Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 190445
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1145 PM CDT Tue Sep 18 2018

.UPDATE...

Thunderstorms are starting to form across Iowa at this hour, and
will continue to develop to our west and northwest tonight, moving
into the region Wednesday morning. At this point, it`s looking
increasingly likely that we`ll be dry until sunrise.

&&

.AVIATION(06Z TAFS)...

MVFR stratus has developed across much of the area as of late
Tuesday evening, and will remain in place through morning.
Occasional periods of IFR will be possible as well.

Precipitation will begin to move into the area early Wednesday
morning, likely after sunrise. Rain and occasional thunderstorms
can be expected. Conditions will likely be VFR outside of any
showers/storms, with MVFR to IFR in and around thunderstorm
activity.

Much like Tuesday, rain is expected to end by late afternoon, with
a period of VFR conditions before more rain arrives Wednesday
night.

&&

.PREV DISCUSSION... (Issued 925 PM CDT Tue Sep 18 2018)

UPDATE...

We should remain dry until at least the pre-dawn hours, and
perhaps until after sunrise, as convection is taking its time in
developing over Iowa and Minnesota.

MARINE...

Light easterly winds will continue through Wednesday, with waves
generally remaining 2 feet or less.

Stronger winds are expected on Thursday and Thursday night ahead
of a cold front. South to southwest winds will be sustained around
20 knots, with gusts to 30 knots. Winds will then become westerly
and then northwest on Friday behind the front, with gusts again
expected to be around 30 knots.

PREV DISCUSSION... (Issued 617 PM CDT Tue Sep 18 2018)

UPDATE...

We should remain dry through the rest of this evening, with just
widespread cloud cover across the area. Temperatures will very
slowly fall a few degrees, with overnight lows in the upper 50s to
low 60s.  Additional precipitation is still on track to arrive
Wednesday morning.

AVIATION(00Z TAFS)...

VFR will prevail through the early evening for most of the area.
The only exception for early this evening will be areas near Lake
Michigan, where an area of low end MVFR ceilings is moving
through. Winds will be easterly this evening.

MVFR ceilings will then begin to move into MSN late this evening,
continuing through the overnight hours. Additional rain and
thunderstorms will be possible across the entire area tomorrow
morning, likely around or after sunrise. MVFR to occasional IFR
can be expected with this activity.

Much like today, conditions are expected to gradually improve to
VFR by afternoon. Additional precipitation is then expected
Wednesday night into Thursday.

PREV DISCUSSION... (Issued 300 PM CDT Tue Sep 18 2018)

SHORT TERM...

Tonight and Wednesday...Forecast confidence is medium.

The convection earlier today has pushed a very shallow surface
boundary well south of Wisconsin.  We should be fairly quiet
through the night as we stabilize for the time being and the focus
shifts upstream across IA/MN, closer to where the weak low level
jet will be impinging on the front.  We should see a complex
develop to the west, then roll in here late tonight, or after
sunrise on Wednesday. Just where it pushes in is under question.
It may focus farther to the north where the elevated frontal
boundary resides. It may cold pool and take a dive south with
time. There are as many possible solutions as we have model
simulations...highlighting the uncertainty level of the forecast.
It does look very progressive, helping to put a lid on any
excessive type rainfall...moving out again by early afternoon. We
will remain north of a shallow boundary on Wednesday, so can`t
rule out lingering scattered stuff. Rainfall amounts most places
would max out around 1/2 inch, higher west than near Lake
Michigan, but the usual caveat applies...locally higher amounts
are always possible.

LONG TERM...

Wednesday night through Thursday...Forecast confidence is medium
to high:

Another round of showers and thunderstorms is expected later
Wednesday night into Thursday morning as a warm front lifts into
southern Wisconsin. This front should lift far enough north by
late morning for a dry, breezy, and warm afternoon. Given enough
sunshine, temperatures could approach 90 toward the Illinois
border.

It will likely stay dry into the evening hours, with a line of
thunderstorms approaching from the west along and ahead of a cold
front. The consensus of models continues to trend slower with the
arrival of this front. The later it arrives, the less instability
will be available. Thus models have backed off on rainfall totals
for Thursday night. Though there will be plenty of shear with
this system, the timing of the front is becoming less favorable
for a severe thunderstorm threat. Still worth keeping an eye on
though given the strong wind field and strength of the cold front.

Friday through Sunday...Forecast confidence is high:

High pressure will bring dry weather for Friday into the weekend.
Clouds will likely hang on into at least the morning, with some
sunshine possible in the afternoon. It will be very fall-like,
with breezy winds and high temps in the 60s most places.

Winds will be lighter Saturday with the high centered more
overhead. Plenty of sunshine is expected, with high temps a few
degrees below normal in the mid-60s.

The high will shift eastward Sunday, allowing a return of
southerly winds. This should push high temps back up to around
normal. Expecting another good round of sunny skies to wrap up the
weekend.

Monday and Tuesday...Forecast confidence is medium:

Low pressure will approach the area Monday, moving through
Tuesday. This system will likely bring more showers and storms to
the area. There are the usual model to model differences of
timing/strength/placement of this system that would be expected
several days out. Right now, looks like temps should be near to a
few degrees above normal, depending on the timing of the front.

MARINE...

Strong southerly winds Thursday into Thursday night will veer to
the west then northwest by early Friday morning and continue at
elevated levels into Friday evening. A small craft advisory will
likely be needed from Thursday into Friday evening.

&&

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

$$

Update...Boxell
Tonight/Wednesday and Aviation/Marine...Boxell
Wednesday Night through Tuesday...99


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