Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 261709 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1209 PM CDT FRI AUG 26 2016

.UPDATE...

Extensive area of middle to high clouds continues to slide
northeast into the area. This should continue this afternoon into
this evening, with partly to mostly cloudy skies expected. There
may be some diurnal cumulus in the sunnier areas as well. Lake
breeze already occurring around Milwaukee and south, and will
continue this afternoon.

Scattered showers continue to fall apart as they approach the
area from the southwest, as there is a good amount of dry air
below 10000 feet above ground level. Thus, any shower activity
should hold off this afternoon.

12Z model runs continue to differ somewhat with the location of
the low level jet nose and focused warm air advection tonight into
Saturday morning. The NAM is the furthest to the northwest of the
area, with the Canadian focused over the area, and the GFS
between them. All models do bring some QPF across the area later
tonight into Saturday morning.

The mesoscale models are showing a similar trend with bringing a
round of showers and storms through the area later tonight into
early Saturday morning. Thus, will continue the higher end POPs
for this period, perhaps raising them up to categorical in at
least the western counties.

Precipitation chances Saturday afternoon are still rather murky,
as it will depend on clouds clearing the area after the warm front
moves to the north. There will be modest deep layer bulk shear
with weak to modest mean layer CAPE, assuming some clearing of the
clouds.

There will still be some upper divergence from the right rear
quadrant of the 250 mb jet streak lingering, and some of the
mesoscale models develop isolated to scattered convection in or
west of the area later in the afternoon. Marginal severe risk and
marginal heavy rainfall risk exists in parts of the area Saturday.
For now, will continue chance POPs for the afternoon hours.

Wood

&&

.AVIATION/18Z TAFS/...

VFR conditions are expected this afternoon and evening across TAF
sites. Lake breeze this afternoon will turn winds east to
southeast at Milwaukee and Kenosha, probably reaching Waukesha as
well. Light and variable winds are expected at Madison. Some
diurnal cumulus is possible in the sunnier areas this afternoon.

Otherwise, middle to high clouds will gradually thicken through
the afternoon and evening. Should see a period of on and off
showers and thunderstorms later tonight into early Saturday
morning across TAF sites, as warm and moist air pushes north into
the area with a warm front. Should see MVFR ceilings and
visibilities at times, down to around 1000 feet and 3 miles.

Winds will become easterly by later tonight, gradually veering
south to southeast on Saturday. Should see a lull in the
precipitation later Saturday morning into the afternoon. May see
more scattered showers and storms later Saturday afternoon into
the evening, but too uncertain at this time to mention in TAFs.

Wood

&&

.MARINE...

Light wind regime will result in northwest winds turning onshore
late this morning and early afternoon. Wind speeds will remain in
the 5 to 10 knot range, with lower wave heights.

Scattered showers and thunderstorms are still expected to affect
the nearshore waters of Lake Michigan late tonight into Saturday
morning. Warm and more humid air will return to the region.

Recent offshore winds continued to reinforce colder upwelling
waters in the shallower nearshore waters. Atwater Beach buoy
measuring a lake surface temperature of 48 degrees, while recent
MODIS imagery measured lake surface temps in the 50s across the
nearshore waters, while mid-lake temps remain in the lower 70s.

MBK

&&

.PREV DISCUSSION... /Issued 326 AM CDT FRI AUG 26 2016/

TODAY AND TONIGHT...Forecast confidence is medium.

High pressure will move across WI today although scattered to broken
cirrus will occur due to swly flow aloft and the upstream
convection. The high clouds will probably keep temps down a degree
or two along with an afternoon lake breeze as well. Highs in the mid-
upper 70s for today.

For tonight, a shortwave trough will track from NE to srn MN. A wave
of low pressure will follow into IA with a sly 30 kt LLJ moving into
srn WI. The models differ on the exact placement of the LLJ with
some focusing farther west than others. Confidence is such to go
with likely PoPs over south central WI with high chance PoPs in ern
WI. PWs will rise to 1.5-1.8 inches with the thetae advection while
elevated CAPE will be very minimal due to mid level lapse rates of
5.5-6.0 C/KM. The showers and storms that do occur should have
moderate to heavy rainfall rates but will likely be brief.

SATURDAY...Forecast Confidence...Medium

Showers/storms will be likely across southern Wisconsin Saturday
as the first wave lifts northward. This first round may be limited
to the morning...with a break possible late morning into the
afternoon between waves. Another wave may then bring more storms
late afternoon into the evening. Overall, models not in great
agreement with timing and placement of convection. Though
confidence is on the higher end that there will be showers/storms
on Saturday, not nearly as confident in the timing at this point.

Should see near normal temps on Saturday.

SUNDAY THROUGH THURSDAY...Forecast confidence...Medium

Deeper moisture will be south of the area on Sunday, so went
mainly dry. Should be a pleasant day.

Near zonal flow Monday will transition to northwest flow between a
ridge building to the west and an upper low passing through well
to the northeast. Could see a couple weak waves move through the
forecast area...so kept some pops going into mid-week.

By Wednesday, the ECMWF and Canadian push the bulk of moisture
and instability south and west of the forecast area. The GFS
remains moist and unstable Wed and Thu. Kept some pops per the
GFS, but would be dry if the ECMWF/Canadian solutions pan out.

Should see temps a bit above normal through Tuesday. There is less
certainty beyond that due to the previously mentioned model
differences for Wed/Thu. Generally kept temps in between the
warmer GFS and cooler ECMWF/Canadian solutions.

AVIATION/12Z TAFS/...

VFR conditions today and this evening with only sct-bkn cirrus today
with a mid level deck of clouds for the evening. After midnight,
scattered to numerous showers and tstorms are expected to develop as
a warm front approaches from the sw. Cigs will lower and may become
MVFR toward sunrise or afterward. Cigs and vsbys will be reduced
with any showers and storms.

MARINE...

Relatively light winds and low wave heights are expected for today
and the weekend over the western shore of Lake MI. A lake breeze is
expected this afternoon with esely winds continuing tonight and
Saturday.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...None.
&&

$$

UPDATE...Wood/MBK
TODAY/TONIGHT AND AVIATION/MARINE...Gehring
Saturday THROUGH Thursday...DDV



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