NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 242044
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
344 PM CDT Wed Apr 24 2024

.KEY MESSAGES...

- Freeze Warning Midnight until 8 AM for below-freezing
  temperatures.

- 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.

&&

.SHORT TERM...
Issued 344 PM CDT Wed Apr 24 2024

Tonight and Thursday:

With dewpoints in the upper 20s this afternoon, and upper teens
toward central WI, confidence in strong radiational cooling with
light winds overnight is increasing. Low temperatures should
drop to around 29 or 30, with 28 a valid concern. The forecast
temperatures are around the 50th percentile of the NBM and the
Median of many models. A Freeze Warning is in effect. Temperatures
in the upper 20s for a few hours can cause damage to blossoming
fruit trees.

Clear skies are expected tonight through Thursday, thanks to
high pressure and dry air over the Great Lakes. With onshore
winds, lakeshore areas will remain cool Thursday while inland
temps should be a little warmer than today, around 60. Look for
afternoon winds to become southeast 10 to 15 mph and remain
fairly steady overnight. Lows Thursday will be milder, between
36 and 42, due to increasing clouds and breezier conditions.

Models continue to trend slower for the precip arrival in
southern WI from west to east on Friday. It is looking like
precip should remain west of Madison until at least 3 PM.

Cronce

&&

.LONG TERM...
Issued 344 PM CDT Wed Apr 24 2024

Friday through Wednesday:

Synoptic Look:

The start of a busy pattern will begin on Friday and continue
into the start of next week. Models are in good agreement of a
multi-part system slowly moving out of the Desert SW and into the
Plains and finally onto the Great Lakes Region over the coming
days. At the synoptic level, we will have in essence, a double
barrel trough ejection which will be the focus of our active
weather pattern. The first trough which is still currently off
the coast of California will slowly move eastward before reaching
the Plains on Friday. Around the same time, a secondary trough
will move into the Pacific Northwest and trek towards the
southeast. On Saturday we'll see the the initial trough weaken as
it moves into the Great Lakes area with an attendant 50kt+ zonal
jet streak somewhere in the vicinity of the Western Great Lakes.
Meanwhile the secondary trough at this point will be exiting the
Rocky Mountains and moving into the Central Plains. Over the next
24 hours this trough will move on a NE track while slowly filling
in before arriving into the Midwest late on Sunday. The jet
streak associated with this trough will be of similar magnitude to
the day prior but orientated much more meridional stretching from
the Deep South and into Western Ontario. By early next week, a
ridge should begin to build over us putting an end to the active
pattern and inducing quieter conditions across Southern Wisconsin.


Convective Potential:
As with any major trough during the spring and summer season we
must keep an eye out for convection and in some cases even severe
weather. This time is no different as we are monitoring 3 days
(Friday, Saturday, and Sunday) for the potential for strong to
severe storms. The latest SPC outlooks have highlighted the
southwestern portion of the CWA in a marginal risk on Friday (Day
3). While both Saturday and Sunday (Day 4 and 5) have the western
portions of our CWA in slight risks for severe weather. It should
be noted that there are many things that will needed to be sorted
out before confidence in any one particular solution grows.

Friday into Saturday AM:
At the onset of this period, the entire region will be in a SE
flow regime in accordance with a intensifying sub-1000mb low
across the Central Plains. Through most of the morning and early
afternoon we should see precipitation hold off due to a dry layer
near the surface. However, by late afternoon and early evening we
should precipitation begin to impinge into our far SW counties
tied to a lifting frontal boundary. With these storms we could see
some scattered showers and storms move through the evening and
overnight hours. Models are suggesting 500-750 j/kg of MUCAPE
which could allow for some lightning, small hail and gusty winds
in some of the stronger cores that reach our CWA. By Saturday
morning, a widespread 0.25-0.4" is likely with isolated 0.5-0.75+"
rainfall totals being seen as well.

Saturday into Sunday AM:
By midday Saturday, the boundary from the night prior will stall
out across Northern Wisconsin. Following it, an EML from the SW
will reach our area keeping us dry until the afternoon when models
diverge on their solutions. With steep lapse rates aloft from the
EML we should see upwards of 1000J/KG form through the day. Tie in
dewpoints reaching into the mid-60s and 40+kts of bulk shear
organized and potentially severe storms are possible. Storms could
either form along the sagging boundary or in the open warm sector
but neither solution is favored at this point. It should be noted
that due to 500mb height rises, confidence in storm firing in the
first place is low with no real forcing mechanism in the vicinity.
Trends towards a drier or towards a more convective Saturday
afternoon/evening will be watched for in coming forecasting
cycles.

By very late Saturday, convection that began across the Central
Plains will eventually arc to the northeast and reach our area.
Once again these storms will pose a threat for rainfall -
potentially heavy at times through the night. Widespread 0.3-0.5"
is likely with 0.5-1.0" totals possible in stronger storms or
where storms trek over multiple times.

Sunday and onwards:

Sunday is the day with the least amount of confidence in what may
transpire. By this point in time the EML from the SW will have
been worked out to some degree by the overnight. We are likely to
see convection through the morning period before some type of
clearing on Sunday appears heading into the afternoon. There will
enough shear for organized storms and once again severe storms if
enough CAPE can build in before some boundary moves through.
Another period of heavy rain is possible Sunday afternoon and into
the evening. The cold front will finally move through our area
early Monday finally putting an to our active weather as a ridge
builds in over the area.

Hydrological Concerns:
All in all, total rainfall values will likely be in the 1-2.5"
over the weekend with localized higher values. While most of our
rivers are not of concern right now, localized ponding and
isolated flooding is possible if we see storms fire over the
same areas on consecutive days. To that degree, the WPC has
placed our entire area in a marginal risk for excessive rainfall
on Friday, Saturday, and Sunday.

Cronce

&&

.AVIATION...
Issued 344 PM CDT Wed Apr 24 2024

VFR conditions will prevail tonight through Thursday with high
pressure overhead. Look for showers and storms to spread in from
west to east Friday, probably later than forecast.

Cronce

&&

.MARINE...
Issued 344 PM CDT Wed Apr 24 2024

Winds will continue to diminish over Lake Michigan this evening
and become light and variable through Thursday afternoon as high
pressure drifts across the Great Lakes. Lingering high waves
will continue to subside so the Small Craft Advisory will be
allowed to expire at 10 PM.

Strong southeast winds will develop over Lake Michigan Friday
afternoon and become southerly Saturday morning, then diminish
Saturday night. Gales are possible Friday afternoon through
Saturday, but confidence is low due to an inversion and
stability from warm air flowing over the cool water.

Cronce

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Freeze Warning...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-
     WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-
     WIZ067-WIZ068-WIZ069-WIZ070-WIZ071-WIZ072...midnight
     Thursday to 8 AM Thursday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 10 PM
     Wednesday.

&&

$$

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