Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 302036
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
335 PM CDT TUE AUG 30 2016
.TONIGHT AND WEDNESDAY - Forecast Confidence...Medium.
Showers and thunderstorms that have developed along an outflow
boundary from previous convection should move southeast out of S WI
by this evening. This outflow boundary is out ahead of a cold front,
which is expected to move through later this evening. The 30.17z
HRRR model is progging perhaps some light showers developing along
the cold front. However, the best frontogenetical forcing associated
with the cold front looks to stay northeast of the area. Otherwise,
mostly cloudy skies are expected overnight, with some gradual
clearing from the north to the south as the cold front departs the
region. There could be some enhanced wind gusts along Lake Michigan
as the cold front moves through, and winds veer to a
north/northeasterly direction. The better fetch off the Lake should
support these gusty winds, with gusts up to 20 kts possible.
Overnight lows look to drop thanks to the cold air advection post-
fropa, as 925 mb temps look to drop into the mid teen Celsius range,
and overnight lows in the upper 50s northwest to mid 60s southeast.
Mainly some valley fog is possible overnight, especially in the
Wisconsin River Valley area.
A mid-level northwesterly flow regime will return as the cold front
departs. Mid-level ridging slowly builds into the High Plains
Wednesday, along with surface high pressure moving in during the day
Wednesday. 925 mb temps rebound into the upper teens by 21z
Wednesday, leading to highs in the mid 70s, with lower 70s along
Lake Michigan, thanks to the on-shore wind flow.
.WEDNESDAY NIGHT THROUGH FRIDAY - Forecast Confidence...High.
A quiet and cooler period is expected as long wave ridging moves
across the area. Before the ridge axis nears the area, a piece of
short wave energy associated with low pressure moving through
southern Canada will graze the western Great Lakes later Wednesday
night into Thursday. In conjunction, a reinforcing push of low
level cooler air will accompany this feature. 925H temperatures
fall into the 10-15C range on Thursday. This surge of cooler air
increases the Delta-T to around 10 degrees on Thursday. Fortunately,
low level moisture remains very limited so only expecting a period
of sct-bkn cu to affect eastern CWA for a time as low level
convergence remains brief and transient. Hence no -shra expected at
this time. Upper level ridge and subsidence takes control Thursday
night and Friday resulting in more sunshine and some recovery in
daytime temperatures. Few low areas will likely fall into the 40s
Thursday night, away from Lake Michigan.
FRIDAY NIGHT THROUGH TUESDAY - Forecast Confidence...Medium to High.
Previous thinking continues to hold for the long holiday weekend.
Broadscale ridging across central Conus and the Great Lakes will be
slow to move eastward at the start of the weekend. This is mainly
due to reamplification of long-wave troffing off east coast,
partially due to remnants of tropical system that will have crossed
FL, getting absorbed into trof. Hence the quiet weather is expected
to continue across southern Wisconsin through at least the first
half of the weekend. Current thinking is Saturday looks to be the
best day of the holiday with sunshine and light southerly
The quiet weather will continue through Saturday night, and possibly
all of Sunday. However by then, the protective ridge axis will have
moved off to the east of Wisconsin. Increasing south winds will
begin to pull deeper moisture into the upper midwest, but the main
influx will remain to the west of WI through Sunday. Best chance for
a period of showers and storms will be later Sunday night and Labor
Day as low level jet pivots across WI ahead of approaching cold
Steering flow remains southwesterly early next week as baroclinic
zone strengthens across the upper midwest. Need to keep
precipitation chances going into Tuesday as both ECMWF and GFS
showing a stronger piece of mid-level short wave energy moving
northeast across the Upper Midwest during this period.
Showers and thunderstorms will slowly move out of S WI this
afternoon and evening. A cold front will also move through S WI this
evening, but the latest short-range guidance indicates the cold
front could develop some light showers with it. Expect some MVFR/IFR
cigs/vsbys with the strongest thunderstorms. Otherwise, expect VFR
conditions once the storms move to the south and east.
Winds are expected to veer to the north and northeast along Lake
Michigan. This direction will be favorable for stronger wind gusts
thanks to the better fetch off the Lake, so gusts could reach up to
20 kts near MKE and ENW TAF sites.
Cold front over central WI will sweep thru nearshore waters this
afternoon and evening. Winds will shift to the north to northeast
and increase, with gusts up to 20 kts possible. Waves look to be
around one foot overnight, with some higher waves between 2 to 4
feet during the day Wednesday as the winds turn to the north and
northeast, resulting in better fetch off Lake Michigan.
Moderate swim risk expected Wednesday afternoon through Thursday as
winds look to veer from the north and northeast and increase during
the day Wednesday. Wind gusts could reach up to 20 kts, with waves
between 2 to 4 feet Wednesday.
TONIGHT AND WEDNESDAY/AVIATION/MARINE/BEACHES...JTS
WEDNESDAY NIGHT THROUGH TUESDAY...Kavinsky