Naperville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

858
FXUS63 KLOT 041737
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1237 PM CDT Mon May 4 2026

.KEY MESSAGES...

- Windy and warm conditions today; areas of blowing dust in open
  areas this afternoon, especially south of I-80.

- Shower and thunderstorms expected tonight with a marginal
  (level 1 of 5) severe risk.

- Much colder temperatures expected Tuesday.

&&

.UPDATE...
Issued at 946 AM CDT Mon May 4 2026

The going forecast appears to be in good shape this morning. The
only change was to let the Special Weather Statement for blowing
dust and brush fire concern expire across northwestern Illinois.
Per the latest guidance, much of northern Illinois will be in a
relative gap in the strongest winds today. So, do not expect
blowing dust to be as prevalent compared to areas to the south
where a Blowing Dust Advisory is in effect.

Update products are in the process of being sent.

Borchardt

&&

.DISCUSSION...
Issued at 258 AM CDT Mon May 4 2026

Through tonight:

Fairly complicated forecast today with strong/gusty winds
leading to blowing dust issues in open areas, followed by an
increasing threat of thunderstorms this evening along an
approaching cold front.

Early this morning, a 984mb sfc low was located over western
Ontario with a cold front trailing south and then southwest
across northern MN west into the northern Plains. This low will
track east to near Hudson Bay this evening as the cold front
moves southeast to the western Great Lakes southwest to the
mid-Mississippi Valley this evening. GOES total precipitable
water imagery depicted an east-west axis of higher moisture from
Missouri east into downstate IL with a sharp gradient to an
unseasonably dry air mass to the north across our area.

Considerable sunshine today should allow for deep mixing,
particularly across our northern CWA where air mass will be
remain very dry. The deeply mixed boundary layer should tap into
some higher momentum air off the sfc and result in another windy
day with southwest winds gusting well over 30 mph at times this
afternoon. Deep mixing should also result in dewpoints mixing
out this afternoon, particularly north of I-80. I have undercut
guidance dewpoints for today, but am concerned that they could
end up a bit lower still.

There were numerous reports of blowing dust across central IL
Sunday afternoon with some videos showing visibility getting
down close to 1/4 mile in spots. Given that today should see
fairly similar winds/gusts, would anticipate more blowing dust
issues this afternoon, particularly southern CWA where things
are still early in the agricultural cycle and there are a lot of
open areas. In coordination with ILX, have opted to issue a
blowing dust advisory for these areas today. Day shift may need
to consider expanding the blowing dust advisory north into our
western CWA where there are also a lot of open areas, but
confidence was lower farther north so held off on the advisory
north of I-80 for now and will let the day shift re-evaluate.

North of I-80 is where lowest afternoon relative humidity is
expected, so will issue an SPS for these areas for the potential
for blowing dust in open areas as well as a somewhat heightened
fire danger. The area has greened up nicely, lessening the fire
danger threat some, but given the very low RH and gusty winds,
there could be a heightened fire risk associated with agricultural
activity in fields that have not greened up.

Southwesterly flow should slowly advect the east-west oriented
moist axis to our south northward today, but deep mixing will
likely slow or stunt that northward progression some. Another
narrow ribbon of higher atmospheric moisture is expected to pool
ahead of the approaching cold front this afternoon. Forecast
soundings ahead of the cold front across southern WI and
northern IL look much more like soundings from the High Plains
than the Mississippi Valley. Soundings exhibit the classic
inverted V profile with LFCs 8-10k ft, suggesting that if any
convection does develop along the cold front this afternoon over
southern WI it will be high based and prone to producing gusty
winds given the high DCAPE. Strong deep layer shear and steep
lapse rates could also support a severe hail risk with the more
intense storms.

As the front continues southeastward into northern IL this
evening and that west-east moist axis shifts continues to slowly
advect north, the two should begin to interact and result in an
increase in coverage of showers and thunderstorms over our CWA
this evening. Confidence in when convection develops and
when/how quickly it increases in coverage is low, with the
severe threat expected to gradually decrease in the evening with
nocturnal cooling/stabilizing of the boundary layer.

Within the west-east moist axis across central IL, ample
heating today is expected to erase convective inhibition and
several CAMS are suggesting isolated-scattered thunderstorms
could develop later this afternoon into early this evening
across central IL, completely separate from the approaching
front. While atmosphere moisture will be greater, forecast
soundings still depict an inverted V, albeit a smaller one, so
these storms could also produce strong/gusty winds. If storms
develop and kick out some strong outflow, particularly if they
cluster today, then potential would exist for a localized more
severe dust storm. Similarly, if storms develop along the cold
front to our northwest this afternoon, they could also kick out
outflow with a threat for localized dust storm conditions
farther northwest in our CWA as well.

Tuesday onward:

Front is expected to slow a bit later tonight as it moves toward
central IL and becomes more parallel to the upper flow. Showers
will likely continue north of the front and into at least our
southern CWA into Tuesday morning as we get into the left exit
region of 110-120kt southern stream upper level jet. The showers
will slowly end from north to south Tuesday as the front and
better forcing gradually shift southeast.

Much colder temperatures are expected Tuesday with highs
generally in the 50s with cloud cover lingering into the
afternoon. Winds off Lake Michigan could leave areas close to
the lake mostly holding in the 40s Tuesday! Temperatures will
moderate back closer to seasonable norms by the end of the week
into next weekend. Northwest flow aloft should keep the better
moisture shunted well to our south, so any weak disturbances
rippling through the northwest flow should be moisture starved.
If we do see any rain late week into the weekend it would likely
only be isolated light showers and not rain out any outdoor
activities.

- Izzi

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1236 PM CDT Mon May 4 2026

Concerns:
-Scattered thunderstorms this evening, isolated this afternoon
-A few wind gusts to 35-40 kt in stronger thunderstorms
-Lake breeze timing on Tuesday

Challenges with the 18z set is the timing of scattered thunderstorms
Confidence is high enough to shift from a Prob30 to TEMPO forecast
for thunderstorms. Recent ensemble guidance would suggest the main
window for scattered coverage will be along and ahead of the cold
front, with more isolated to widely scattered coverage prior to it.
We would anticipate the highest coverage initially in the late
afternoon will be along and south/southeast of ORD/MDW  where better
instability will be, though it could be close enough to MDW to
warrant carrying a VCTS a bit earlier.

Expect showers to continue along the front which should pass through
the Chicago terminals around 5z. On the back side the front there is
another wave that will lead to some lighter rain showers overnight
into early Tuesday, though conditions should remain VFR.

Finally, there will be a lake breeze on Tuesday. TAFs reflect the
best timing but with medium confidence at this distance.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Blowing Dust Advisory until 6 PM CDT this evening for ILZ019-
     ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ107-ILZ108.

IN...Blowing Dust Advisory until 6 PM CDT /7 PM EDT/ this evening
     for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 7 PM CDT this evening for the IL
     and IN nearshore waters.

&&

$$

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