Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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670
FXUS63 KMKX 262044
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
344 PM CDT Wed Apr 26 2017

.TONIGHT AND THURSDAY...Forecast Confidence Is Medium.

The next 500 mb shortwave trough is expected to slide northeast
toward the area later tonight, then across the area Thursday
morning. Differential cyclonic vorticity advection with this
feature is expected by later tonight, along with some middle
level frontogenesis response.

This should result in another area of rain showers moving north
northeast through the area, especially in the eastern counties.
This was supported by several mesoscale models. Also added more
chances for thunder this evening into later tonight in the
southeast counties, as forecast soundings were showing some weak
elevated CAPE. Thus, continued high PoPs for mainly later
tonight into Thursday morning in the eastern 2/3 of the forecast
area.

Low pressure will gather some strength as it shifts northeast into
the Lake Michigan area later tonight, then northeast of there
Thursday. Gusty west winds developing Thursday should aid cold
air advection, and bring colder temperatures into the region. Low
clouds are expected to linger tonight into Thursday. Lows tonight
will remain mild, in the upper 30s far west to the middle 40s east,
Highs will not rise much on Thursday, with middle to upper 40s
expected.

.THURSDAY NIGHT...Forecast confidence is medium.

It looks dry Thursday night as brief ridging takes hold in the
wake of the departing low pressure system to the north. There is
a small window of opportunity after midnight where skies will
scattered out and the boundary layer decouples. If this happens,
we could see some frost in areas mainly to the northwest of
Madison.

.FRIDAY AND FRIDAY NIGHT...Forecast confidence is medium.

There is a surge of warm air advection coupled with a mid level
short wave that lifts north into the area, then quickly scoots off
to the east northeast. This should bring some showers to the area
from about mid morning on Friday into Friday evening. As that wave
pulls away, we should dry out for the rest of Friday night through
Saturday morning.

.SATURDAY THROUGH MONDAY...Forecast confidence is medium.

The highlight of this period is the big closed system that
gradually tracks from the southwest U.S. into the Great Lakes
during this period. The initial deep warm air advection surge
arrives later Saturday afternoon and Saturday night. This signals
the arrival of the first wave of rain. The surface system will be
occluded by the time it gets up here Sunday-Sunday evening.
Sunday looks very wet, but given the occlusion, the precip will
likely become banded and placing the location of these bands this
early is impossible. Where they set up, expect some decent
rainfall amounts. An inch or better is possible in some spots.
Peak rainfall at this point should be in the Sunday afternoon to
Sunday evening timeframe, with a few storms possible. Look for
things to taper off late Sunday night into Monday as the big,
occluded system lifts off to the north.

.TUESDAY AND WEDNESDAY...Forecast confidence is medium.

For now, the long range guidance is in pretty good agreement that
this period will allow us to dry out.  Still cool, though.

&&

.AVIATION(18Z TAFS)...

First batch of showers have moved north of the forecast area.
There will be a lull in the shower activity this afternoon, though
some drizzle may occur. Low stratus clouds should continue to move
northeastward into the area this afternoon, remaining between 700
and 900 feet above ground level. Southwest winds will become west
toward evening, with some gusts to around 20 knots in eastern
portions of the area.

The low stratus will linger tonight into Thursday morning, before
rising to around 2000 to 2500 feet above ground level Thursday
afternoon. Winds will become northwest tonight, then back to the
west on Thursday. Gusts of 20 to 25 knots are forecast for
Thursday afternoon, especially in eastern portions of the area.

Rain showers should move northeast into the area again during the
middle and late evening, lingering into Thursday morning. The
showers should move northeast out of the area during the late
morning.

&&

.MARINE...

A Small Craft Advisory continues until 11 PM CDT this evening
across the nearshore waters of Lake Michigan. South to southwest
winds are expected to gust to around or just below 22 knots into
early this evening. The winds will then weaken this evening, as
the pressure gradient weakens. Elevated waves, highest toward
Sheboygan, will subside by later this evening.

Another Small Craft Advisory may be needed for late morning and
afternoon on Thursday, as gusty west winds develop with
strengthening low pressure to the northeast. Frequent gusts of 22
to 25 knots are possible during this time. Elevated waves will
remain over the open waters of Lake Michigan.

A period of gusty winds and elevated waves are possible this
weekend into early next week, as a strong low pressure system
moves northeast toward and through the region.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 11 PM CDT this evening for LMZ643>646.

&&

$$

Tonight/Thursday and Aviation/Marine...Wood
Thursday Night through Wednesday...Davis



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