Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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909
FXUS63 KMKX 242316
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
616 PM CDT Wed May 24 2017

.AVIATION(00Z TAFS)...Breaks in the overcast over eastern CWA
continues to advance wwd toward south central WI. Thinking the
breaks may slow down this evening with loss of insolation. Low to
mid-level cyclonic curvature and low level RH should result in the
clouds filling back in across eastern CWA overnight, likely
dropping back to MVFR and IFR levels. Keeping an eye on convection
over eastern Lake Michigan. Appears to be weakening but trajectory
and current speed would carry it into the near shore waters and
lakeshore areas around 01z.

&&

.PREV DISCUSSION... (Issued 322 PM CDT Wed May 24 2017)

DISCUSSION...

TONIGHT AND THURSDAY...Forecast Confidence Is Medium.

Mostly cloudy skies are expected to remain into Thursday across
the area, as cyclonic flow with the 500 mb low to the southwest
continues to influence the area. Some breaks are possible later
tonight into Thursday across south central Wisconsin, as the low
levels finally try to start drying out in that area.

Dew points remain relatively high overnight into Thursday
morning. This may combine with somewhat weaker winds to allow for
patchy fog development. If the clouds break up more than expected,
there may be more widespread fog with some dense fog possible.
Certainly some uncertainty here with how this will evolve
overnight.

After seasonable lows in the upper 40s tonight, warmer
temperatures are expected for Thursday. Highs in the upper 60s to
around 70 are forecast inland, with north northeast winds keeping
lakeshore areas cooler. Temperatures may remain cooler if clouds
linger longer than expected across south central Wisconsin.

Thursday night and Friday - Confidence...Medium
Mid level ridge axis translates east across WI. Some rather noisy
vorts appear within the ridge axis. However pattern does favor a
transition to a WAA regime late in the night so have some POPS in
place for some SHRA potential. The WAA continues into Friday with
the help of a ridge breaking shortwave. The NAM focuses the
heavier precip to our south.

Saturday and Saturday evening - Confidence...Low to Medium
Energized southwest mid level flow persists with more shortwave
activity swinging through. There is also a frontal boundary
extending south from low pressure to our north. The GFS blossoms
convection across extreme southern WI/northern IL while other
models show lighter and scattered shra. Will carry a chance of
SHRA/TSRA with these features. 925 temps in the 16-18c range will
be supportive of temps in the 70s.

Sunday - Confidence...Low
Some model differences keeps confidence on the low side. The GFS
is much more pronounced in carving out a pronounced trough across
the Upper Midwest that would generate a decent shot of SHRA/TSRA
right into Sunday evening. Meanwhile the ECMWF and GEM keep this
energy further north along with the better rain chances, so middle
of the road again on the POPS at this time.

Sunday night through Wednesday - Confidence...Medium
A parade of shortwaves/vort maxes in the 500 millibar northwest
flow regime will continue to traverse the Great Lakes. So periodic
chances of SHRA/TSRA will persist. The 850 temps will be quite
chilly in the single digits celsius so no overall change to this
damp and cool pattern.

AVIATION(18Z TAFS)...Showers have diminished across the area, and
it should remain dry for the rest of the afternoon. Low ceilings
early this afternoon should rise to around or above 3000 feet
above ground level by later this afternoon at most locations.
Gusty north winds should linger, especially near Lake Michigan.
Visibilities should remain above 6 miles at most sites.

Ceilings will gradually lower again tonight, with values near
alternate minimums by later tonight into Thursday morning. They
should rise above 3000 feet once again during the afternoon.
Visibilities should lower to 3 to 5 miles later tonight into
Thursday morning, with light fog. May see lower values near Lake
Michigan at times. They will rise again by midday Thursday. North
winds should weaken somewhat tonight into Thursday, though may
become gusty near Lake Michigan again on Thursday.

MARINE...A tight pressure gradient into this evening will continue
to allow for gusty north winds of 15 to 25 knots. Waves of 3 to 6
feet are expected as well. A Small Craft Advisory is in effect
for the nearshore waters of Lake Michigan until midnight tonight.

There may be some light fog development later tonight into
Thursday morning across the lake, as winds weaken somewhat and
moist air remains. North northeast winds will gust up to 20 knots
on Thursday, with waves remaining under 4 feet. Small craft should
exercise caution if venturing out on the lake Thursday.

BEACHES...There is a high swim risk for the beaches of Lake Michigan
into this evening. Waves of 3 to 6 feet are expected, along with gusty
north winds of 15 to 25 MPH. No Beach Hazards Statement will be issued,
as the water temperatures remain below 50 degrees Fahrenheit. However,
life threatening waves and currents are still expected along the
shore. Stay out of the water.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until midnight CDT tonight for LMZ643>646.

&&

$$

Aviation...MBK
Tonight/Thursday/Marine/Beaches...Wood
Thursday Night through Wednesday...PC



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