764
FXUS63 KLOT 282327
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
627 PM CDT Tue May 28 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.

&&

.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 /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 620 PM CDT Tue May 28 2024

Key Aviation Messages:

- Scattered thunderstorms ending early this evening. Spotty SHRA
  may linger into the night for the Chicago metro terminals.

- Period of MVFR ceilings possible especially at KGYY overnight.

- NNW winds turn NE midday/early afternoon Wednesday.

Scattered showers and thunderstorms continue to track east-
southeast across southern Lake Michigan and northwest IN at
issuance time. With the potential for isolated TS remaining in
ORD`s arrival paths over the next hour, maintained a VCTS
mention. Otherwise, it will dry out across inland parts of
northern IL this evening, though scattered showers may continue
to shift south from WI along the IL Lake Michigan shore area
past midnight as a mid-level disturbance tracks across the
western Lakes. Some patchy MVFR ceilings occur with this
activity, with high-res guidance indicating the greatest
potential over the lake into KGYY. VFR conditions are then
expected on Wednesday.

Surface winds will become north-northwest early this evening,
with a few gusts near 20 kts possible for a brief time. Winds
are expected to eventually turn northeast midday to early
afternoon Wednesday.

Ratzer

&&

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

IN...Beach Hazards Statement from 4 AM CDT Wednesday through
     Wednesday evening for INZ001-INZ002.

LM...Small Craft Advisory from 4 AM to 10 PM CDT Wednesday for
     Wilmette Harbor IL to Michigan City IN.

&&

$$

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