Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 231524
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1024 AM CDT TUE AUG 23 2016
.AVIATION/18Z TAFS/...Influence of low level anticyclonic flow
will persist into this evening with mostly sunny skies. Precip
associated with upstream shortwave and low level moist axis will
remain to our west. Influence of the upper shortwave and at least
a portion of the LLJ will arrive mainly after 06z tonight. So
expect an uptick in shra/tsra activity associated with these
features.Appears that towards mid morning that precip should wind
down as LLj and axis of shortwave shift east. Some redevelopment
possible Wednesday afternoon depending on where sfc/850 millibar
convergence and instability set up.
.MARINE...Latest RAP forecast soundings show south winds increasing
through the morning with deepening boundary layer mixing...though
wind gusts look to stay at, or just below 20 knots through the
afternoon and early evening. However the longer fetch will build 3
to 5 foot waves from Port Washington north per the latest wave
model output, so timing and location of Small Craft Advisory look
on track. Winds will decouple and lower for a time tonight, then
increase again on Wednesday. Expected showers and storms may limit
the depth of mixing and strength of wind gusts, but they could be
strong enough to build high waves in the northern zone again if
directional shift from south to southwest is delayed until late in
.PREV DISCUSSION... /Issued 517 AM CDT TUE AUG 23 2016/
TODAY AND TONIGHT...Forecast Confidence Is High.
Sly flow will continue today and tonight as a shortwave trough
from NE approaches. Low level warm advection will boost temps into
the lower 80s today, with a lake breeze expected during the
The NE shortwave trough is expected to track into wrn WI late tnt,
with a surge of PWs up to 1.70 inches complementing it. Forecast
soundings show decent saturation with the surge of moisture, along
with elevated CAPEs up to 500 joules/kg. Showers and tstorms will
be likely late tonight over south central WI, with chances over
ern WI. The sly winds and clouds will make for a mild night, with
lows in the middle to upper 60s.
WEDNESDAY THROUGH THURSDAY NIGHT...Forecast Confidence Is Medium.
Models generally show the 500 mb shortwave trough sliding
northeast of the area by 18Z Wednesday. NAM/GFS/ECMWF has slowed
the cold frontal passage to Wednesday night or early Thursday
morning, with the Canadian taking it southeast of the area
Wednesday evening. QPF lingers across the southeastern half of
the area Wednesday night with the slower frontal passage.
The frontogenesis response with the front is rather weak. In
addition, the low level jet nose is now further to the south of
the area Wednesday morning, so it may not be much of a factor for
Still enough deep moisture in the area, with rather moist
adiabatic moisture profiles on area forecast soundings, to
continue likely POPs Wednesday morning across the area. These
likely POPs linger into the afternoon in the southeast half of the
area, and in the far southeast into the evening, as the front
slowly moves through.
The showers and storms may be more scattered about than in an
organized area Wednesday afternoon and night, with the modest at
best upward vertical motion fields. Warm and humid conditions are
Marginal risk for severe storms from the Storm Prediction Center
Day 2 Outlook may be overdone, as there is uncertainty with how
long clouds will linger with precipitation and its effect on mean
layer CAPE values. Deep layer shear is also weak to modest,
perhaps reaching 20 to 25 knots or so.
Precipitable water values do get high Wednesday, up to near 2.00
inches, with some other favorable heavy rainfall parameters.
However, lack of a decent low level jet nose and persistent upward
vertical motion may limit any heavy rainfall risk.
Cold air advection Thursday into Thursday night behind the front
is expected, with quiet weather. High pressure will move eastward
into the Upper Midwest during this time. Less humid conditions are
expected, with mild temperatures.
FRIDAY THROUGH MONDAY...Forecast Confidence Is Medium.
GFS/ECMWF show the high moving east across the region Friday into
Friday night. East to southeast flow should be rather dry, so this
may limit any eastward push of warm air advection showers and
storms to the west. Models are trending drier in the western
counties Friday night. Left small POPs there in forecast but may
need removal if dry look continues. Mild temperatures will
GFS/ECMWF continue to show warm air advection moving back into the
region for Saturday into Sunday, though differ on path of 500 mb
shortwave trough. ECMWF brings weak cold front faster through the
area than the GFS Sunday into Sunday night. A broad 500 mb
shortwave trough then approaches the area from the southwest
Continued with the consensus POPs for Saturday into Monday, given
some model uncertainty. Warm and humid conditions should return
during this period.
AVIATION/12Z TAFS/...VFR conditions today and this evening. Stratus
and low cigs forming after midnight as moist air and showers and
tstorms arrive. The cigs will fall below 1 kft over south central WI
and over portions of SE WI. The cigs will fall to MVFR to IFR over
far ern WI toward sunrise on Wed. MVFR vsbys will accompany the low
cigs and rainfall.
A Small Craft Advisory (SCA) is in effect north of Port
Washington from noon until 10 pm, for breezy sly winds and waves
of 3 to 5 feet. The winds and waves will decrease some by late
evening, but again may reach SCA conditions for Wednesday
A Beach Hazards Statement is in effect from Port Washington to
Sheboygan from noon until 10 pm. Sly winds will generate high
waves, that will cause strong structural and longshore currents.
Rip currents will also be possible. Thus, dangerous swimming
conditions will exist this afternoon and evening.
WI...BEACH HAZARDS STATEMENT until 10 PM CDT this evening for WIZ052-
LM...SMALL CRAFT ADVISORY until 10 PM CDT this evening for LMZ643.
TODAY/TONIGHT AND AVIATION/MARINE...Gehring
Wednesday THROUGH Monday...Wood