716
FXUS63 KLOT 061948
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
248 PM CDT Thu Jun 6 2024

.KEY MESSAGES...

- Gusty west to northwesterly winds will continue tomorrow
  morning and ease tomorrow afternoon.

- Chances for showers will return on Saturday.

- Pleasant conditions are expected Sunday through early next
  week. A return to warm and humid conditions is poised to
  return toward the end of next week.

&&

.DISCUSSION...
Issued at 241 PM CDT Thu Jun 6 2024

Through Friday night:

A recent hand surface analysis revealed a sprawling 992mb surface
low pressure system is centered in central Ontario well to the
northeast of a 1016mb high pressure system over the Plains. The
Great Lakes are positioned directly inbetween both features and
indeed within a seasonably tight low-level pressure gradient,
which continues to support gusty northwest winds of 35-45 mph.
Efficient mixing has also allowed for humidity levels to plummet
today, which when combined with temperatures in the mid to
upper 70s, is leading to a dry, summer-like day.

Tonight, a subtle mid-level shortwave anchored by a modest pocket of
locally cooler 850mb air diving southeast into Minnesota will reach
northern Illinois and northwestern Indiana allowing for at least
patches of partly cloudy skies and perhaps even a few rain showers
(mainly near the Wisconsin state line). Even as diurnal mixing
ceases, modest cold-air advection associated with the wave may allow
for breezy west winds (20-25 mph) to continue through the
overnight hours, partially offsetting nocturnal cooling and
limiting overnight lows to the low to mid 50s (warmer in the
urban heat island of Chicago).

Over the next 24 hours, the low pressure system responsible for our
gusty winds will only slowly move eastward. As a result, tomorrow
looks to start similarly to today with mostly sunny skies and a
"pop" of gusty west to northwest winds. In fact, if we don`t totally
decouple tonight, one can envision a scenario where winds quickly
gust over 45 mph by 7 or 8 AM, as hinted by forecast BUFKIT profiles
from the HRRR. Confidence in such a scenario is too low to include
in our formal forecast (will instead cap gusts at 35-40 mph), but
we`ll need to keep a close eye on observations overnight just in
case. Winds should begin to finally ease during the afternoon
as the surface low finally moves far enough away and the surface
high approaches to slacken the low-level pressure gradient. In
fact, a lake breeze may sneak into northwestern Indiana by
dinnertime. Highs tomorrow should be a tad cooler than today and
in the mid to upper 70s.

Tomorrow looks quiet with light winds and thickening upper-level
cloud cover. Chances for rain will increase toward daybreak (see the
next section of our AFD for more information below).

Borchardt


Saturday through Thursday:

Coming Soon.

NWS Chicago

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1223 PM CDT Thu Jun 6 2024

Key Aviation Messages:
- WNW gusts to around 35 knots this afternoon and over 30 knots
  Friday morning.

VFR conditions are expected through the period amid gusty WNW
winds. Gusts to around 35 knots will persist through much of the
afternoon before diminishing under 25 knots this evening and
overnight. Gusts will quickly increase to over 30 knots again
shortly after sunrise Friday as mixing into 40-50 knot low-level
winds ensues. As the low- level wind field abates during the
afternoon, gusts will slowly diminish to 25 knots or less.

Kluber

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Gale Warning until 7 PM CDT this evening for the IL nearshore
     waters.

     Small Craft Advisory from 7 PM this evening to 7 PM CDT Friday
     for the IL nearshore waters.

     Small Craft Advisory until 10 PM CDT this evening for the IN
     nearshore waters.

&&

$$

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