Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 180826
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
326 AM CDT Fri Aug 18 2017

.SHORT TERM...

TODAY AND TONIGHT...Forecast Confidence Is Medium.

Area of low clouds over most of the area early this morning is
expected to gradually shift to the east by later in the morning.
Rather tight pressure gradient will continue to bring gusty west
northwest winds to the area into this morning. The pressure
gradient will gradually weaken this afternoon, which should help
ease the gusts.

Diurnal cumulus clouds should develop by this afternoon. An area
of middle to high clouds will try to push into portions of the
area from the west as well, with the lead 500 mb vorticity
maximum. There should still be some sunshine that filters through,
so expect highs to reach the upper 70s in most areas.

Main 500 mb shortwave trough is expected to slide southeast across
the region this evening, then exit later tonight. It appears that
the best upward vertical motion from differential cyclonic
vorticity advection, as well as low level frontogenesis response,
will be just south of the area. This is where the best QPF from
the models is located.

Still, kept chance/slight chance PoPs going for showers for
mainly tonight, highest in the south near the Illinois border.
Kept small thunder mention as well, though area forecast soundings
look a bit overdone with surface dewpoints and subsequent mean
layer CAPE. May see light fog later tonight, but kept out of
forecast for now. Lows look to reach the upper 50s in most areas.

.LONG TERM...

Saturday through Sunday... Forecast confidence is high.

The upper trough should be east of southeast WI by Saturday
morning, so expecting a dry weekend with light winds and
increasing temps and humidity. Look for a lake breeze on Saturday.
Highs Sat will be around 80 and up to 82-85 on Sunday.

Monday through Tuesday... Forecast confidence is medium.

A front will slowly sag southeast through WI Monday and Tuesday.
There are weak ripples in zonal flow across the Midwest, along
with the right entrance region of an upper jet. Any one of these
could trigger a thunderstorm complex either upstream of WI or over
WI. One scenario is a decaying MCS over southern WI Monday
morning, clearing up just in time for another round of showers and
storms developing on the nose of the low level jet in the late
afternoon/evening. Another scenario would be an upstream complex
slowly tracking across central WI all day.

The GFS and Canadian models are showing very high precipitable
water values over southern WI, in 1.75 to 2 inch range. Models
also show moderate CAPE and marginal shear. A few severe storms
look possible, but this could end up as mainly a heavy rain event.

Unfortunately, there is a pretty good chance of clouds hindering
the view of the solar eclipse in WI on Monday.

Conditions will remain favorable for scattered storms through
Tuesday evening until that front gets south of the IL border.

Wednesday through Friday... Forecast confidence is high.

Dry high pressure will bring pleasant weather to southern WI for
the remainder of the work week. Temperatures will be below
average.

&&

.AVIATION(09Z TAFS)...

Area of low clouds with ceilings varying between 1500 and 3500
feet are expected to gradually slide to the east of the area by
later this morning. Scattered diurnal cumulus clouds should
develop by this afternoon. More middle to high clouds should move
into the area this afternoon, though some sunshine should still
occur. Gusty west northwest winds are expected this morning,
before gradually weakening this afternoon.

May see some showers and a thunderstorm or two move southeast
through the area mainly tonight. Best chances will be near the
Illinois border. Light winds are expected tonight, with VFR
category ceilings. Light fog may develop later tonight, though
there is some uncertainty if clouds hang around. Fog is expected
in the Wisconsin River Valley later tonight.

&&

.MARINE...

A Small Craft Advisory is in effect until 18Z today across the
nearshore waters of Lake Michigan. A rather tight pressure
gradient into this morning will continue to bring gusty west
northwest winds. Gusts to 25 knots are expected. The pressure
gradient will gradually weaken this afternoon. This will help
weaken the gusts below 22 knots. High waves will remain over the
open waters.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 1 PM CDT this afternoon for
     LMZ643>646.

&&

$$

Today/Tonight and Aviation/Marine...Wood
Saturday through Thursday...Cronce


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