Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 221725 AAC
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1225 PM CDT Sat Apr 22 2017

.UPDATE...

.AVIATION(18Z TAFS)...

VFR conditions will prevail through Sunday. Expecting a wind
shift tomorrow, likely zipping down lake Michigan from early
afternoon to early evening while gradually pushing inland as well.
Winds will switch from westerly to east/northeast.

&&

.PREV DISCUSSION... (Issued 916 AM CDT Sat Apr 22 2017)

UPDATE...

The forecast looks to be on track for the rest of the day, with
mostly sunny skies and near seasonable temperatures.

MARINE...

Mainly quiet weather will continue this weekend. There will
likely be a quick wind shift along with gusty conditions for a
time tomorrow afternoon into the evening as colder air pushes into
the area.

PREV DISCUSSION... (Issued 715 AM CDT Sat Apr 22 2017)

AVIATION(12Z TAFS)...Upstream cirrus clouds continue to thin
across northern IA and MN. Hence VFR conditions with few-sct high
clouds for today with clear conditions tonight.

PREV DISCUSSION... (Issued 330 AM CDT Sat Apr 22 2017)

SHORT TERM...

TODAY and TONIGHT - Confidence...High.

GOES-16 imagery showing much of the cirrus clouds has thinned and
pushed off to the east overnight.  These high clouds originated from
southern impulse moving eastward along baroclinic zone draped across
central/lower MS Valley region.  Another batch of sct-bkn cirrus
located upstream over northern IA/southern WI but has been
transforming from opaque to translucent over last several hours as
it runs into parched atmosphere over western Great Lakes. Also,
northern Plains high pressure ridging will continue to build into
Wisconsin and the region today as southern CONUS low pressure moves
eastward.  Hence looking at a mostly sunny day with lighter
northeast winds than on Friday.  With lighter winds and more
sunshine, expect daytime temperatures to warm several degrees over
yesterday`s readings, except of course by Lake Michigan.  Lake
Michigan water temperatures mostly in the 40 to 45 degree range
which will keep areas close by the lake 5 to 10 degrees cooler than
inland areas.

With lighter boundary layer winds and mostly clear conditions
tonight, temperatures will fall back into the mid 30s to around 40
late tonight.  Colder areas will be susceptible to some patchy late
night frost.  We are close or a little early for the average date of
the last 32 degree reading across southern WI, so wl hold off
on any frost headline.

SUNDAY AND MONDAY...Forecast confidence is medium.

High pressure looks to dominate both days. The only concern will be
on Sunday, when a considerable surge of cold air will push through
southern Canada into the upper midwest. Nearly all guidance has this
cold air continuing down Lake Michigan and into our eastern CWA,
but there is still some uncertainty regarding how far south it
makes it. Nonetheless, it seems likely that areas near the lake
will be considerably cooler than inland locations on Sunday
afternoon.

By Monday, developing low pressure over the Northern Plains will
ramp up southerly winds as the pressure gradient tightens. With a
dry column and clear skies, these winds should usher in even
warmer temperatures, potentially reaching into the 70s across our
south on Monday afternoon.

LONG TERM...

MONDAY NIGHT THROUGH WEDNESDAY NIGHT...Forecast confidence is medium.

There is good model consensus on the general pattern in the period,
but quite a bit of disagreement with the regards to the details.
Generally, we`ll see an active pattern with the previously mentioned
low pressure system moving out of the Northern Plains passing to our
north on Monday night and Tuesday morning. Another low will then
quickly move out of the Southern Plains, passing over the CWA
sometime on Wednesday.

The details in the model solutions are largely similar with the
initial low, pushing it through northern Wisconsin, and keeping much
of the associated moisture confined to northern and central WI. A
weak trailing cold front will be drug through southern Wisconsin on
Tuesday morning bringing a slight chance of rain to our north. The
secondary low then moves in so quickly that winds barely veer behind
the cold front front before the pressure gradient tightens back up
and winds shift back toward the south.

The real model discrepancies come with the second low passage.
The Euro is the fastest and weakest, the GEM is the slowest and
strongest, and the GFS is somewhere in the middle. Meanwhile,
there appears to be some limited instability associated primarily
with the second low in each solution. Therefore have introduced
slight chance thunder on Tuesday night and Wednesday morning.

THURSDAY THROUGH SATURDAY...Forecast confidence is low.

Weak high pressure will build in on Thursday before another low
moves through the region on Friday. Models are again in reasonable
agreement with the overall pattern on Thursday and Friday, with
the low developing in the Southern Plains and moving through the
upper midwest. However, differences remain in the timing and
placement of the low. By Saturday, model solutions really diverge,
with the GFS/GEM putting us under high pressure and the Euro
pushing a well developed cyclone across the region.

AVIATION(06Z TAFS)...

VFR conditions for Sat into Sun.

MARINE...

High pressure passing through the western Great Lakes and a frontal
boundary located well south of the region will result in mostly
onshore, northeast winds over the near shore waters today.  Wind
speeds will remain less than 20 knots, with the highest winds and
gusts over the southern zone, from Wind Point to Winthrop Harbor.
The lightest winds will be across the northern zones, closer to the
high pressure center.

There is a possibility of a back door cold front and abrupt wind
shift sagging rapidly south across Lake Michigan Sunday afternoon.
At this point, this front should affect the northern zones, but
unsure how far south it will progress.  Leaning toward front
accelerating southward through all of the nearshore waters by mid-
late afternoon due to synoptic setup.  This will also be during the
time of peak heating over the land creating a tighter gradient of
temperature along the shore area.  Will have a better idea later
today and tonight.

&&

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

$$

Update...DDV
Today/Tonight and Aviation/Marine...MBK
Sunday THROUGH Friday...BSH


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