Nashotah, Wisconsin Weather Forecast Discussion

651
FXUS63 KMKX 211932
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
232 PM CDT Sun Sep 21 2025
.KEY MESSAGES...
- Chances (~15-35%) for widely scattered showers &
  thundershowers through early evening, though many locations
  will remain dry.
- Areas of fog possible late tonight through early Monday morning.
- Additional chances (~30-50%) for scattered showers & storms
  Monday through Monday evening. An isolated stronger storm
  with gusty winds is possible.
- Periodic rain chances (~15-35%) continue Tuesday through
  Thursday, with high temperatures hovering near normal.
- Conditions dry out by next weekend.
&&
.SHORT TERM...
Issued 232 PM CDT Sun Sep 21 2025
Rest of this Afternoon through Monday Night:
Synopsis/Mesoanalysis: A slow-moving upper disturbance is centered
over the Minnesota-North Dakota border early this afternoon, with
accompanying surface low pressure evident along the Ontario-Manitoba
border. A diffuse surface trough/effective warm front extends
southeast of the surface low, with observations placing the boundary
along an approximate International Falls, MN - Rochester, MN axis as
of 1 PM. Daytime heating has combined with weak lift along the
surface boundary, in addition to increasing mid-level ascent ahead
of the MN disturbance, to support widely scattered shower and
thundershower development over the northern half of the state.
Additional widely scattered development is expected further south
through the remainder of the afternoon, though many locations will
remain dry. The disturbance currently over Minnesota will advance
toward Lake Superior tonight, allowing surface low pressure to
progress toward the Hudson Bay. The low`s advance will pull a weak
cold front into the Upper Mississippi Valley, with the boundary
subsequently working into southern Wisconsin during the day on
Monday. Additional showers and scattered thunderstorms are thus
possible along/ahead of the approaching boundary Monday
afternoon/night, though coverage remains uncertain. An isolated
stronger storm is possible in the Monday round of activity, with
gusty winds being the primary concern. Areas of fog are possible
away from Lake Michigan tonight.
This Afternoon & Evening: Continue to anticipate shower and
thundershower development given continued surface heating. Similar
to ongoing trends, expect that precip will be widely scattered in
nature, with shower/thundershower potential being maximized in
locations experiencing the greatest amount of sun. Severe weather is
not expected, though any thundershowers will be capable of producing
cloud to ground lightning & brief gusty winds (~30-40 MPH). Brief
heavy downpours will also be possible in any thundershowers given
1.1-1.3"+ precipitable waters sampled in regional 7 AM soundings.
Keep an eye on the sky if heading outdoors, and move indoors if a
thundershower approaches your area.
Tonight: Areas of fog are possible once again. Coverage and density
of fog will depend on the amount of mid-upper cloud cover moving in
from the southwest. Will thus be monitoring visibility trends this
evening and tonight.
Monday & Monday Night: Additional scattered showers & storms are
expected, with coverage once more being dependent on the amount of
sunshine/attendant surface heating that occurs across the area.
Should broken to full sun occur through part of the day,
shower/storm potential & coverage would likely increase further from
the scattered levels implied in the current forecast (precip
probabilities restricted at and below 50%). In the greater
sun/surface heating scenario, an isolated strong to severe storm
would also be possible, particularly from the afternoon through the
first half of the evening. Gusty straight line winds, small hail,
and cloud to ground lightning would be the primary hazards. Still
elevated precipitable water values in the 1.1-1.3" range would
support the potential for heavy downpours as well. CAM guidance
suggests that most locations will see rain accumulations in the 0.10-
0.25" range, with locally higher totals in the 0.50-1.00" range
where heavier storms track. Stay weather aware if planning to be
outdoors Monday afternoon and evening.
Quigley
&&
.LONG TERM...
Issued 232 PM CDT Sun Sep 21 2025
Tuesday through Sunday:
Synopsis: Monday afternoon/evening`s surface front should be south
of the state line by daybreak Tuesday, though an upper disturbance
will continue to linger across the western Great Lakes through the
middle of the upcoming work week. With broad synoptic ascent still
in place, additional periods of showers and isolated thunderstorms
will continue through the day on Tuesday. Low pressure will develop
in the middle Mississippi Valley Tuesday afternoon, gradually
progressing toward southern Lake Michigan Wednesday into Thursday.
