Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 241529
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1029 AM CDT WED AUG 24 2016
A few showers have developed across the western CWA associated
with a weak 500mb shortwave and thunderstorms have developed in
far SE MN/NE IA along the surface trough axis. These features will
shift east today and overcast clouds becoming broken in some areas
will help increase afternoon instability. So, think there will be
isolated showers and maybe a thunderstorm this afternoon.
Surface trough axis and mid level shortwave will move through
overnight bringing a good chance for showers and some
thunderstorms, mainly for the southern half of the CWA. Most meso
models show the majority of the activity will be on the state line
MVFR ceilings at times today until the cold front moves through
tonight. Otherwise expect broken stratocumulus or cumulus today.
There may be isolated showers and possibly a thunderstorm but
confidence is low so will not include in TAFS at this time. There is
a better chance for showers and thunderstorms tonight with
reduced cigs and vsbys. There may be a period of MVFR fog overnight.
A Small Craft Advisory continues until noon north of Port
Washington for breezy sly winds and 3 to 5 foot waves. South of
Port Washington the waves will be slightly lower and more swly
although brief wind gusts in the 20 knot range are expected. The
winds will gradually weaken during the afternoon.
.PREV DISCUSSION... /Issued 427 AM CDT WED AUG 24 2016/
TODAY AND TONIGHT...Widespread showers and tstorms are expected to
move ewd across srn WI this morning. Other than the slow moving MCS
over sw WI, additional showers and storms have developed over ern
IA. This area of storms is associated with a shortwave trough over
srn IA as well as the veering of the LLJ and associated warm
advection and moisture transport. PWs have increased to 1.8-1.9
inches with locally heavy rain expected. The flash flood threat is
low other than the typical higher threat in large urban areas.
There will be a minimum in shower and tstorm activity during the
afternoon as differential AVA behind the upper wave takes hold.
Mostly cloudy skies will likely continue due to low level
instability but with some breaks in the cloud cover.
For tonight the cold frontal passage will slowly begin across srn WI
while another shortwave trough approaches far srn WI from IA. Thus
good chances of tstorms are forecast for far srn WI including the
The cold front is expected to push the rest of the way through the
forecast area Friday morning. Deeper moisture and lingering
instability will hang around in the southeast for at least the
morning. Kept some pops southeast half in the morning as a result,
winding things down early afternoon as a drier and more stable
airmass moves in behind the departing front. Temps aloft will not
fall quickly behind the front, so highs in the upper 70s and low 80s
still seem reasonable.
High pressure will bring very pleasant weather to southern Wisconsin
on Friday. Skies should be mostly sunny, with light winds and highs
just a tad under normal values for late August.
SATURDAY THROUGH TUESDAY...Forecast Confidence...Medium
Low pressure will approach on Saturday. Southerly low level flow
ahead of the low will bring milder temps and dewpoints to the area.
Storms are expected to develop by afternoon, particularly in the
west/northwest forecast area. Better chance for storms will likely
be overnight as the shortwave moves through.
Moisture and instability are expected to linger into Sunday, with
another wave possibly bringing more storm chances.
The GFS and ECMWF both have surface high pressure in place for
Monday and Tuesday. The GFS is milder though with an upper ridge
building in. It also has higher dewpoints and storm chances both
days as weak waves pass through the northern extent of the ridge.
Then ECMWF on the other hand has more of a troughing look both days,
keeping somewhat cooler and drier conditions across the forecast
area. Despite showing a wave or two moving through, the ECMWF looks
dry because of the lower overall moisture and instability compared
to the GFS. The Canadian looks similar to the ECMWF through Monday.
Gave a nod to the GFS and kept some low pops both days, but could
end up being dry if the ECMWF/Canadian solutions pan out.
AVIATION/12Z TAFS...Showers and tstorms this morning with good
chances of more storms over the area tonight. Cigs will lower this
morning over se WI to 1-2 kft with cigs below 1 kft over south
central WI. Broken stratocumulus or cumulus are expected through the
day with cigs rising to MVFR cigs later this morning and becoming
3.5-4 kft this afternoon although areas of MVFR cigs will still
exist. More areas of MVFR cigs are possible tnt along with MVFR
vsbys via light fog. Reduced vsbys and cigs expected in showers and
MARINE...A Small Craft Advisory will continue until noon north
of Port Washington for breezy sly winds and 3 to 5 foot waves. South
or Port Washington the waves will be slightly lower although brief
wind gusts in the 20 knot range are expected. The winds will
gradually veer to swly for the afternoon with some weakening.
LM...SMALL CRAFT ADVISORY until noon CDT today for LMZ643.
TODAY/TONIGHT AND AVIATION/MARINE...Marquardt
Thursday THROUGH Tuesday...Collar