Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 161820 AAB
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1220 PM CST Thu Nov 16 2017

.UPDATE...

The clouds are thinning and locations northeast of a line from
Milwaukee to Green Lake are seeing sunshine. Look for more breaks
to develop in the clouds as the day goes on. There could be
another period of gusty winds this afternoon along the lakeshore
as winds turn around to the north-northeast. Look for lake clouds
to make their way back inland to lakeshore counties during the
evening hours as winds turn around to the east.

Breezy southerly winds will usher moisture into southern WI on
Friday. Drizzle in the morning should evolve into steadier rain
during the afternoon/evening as low pressure tracks across
Illinois.

The 12Z models are showing more widespread precip on the cold side
of the frontal system Saturday morning. The NAM is showing snow
while the GFS keeps surface temps warm enough to stay rain. I will
be mentioning the rain/snow for Saturday morning in the forecast.

&&

.AVIATION(18Z TAFS)...

Clouds will gradually thin/diminish through late afternoon, but
expect bases to remain in the 2000-3000 ft range. Mid level
clouds will spread into southern WI this evening. Lake clouds
should spread inland to lakeshore counties as winds turn around to
the east this evening. These could stick around through the
overnight hours.

Look for MVFR ceilings and drizzle to develop Friday morning, then
evolve into steadier rain for the afternoon/evening hours. There
is a chance for snow on Saturday in south central WI (warmer in
southeast WI), but still lots of uncertainty.

&&

.PREV DISCUSSION... (Issued 943 AM CST Thu Nov 16 2017)

UPDATE...

There is an expansive area of stratus clouds over the Upper
Midwest this morning due to cyclonic flow. An AMDAR sounding near
MKE around 7am shows a solid cloud layer from 2500 to 4500 ft.
This layer will continue to thin through the afternoon. A hole in
the clouds developing over northeast WI will help to diminish
clouds over southeast WI this afternoon, but confidence in timing
and area is low.

The low clouds should clear out by late this afternoon, just as
mid level clouds begin to spread in from the west. Meanwhile, low
level flow over the lake will switch from north to east later this
afternoon, which may advect lake clouds inland to the lakeshore
counties this evening. Increasing southerly winds will help push
these back out over the lake early Friday morning.

AVIATION(15Z TAFS)...

See the Update discussion (above) about the extensive cloud cover
today and lake clouds this evening.

MARINE...

Northwest winds are diminishing quickly, so I cancelled the small
craft advisory. Look for winds to increase rapidly out of the
south- southwest Friday morning. Gusts may reach small craft
advisory levels on Friday, and a new headline may be needed.

PREV DISCUSSION... (Issued 533 AM CST Thu Nov 16 2017)

UPDATE...

It`s a real struggle trying to figure out what this stratus will
do. The time of year dictates a pessimistic approach to clearing.
Yet, nearly all the guidance shows a rapid clearing toward late
morning. This happens as subsidence and dry air just rips a big
hole in the overcast and the clouds erode very quickly. I`m
pushing off the clearing a few hours, but will still go with some
sunshine this afternoon. The rest of the forecast remains on
track.

AVIATION(12Z TAFS)...

The MVFR stratus remains widespread across the region early this
morning, but is expected to gradually break up later this morning
with VFR conditions expected toward late morning. Exact trends
and timing are always difficult with stratus this time of year, so
confidence is a bit challenged with respect to cloud cover. Once
the MVFR CIGS scatter out, we will be VFR through the rest of the
TAF period.

Expect the northwest winds to steadily decrease this morning as
high pressure pushes in from the northwest. As the ridge slides to
the east this evening, look for winds to become very light, then
veer to the southeast. Warm air advection into the region on the
increasing southerly flow will bring a surge of mid and high level
clouds overnight.

PREV DISCUSSION... (Issued 242 AM CST Thu Nov 16 2017)

SHORT TERM...

Today and Tonight...Forecast confidence is high.

High pressure will slide across the area today, exiting to the
east by early evening. The main challenge for this period will be
with the behavior of the low clouds still streaming across the
area early this morning. We do see clearing approaching from the
north, likely bringing clearing skies first to Fond du
Lac/Sheboygan counties on south. The stratus will be tougher to
clear over the southwest forecast area. But, nearly all the
guidance does show the area clearing out toward mid day, so will
go with it. Subsidence with the ridge should rip expanding holes
in the shallow stratus this morning, so sunshine for the
afternoon.

As the ridge slides east tonight, we quickly get into a return
southerly flow and strong warm air advection. There is a lack of
deep moisture with this WAA, so just expecting an increase in
clouds with no precipitation. The low temp for tonight will
likely be reached in the evening, with temps then holding nearly
steady overnight.

LONG TERM...

Friday and Saturday...Forecast confidence is high:

Models continue to come into good agreement with the track of
strengthening low pressure late in the week. The low is expected
to pass by just south the the WI/IL border Friday night, heading
northeast into Ontario Saturday. Pretty good moisture surge with
this low, as precipitable water values will rise to around an
inch in the south. Plenty of lift to work with, so rain is a good
bet Friday into Saturday.

Held off on mixed precip most places Friday morning, as models
suggest temps should be warm enough for rain by the time
saturation is deep enough for precip. Most places should see a
little light rain by Friday afternoon, with the best chance for
widespread rain Friday evening into Saturday morning. Not out of
the question that the rain could mix with or change over to snow
for a time late Sat morning into the afternoon before the precip
comes to an end. Not expecting any accumulations though, as the
window of opportunity for snow will be short lived and any snow
that does fall will likely melt quickly.

Southerly winds ahead of the low will be breezy Friday, with even
stronger winds on the back side of the low Saturday.

Sunday through Wednesday...Forecast confidence is high:

High pressure will be in place for much of the time during the
first half of next week. Models do bring a wave through Monday
night or early Tuesday, but went with a dry forecast due to
limited available moisture.

Temps are expected to be chilly Sunday behind the departing low,
but then will likely recover nicely on Monday with temps
approaching or hitting the 50 degree mark. Cooler temps will
return for mid-week behind the departing trough.

AVIATION(09Z TAFS)...

The MVFR stratus that is widespread across the region early this
morning is expected to gradually break up this morning with VFR
conditions expected toward late morning. The clearing should work
down the southeast counties first, from Fond du Lac, south toward
Milwaukee. It will likely hang on longer in the KMSN area. Exact
trends and timing are always difficult with stratus this time of
year, so confidence is a bit challenged with respect to cloud
cover. Once the MVFR CIGS scatter out, we will be VFR through the
rest of the rest of the TAF period.

Expect the northwest winds to steadily decrease this morning as
high pressure pushes in from the northwest. As the ridge slides to
the east this evening, look for winds to become very light, then
veer to the southeast. Warm air advection into the region on the
increasing southerly flow will bring a surge of mid and high level
clouds overnight.

MARINE...

The small craft advisory remains in effect until noon. The gusty
northwest winds will gradually diminish today as high pressure
approaches from the northwest. Southerly winds will increase again
late tonight into Friday with another small craft advisory likely
for Friday through Friday evening.

Strong northwest winds are expected in the wake of a passing cold
front on Saturday. Gale force winds are possible Saturday
afternoon into Saturday evening. Small craft advisory conditions
would then likely stretch into early Sunday afternoon.

&&

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

$$

Update...Cronce
Today/Tonight and Aviation/Marine...Davis
Friday THROUGH Wednesday...DDV



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