The feature`s approach will maintain northeasterly surface winds
into the late week period, with modestly drier air advecting into
southern Wisconsin Wednesday through Friday. The drier air`s arrival
will shunt the majority of precipitation chances to the south and
east of the region during the second half of the work week, though a
few isolated showers will remain possible across far southeast
Wisconsin during each afternoon period. Upper ridging will build in
from the Northern Plains Friday through Sunday, bringing mostly
sunny skies and rain-free conditions to all of southern Wisconsin.
Tuesday: With upper low pressure lingering overhead, rain chances
will continue. Anticipate the best potential to overlap with peak
daytime heating during the afternoon hours. Strong storm potential
should be lower relative to Monday given post-frontal, northeasterly
surface winds in place across southern Wisconsin & attendant lower
instability. 1.1-1.25" precipitable water values will still be
lingering behind the departed frontal boundary, however, so brief
heavy downpours will remain a possibility in Tuesday afternoon
showers & storms.
Quigley
&&
.AVIATION...
Issued 232 PM CDT Sun Sep 21 2025
Flight categories continue to improve early this afternoon, with
most terminals having returned to VFR as of 19Z. MVFR CIGs
linger at MKE, and have been accounted for in a recent
amendment. Scattered -TSRA and -SHRA remain possible through
peak heating this afternoon. Given a lack of pronounced surface
boundaries across the region, confidence in development
locations of precip remains low, with PROB30 groups being
maintained at all terminals through mid- late afternoon. If
radar trends warrant, will insert TEMPO or prevailing precip
groups if activity develops in the vicinity of a terminal this
afternoon. Expect -SHRA and -TSRA to taper this evening.
Anticipate a mostly dry forecast through the remainder of the
period, so have thus removed the majority of other PROB30 groups
in the 18Z update. Additional FG development is possible away
from Lake Michigan late tonight, with potential being accounted
for in the 18Z update.
Quigley
&&
.MARINE...
Issued 232 PM CDT Sun Sep 21 2025
1030 mb high pressure is centered off the northeastern United States
this afternoon, with a broad area of 1010 mb low pressure positioned
over western Ontario. The placement of the two features is resulting
in generally light south to southeast winds across the open waters
of Lake Michigan. The aforementioned low will move northeast toward
the Hudson Bay tonight through Monday morning, allowing winds to
shift out of the southwest. The low will progress into Quebec Monday
afternoon and night, pulling a weak cold front across Lake Michigan
in the process. The passage of the front will result in a north-
northeast wind shift by daybreak Tuesday. Unsettled weather will
continue ahead of the approaching front this afternoon through
Monday night, with periods of scattered showers and thunderstorms
expected. An isolated stronger storm is possible Monday
afternoon/evening, with gusty winds and hail being the primary
threats.
Northeast winds will pick up Tuesday afternoon through
Wednesday as 1024 mb high pressure forms near the Hudson Bay and
1010 mb low pressure develops in the middle Mississippi Valley. The
low will slowly pass near or just southeast of southern Lake
Michigan Wednesday night through Thursday. Wind gusts are expected
to remain below gale thresholds during the lows approach & passage,
though trends will be monitored in coming forecasts. Periods of
showers and isolated thunderstorms will accompany the approaching
low Tuesday afternoon through Thursday, with the best shower/storm
potential being over the southern half of Lake Michigan. Severe
weather is not anticipated at this time.
Periods of showers and scattered thunderstorms continue in nearshore
zones through Monday evening as a cold front slowly approaches Lake
Michigan. A few stronger storms are possible Monday
afternoon/evening, with gusty winds and hail being the primary
concerns. Northeast winds will become breezy Tuesday afternoon
through Thursday as low pressure passes over or just to the
southeast of southern Lake Michigan. Small Craft Advisories are not
expected at this time, though trends will continue to be
monitored.
Quigley
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&
$$
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NWS MKX Office Area Forecast Discussion