Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

384
FXUS63 KLOT 141950
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
250 PM CDT Sun Jun 14 2026

.KEY MESSAGES...

- Dangerous swimming conditions at Indiana Lake Michigan beaches
  through this evening, then possibly again Thursday.

- Severe thunderstorms are possible Tuesday afternoon and again
  Wednesday. However, Wednesday is currently the day of most
  concern for severe weather in, or very near, our area. Heavy
  rain and flash flooding is also possible with the storms on
  Wednesday.

&&

.DISCUSSION...
Issued at 250 PM CDT Sun Jun 14 2026

Broad mid and upper-level troughing (anchored by a Hudson bay
area low) will foster an unseasonably strong belt of west-
northwesterly mid and upper-level flow oriented from the
northern Plains, east- southeastward into the the lower Great
Lakes region through much of the week. This pattern will
essentially steer two notable weather impulses across our region
through midweek, with associated shower and thunderstorm
chances, particularly on Tuesday and again on Wednesday. Both
days will carry a threat of heavy rain, along with the potential
for some strong to severe thunderstorm threat, though Wednesday
continues to be the day of most concern for severe weather and
potential heavy rain and flooding.

Prior to our potential periods of active weather, Monday is
expected to be another quiet and pleasant weather day across the
area. Dry weather can be expected with temperatures topping out
in the mid 70s under partly cloudy afternoon skies. Thereafter,
our chances for showers and thunderstorms will increase,
particularly during the day on Tuesday as the first impulse
shifts over the region. As it does, an associated weak surface
cold frontal boundary is expected to shift eastward across
eastern IL into northwestern IN late in the day. Low-level
moisture return is expected to remain somewhat muted ahead of
this frontal boundary, owing to remnant surface ridging across
the deep south blocking Gulf moisture trajectories. Accordingly,
prefrontal surface dewpoints and associated instability are
expected to remain modest (upper 50s to low 60s). Nevertheless,
the presence of ~50 kt mid-level westerly flow overhead Tuesday
afternoon should support some storm organization, and thus the
potential for a few strong to severe storms. Currently, it
appears the primary threat with any storms would be strong
damaging wind gusts, and possibly some hail. This threat looks
to be favored mainly across eastern IL into IN, similar to the
region highlighted in a level 1 of 5 severe threat in the SPC
Day 2 outlook.

The shower and thunderstorm threat should diminish quickly
Tuesday evening as the main impulse and surface boundary sweep
east of the area. However, our next weather maker will be
quickly taking shape across the northern Plains Tuesday night.
Model and ensemble guidance remain in agreement that an
unseasonably strong surface low (potentially into the low 990s
mb) will track eastward across t he Upper Midwest and into the
western Great Lakes region late Wednesday into Wednesday
evening. As it does, a strong southerly mass response is likely
to result in a northward surge of deeper Gulf moisture into the
Midwest as a surface warm front shifts northward across IL.
Daytime heating of the airmass south of this warm front is
expected to result in moderate to strong instability in the
presence of a strongly sheared environment. Accordingly, as
severe thunderstorms will be a big concern Wednesday afternoon
and evening, particularly across parts of the Midwest into the
lower Great Lakes region.

Locally, there remains some question as to how far north this
severe threat may extend Wednesday afternoon and evening,
particularly considering our area does look to be along the
northern periphery of the better severe weather threat expected
across the Midwest. Nevertheless, Wednesday afternoon and
evening is a period we will be watching closely. In additional
to the severe threat, deep Gulf moisture (PWATs near 2") will
also support very heavy rainfall with these storms, and with our
area likely to reside near the surface warm front where storms
could move over the same areas, the threat of flash flooding
will also need to be monitored closely.

A period of breezy northwesterly winds and cooler weather looks
in store for the area again for a period later in the week
following Wednesday`s system. These breezy northwest winds on
the lake into Thursday may support build waves and the need for
another beach hazard statement for northwest IN Lake Michigan
beaches.

KJB

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1227 PM CDT Sun Jun 14 2026

There are no significant aviation weather concerns anticipated
through the period.

The rain has ended across the terminals, but a VFR deck of
strato cu will persist this afternoon before scattering out
towards sunset. Northwest winds will remain breezy this
afternoon, with gustiness of 20-25 kt at times. A lake breeze
will develop this afternoon across southeastern Cook eastward
into northwesterly IN. It remains possible that as the winds
ease towards sunset that this lake breeze makes a run towards
ORD and MDW. Accordingly, there could be a brief period in
which the winds turn north-northeasterly around sunset.
Fortunately, it appears wind speeds would be light and on a
diminishing trend. For this reason, we opted to leave a formal
mention out of the TAF. Otherwise, expect winds to become light
from the west-southwest overnight, then turn westerly around
10-15 kt during the day Monday.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Beach Hazards Statement until 10 PM CDT this evening for
     INZ001-INZ002.

LM...None.

&&

$$

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