Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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416
FXUS63 KMKX 201524
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
924 AM CST Sat Jan 20 2018

.UPDATE...

Previous forecast is on track.

&&

.MARINE...

A weak pressure gradient across the region is resulting in light
winds and wave across much of Lake Michigan. These conditions
should persist in the nearshore waters of southern Wisconsin until
Monday morning. At that time, ESE winds will pick up as a strong
low pressure system moves into the region, resulting in wind gusts
and waves well above SCA criteria. After a brief lull on Monday
night, winds will swing around to the NNW, and increase back to
SCA criteria. Small Craft Advisories will likely be needed on both
Monday and Tuesday.

&&

.PREV DISCUSSION... (Issued 546 AM CST Sat Jan 20 2018)

UPDATE...

No changes this morning, with everything appearing to be on track.

AVIATION(12Z TAFS)...

VFR will prevail through mid to late evening today, with light
southwest winds becoming light and variable by late afternoon.

Later tonight, flight conditions are expected to deteriorate
rapidly as a warm front lifts into the area. Ceilings and
visibility are likely to drop to IFR or LIFR around or shortly
after midnight, with very low flight conditions likely persisting
through most of the day Sunday. Winds will be light through this
TAF period, but will begin to increase from the east and southeast
later Sunday.

PREV DISCUSSION... (Issued 330 AM CST Sat Jan 20 2018)

SHORT TERM...

Today...Forecast Confidence is High...

The region will be situated in an area of weak pressure gradient
today, with southwest winds this morning becoming light and
variable by this afternoon as a result. Temperatures today will
be rather pleasant, with highs topping out around 40 degrees under
high clouds.

LONG TERM...

Tonight and Sunday... Forecast confidence is Medium.

Low level moisture will gradually make its way northward into
southern WI Sunday morning. This is within a region of warm air
advection out ahead of low pressure organizing in the Plains.
Surface temperatures will be increasing, but if we moisten up
enough for drizzle early enough on Sunday morning, then
temperatures will still be below freezing and we could see some
freezing drizzle cause a light glaze.

Models are having a hard time with temperatures during this
period. The NAM and WRF seem too cold, probably because they`re
assuming snow cover over the area. We will lose most of our
remaining snow today.

Temps will warm above freezing by mid Sunday morning and precip
type will become all rain in southern WI.

Sunday night through Tuesday... Forecast confidence is Medium to High.

The closed upper low and associated surface low will track from
Kansas to Iowa Sunday night into Monday, and across the IL/WI
border Monday afternoon/early evening. There is better agreement
in timing and track of this low with the 00z model runs.

Cold advection on northerly winds will quickly drop temperatures
from north to south Monday night. Rain will transition to snow,
and areas could pick up a quick inch by the Tuesday morning
commute. We could see some lingering flurries or light snow
showers into late Tue morning, but overall it looks like we`ll dry
out fairly quickly on the back side of this system. Temps will dip
into the lower/mid teens Tue night.

Wednesday through Friday... Forecast confidence is high.

There is a weak signal for a shortwave to bring some light snow to
portions of WI on Wed or Thu, but no mention of it in the
forecast yet. Wed highs will only be in the 20s, but warmer air
will spread back in for later in the week. Highs by Friday should
be in the 40s.

Next Weekend... Forecast confidence is Medium.

Another amplified upper trough crossing the country could bring
rain to southern WI on Saturday. There may be light snow on the
back side that would get us on Sunday. There is good agreement
between the GFS, ECMWF, and even the Canadian models at this
time.

MARINE...

Winds will continue to diminish as the day goes on, becoming light
and variable this afternoon and tonight. Low clouds and fog are
expected to build into the area tonight into early Sunday morning,
and it`s possible that a Dense Fog Advisory may be needed for the
nearshore waters at some point.

Winds will begin to increase from the east and southeast later
Sunday and especially into Monday. This will result in increasing
waves along the WI shore. A Small Craft Advisory will be needed
for this timeframe.

&&

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

$$

Update...BSH
Today/Tonight and Aviation/Marine...Boxell
Sunday THROUGH Friday...Cronce



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