674
FXUS63 KLOT 080842
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
342 AM CDT Sun Jun 8 2025

.KEY MESSAGES...

- Isolated to scattered showers and thunderstorms will move
  through the area this afternoon and Monday afternoon.

- A few instances of pea to nickel size hail as well as 40 to 50
  mph winds may occur with the strongest storms today and
  Monday.

- A period of dry and warmer weather is expected Midweek.

- Shower and thunderstorm chances return late in the week.

&&

.DISCUSSION...
Issued at 342 AM CDT Sun Jun 8 2025

Through Monday:

Lingering showers continue to be observed across portions of
northeast IL and northwest IN associated with a shortwave trough
pivoting overhead. These showers will continued to taper over
the next 2-3 hours as the shortwave exits to the east with skies
clearing shortly thereafter. As skies clear, there remains the
potential for some patchy fog to develop, particularly along
I-39 and west of the Fox Valley, where surface dew point
depressions are within a degree or two. Any fog that does
materialize will quickly erode after 8 AM.

While our morning will start off on a quiet note, our attention
will quickly turn to the deepening trough over the ND-Canadian
border and the surface cold front stretching from northeast MN
to eastern NE. Scattered showers and a few thunderstorms are
already ongoing just ahead of the cold front in MN and western
WI this morning and with temperatures and dew points expected to
increase after sunrise (into the mid to upper 70s and lower 60s
respectively) conditions will be in place for additional
showers and thunderstorms to develop into our area towards
midday and persist through the afternoon. Additionally, an 80 kt
jet streak is also being analyzed rounding the base of the
trough which will lead to an increase in deep layer shear over
our area this afternoon. Given that instability will be somewhat
modest (around 700-800 J/kg of MLCAPE) the severe threat
remains low. However, stronger storms will be capable of
generating gusty to locally damaging winds (up to 50-60 mph) and
small hail (up to nickle size).

The cold front is expected to swing through the area by this
evening which should allow the thunder (and any severe) threat
to diminish after 7 PM. That said, scattered showers are
expected to fester behind the front through the evening as the
trough pivots overhead but will gradually taper after midnight.
Otherwise, temperatures to dip into the low to mid-50s overnight
with decreasing cloud cover.

Heading into Monday, the upper trough will be centering over
the Great Lakes which will allow another shortwave to dive
across northern IL and northwest IN Monday afternoon. While
moisture will be notably lower on Monday (dew points in the
lower 50s), the cold 500 mb temps overhead will steepen mid-
level lapse rates and allow scattered showers and storms to
redevelop Monday afternoon. Though the greatest coverage does
look to be along and east of a Rockford to Rensselaer line.
Given that modest flow aloft will be present, cannot completely
rule out another low end severe threat in the form of gusty
winds and small hail Monday as well.

Outside of the showers and storms, winds on Monday will also
become breezy with non-thunderstorm wind gusts in the 25-30 mph
range expected during the afternoon. Temperatures will otherwise
be once again in the low to mid-70s.

Yack


Monday Night through Saturday:

The upper-level flow pattern will begin to deamplify on Tuesday
as the Great Lakes trough/low ejects into southeastern Canada.
Rising heights in its wake will result in the development of a
quasi- zonal type flow pattern across the northern CONUS for the
second half of the week. The main result of this changing
weather pattern for our weather will be the turn from seasonably
cool conditions on Tuesday (highs in the 70s) to much warmer
temperatures (highs back in the 80s) by Wednesday.

Primarily dry weather is anticipated for Tuesday and Wednesday,
and it is certainly plausible that most of our area will remain
free of precipitation and very warm through the end of the work
week. In spite of this, the official forecast will begin to
carry some chances (~30-50%) for showers and thunderstorms
during the Wednesday night through Friday timeframe. However,
storm chances during this period will ultimately be dependent
upon how far south a west-to-east oriented surface cold frontal
boundary reaches before stalling ahead of the next impulse
shifting into the Dakotas late in the week. If this front ends
up stalling to our north across WI, the primary focus for waves
of showers and storms Wednesday night through much of Friday
would also likely largely remain to our north in WI. However,
due to the inherent uncertainties at this time range, we made no
changes to the NBM POPs.

Another feature that will need to be monitored for driving
storm chances later next week is the southern stream impulse
that is expected to slowly migrate its way eastward from the
Desert Southwest on Tuesday into the Ozarks region into early
next weekend. This feature will also be a daily driver of
showers and thunderstorms, but with it`s slow eastward movement,
much (if not all) of the thunderstorm activity will remain
south and southwest of our area through the end of the week.

Ultimately, our best shot at a period of higher coverage storms
may end up coming sometime next weekend (possibly on Saturday?)
as the late week system moving across the Dakotas finally looks
to drive the surface cold front southward across our area.
Unfortunately, the specifics with timing this far out are of low
confidence. Stay tuned.

KJB

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1219 AM CDT Sun Jun 8 2025

Key Messages:

- Period of -SHRA through 08Z at the Chicago area terminals

- Possibility of some reduced VSBYs in fog overnight, mainly at
  KRFD.

- Period of TSRA possible ahead of next cold front this
  afternoon.

A period of -SHRA continues across northern IL as of this
writing. This activity is expected to gradually tapper off
across the Chicago area terminals by 08Z, with dry conditions
expected the remainder of the night. While generally VFR
conditions are expected, there is a threat of a period of low
end MVFR to IFR VSBYs in fog around daybreak, primarily at
KRFD. However, this threat will hing on the amount of scattered
mid-level cloud cover that can occur there over the next few
hours. For the 06Z TAFs, I did not make any changes to the going
tempo mention of 3SM BR at RFD. Otherwise, expect the winds
across the area to remain light and variable through the predawn
hours.

Winds will settle into a west-southwesterly direction later this
morning, and will likely become a bit breezy in advance of an
approaching cold front this afternoon (some gustiness up around
20 kt). This cold front is expected to become the focus for some
scattered showers and thunderstorms as it shifts eastward across
northern IL through the afternoon. The inherited TAFs have the
timing of these showers and potential thunderstorms handled
well, so no changes were made. A general timing of 19 to 21Z is
anticipated at RFD, and 21 to 00Z for the Chicago area
terminals.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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