NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 170409
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1109 PM CDT Thu Apr 16 2026
.KEY MESSAGES...
- Mostly dry tonight into tomorrow, save for a few potential
showers along the lake breeze this afternoon.
- Dense fog Advisory in effect mainly for counties close to Lake
Michigan but extension further west may be needed. Marine
Dense Fog continues through Friday.
- A Flood Watch is out for all of southern Wisconsin from 1pm
Friday to 7am Saturday for more heavy rain Friday afternoon
and evening.
- Another round of heavy rainfall, flooding, and severe
thunderstorms is expected Friday afternoon into Friday night.
An Enhanced Risk (3 out of 5) for severe weather exists over
the western half of the CWA.
&&
.SHORT TERM...
Issued 1115 PM CDT Thu Apr 16 2026
Today through Saturday night:
Dense Fog Advisory has been expanded for areas further inland
as dense fog continues to push west in off the lake causing the
expectation that with model guidance we should see dense fog
overspread at least eastern portions of the CWA but expansion
may be needed further west. Low clouds and fog concerns may
extend as far west as Madison tonight and likely clear by mid
morning. This will be the main concern for the tonight period as
conditions otherwise remain quiet and dry with weak high
pressure over the east with some easterly flow off the lake
guiding the low clouds and fog inland. Even after skies clear
Friday morning easterly component to the winds off the lake will
cause a lake breeze for at least areas closest to the lake
perhaps more inland than expected as well.
Then attention turns toward the severe storm potential during
the day and evening Friday. Still plenty of uncertainty on the
timing of storm initiation and who will get hit when but storms
appear likely to impact all of southern WI at some point with
storms into western WI as early as noon. However, more
widespread chances are to be expected by the later afternoon
and early evening with storms tracking across southern WI into
the evening. Initiation is possible with the pre-frontal wave
aloft and although it appears weak in models several CAMs show
an earlier initiation of storms toward midday. The better and
more widespread initiation potential appears likely to come
along the front from a low swinging NNE into northern WI
through the day. Instability across western parts of southern WI
will climb to around 2000-3000J/kg of MUCAPE by around early to
mid afternoon, though the instability simply is not as good
further east . In addition, ~300m2/s2 of 03km SRH and 150 m2/s2
of 0-1km SRH as a result of the LLJ sliding through will add
significant low level turning in the low to midlevels. While a
cap may be in place in the morning the combination of low level
warming, increased moisture and strong forcing will trigger
storms, the only uncertainty is with any pre frontal storms in
that respect. Turning to the hodograph and we get a much clearer
picture of our low level environment in its entirety. Model
soundings are suggestive of massive low level turning with
plenty of speed shear aloft with very high STP values of 2-4
across our west and potentially higher in mesoscale
environments.
There are a few things with this event however, that will
greatly impact exactly what we could see in our CWA Friday.
First, where/when will initiation begin along the front? If this
occurs earlier and further west the initially discreet storms
will eventually become linear by the time storms reach or west
bring primarily a QLCS wind/embedded tornado risk. If initiation
is later and further east then we likely see some of the
discreet supercells and all hazards would be possible with much
stronger tornadoes possible. Even then storm mode would still be
expected to be linear by the time storms reach the eastern half
of the CWA.
Second, do we see a few pre-frontal storms? While
this is the most uncertain aspect of this event given limited
forcing ahead of the front and some capping concerns, but it is
most certainly the most dangerous. Isolated supercell
convection earlier on and out ahead of the eventual frontal
based convection will bring the highest risk for an isolated
supercell with an uncontaminated and ripe air mass with plenty
of instability and the shear conditions will remain the same.
All hazards would be possible with a storm of this type but
would also yield much higher potential for a very strong
tornado, very large hail (2+ inches) and strong winds within
the RFD. Impacts would be more localized but high impacts would
be possible. This remains uncertain but the potential is there
in some CAMs.
