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

Update...Davis
Tonight/Monday and Aviation/Marine...Gehring
Monday Night through Sunday...Gehring



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