Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 240434

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1134 PM CDT Mon Oct 23 2017


Rain continues to expand as expected across the area. Winds have
started to increase in response to the deepening area of low
pressure, which is currently centered near Alpena, MI at this
hour. This low will continue to deepen and rotate a bit back to
the west through morning, and northwest winds will respond
accordingly. Expect speeds to increase through the night, with
peak gusts expected from mid morning through mid to late



Northwest winds will continue to strengthen overnight, becoming
quite gusty through the day on Tuesday. The strongest gusts look
to be from mid to late morning through Tuesday afternoon, with
gusts to 35 kt at times.

Cigs and vis are also expected to deteriorate overnight tonight,
with MVFR to IFR expected at all sites by morning. This will
continue through much of the morning and early afternoon, with
gradual improvement expected by evening.


.PREV DISCUSSION... (Issued 912 PM CDT Mon Oct 23 2017)


No major changes to the going forecast this evening. An area of
rain continues to expand across southern Wisconsin, with northwest
winds becoming gusty as low pressure deepens over central
Michigan. Rain activity may become somewhat more showery in nature
by the early morning hours, but at any rate, the combination of
rain, temps in the 40s and brisk northwest winds will make for a
rather raw Monday night and Tuesday for the region.


Northwest winds will begin to increase tonight as low pressure
over Michigan rapidly deepens. Gales are expected to develop by
mid morning Tuesday, with the strongest winds expected from late
morning through Tuesday afternoon. Waves will increase overnight
tonight and especially on Tuesday, wave heights approaching six
feet near open waters. A Small Craft Advisory is in effect for the
nearshore waters from early Tuesday morning into mid morning,
before being upgraded to a Gale Warning from mid morning through
Tuesday night.

PREV DISCUSSION... (Issued 648 PM CDT Mon Oct 23 2017)

.00Z Aviation Update...


A strong cold front is advancing east across the region this
evening. Along with increasing potential for rain, cigs and vis
will fall behind the front, with widespread MVFR and occasional
IFR developing at the terminals overnight, and continuing through
most of the day Tuesday. Northwest winds will also become quite
strong heading into Tuesday, with gusts peaking around 35 KT
Tuesday afternoon.

PREV DISCUSSION... (Issued 315 PM CDT MON OCT 23 2017)

TONIGHT AND TUESDAY - Forecast Confidence...Medium.

A 150+ knot speed max will dive south-southeast from
the northern Great Plains into the mid Mississippi valley today,
as troughing digs equatorward into the upper Midwest and western
Great Lakes. As the upper wave approaches, surface low pressure
will rapidly deepen while progressing from northern Indiana
towards far northern lower Michigan by tonight. Rain showers will
begin pushing back into our area from the west later this
afternoon with chances increasing tonight as forcing for ascent
arrives via jet-level divergence and increasing DCVA. The rain
should end from west to east on Tuesday as deep layer troughing
slowly pushes away to our east. A very strong pressure gradient
will ensue on Tuesday as the low deepens over lower Michigan.
While there is still some uncertainty in the evolution and
ultimate mixed layer depth, northwesterly wind gusts at least into
the 30 to 45 mph range are expected. With it being a bit too close
for comfort, went ahead and pulled the trigger on a Wind
Advisory, in collaboration with our neighboring offices. Looks
like a good indoor day for Wednesday given the combination of cool
temperatures, high wind, and rain.

TUESDAY NIGHT THROUGH THURSDAY - Forecast Confidence...Medium.

Over the past 24 hours, short term guidance has been varying its
tune in regards to location and strength of isentropic lift/warm air
advection event sliding southeast from southern Canada.  00Z
guidance backed off on strength of this weak system and shifted it
well to the north into southern Canada.  Only the ECMWF kept the
weak event progressing rapidly southeast across Wisconsin late
Tuesday night and Wednesday morning.  12Z GFS has flip-flopped and
is now carrying weak lift across central and northeast WI during
this period with light qpf grazing the northeast CWA.  Meanwhile 12Z
ECMWF remains consistent with earlier runs in showing vigorous mid-
level short wave moving rapidly southeast across western and
southern Wisconsin.  NAM solution farther east over eastern
Wisconsin, while GFS even farther east over northeast WI into
southern lower MI.  Enough weak layer q-vector convergence and
higher rh to warrant returning small pops for rain and snow showers
to the area for about a 6 hour period. Also, impressive burst of
700H potential vorticity advection with mid-level lapse rates of 6.5

Low level thermal structure still shows a mix of rain and snow
or all snow may occur with this event during the Wednesday morning
commute. If full potential vorticity is realized and ECMWF
solution turns out correct, then briefly lower visibilities with
-shsn could impact Wednesday morning commute. Too much uncertainty
at this point to include in HWO.

Some moderation in temperature is expected Wednesday night into
Thursday ahead of next in a series of amplifying short wave
trofs that will move through the upper midwest and Great Lakes
around Thursday.  Strengthening low pressure will move across
Wisconsin later Thursday into Thursday night dragging another
strong cold front through the area.  Even colder air will surge
in to finish off the work week.  The atmosphere is expected to
be pretty dry so no -shra are expected with the frontal passage.


THURSDAY NIGHT THROUGH MONDAY - Forecast Confidence...Medium.

Medium range guidance in good agreement on amplifying long wave
trof over the Great Lakes and upper midwest remaining
nearly station through the weekend on into the following
week.  In fact, both GFS and ECMWF show secondary area of
low pressure sagging southward from Canada into the Great
Lakes early in the weekend.  This will reinforce the
unseasonably cold conditions expected over the area, and
linger the cold into Monday.  925H temperatures will drop
below zero on Friday and remain in the 0 to 5C range
through the period.  A few periods of rain and snow showers are
expected with below freezing nighttime temperatures looking more
likely, pending cloud cover and boundary layer mixing.

GFS 500H standardized anomalies not as encouraging for next week as
yesterday, with below normal heights now lingering through the first
days of November.


WI...Wind Advisory from 7 AM to 7 PM CDT Tuesday for WIZ046-047-051-

LM...Small Craft Advisory from 6 AM to 9 AM CDT Tuesday for

     Gale Warning from 9 AM Tuesday to 4 AM CDT Wednesday for



Tuesday Night through Monday...MBK is the U.S. government's official web portal to all federal, state and local government web resources and services.