Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 190147
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
847 PM CDT SUN SEP 18 2016

.UPDATE...

The showers across northwest Wisconsin and the increasing high
clouds across the south are associated with warm air advection
ahead of the next approaching trough. It`s not out of the question
that a few showers or a thunderstorm could sneak in here late
tonight and tomorrow morning with the warm advection...mainly from
Madison on west and north. The current forecast has this handled
adequately with slight chance pops. Generally quiet overnight. The
main focus will be on the potential for stronger convection along
the approaching trough/cold front over the southeast half of the
forecast area late Monday afternoon and evening. No adjustments to
that scenario this evening.

&&

.AVIATION/06Z TAFS/...

We should remain VFR across the area overnight into Monday as
clouds increase from the west due to warm air advection ahead of
an approaching trough of low pressure and cold front. This could
result in a some clouds developing between about 30-40kft late
tonight around KMSN. Widely scattered showers or a thunderstorm
are possible as well. The cold front will reach KMSN around 21z
Monday and push southeast of Milwaukee after about 03-05z Tuesday.
We should see more widespread development of thunderstorms along
the front after about 21z, so mainly focused over the southeast
half of the forecast area. This activity would likely produce
brief periods of MVFR or IFR conditions if the storms move through
the TAF sites. Once the front clears, conditions will improve
Tuesday evening.

&&

.MARINE...

Southwest winds will be gusty tomorrow ahead of an approaching wave.
Decided to issue a Small Craft Advisory based from mid-morning
through late afternoon.

&&

.PREV DISCUSSION... /Issued 335 PM CDT SUN SEP 18 2016/

SHORT TERM...

TONIGHT AND MONDAY...Forecast Confidence...Medium

Quiet weather is expected through most of the night as high pressure
continues to pull away ahead of an approaching trough. Could see a
few showers far northwest toward morning as moisture/instability
begins to increase.

Kept some low pops going Monday morning into the afternoon due to
increasing moisture and warm advection aloft. Soundings showing a
bit of a cap which may keep it mainly dry until late afternoon when
the cap weakens. Thus have highest pops late in the afternoon.

Above normal temperatures will continue tonight and Monday.

Monday night through Thursday...Forecast confidence medium.

The cold front is expected to initiate scattered to numerous
thunderstorms by late Mon afternoon or early evening from nw IL
into se WI. MLCAPE values will be around 1000 J/kg while deep
layer shear of 40-45 kts will be present. Some modest low level
wind shear as well. Thus some supercell storms will be possible
and SPC marginal risk is placed well over much of the CWA. The
cold front should move out of far se WI around 06z with dry air
and high pressure to follow for Tue.

A trough of low pressure and associated low to mid level warm
advection and frontogenesis will then develop newd from NE to nrn
WI from late Tue nt-Wed nt. A shortwave trough tracking from the
central Great Plains through WI will aid in the overall lift and movement
of the surface trough. Much of the lift, and showers and tstorms
will remain north and west of Madison until Wed night when the
shortwave trough tracks across the state. Thus higher confidence
for showers and storms will be Wed night, possibly lingering into
Thu morning.

LONG TERM...Friday through Sunday...Forecast confidence medium.

A front will then stall in the vicinity of srn WI into the weekend
with ridging aloft ahead of a sharp upper trough and associated
cold front moving east across the Great Plains. Thus tstorm
chances will continue with above normal temps and humidity.

AVIATION/00Z TAFS/...

VFR conditions will continue through at least the evening. The NAM
is hinting at some lower clouds in the west later tonight into
Monday morning as a weak trough approaches, but still leaning toward
keeping the forecast VFR through Monday.

There will be a chance for showers/storms late tonight and Monday as
the wave moves through, with the best chance coming late afternoon
into the evening.

A period of low level wind shear tonight still looks possible per
the 12Z NAM, mainly across the northwest half of the forecast
area.

MARINE...

Southwest winds will be gusty tomorrow ahead of an approaching wave.
Decided to issue a Small Craft Advisory based from mid-morning
through late afternoon.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...SMALL CRAFT ADVISORY from 10 AM to 6 PM CDT Monday for
     LMZ643>646.

&&

$$

UPDATE...Davis
TONIGHT/Monday AND AVIATION/MARINE...DDV
Monday NIGHT THROUGH Sunday...Gehring



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