176
FXUS63 KMKX 190930
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
430 AM CDT Sun May 19 2024

.KEY MESSAGES...

- Unsettled Monday and Tuesday with several rounds of
  rain/storms.

- Increased risk for strong/severe storms Tuesday and Tuesday
  evening.

&&

.SHORT TERM...
Issued 430 AM CDT Sun May 19 2024

Today through Tuesday night:

Another warm day in store for southern Wisconsin. Temperatures
will be a little cooler than the previous day with high
temperatures expected to climb into the low 80s. This is in part
due to some weak cold air advection behind the cold front.
However, based on guidance leaned more toward the bias corrected
again to increase temps bringing 80s into more areas of
southern Wisconsin than previous runs. The best chance for temps
near 85 will be across far southern Wisconsin with cooler
temperatures as you head north. Temperatures early this morning
remain high with many urban heat islands still in the 70s. More
rural areas are finally falling into the mid 60s. This is the
main reason for the change of increasing beyond guidance. 925mb
temperatures will be warm again near 20 and the surface temps
overnight are elevated. This does leave a small window for
temperatures to slightly overperform today.

Tonight into Monday the chance for rain and a few thunderstorms
returns. A low pressure system will advect east from the
central/northern plains. Tonight the main forcing for any
rain/storms will the be the strong low level jet moving into the
state. The low level jet doesn`t look to make an appearance in
southern Wisconsin until after midnight. As the upper level
shortwave pivots into the state Monday, there will be
additional chances for shower and storms. Some capping could
inhibit convection initiation initially in the afternoon and
early evening. There is a potential that if the shortwave moves
through quickly that the evening remains mostly dry as the
synoptic support will be gone. Overall the best potential for
showers and storms will be late tonight through Monday morning.
There is a potential for some stronger to severe storms with the
main concern being hail given the good mid level lapse rates.
Any storms that towers up quickly could provide an isolated wind
threat.

Tuesday brings the next chance for rain and storms as the next
upper level shortwave moves through the state. In comparison to
Monday, Tuesday`s system looks to be more robust. This would be
the best chance for strong to severe weather out of the two
days. Guidance is overall a bit of a mess with this system which
leads to a more complex forecast. The GFS seems to be the
biggest of the outliers with the low pressure system moving
faster and further east/north than the other guidance. This has
resulted in storms firing along the warm front as it progresses
northward during the morning/afternoon as there will be synoptic
support. In comparison, other guidance seem to be slower with
the system movement. Which allows the warm front to move in and
limits the amount of rain in the morning/afternoon hours, even
leaving portions of the forecast area completely dry when
considering ensemble guidance. This slower progression could
lead to greater surface heating and instability for when the
cold front moves through in the evening. The cold front will be
the main driver for our severe potential. All storm modes will
be possible with the main hazard concerns being winds and
tornadoes. Tornadic potential at this point leans toward the
short-lived quick spin up type.

Tuesday`s biggest issues will be the convective potential along
the warm front in the morning/early afternoon. If showers and
storms start to develop early then the instability may be
lacking when the cold front begins to move through in the
evening leading to the severe threat being undercut.

Patterson

&&

.LONG TERM...
Issued 430 AM CDT Sun May 19 2024

Wednesday through Saturday:

The cold front will be clear of southern WI by Wednesday morning,
per the majority of models and ensembles. The GFS tries to delay
the front through our area until later Wed and sneaks in a
shortwave trough along it to bring in additional precip chances,
but this is an outlier, even from most of the GFS ensemble. I kept
a slight chance (20%) of showers in our north toward central WI
due to the potential for strato-cu showers with any wrap-around
precip from the exiting upper low. Otherwise, expect gusty
westerly winds and cooler temperatures around 70.

Thursday through Saturday high temps will also be in the lower to
mid 70s, with lows in the lower 50s, much more seasonal for this
time of year. The next chance for showers and thunderstorms will
arrive Friday afternoon or night to kick off Memorial Day
Weekend. This is associated with an upper low tracking across
southern Canada. As the case has been lately, the GFS goes crazy
with the QPF and also brings the front through WI earlier than the
ECMWF (by at least 12 hours). Given forecast model trends and
biases, I would not be surprised if Friday-Fri nt ends up dry.

Regardless of having chances for showers and storms all weekend in
the forecast, it looks like we will have one front with the
potential for storms to deal with over this holiday weekend.
Overall, most of the weekend looks dry and just barely on the
warmer side of normal.

Cronce

&&

.AVIATION...
Issued 430 AM CDT Sun May 19 2024

VFR conditions are expected through midnight tonight. Beyond
midnight into Monday morning, MVFR conditions will be possible.
Partly to mostly sunny skies remain for much of the day before
some clouds cover begins to work in from the northwest this
evening into tonight. Northwest winds this morning will shift to
the northeast continuing to easterly by this afternoon. Inland
areas will have a period of light and variable winds while
lakeshore ares will seamless transitions to east winds. The wind
shift will be due to a combination of high pressure moving
quickly overhead and the lake breeze advancing inland. A low
pressure system will advance toward the state bring a chance for
rain and a few thunderstorms starting tonight. Southeasterly
winds and the chance for rain/storms look to hold off until
after midnight. Rain chances will increase from west to east
throughout the early morning hours with MVFR ceilings expected
with the rain. Some MVFR visibilities will be possible with
more moderate rainfall. The rain and storm potential will
continue through Monday morning.

Patterson

&&

.MARINE...
Issued 430 AM CDT Sun May 19 2024

A cold front is passing over the lake early this morning,
locations east of the front will continue to have southwest
winds while those behind the front will have northerly winds. As
high pressure moves quickly through the Great Lakes Region
today, light and variable winds will be expected. Ahead of an
approaching low pressure system, winds will shift to southerly
and become breezy. The breezy southerly winds are expected
through Tuesday. A Small Craft Advisory may be needed during
this time.

Patterson

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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