000
FXUS63 KMKX 231535 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1035 AM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Elevated fire weather risk this afternoon due to gusty west to
  southwest low relative humidity values.

- Widely scattered thunderstorms from 2 to 9 PM. The severe risk
  is low, but expect small hail and locally gusty winds with a
  few storms.

- Conditional frost/freeze risk late tonight and again Wednesday
  night with temperatures around or just below freezing.

- Active pattern Friday through this weekend. Multiple rounds of
  showers/storms will result in locally heavy rainfall. The
  severe storm risk is more uncertain, but bears monitoring.

&&

.UPDATE...
Issued 1035 AM CDT Tue Apr 23 2024

Solid swath of mid/high level clouds continue to stream across
southern Wisconsin. These clouds will gradually shift to the
east and thin, resulting in increasing breaks in the overcast
and eventually some clearing. A compact shortwave diving south
through MN will continue to surge to the south, southeast today.
Combination of partial clearing and cyclonic flow will result in
a resurgence of cumulus development.

Incoming suite of mesoscale models are a little less certain
with shower/storm initiation. While mid level lapse rates are
steep, leading to very modest MUCAPE, the overall thermo
profiles are quite dry and deeply mixed.

A primary concern this afternoon will be elevated fire weather
conditions with gusty west/northwest winds in excess of 30mph
and relative humidity values approaching 20%.

If storms can indeed fire in this dry airmass, they will be high
based producing gusty winds and small hail (peas to half inch).
However, trends indicate the better potential for development
this afternoon will be to our southeast over Lake Michigan,
northern IL/IN. Trends indicate we will need to wait for the
cold front to our north to provide enough moisture/lift for
showers and a few storms during the evening hours.

As the shortwave and front exits overnight and clearing begins,
concern turns to a few hour period where temperatures may reach
at/below freezing along/north of I-94 and away from Lake
Michigan. Still a lot of ifs here regarding full clearing and
winds keeping things rather mixed. The better combination of
high pressure placement, clearing and light winds is Wednesday
night into Thursday morning.

Gagan

&&

.SHORT TERM...
Issued 434 AM CDT Tue Apr 23 2024

Today through Wednesday:

Showers have moved east of the area, with some middle to high
clouds lingering in its wake. Gusty southwest winds with fairly
deep mixing should continue into this afternoon. Dew points
should drop to or remain in the 30s this afternoon, which should
bring low to very low relative humidity values. See Fire
Weather section for more information.

Temperatures should rise into the upper 60s over most of the
area, despite middle to high clouds at times. The mild start to
the day should allow these highs to be reached. There may be
some breaks in these clouds at times.

Latest CAMs and deterministic models are bringing the cold front
somewhat faster through the area this afternoon, exiting to the
southeast by early this evening. There is still good synoptic
upward vertical motion with this and the 500 mb shortwave trough
shifting through the region.

Dew points are one caveat, as mentioned previously should be in
the 30s this afternoon, which should lead to any shower or
thunderstorm be rather high-based. Still expecting scattered
areal coverage of showers and some storms by middle afternoon
into early evening.

Dry air below these bases on forecast soundings suggest gusty
winds may occur with stronger storms, and small hail with up to
500 J/kg of elevated CAPE in a rather strongly-sheared
environment. Best potential for these would be in southeast
parts of the area, where the cold front will exit by early
evening and have a little more instability to work with.

Once showers and storms exit the area, a secondary backdoor cold
front will sweep southwestward across the area by early to middle
evening. This will bring the strong cold air advection and gusty
north to northeast winds into the area, and should help scour
out the clouds. Lake effect clouds should develop and may linger
for lakeshore areas tonight into Wednesday morning.

Colder lows in the upper 20s to around 30 north and lower to
middle 30s south are forecast for later tonight. Will let day
shift have another look at this forecast and determine if any
freeze headlines will be needed for later tonight.

High pressure working southeast into the region will bring dry
and cool conditions for Wednesday, with weakening winds.

