NWS Chicago Decision Support Briefing - Forecast (2024)

FXUS63 KLOT 011117

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
617 AM CDT Mon Jul 1 2024


- Typical July warmth and humidity through the week with
periodic chances for showers and storms Tuesday through


Issued at 308 AM CDT Mon Jul 1 2024

Through Tuesday Night:

Dry and seasonably cool weather is on tap again for today.
Easterly winds off the lake will once again hold temps in the
60s near the lake, but away from the cooling influences of the
lake, the majority of the CWA should climb well into the 70s.
Sunny skies this morning will give way to some increase in high
cloudiness this afternoon. The dry weather and mild temps will
continue most of tonight.

Late tonight into Tuesday attention will turn to a pair of
shortwave troughs. The first, a large trough over the Pacific
Northwest and northern Rockies will move to the east today and
tonight. A surface trough/dryline will develop and sharpen up
today across the northern and central High Plains in response to
the upper trough. Strengthening southerly flow in advance of
this trough will transport higher theta-e air mass northward
across the plains today and tonight.

A second, small and more subtle shortwave trough over the
southern Rockies is forecast to move into the central Plains
tonight and likely be the impetus for a MCS developing across
Nebraska spreading east toward the mid-Mississippi valley by 12z
Tuesday. A few showers could reach our far northwestern CWA
prior to 12z Tuesday, but most of tonight should be precip-free
in our area.

This MCS should be in a weakening phase late tonight and
especially Tuesday morning as it tracks into a drier, more
stable air mass to the east of the Mississippi River and as the
low level jet diurnally weakens and veers tomorrow morning. How
quickly this precip dissipates and how far south it spreads
before it does varies considerably among the various models. The
HRRR is generally farthest south and holds onto lingering
showers and a few storms late into the morning hours Tuesday,
while other guidance barely has any precip south of the IL/WI
border. The ECMWF looks more HRRR-like and for that reason,
opted to bump pops up Tuesday morning north of I-80.

Debris cloudiness and perhaps rain, will likely keep temps
somewhat cooler northern CWA. How much cooler will depend on the
footprint of the potential rain/cloudiness. Opted to nudge temps
down somewhat, but still warmer than the HRRR which holds temps
in the low to mid 70s near the WI border Tuesday afternoon.
Southerly winds Tuesday will advect warmer and more humid air
north into the area, so even a couple/few hours of clearing in
the afternoon could allow for a rapid recovery in temps (and
dewpoints) across our northern CWA.

Showers and thunderstorms are expected to redevelop along the
cold front to our north and west Tuesday afternoon. Those
showers and storms will track east toward our area Tuesday
night, but it appears that they will be in a weakening phase as
they outrun the better synoptic forcing which should remain well
to our north and also encounters a more stable air mass. Still
anticipate this activity to make it into the northwest half of
our CWA where low end categorical pops from the NBM are within
the realm of possibility. Precip chances will decrease with
east and southeast extent across the CWA as this activity is
expected to be weakening as it moves across the area Tuesday

- Izzi

Wednesday through Sunday:

An upper-level trough will be in the process of pivoting into
the eastern Great Lakes on Wednesday as its associated cold
front continues to move southward across northern IL and
northwest IN. Therefore, an area of showers and thunderstorms is
expected to be ongoing along the front Wednesday morning, but
should taper Wednesday afternoon as the front exits to our
south. However, depending on the exact speed of the front there
is the potential for some lingering showers and storms in the
southern 1/3rd of our forecast area into the early hours of
Wednesday evening. Regardless, the better kinematic field should
be removed from the front by Wednesday afternoon which should
keep the threat for any strong to severe thunderstorms low.

Despite the front`s name, temperatures and dew points behind
the front are not expected to be cool in any sense of the word.
In fact, Wednesday afternoon is forecast to be one of the warmer
periods of the week with highs forecast to be in the mid to
upper 80s areawide. Couple these temperatures with dew points
still in the upper 60s to around 70 and conditions look to be in
place for many areas to see peak heat indices in the low to
possibly mid-90s. While these values are nothing uncommon for
this time of year, it will be a day where those sensitive to
heat should use caution.

