934
FXUS63 KLOT 091933
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
233 PM CDT Sun Jun 9 2024

.KEY MESSAGES...

- A cold front will arrive this evening with gusty northerly
  winds lasting through Monday along with building waves and
  dangerous swimming conditions for Lake Michigan beaches.

- Tuesday through the end of the week will feature increasing
  temperatures and chances for showers and thunderstorms, with
  the latter particularly on Thursday and Friday.

- After a brief respite on Saturday, summer-like temperatures
  are poised to return early next week.

&&

.DISCUSSION...
Issued at 233 PM CDT Sun Jun 9 2024

Through Monday night:

A mid-level trough and associated surface trough/front will
shift S/SSE across the forecast area this evening into the early
overnight hours. A wind shift from WNW to NE with gusts to 20
knots is expected along the Lake Michigan shore early to mid-
evening and will result in deteriorating swimming conditions. A
Beach Hazard Statement remains in effect beginning 9pm this
evening for the entire Lake Michigan shore in IL and IN, with
the potential for dangerous swimming conditions to begin as
early as 8pm if the front exhibits a quicker forward motion over
the next several hours. A secondary wind push late this evening
with gusts of 25 knots or higher will generate continued
dangerous swimming conditions through the day Monday.

A mixed nocturnal PBL owing to modest CAA overnight may allow
the post frontal stratus to grow sufficiently deep to squeeze
out some sprinkles or patches of drizzle. This is particularly
the case near the lake where added lake moisture from a long
fetch will counteract overall synoptic dry air advection. Have
opted to include slight chance sprinkles roughly around the
lake-adjacent counties late this evening through sunrise Monday.

Otherwise, diurnal heating and continued dry advection should
erode the stratus or lift and scatter the stratus into shallow
cumulus from north to south through the morning Monday. Max
temps will be well below normal for early/mid June, with highs
ranging from the low 60s along the shore to the low 70s well
inland. Mostly clear skies and a passing ridge Monday night will
yield a chilly night with lows in the mid to upper 40s inland
to the low 50s in the core of the Chicago metro.

Kluber


Tuesday through Sunday:

Next week, a quintessential summertime ridge is expected to
develop across the west-central United States leading to quasi-
zonal to northwesterly upper-level flow across the Great Lakes.
The result locally will be gradually warming temperatures
Tuesday through the rest of the workweek. Highs on Tuesday in
the upper 70s will warm to the mid to upper 80s by Thursday,
with overnight lows climbing into the low to mid 60s.

Chances for precipitation will be tied to upper-level
shortwaves embedded in the flow aloft. The first wave will swing
through the Great Lakes in the Tuesday night into Wednesday
morning timeframe, though low-level moisture return ahead of the
wave looks rather limited. As a result, only a few scattered
non-soaking showers are our expectation, warranting low-end
(15-20%) PoPs. The next wave (or series of waves) will move
through the general region in the Wednesday night to Friday
timeframes. With plenty of upper-level shear (thanks to the
proximity of the upper-level jet focused to our north) and
moisture-laden instability, the pattern will be supportive of
episodic mesoscale convective systems (MCSs) with gusty to
damaging winds and soaking downpours. Pinpointing the times and
locations of summertime MCSs is a futile effort more than 48
hours out, so for now, will carry mid-range chance (30-40%) PoPs
centered on Thursday in favor of refinements in the coming
days. It`s worth noting temperatures Thursday and Friday will
depend on the cadence of convective episodes, any debris upper-
level cloud cover, and the eventual placement of an effective
(outflow-reinforced) front.

By Saturday, any effective front reinforced by episodic
convective episodes should slip south of our area leading to
onshore flow and a modest break in seasonably warm temperatures.
Highs should range from the lower 70s lakeside to the low to
mid 80s inland. Thereafter, ensemble guidance supports the
development of pronounced troughing across the western US and
ridging over the Great Lakes, which should lead to a return of
summer-like warmth (as well as humidity) at some point early
next week.

Borchardt

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1221 PM CDT Sun Jun 9 2024

Forecast concerns for the terminals...

- Gusty northwest winds of 25-30 kts this afternoon

- Lowering ceilings with cold front this evening along with a
  northeast wind shift


West-northwest winds will continue to increase this afternoon
with gusts expected to top out in the 25-30 kt range. Though,
pockets of locally higher gusts in excess of 30 kts may occur if
deeper mixing is achieved. The gusts will begin to subside a
bit this evening as a cold front begins to drift out of
Wisconsin. While no precipitation is expected with the front,
ceilings will lower into the 2000 to 2500 ft range and persist
into the predawn hours Monday morning. Additionally, winds will
also turn northeasterly behind the front and remain breezy as
they do so. It should be noted that timing of the northeast wind
shift remains somewhat uncertain, but the general consensus is
that the wind shift should occur in the 01z to 03z timeframe.

Heading into Monday morning, winds will turn more northerly
around daybreak with speeds holding in the 10 to 14 kt range.
However, a lake breeze is expected to drift into the Chicago
terminals and turn winds back northeasterly around midday
(18-19z). Otherwise, expect ceilings to scatter to VFR
conditions Monday morning and remain as such through the rest of
the period.

Yack

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement from 9 PM CDT this evening through
     late Monday night for ILZ006-ILZ103-ILZ104.

IN...Beach Hazards Statement from 9 PM CDT this evening through
     late Monday night for INZ001-INZ002.

LM...Small Craft Advisory until 9 PM CDT Monday for the IL
     nearshore waters.

     Small Craft Advisory from 9 PM this evening to 9 PM CDT Monday
     for the IN nearshore waters.

&&

$$

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