Waukegan, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

831
FXUS63 KLOT 021850
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
150 PM CDT Wed Apr 2 2025

.KEY MESSAGES...

- The threat for severe weather through early this evening is
  expected to focus roughly south of a Streator IL to Gary IN
  line, and particularly from southwest Ford County to far
  southeast Porter County IN and points south and southeast.
  Severe threats will include damaging wind gusts, tornadoes,
  and isolated instances of large hail.

- For locations off to the north and northwest, the severe
  weather threat is lower, with a continued localized flooding
  threat into the Chicago metro.

- Strong south winds this afternoon, especially south of I-80
  where gusts in excess of 45 mph are probable.

- Periods of rain, possibly heavy, late Friday afternoon into
  Saturday morning, with possible localized flooding south of
  I-80.

&&

.MESOSCALE...
Issued at 150 PM CDT Wed Apr 2 2025

The surface warm front has been able to recently reach roughly
the US Highway 24 corridor, though with a better northward push
into Newton and Jasper Counties. The airmass south of the front
is exceptionally warm and moist for early April with temperatures
into the low-mid 70s and dew points into the 60s. Despite
extensive cloud cover, latest mesoanalysis is indicating 1k J/kg
or more of minimally capped MLCAPE. Extreme low-level
shear/helicity and 0-3km MLCAPE increasing to upwards of 100
J/kg owing to the unseasonably moist airmass in the warm sector
have contributed to an exceptionally favorable environment for
tornadoes, some significant, of course contingent upon intense
convection.

A few low-topped supercells were able to develop right near the
front but have since mostly crossed north of the front as they
race northeast at over 70 mph (exiting Jasper County before the
top of the hour). It`s tough to be very specific on the timing
of new convective initiation, though generally speaking, chances
should uptick after 4pm given most recent radar trends and high
resolution ensemble system WarnOnForecast (WoFS) runs. The
potential higher end severe threat area (damaging wind and
tornadoes) dovetails fairly well with the current level 3 of 5
(enhanced risk) threat delineation in the SPC Outlook.

Castro

.PREVIOUS MESOSCALE UPDATE...
Issued at 1118 AM CDT Wed Apr 2 2025

Ongoing elevated convection from Livingston County to the south
and southwest suburbs of Chicago will continue to pose a small
hail and gusty wind threat with strongest embedded storms. In
addition, with pockets of heavy rain onto areas that had near or
upwards of an inch of rain overnight, localized ponding an even
minor street flooding may develop.

Regarding the near term convective threats, the northward surge
of the warm front will progress into areas near/south of US-24
over the next hour, with Rantoul, Champaign, and Danville having
jumped into the 65-70F range with dew points in the lower 60s
and south winds gusting to ~30-40 mph.

Given the progress of the warm front, the very strong low-level
wind fields and shear, the southern portion of the current
convection over eastern McLean County (as of this writing) is
the most concerning for a localized severe wind and perhaps a
brief tornado threat into far southern sections of the LOT CWA
(southern Livingston eastward to southern Newton, Jasper, and
all of Benton Counties through about 1pm.

Looking ahead to this afternoon and early evening, current
radar and observational trends tend to suggest that the focus
for a renewed severe threat should tend to focus roughly
southeast of a line from Streator to Gary IN. This would be
associated with another impulse and corresponding thunderstorms
west and northwest of the St. Louis metro. Given the dynamics,
wind shear, and air mass at play, fairly limited instability
(ie. under 1k J/kg of MLCAPE) may still support pockets of
significant severe winds as well as tornadoes from a mixed storm
mode. The strong forcing should keep things on the messy side
with small bowing segments and perhaps embedded supercells.

There remains a more highly conditional severe threat northwest
of the aforementioned Streator to Gary line later this
afternoon. However, it does appear the window for
destabilization ahead of an approaching cold front will be
rather limited given ongoing convection and the warm front`s
current position. This may keep any storms that develop ahead of
the front primarily sub-severe. All in all, while we certainly
can`t rule out severe storms with a wind and tornado threat
initiating ahead of the cold front across northern Illinois,
this does not currently appear to be the most likely scenario.
The more likely scenario favors the higher severe threat
focusing farther south, as outlined above. We`ll continue to
closely monitor trends into the afternoon.

Castro

&&

.DISCUSSION...
Issued at 330 AM CDT Wed Apr 2 2025

Through Thursday:

The main focus remains the potential for waves of thunderstorms
through early evening, some of which could be severe with all
hazards possible.

Low pressure continues to consolidate early this morning across
central Kansas. Meanwhile a line of mainly pre-frontal strong
to severe thunderstorms currently extends from Kansas City
southwest into north central Oklahoma and is drifting northeast
toward the region. Embedded within this line appears to be one
or two developing embedded MCVs that we will have to keep an eye
on as they approach. Well ahead of the low, warm advective
showers and thunderstorms have begun to increase in coverage
across the area, with more robust clusters of storms currently
in southern IA/northeast MO and central IL. This will continue
to consolidate and lift across the local area between now and
daybreak as a mid-level lapse rate plume moves overhead
allowing storms to tap into better elevated instability. Main
hazards this morning are frequent lightning, large hail up to 1"
in diameter and localized flooding in poor drainage areas. We
will also continue to watch for the potential for a gusty wind
threat if any gravity wave associated convection develops (some
guidance continues hint at this potential and storms over Kansas
City are beginning to take on this appearance) which could
allow for strong downbursts to punch through the stable surface
layer in spite of storms remaining elevated.