The aforementioned front is expected to stall somewhere in
south- central IL Wednesday night before lifting back north as a
warm front on Thursday. At the same time, guidance continues to
show a thunderstorm complex developing across the central
Plains Wednesday night and tracking eastward along the frontal
boundary into IL Thursday morning. Depending on how far north
the warm front gets prior to Thursday morning will determine how
much of our area will see thunderstorms for our July 4th
holiday. The latest 00z guidance suite continues to favor a more
southern track with the aforementioned storm complex which may
keep the northern 1/3rd to half of our area (roughly I-80 north)
dry through Thursday afternoon with better coverage of storms
in our southern CWA. However, I will caution that the courser
resolution of long range guidance can struggle with the
mesoscale processes that drive storm complexes and their impacts
on frontal boundaries especially 3+ days out. Thus, recommend
keeping an eye on this period of the forecast for changes as you
work to finalize your July 4th plans.

Regardless of how the daytime hours on Thursday play out,
another cold front is forecast to get pushed into northern IL
Thursday night as an upper-level trough pivots into the Upper
Midwest and Great Lakes. Given that the airmass ahead of the
front will still be warm and humid have no doubts that shower
and storm coverage will increase along the front and persist
into the day on Friday. As the front exits the area Friday
night, a surface high pressure center is expected move into the
Ohio River Valley and southern Great Lakes. This high should
bring the periods of showers and storms to a close as we head
into next weekend, but guidance does continue to depict broad
troughing residing over the Great Lakes through the weekend.
Therefore, there is a chance (albeit low at this time) that some
isolated showers and/or storms could materialize during this

Otherwise, expect temperatures and humidity to remain near
typical July levels with highs in the low to mid-80s and dew
points in the 60s into early next week.



Issued at 617 AM CDT Mon Jul 1 2024

Forecast concerns for the terminals...

- Chance for showers and thunderstorms late tonight into Tuesday
morning, especially near RFD

- Breezy south-southeast winds Tuesday afternoon

High pressure overhead today will continue to support VFR
conditions and light winds generally under 10 kts. Wind
directions, however; will become easterly at the Chicago
terminals before turning southeasterly this evening and
overnight. Though, terminals away from Lake Michigan should
favor a more east-southeast direction through this afternoon and

An upper-level disturbance, currently over the northern Rockies,
will move towards the upper Midwest tonight into Tuesday
generating an area of showers and storms as it does so. While
the current trajectory of this disturbance keeps the better
shower and storm coverage north of the IL-WI line, some showers
and storms are forecast to spill over into northern IL late
tonight into Tuesday morning. Given that low-level moisture will
be a limiting factor, especially with southward extent,
confidence on coverage at the terminals is somewhat low.
Therefore, have decided to maintain dry forecasts for ORD and
MDW for now. However, there is enough of a signal in guidance to
support a PROB30 mention for -SHRA at RFD where confidence is a
bit higher.

Additionally, winds will also begin to increase Tuesday morning
as the system approaches with gusts expected to top out in the
20-25 kt range Tuesday afternoon. Winds should favor a south-
southeast direction on Tuesday, but a brief period of southwest
winds may occur with any storms. Otherwise, expect VFR
conditions to prevail but with increasing cloud cover through
the period.



IL...Beach Hazards Statement until 7 AM CDT this morning for ILZ006-

IN...Beach Hazards Statement until 7 AM CDT this morning for INZ001-

LM...Small Craft Advisory until 7 AM CDT this morning for the IN
nearshore waters.



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NWS Chicago Decision Support Briefing - Forecast (2024)


How hot does it get in Chicago? ›

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What is the average snowfall in Chicago? ›

Winters in Chicago bring picturesque snow, magical light displays, and unique holiday traditions. The average annual snowfall is approximately 37 inches (949 mm). Average daily highs are around 30 – 38°F (-1°C – 3°C). Visit the National Weather Service or weather.com for the latest weather information.