Wood

&&

.LONG TERM...
Issued 434 AM CDT Tue Apr 23 2024

Wednesday night through Monday:

High pressure should slowly shift east of the region Wednesday
night into Thursday, with dry conditions lingering as winds
shift to the southeast.

Ensembles suggest an active weather pattern for Friday into the
upcoming weekend, with one low pressure system tracking
northeast from the Central Plains into the Upper Midwest Friday
into Saturday. Another low on its heels then may shift along a
similar path for Sunday into Monday. There is more uncertainty
with the details with the second low track.

Overall, it looks like rounds of showers and thunderstorms
should occur for at least portions of Friday into the weekend.
It is still too early to determine if strong to severe storms
may occur, but will be something to watch. In addition, most
ensemble members have solid rainfall occurring, so another thing
to watch. Warm temperatures and perhaps some more humid air may
move into the area by Saturday and linger longer. Gusty winds
may occur at times, as each low pressure system moves through.

Wood

&&

.AVIATION...
Issued 1035 AM CDT Tue Apr 23 2024

Mid/high level clouds will gradually thin out, with high based
cumulus developing during the afternoon. West winds will be
gusty this afternoon, gradually shifting to the northeast
through this evening. A few showers and storms may develop as
early as mid afternoon near MKE/RAC/ENW, but the better
coverage is trending to be to the east/south of these locations.
Will be monitoring an incoming cold front from the north, which
will bring enough moisture to instigate additional showers and
a few storms this evening.

With a dry airmass in place, cloud development will be in the
VFR category (at or above 5000 ft). The front quickly surges
through the area by late this evening with some clearing. Will
need to monitor for MVFR cigs near the lakefront overnight.

High pressure builds into the region for Wednesday with quiet
weather conditions expected with a scattered VFR stratocumulus
deck. North winds will remain gusty, but gradually decrease
through the day.

Gagan

&&

.MARINE...
Issued 434 AM CDT Tue Apr 23 2024

Gusty southwest winds will persist today, as low pressure
around 29.5 inches moves from Lake Superior to Lake Huron. The
low will bring a cold front southeast through the region today
into this evening. Showers and some thunderstorms are forecast
with the frontal passage.

Expect gusty west winds to turn north later this afternoon into
this evening, from north to south across Lake Michigan. A
period of north gales are expected tonight behind the cold
front across the open waters, and a Gale Warning has been
issued. Building waves are expected as well tonight.

A Small Craft Advisory continues for the nearshore waters today
into Wednesday, for gusty winds through the period and building
waves tonight into Wednesday morning. A few north gales may
occur tonight.

Winds and waves will gradually lighten up Wednesday into
Thursday, as high pressure around 30.4 inches moves southeast
across the region.

South winds will then increase again Friday and remain gusty
into the upcoming weekend, as multiple low pressure systems move
northeast through the region. Some periods of gale force gusts
may occur over the open waters, with winds and waves possibly
reaching Small Craft Advisory levels in the nearshore waters.

Wood

&&

.FIRE WEATHER...
Issued 434 AM CDT Tue Apr 23 2024

Gusty southwest winds with fairly deep mixing to 6000 to 7000
feet AGL should continue this afternoon. Dew points should drop
to or remain in the 30s this afternoon, which should bring low
to very low relative humidity values of 25 to 35 percent over
the area. Given the scattered shower and storm activity by
middle afternoon, will not issue a Special Weather Statement
for elevated fire weather conditions. Still, any burning should
be done with caution with the gusty winds and low relative
humidity values.

May see very low relative humidity values of 20 to 30 percent on
Wednesday afternoon, though winds will be light. Vales in the 25
to 35 percent range may linger on Thursday afternoon, before a
wet period arrives for Friday into the upcoming weekend.

Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ868...7 PM Tuesday to 4 AM Wednesday.

     Gale Warning...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-
     LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...10 PM Tuesday
     to 7 AM Wednesday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM
     Wednesday.

&&

$$

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