Rockford, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

283
FXUS63 KLOT 201552
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1052 AM CDT Fri Jun 20 2025

.KEY MESSAGES...

- A localized area of strong winds will occur in the wake of
  late morning/early afternoon showers, mainly across interior
  portions of northern Illinois.

- First heat wave of the summer expected this weekend into early
  next week with multiple days of highs well into the 90s and
  peak afternoon heat indices of 100-105F likely.

- Extreme Heat Warning issued for the city of Chicago and Cook
  Co. where special 3 day extreme heat warning criteria of peak
  heat indices of 100F+ are likely to be reached.

- Heat Advisory issued issued the rest of the area Saturday-Monday.

&&

.UPDATE...
Issued at 1051 AM CDT Fri Jun 20 2025

A somewhat disorganized mesoscale convective complex continues
to slowly chug southward across central/eastern parts of Iowa
late this morning. The outflow that this convection is
developing along will continue to push southwestward, and with
the associated anvil crawler lightning bolts struggling to make
it to the Mississippi River, it now seems highly probable that
our forecast area should remain lightning-free through the
remainder of the day. Most areas will still see a period of
light rain through mid-afternoon, though. We`ll also need to
monitor for new shower development along the northern edge of
the nose of the low-level jet/theta-e plume to our west as it
slides eastward later this afternoon, but the stabilizing
effects of the earlier rain/convection should mute the coverage
of any showers that manage to develop later in the day.

The main weather item of note for us with this convection will
actually be the winds. Multiple personal weather stations and
ASOS/AWOS sites in northeast Iowa, southwest Wisconsin, and
northwest Illinois have gusted into the 40-50 mph range in the
past hour or so due to mesoscale subsidence/drying and the
development of a wake low along the northern periphery of the
rain shield. These stronger winds should be relatively brief in
duration (likely lasting no more than 1-2 hours at any one
location) and should weaken with time and southward and
eastward extent. However, with the increased likelihood of 40+
mph wind gusts briefly being observed in our western CWA
through the early afternoon, will be hoisting a Special Weather
Statement for our western counties to highlight this.

Ogorek

&&

.DISCUSSION...
Issued at 331 AM CDT Fri Jun 20 2025

Through Saturday:

Early this morning, we find a complex of showers and embedded
thunderstorms moving across IA and southern MN and on a
trajectory toward northern IL. These storms had developed on the
nose of a moisture-rich low level jet, but they should weaken
prior to arrival and continue to decay through the morning as
they outrun the better forcing and deeper moisture tied to that
jet. While there remains a couple of healthier updrafts embedded
in the cluster, we`re already seeing an overall downward trend
in rain intensity and lightning activity out west. We should
start to see rain approach our CWA around mid-morning and spread
eastward into the early afternoon, all while expected to be
dropping in intensity and coverage. It`s possible that a couple
of storms maintain themselves long enough to reach our western
CWA, but thunder coverage should be little to none into the
Chicago metro this morning. A few isolated light showers may
linger through mid-afternoon or so, but a big majority of the
area will be rain-free following this morning.

A handful of high-res model camps are resolving a period of
gusty winds this morning and afternoon as a result of a wake low
behind this morning`s system of showers. Already we`re seeing a
handful of 30 to 35 mph gust reports well behind the rain in
parts of IA and MN, and models suggest this mass response will
only strengthen in the next several hours on its way here. So a
period of 30 to 40+ mph gusts is looking exceedingly probable
with time, especially for areas west of the Fox Valley, and it
would be here during the late morning and afternoon.

Winds should come down a few steps during the evening after the
boundary layer decouples. However, we`ll then see a ripe low
level jet move just overhead Friday night with upwards of 45 kt
of flow at 925mb by early Saturday. This will bring gusty
conditions to our Saturday, because while daytime mixing does
not look overly deep on model soundings, it should be more than
enough to tap into 35 to 40 kt of low level flow and pull some
of that down to the surface. The windiest conditions should be
found near and north of I-80 beneath the core of the jet.
Conditions will subside but will remain breezy during the night.

As far as the heat goes, today will certainly be a warm summer
day, but not nearly as oppressive as what`s expected over the
next several days. Temperatures this afternoon are forecast in
the mid 80s. Dewpoints in the mid 60s should make conditions
feel a few degrees hotter but the heat index should be capped at
around 90 today. Tonight, a formidable upper high will meander
from the Plains into the Mississippi Valley centering a 590 dam
500mb ridge right over the Midwest. By Saturday evening, the
NAEFS and ENS ensembles are forecasting 500mb heights and 850mb
temps in the 99th percentile for mid-late June over northern IL
and climatological max 700mb temps! Temperatures are forecast to
climb into the mid 90s for Saturday afternoon. Peak heat
indices should easily surpass 100F around just about the whole
area. Exact heat indices are still to be determined with
uncertainty regarding afternoon dewpoints, with the few degree
spread meaning a several degree difference in the heat index.
But given that heat indices to around 105F are looking probable
around a majority of the area with more of the same expected in
the couple of days to follow, made the decision to issue a Heat
Advisory around the CWA from Saturday morning through Monday
evening. The only exception is Cook County where the Extreme
Heat Watch was upgraded to an Extreme Heat Warning for the high
likelihood of three consecutive days of 100+ heat indices, a
threshold exclusive to the heavily-developed and densely-
populated Cook County where the impacts of extreme heat are
generally greater. See the long term discussion below for more
details on the heat continuing into next week.

