Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 310258
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
958 PM CDT SAT JUL 30 2016
.UPDATE...Far ern WI will remain of the wrn periphery of the
moist ely flow across lower MI and Lake MI tonight into Sun AM.
Thus stratus clouds will occur at times but especially toward
sunrise when RH will be at its highest. Patchy fog will also be
possible during the early morning hours, including inland via
radiational cooling. Otherwise partly cloudy skies and seasonal
temps and humidity are forecast for Sun. There is a very remote
chances of a shower or tstorm along the lake breeze front.
.AVIATION/06Z TAFS/...Patchy light fog via mvfr vsbys will be
possible during the early morning hours and through sunrise.
Broken stratus clouds around 1-2 kft are expected over far ern WI
during the early morning hours especially around sunrise for KMKE
and KENW. KUES could also see scattered stratus but lesser
chances for broken coverage. Otherwise scattered to briefly broken
cumulus clouds at 4 kft for the late morning and afternoon hours.
A slight chance of showers and tstorms is forecast.
.MARINE...A nnely flow will continue through Sun but the magnitude
of the winds and waves will remain fairly low. A light sely flow
is expected for Mon into Mon nt.
.PREV DISCUSSION... /Issued 304 PM CDT SAT JUL 30 2016/
TONIGHT AND SUNDAY...Forecast confidence is medium.
Look for mostly clear skies by late this evening with the loss of
daytime heating. The clear skies and light winds will allow
temperatures to drop into the upper 50s/lower 60s inland from the
lake. This should bring us pretty close to the expected dewpoint
values, so patchy fog is expected tonight.
Easterly winds in the low levels will nudge an area of high 925-
850mb relative humidity that is currently over southern Michigan
westerly across southern Lake Michigan and into Southeast Wisconsin
early Sunday morning. Expect low clouds and possibly some drizzle
through late morning. Low level mixing will help to scour out the
low clouds by late morning, but wherever this weak moisture boundary
ends up by that time, it will serve as a weak focal point for
thunderstorm potential. Models are picking up on light precip in an
area from Janesville to Madison along this boundary. CAPE/shear
values are on the low side, so no severe is expected. Whatever
develops will be brief.
SUNDAY night AND MONDAY...Forecast Confidence...Medium
An upper ridge builds across the eastern Dakotas before moving
into Wisconsin Monday. Weak upper divergence begins monday. A subtle
500 mb shortwave (possibly convectively induced) enters south
700 mb upward motion increases Monday. 700 mb RH is low Sunday
night but increases south central late Monday afternoon. 700 mb
temperatures begin to warm and reach 10 Celsius late Monday
afternoon, as a 30 knot speed max enters southwest Wisconsin.
850 mb winds are weak but gradually become southwest across south
central Wisconsin, at the nose of a modest wind max. GFS model
surface dewpoints begin to rise to near 70, especially over south
central Wisconsin. High pressure begins to weaken over the Great
Lakes with the light surface winds becoming more southeast. Little
in the way of Zero to 1 km mixed layer CAPE, especially southeast.
Monday night and Tuesday...Forecast Confidence...Medium
The upper flow becomes zonal as the ridge moves east and a
shortwave moves across south central Canada. Mainly Weak upper
divergence continues. 700 mb temperatures are around 10 to 11
Celsius. 700 mb upward motion increases and is moderate to strong
Tuesday afternoon. 850/700 mb RH increases with 850 mb dew points
around 14 Celsius. The 850 mb winds increase a little but are
Deeper moisture will return with the warm front possibly reaching
southern Wisconsin on the GFS. The GFS now produces light
to moderate precipitation Monday night, with moderate to heavy
amounts Tuesday afternoon.
GFS forecast soundings moisten as precipitable water values
increase to around 2 inches. Elevated CAPE increases to around 900
Joules/kg MOnday night. By Tuesday afternoon Mixed layer CAPE to
close to 3000 joules/kg with only a weak cap. The severe weather
parameters do increase on the GFS Tuesday afternoon. The GFS
brings back upper 70s dew points Tuesday.
Tuesday night and Wednesday...Forecast Confidence...Medium
The upper flow remains fairly zonal with a weak ridge across
The GFS has an MCS across southern Wisconsin Tuesday night into
Wednesday morning, wile the 00Z ECMWF only has some light
precipitation mainly Tuesday evening.
Thursday and Friday...Forecast Confidence...Medium
The upper flow remains fairly zonal but increases as a rather
strong shortwave moves across south central canada.
There will be a chance for thunderstorms Thursday night and
friday morning, as a cold front moves through.
As the southern Canada shortwave moves east, the upper flow
becomes more northwest with a ridge building over the plains.
The ECMWF builds a high into the upper Mississippi river with the
surface boundary well south. The GFS slows the front across
Illinois with some showers across southern Wisconsin.
Clear skies expected for most of the night. Then an area of low
level moisture will spread westward into southern WI early Sunday
morning. Expect an area of MVFR ceilings through mid to late
morning, especially near the lake. There is a small chance for
thunderstorms inland Sunday afternoon.
Northeast winds of 10 to 15 knots with gusts to 20 knots will
gradually relax this evening. Look for waves of 2 to 4 feet to
diminish to 1 to 3 feet this evening, then persist at that level
through Sunday afternoon with a persistent easterly breeze. Winds
and waves are expected to remain below small craft advisory levels
through much of next week.
Persistent northeast winds and waves up to 2 to 4 feet should
continue to bring a Moderate Swim Risk to the beaches along Lake
Michigan into early this evening. Waves will then subside a
TONIGHT/Sunday AND AVIATION/MARINE...MRC
Sunday NIGHT THROUGH Saturday...Hentz