Unfortunately confidence in how the rest of the day unfolds
remains quite low so expect frequent updates from us throughout
the day. The surface low is expected to gradually deepen as it
lifts north northeast toward the Upper Mississippi Valley
through the day today. The aforementioned line of pre-frontal
convection is expected to lift across the area through the
morning hours. While there continue to be notable model
differences in handling the various waves/lines of convection,
particularly around midday, if some clearing can occur during
this time, strong low-level flow would support rapid recovery
of the low-level thermal environment, especially south and east
of I-55. Areas further north we continue to have the lowest
confidence. Will also have to keep an eye on the cold front
which could serve as another focus for renewed development in
the late afternoon into early evening with the 6Z NAMNest still
showing this scenario.

Thus we plan to continue messaging the conditional potential
for severe weather across the entire area, though with greater
confidence (albeit still relatively low) in areas mainly south
and east of I-55 this afternoon into early evening. All hazards
remain possible with the afternoon/early evening thunderstorms,
including damaging winds, large hail, and tornadoes. Lastly,
given the expected multiple rounds of convection, localized
flooding will be possible in low-lying, urban, and poor drainage
areas.

Non-Thunderstorm Winds:

There is a window where if storms are able to clear out even
briefly in the afternoon, with a strong low-level jet overhead,
slightly deeper mixing would tap into these stronger winds. Due
to this potential, opted to issue a Wind Advisory for our
southwestern counties (mainly south of a Mendota to Kankakee to
Fowler line where non-thunderstorm wind gusts could exceed 45
mph in the afternoon. Further north, wind gusts to 35-40 mph
will remain possible with perhaps a short 1-2 hour period where
sporadic gusts to 45 may still occur.

Tonight through Thursday:

After storms clear the area, expect winds to ease and
temperatures to drop into the 40s across the area. Heading into
Thursday we warm back into the 50s with our next weather system
beginning to lift toward the area toward the end of the day with
increasing rain chances south of I-80.

Petr


Thursday Night through Tuesday:

There remains uncertainty for a period of showers Thursday
night, generally south of I-80. The NAM was the first to show
this potential as it entered the end of its runs and it still
shows showers across the southern half or so of the cwa Thursday
night. The 03z RAP is now out through part of this time period
and it too is showing showers across much of the southern cwa
Thursday night. Otherwise, not much support for this potential.
Chance pops seem reasonable for now.

If those showers develop, a short break is expected from early
Friday morning through early Friday afternoon and then the
models continue to bring the next system further north with each
run with periods of rain, possibly heavy at times from late
Friday afternoon into early Saturday morning. Precipitable water
values increase to an inch or so across the north to as high as
1.5 inches across the south during this time period. With the
possibility of hours of moderate/heavy rain, there could be a
band of qpf amounts in the 2-3 inch range across the southern
cwa. While confidence is increasing with the northern shift to
this rain/qpf axis, still 3 days away and more changes are
possible. If these trends were to continue, hydro concerns may
develop across the southern cwa. Precipitation looks to
dissipate by mid/late Saturday morning and then one more push of
precip Saturday afternoon/evening as the system finally pulls
away. GFS actually turns some of the precip to snow early Sunday
morning, as the system departs and colder air moves into the
area. No snow mention planned with this forecast.

Now appears there will be a stronger cold front moving south
sometime Monday that will bring colder air into the region with
perhaps a low chance for precip, maybe snow showers, as it
passes the area. cms

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1255 PM CDT Wed Apr 2 2025

Key Aviation Messages for the current TAF period:

- Waves of showers and scattered thunderstorms through the
  afternoon

- MVFR conditions mainly driven by lower visibility from rain
  showers

- Easterly winds will shift southerly as a warm front moves
  through with strong gusts around 30 knots possible

- Chances for rain diminish this evening as winds become
  westerly behind a cold front

At the moment this discussion was sent, most of the lightning
activity has moved east of area terminals, with lingering
showery activity in its wake. Conditions remain around MVFR
conditions, but mainly due to lower vis with the showers rather
than the cigs. Winds remain out of the east ahead of the warm
front with occasional gusts around 20 knots. As that front
lifts (along with the timing of the next round of storms), winds
are expected to swing to the south and increase.

The next complex of thunderstorms is moving in from the
southwest and should arrive at Chicago terminals just before 19Z
providing heavier rain with lightning, as well as lower cigs and
vis through the early afternoon. There remains lower confidence
in the severe threat, but the main hazard would be gustier
winds with the storms. Behind this thunderstorm risk, winds will
slowly become more southerly if not southwesterly with gusts to
30 knots. High res models are still suggesting one last
developing wave of showers that can move from RFD after 21Z
through the Chicago terminals by 00Z. If there was a chance for
severe weather, it would likely come with this time window for
thunderstorms at terminals. However, confidence remains low so
it was kept as a PROB30 at area terminals, though the better
chances remain around KGYY and areas to the south.

Cigs and vis will gradually improve after this boundary passes.
Drier conditions are expected behind it as winds turn to the
west. Gusts between 20 to 25 knots are expected through Thursday
morning.

DK

&&

.MARINE...
Issued at 330 AM CDT Wed Apr 2 2025

- Gale Warning in effect through 7 PM CDT this evening.

Southeast gales gusting to 35 kt are expected to continue
through daybreak this morning. It is possible there is a brief
lull in gales toward midday. However, expect wind gusts to
increase out of the southwest during the afternoon to 35 kt as a
deepening surface low lifts across the Upper Mississippi
Valley. Winds then gradually ease toward sunset behind a
departing cold front.

NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 7 PM CDT this evening for ILZ019-ILZ021-
     ILZ023-ILZ032-ILZ033-ILZ039.

IN...Wind Advisory until 7 PM CDT /8 PM EDT/ this evening for
     INZ010-INZ019.

LM...Gale Warning until 7 PM CDT this evening for the IL and IN
     nearshore waters.

&&

$$

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