Why is it so cold in Chicago? ›

The sun, primary energy source for virtually all weather phenomena, in large part determines air temperatures and seasonal variations. Solar energy is three to four times greater in early summer than in early winter at Chicago's mid-latitude location; which results in warm summers and cold winters.

What type of climate is Chicago? ›

The widely used Koppen climate classification system designates Chicago's climate as “humid continental.” A humid continental climate “exhibits large seasonal temperature contrasts with hot summers and cold winters.

What is the hottest day ever recorded in Chicago? ›

Chicago's official allâ€'time high temperature of 105 (University of Chicago) was set July 24 1934. It was 109 at Midway on July 23, 1934, the highest temperature ever recorded at a Chicago location (but Midway was not the official observatory for Chicago in 1934).

How many people died in the Chicago heat wave in 1988? ›

This produced tragic consequences with more than 750 heat-related fatalities. The 1988 drought summer, with a record 47 90-degree plus days that included seven days of triple-digit heat, featured many days with a Chicago version of “desert-like” heat.

Has it ever snowed in June in Chicago? ›

Since the start of the city's snow records in 1884-85, snow has been recorded only once in June and that was on June 2, 1910. It was a chilly day with a high of 55 and a low of 43 and a thunderstorm (probably during the early morning hours) brought a mixture of rain, hail, and snow pellets.

Has it ever snowed in May in Chicago? ›

The latest measurable snowfall on record occurred in 1966, when the city recorded an accumulating snow on May 11. As for the final trace of snow of the year, that average date falls on April 14, according to officials. The latest trace amount of snow recorded in the city occurred on May 25, 1924.

Which US city has the worst winters? ›

Fairbanks, Alaska

With a minimum average temperature of about minus 17 degrees Fahrenheit, Fairbanks takes the cake as the coldest city in the U.S. The northernmost major city in Alaska, Fairbanks has seen record cold temperatures reaching minus 66 degrees in the past.

Are Chicago winters getting better? ›

In Chicago, winter has warmed 0.55 degrees per decade since 1980, the analysis showed.

Is Michigan colder than Chicago? ›

It depends on the day. On a cold, windy day in either city both will claim to be the coldest but the difference is not great. A strong wind and a high wind chill factor will make the difference even if both cities have the same temperature. At that point the windiest would be considered colder.

Which world city has the same climate as Chicago? ›

Chicago & Bucharest, Romania

The two towns share nearly identical seasonal temperatures, with Bucharest having slightly warmer summers and Chicago having slightly colder winters.

Is Chicago a good city to live in? ›

Yes! There are plenty of job opportunities, and the housing costs are less than many coastal cities. You also have access to all kinds of cultural activities, the food scene is thriving, and there's always something to do. Q: What are the pros of living in Chicago?

What is the hottest month of the year in Chicago? ›

Average Temperature

In the summer months, the hottest month of the year in Chicago is July, with an average high of 84°F and average low of 67°F. In the winter months, the lowest temperatures are reached in the month of January with average high of 32°F and average low of 19°F.

Has it ever been 100 degrees in Chicago? ›

The city's earliest-in-the year 100 was a high of 102 on June 1, 1934, and the latest, 100 degrees on Sept. 7, 1960. Chicago's all-time official highest temperature was 105 on July 24, 1934, but though not official, Midway recorded 109 degrees the day before.

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Afternoon high temperatures tend to be in the lower 80s F (27-28 C) with a few days reaching into the lower 90s F (32-33 C). About 6 days this month will record high temperatures of 90 F (about 32 C) or more with the record high temperature for Chicago during July is 104 F (40.0 C).

How many days over 90 degrees in Chicago? ›

The Great Sweatening: Days of Fury (or at Least 90 Degrees)

According to the National Weather Service (those lovely folks who ensure we aren't caught off guard by a rogue blizzard in July), Chicago averages a cool (ha!) 14 days where the mercury rockets past the 90-degree mark. But that's just an average, folks.

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