Naperville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

968
FXUS63 KLOT 211939
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
239 PM CDT Wed May 21 2025

.KEY MESSAGES...

- Periods of showers and drizzle to persist through Thursday afternoon.

- Increasing winds and waves tonight through Thursday will make
  for hazardous conditions at Cook County and Indiana Lake
  Michigan beaches.

- Below to well below normal temperatures are favored through
  the Memorial Day holiday weekend.

&&

.DISCUSSION...
Issued at 239 PM CDT Wed May 21 2025

Through Thursday Night:

A vertically stacked low pressure system continues to slowly
propagate eastward across the Great Lakes this afternoon
resulting in areas of showers and drizzle across Lower MI, WI,
northeast IL and northwest IN. While the drizzle threat should
diminish this evening as moisture depths increase, periods of
off and on showers are expected to persist through tonight as
shortwaves pivot overhead. Otherwise, expect temperatures to
hold nearly steady in the low to mid-50s this afternoon under
cloudy skies before temperatures gradually cool into the mid to
upper 40s overnight.

Heading into Thursday, the stacked lows will be moving into the
northeast CONUS allowing showers to gradually taper through the
morning. However, forecast soundings do show at least some
modest low-level moisture lingering through Thursday afternoon.
Therefore, an additional period of scattered showers (20-30%
chance) looks likely during the afternoon hours as another
shortwave dives through the region and interacts with a lake
breeze. Given the scattered nature, many hours will should
remain dry especially those in northwest IL and behind the lake
breeze (far northeast IL). On the bright side, temperatures are
expected to be warmer than today with highs in the lower 60s
inland and mid to upper 50s near the lake.

Outside of the showers, north-northeast winds will also be
increasing (especially over the lake) on Thursday which will
lead to increasing waves at Cook County and Indiana Lake
Michigan Beaches. While the weather is not highly conducive for
beach activities, still felt that maintaining the Beach Hazard
Statements through Thursday night for Cook, Lake IN, and Porter
counties was warranted due to the high waves and currents. Winds
and waves will gradually subside Thursday night with otherwise
clear skies and cool temperatures in the lower to mid-40s.

Yack

Friday through Wednesday:

The main weather message for the extended part of the forecast
is that Memorial Day Weekend will (unfortunately) not live up to
its nickname (unofficial start of summer) temperature-wise this
year. Expect solidly below normal temps all the way through
Wednesday, although the strong late May sun certainly will make
it feel warmer when its not obscured by clouds. Mid and upper
troughing over northeastern North America will keep us in
northwest flow aloft through Sunday, followed by a transition to
a somewhat blocky pattern by Monday and Tuesday. In this blocky
regime, yet another upper level low may affect our weather in
the Tuesday-Wednesday period.

Surface high pressure will build in over the western and
central Great Lakes through the weekend. This will keep the
baroclinic zone mostly shunted to our south and limit chances
for any meaningful rainfall. A stronger short-wave may take a
close enough approach to our southwest on Saturday night into
Sunday when some showers are possible primarily over the
southwest 1/3 or so of the CWA (20-30% PoPs). Then on Memorial
Day, rain chances with the next possible system should be
confined to primarily south of I-80 with high pressure still
anchored over the Great Lakes. While some spotty showers may
return Tuesday-Wednesday if upper level low pressure sets up
overhead, the prospects for any widespread soaking rain appear
low. The 12z EPS (ECMWF Ensemble) in fact keeps probabilities of
24 hour QPF >=0.5" at 10-20% or less through next week and into
the first weekend of June.

High temperatures inland will only be in the 60s (primarily
mid-upper 60s) Friday through Wednesday. Meanwhile, persistent
onshore winds will keep the lakeshore several degrees cooler.
Keep that in mind if you have any tentative plans to head to the
shore for the holiday weekend. Overnight lows will be primarily
in the 40s to around 50F, though some spotty upper 30s are
possible across portions of far northern Illinois early
Saturday.

Castro

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1247 PM CDT Wed May 21 2025

- IFR ceilings persist through early Thursday, along with
  occasional MVFR visibilities in SHRA/DZ.

- North-northwest winds around 10-12 kts for much of the
  period, with some gusts 15-20 kt this afternoon.

- Wind shift to northeast expected for ORD/MDW Thursday
  afternoon. A few scattered SHRA may develop on the wind shift
  boundary.

Midday surface analysis depicts low pressure to the east of the
terminals over northern OH, with a nearly stationary surface
trough extending back across northern IN/IL, just south of the
terminals. Aloft, an elongated upper level trough will remain
across the region into Thursday, with a series of smaller scale
disturbances rotating across the area. An extensive area of low
clouds (mainly IFR and low-MVFR) lingers across the area in
association with the surface and upper level trough axis, and
are expected to remain in place into Thursday morning before
more robust drying occurs in northerly low level flow. In
addition, periodic showers and/or drizzle will continue to
affect the area - most notably early this afternoon and again
tonight. Some daytime lifting was occurring, though cloud bases
are expected to settle back toward 500 feet or so with sunset
and the return of precipitation this evening. Improvement does
look to begin to occur predawn Thursday as the drier low-level
air spreads in, with a transition to MVFR and eventually VFR
ceilings after sunrise.

Surface winds are expected to be primarily from the north-
northwest this afternoon through midday Thursday. Some gusts in
the 15-20 kt range are possible this afternoon, and again early
Thursday morning. A wind shift to the northeast is expected
during the afternoon for the Chicago terminals. While no
additional widespread precipitation is expected for most of the
terminals Thursday, convergence along this wind shift may
support some showers across the Chicago metro sites late morning
and early afternoon. Have included a prob30 for this in the
ORD/MDW 30 hour forecasts.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement from Thursday morning through Thursday
     evening for ILZ103-ILZ104.

IN...Beach Hazards Statement from 1 AM CDT Thursday through late
     Thursday night for INZ001-INZ002.

LM...Small Craft Advisory from 9 AM to 10 PM CDT Thursday for
     Wilmette Harbor to Calumet Harbor IL.

     Small Craft Advisory from 4 AM Thursday to 1 AM CDT Friday for
     the IN nearshore waters.

&&

$$

Visit us at weather.gov/chicago