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045
FXUS63 KLOT 290533
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1233 AM CDT Wed May 29 2024

.KEY MESSAGES...

- Scattered thunderstorms will continue into early this evening,
  the strongest storms could produce gusty winds and small hail.

- Dry conditions with seasonable temps Wed-Fri, followed by at
  least periodic chances of showers/storms over the weekend into
  early next.

&&

.UPDATE...
Issued at 818 PM CDT Tue May 28 2024

Thunderstorm threat has ended across the area, with most areas
currently precip-free as of 815 pm. Did maintain pops across far
northeast IL and northwest IN/Lake Michigan areas later this
evening into the overnight hours however, as showers across
southeast WI are expected to track south-southeast across the
area as the mid-level trough moves through the region. Touched
up sky cover as well to account for current satellite trends.

Updated forecast products available.

Ratzer

&&

.DISCUSSION...
Issued at 244 PM CDT Tue May 28 2024

Through Wednesday Night:
Scattered thunderstorms have developed ahead of the wave moving
down from Wisconsin. As they moved down, 1000 J/kg of CAPE is
assisting in convective development and sporadic lightning. This
actively is expected to continue through the rest of the
afternoon and evening with chances diminishing after sunset.
Better mid level lapse rates look to be farther to the south and
west, and wind shear values are fairly minimal keeping the
severe risk marginal (level 1 out of 5 from the Storm Prediction
Center). The main threats are expected to be the potential for
small, up to penny size, hail as well as localized wind gusts
capable of downing some tree branches. As stronger storms
develop, there is also the risk for heavier downpours than may
result in ponding on roadways and localized flooding, especially
for urban areas. Lastly, while the chances may be low, with the
cold air aloft that is moving in and potentially interacting
with the lake breeze boundary that arrived earlier today, it
would not be surprising if there were a few funnel clouds that
get reported.

The wave will gradually move east through the night, and shower
chances will gradually diminish. The HRRR/RAP/RRFS have a little
moisture wrapping around the back side of the wave, so added a
slight chance for a few sprinkles overnight, though confidence is
low and impacts should be minimal.

Winds behind the wave will turn to the north and strengthen. Cooler
air will be advected in for temperatures in the low 50s and isolated
ares in the upper 40s. Stronger winds over the lake will increase
wave heights creating high swim risk for beaches from Cook County
and down the Indiana shores of Lake Michigan on Wednesday.
Otherwise, an upper level ridge grows over the region allowing for
height rises and drier conditions with temperatures in the 70s
inland and 60s along the lakeshore on Wednesday.

DK

Thursday through Tuesday:

Break in the active pattern should continue through the rest of
the work week with dry conditions expected. Seasonable
temperatures are expected Thursday, though lake breeze will keep
temperatures cooler near the lake. Friday will be a bit warmer as
narrow upper ridging moves across the area. Lake cooling Friday
looks more likely to be confined to the IL shore.

EPS and GEFS both suggest there will be a transition to a more
zonal flow pattern across the country this weekend into early next
week. There will undoubtedly be low amplitude waves rippling
through the zonal flow this weekend into early next week.
Unfortunately, these type of waves can easily become convectively
enhanced and are notoriously have low predictability in the medium
range. NBM PoPs are in the chance range over the weekend into
early next week and this is certainly reasonable. Also worth
noting that there will be many day hours over the weekend into
early next week, so important not to be deceived by precip
chances every period of the forecast, the weekend shouldn`t be a
washout. Temperatures this weekend into early next week will be
above average, outside of any convective interruptions.

- Izzi

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
-- Changed Discussion --
Issued at 1232 AM CDT Wed May 29 2024

The primary aviation weather concerns through the 06Z TAF period
include:

* Continued intermittent showers and MVFR cigs through the middle of
  the overnight, mainly at the Chicagoland sites.

Light rain showers and MVFR cigs are now expected to hang around
through the middle of the night or even the predawn morning hours
over Chicagoland. At RFD, MVFR should clear out closer to 06 or 07Z
with no more rain expected. VFR is then expected through the rest of
the period.

Near-northerly winds, favoring a 340-350 direction, will stay up
near 10 kt through the night and Wednesday morning. Winds will veer
to NE around 18Z at the Chicago sites, closer to 21Z at DPA, and not
until mid-evening at RFD. Light near-northerly winds can be expected
Wednesday night.

Doom
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&&

.LOT WATCHES/WARNINGS/ADVISORIES...
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IL...Beach Hazards Statement from 4 AM CDT early this morning
     through this evening for ILZ103-ILZ104.

IN...Beach Hazards Statement from 4 AM CDT early this morning
     through this evening for INZ001-INZ002.

LM...Small Craft Advisory from 4 AM early this morning to 10 PM CDT
     this evening for Wilmette Harbor IL to Michigan City IN.
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&&

$$

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