Lastly, how long into the night does the severe
risk last? The answer to this is likely through the evening
carrying through the entirety of the CWA. However, storms are
generally expected to weaken as they push east especially with
the afternoon lake breeze potentially being fairly strong and
impacting convection further east. This weakening could be
faster than expected given the quickly declining instability to
the east and the impacts of the lake breeze could cause
convection further east to become elevated. But the other issue
is it could actually help locally increase severe concerns as it
has earlier this week. The storms could simply overpower the
lake breeze and the storms could end up using any lake breeze
boundary to enhance the low level environment locally increasing
shear. This could increase the QLCS tornado threat.
Lots of factors and elements to consider with this event that
add to uncertainties but the key is the environment will be
ripe for severe weather, especially for the western half of the
CWA.
Friday night front will push through and this will usher in a
much cooler and drier air mass across southern WI with higher
pressure pushing in. Despite the upper low expected to be
overhead Saturday the upper levels will be too dry likely
allowing for clear skies though chiller temperatures with highs
in the mid to upper 40s and breezy west to northwest winds.
Kuroski
&&
.LONG TERM...
Issued 1115 PM CDT Thu Apr 16 2026
Sunday through Thursday:
Into next week looks likely to bring a period early on of drier
conditons with higher pressure remaining in large part overhead
with weak ridging aloft. Monday night into Tuesday will bring
the next best chance for precip though there are question in
regard to midlevel moisture but the upper level dynamic and
surface front pushing through suggest at least a decent chance.
There would likely be somewhat of a chance for thunder given
some weak instability in models. Into the middle of next week
temperatures will remain fairly warm with limited precip chances
ahead of Friday.
Kuroski
&&
.AVIATION...
Issued 1115 PM CDT Thu Apr 16 2026
VLIFR/LIFR CIGS and VSBYS continue to push west. With that we
have expanded the Dense Fog Advisory further west through 14z
Friday for expected expansion of dense fog across areas further
inland tonight. Model guidance slows the progression of fog
further west toward Madison but could reach as far as MSN for a
period overnight. As we break into daylight Friday morning
expect fairly rapid dissipation of the fog and low CIGS by mid
morning.
Then attention turns toward the severe storm potential during
the day and evening Friday. Still plenty of uncertainty on the
timing of storm initiation and who will get hit when but storms
appear likely to impact all of southern WI at some point with
storms into western WI as early as noon. However, more
widespread chances are to be expected by the later afternoon
and early evening with storms tracking across southern WI into
the evening. Storms are generally expected to weaken as they
push east especially with the afternoon lake breeze potentially
being fairly strong and impacting convection further east.
Storms are generally expected to push out of southern WI by the
late evening hours. Some VSBY and CIGS concerns will come with
the storms as well though they would be associated directly with
storms.
Kuroski
&&
.MARINE...
Issued 1115 PM CDT Thu Apr 16 2026
Winds becoming light and variable tonight for a time as a weak
surface ridge moves over the lake. Dense fog will continue over
the lake through this time and perhaps until the front comes
through Friday night. Winds then come around to southerly
tomorrow morning as a surface low of 29.5 inches approaches from
the central plains. This surface low will quickly move from
Omaha to Duluth from the morning into the afternoon. Winds will
become gusty and southeasterly Friday night, and strong to
severe storms will move east over the lake as a cold front
sweeps through the area. Winds then become northwesterly behind
the cold front Saturday morning. Breezy northwesterly winds then
continue Saturday through Sunday as the low then races
northeast toward Hudson Bay. Winds ease Monday morning as high
pressure move southeast over the upper Great Lakes.
Small Craft Advisory is now in effect Friday afternoon until
Saturday evening for breezy winds and high waves in the
nearshore. Southerly winds ahead of the front and then gusty
WNW winds behind the front.
Kuroski
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Dense Fog Advisory...WIZ052-WIZ059-WIZ060-WIZ065-WIZ066-WIZ070-
WIZ071-WIZ072 until 9 AM Friday.
Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058-
WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-WIZ067-
WIZ068-WIZ069-WIZ070-WIZ071-WIZ072...1 PM Friday to 7 AM
Saturday.
LM...Dense Fog Advisory...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-
LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 until 7 PM
Friday.
Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...1 PM
Friday to 10 PM Saturday.
&&
$$
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