Doom


Saturday Night through Thursday:

There are no major changes in our thinking for the multi-day
stretch of oppressive heat which is expected to persist through
at least Monday as an impressive upper level ridge for this
early in the summer becomes established across the eastern half
of the CONUS (peak 500mb heights approaching 600dm!).

While the overall message remains the same, in contrast to
Saturday, heat indices >100F will more likely be achieved Sunday
and Monday via deeper mixing leading to warmer temperatures and
slightly lower dewpoints. This should keeping heat indices in
check and below the local Extreme Heat Warning criteria of 110F
(for areas outside of Cook County). Potentially record warm
overnight temperatures will lead to little in the way of relief,
especially in Chicago where low temperatures may only drop into
the upper 70s. This limits the ability to cool down before the
next hot day, especially any buildings without air conditioning.
Be sure to check on vulnerable friends, family, and neighbors
over the next few days.

The upper ridge begins to break down toward the middle of next
week which would place the area on the northern periphery of the
ridge and along a more favorable storm track. Accordingly, the
blended guidance has shower/storm chances (20-40%) Tuesday
through the end of the upcoming workweek. Strong to severe
storms would certainly be a possibility in this regime. It is
also worth noting that a slower weakening of the ridge would
lead to oppressive heat indices >100F potentially continuing
longer into the work week and lead to extensions of the current
heat headlines.

Petr

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 645 AM CDT Fri Jun 20 2025

Key Messages:

- Period of -SHRA this morning into early afternoon (30% chance
  of TSRA at RFD 17-20Z).

- Strong SSW winds may develop in "wake" of -SHRA with localized
  gusts >35 kt possible.

A band of VFR rain is beginning to move into far northwest
Illinois this morning. This is expected to gradually drift
across the area through the morning hours. Associated lightning
activity remains well to the west over Iowa and Minnesota.
While thunder is not currently expected to reach the Chicago
area terminals (<15% chance), a few trailing storms across south
central MN may hold together long enough to reach RFD by early
afternoon as depicted in some of the latest HRRR runs.
Accordingly, shifted the PROB30 group for -TSRA to 17-20Z.

We will also be closely monitoring surface observations in case
stronger winds develop in the wake of these showers. Hi-res
guidance has been consistent in such a scenario occurring though
confidence in them developing as far east as the Chicago metro
terminals has decreased. Southwesterly wind gusts upwards of 35
kts would be possible, with a narrow corridor of wind gusts >40
kt not out of the question near RFD. In the event these
stronger winds don`t materialize, wind directions could end up
variable for a couple hours behind the rain (some upstream
observations ranging from SE to NW to SW around 10kt). By this
afternoon, steady southwest winds in the mid 20kt range are
expected.

A period of low-level wind shear will be possible this evening
and overnight as a 45-50 kt southwesterly low-level jet sets up
overhead and surface gusts ease. However, at least sporadic
gustiness will continue overnight at the surface with
prevailing gusts >20 kt expected by daybreak Saturday then
increasing to near 30kt by the afternoon.

Petr

&&

.CLIMATE...
Issued at 114 PM CDT Thu Jun 19 2025

Temperatures this weekend into early next week could potentially
threaten record highs and record warm lows for Chicago and Rockford.
Here are the current records:

Chicago              High       Warm Low
Saturday 6/21     101 (1988)    74 (1923)
Sunday 6/22        97 (1988)    76 (1923)
Monday 6/23        97 (1930)    79 (1923)

Rockford             High       Warm Low
Saturday 6/21     100 (2022)    71 (1995)
Sunday 6/22        97 (1923)    73 (1908)
Monday 6/23 97 (1923) 74 (1908)

NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory from 10 AM Saturday to midnight CDT Monday night
     for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
     ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
     ILZ039-ILZ106-ILZ107-ILZ108.

     Extreme Heat Warning from 10 AM Saturday to midnight CDT
     Monday night for ILZ103-ILZ104-ILZ105.

IN...Heat Advisory from 10 AM CDT /11 AM EDT/ Saturday to midnight
     CDT /1 AM EDT/ Monday night for INZ001-INZ002-INZ010-
     INZ011-INZ019.

LM...None.

&&

$$

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