Elgin, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

899
FXUS63 KLOT 071804
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
104 PM CDT Sat Jun 7 2025

.KEY MESSAGES...

- Showers and a few thunderstorms will develop this afternoon
  and last through the evening. A few localized instances of
  ponding of water may occur where rain is heaviest.

- Sunday afternoon will have a better chance of scattered
  thunderstorms, particularly near and northwest of I-55, with a
  corresponding threat for strong to damaging winds.

- Following another chance for scattered showers and storms
  Monday afternoon, a period of drier and warmer weather is
  expected by the middle of next week.

&&

.UPDATE...
Issued at 1010 AM CDT Sat Jun 7 2025

A recent hand surface analysis combined with regional radar and
GOES-19 water vapor imagery depicts a convectively-augmented
low pressure system near the NE/IA/MO/KS border regions to the
northwest of a broader surface low passing just south of Kansas

- Following another chance for scattered showers and storms
  Monday afternoon, a period of drier and warmer weather is
  expected by the middle of next week.

&&

.UPDATE...
Issued at 1010 AM CDT Sat Jun 7 2025

A recent hand surface analysis combined with regional radar and
GOES-19 water vapor imagery depicts a convectively-augmented
low pressure system near the NE/IA/MO/KS border regions to the
northwest of a broader surface low passing just south of Kansas
City, MO. A composite warm front extends eastward from both low
pressure systems across southern Iowa and into central Illinois
and back into northern Indiana, which delineates a pocket of dry
air across northern IL (dew points in the lower 50s) from
comparatively more moist air to the south and east (dew points
in the low to mid 60s).

As the convectively-augmented wave moves toward northern
Illinois this afternoon, the warm front will lift northward and
stall somewhere near the I-88 or I-80 corridors (near the outer
influence of onshore flow off Lake Michigan). Showers may
develop along and south of the front as early as 1 to 2 PM owing
to the boundary layer nearing convective temperatures. Coverage
of showers should then increase markedly by 4 to 5 PM and
continue through 10 or 11 PM as the convectively-augmented wave
arrives and moves directly overhead. With very poor/nearly
psuedo-moist adiabatic mid-level lapse rates (near 6 to 6.5
K/km), cylonically-driven forcing along a warm frontal boundary
(MCV-like forcing), slow cell motions (mean flow less than 25kt
from the surface to 15kft), and respectable moisture (PWATs
nearing 1.5"), the stage appears to be set for deceptively
efficient rain-rates in the most organized showers this
afternoon and evening. Such a regime may lead to a few highly
localized areas where 3 to 6-hour rainfall totals tally up to 2
to locally 4 inches. If such rainfall amounts were to
materialize, certainly can`t rule out nuisance flooding in
ditches and low-lying areas and perhaps even a lower-end flash
flood threat particularly if the heaviest rainfall overlaps with
urban areas. So, did opt to increase rainfall amounts and
overall chances for showers to peak in the 60 to 80% range
along/south of I-88 in our gridded database with the morning
update.

Finally, a lightning strike or two cannot be ruled out
in the tallest showers this afternoon and evening, though the
low-centroid instability profiles with effective equilibrium
levels only near -20C suggest lightning should be more isolated
than widespread.

Updated products are in the process of being sent.

Borchardt

&&

.DISCUSSION...
Issued at 321 AM CDT Sat Jun 7 2025

Through Sunday Night:

The weak surface high that brought us the tranquil weather
overnight will begin to get shoved east as the shortwave trough
currently over the central Plains propagates into the
Mississippi Valley and southern Great Lakes later today. While
recent forecast trends continue to show the core of the wave
and developing surface low tracking across central IL and IN, an
area of scattered showers is expected to develop across
portions of northern IL and northwest IN this afternoon. The
highest coverage of any showers will be south of I-80 where the
combination of better forcing and moisture overlap, but an
isolated shower or two cannot be ruled out for the rest of the
area. As for the thunder potential, the bulk of the instability
this afternoon is expected to develop south of our area in
central IL but some modest instability is still forecast for the
southern portions of our area. Therefore, think that an
isolated storm or two remains possible (20% chance) south of
I-80 as well.

Despite the showers and much more cloud cover than yesterday,
temperatures are still expected to warm into the upper 70s this
afternoon. However, persistent onshore winds will keep highs
near the lake only in the mid-60s.

The shortwave will continue to move east into IN and OH this
evening thus allowing showers to gradually taper from west to
east overnight. While most of the area should be rain-free
shortly after midnight, isolated showers may persist east of
I-57 into the predawn hours of our Sunday. As we enjoy a brief
hiatus from the rain Sunday morning, another upper trough will
be digging into the Upper Midwest and pushing a cold front
towards our area. Ahead of the front temperatures will warm
quickly into the upper 70s and low 80s under mostly sunny skies
with dew points climbing into the upper 50s to around 60. These
conditions are forecast to result in a few hundred joules of
CAPE developing across northern IL which should be sufficient to
generate scattered showers and thunderstorms Sunday afternoon
along the front especially northwest of I-55.

Furthermore, a stout 500 mb jet streak is expected to pivot
around the base of aforementioned trough on Sunday resulting in
30-35 kts of bulk shear across the area. While shear of this
magnitude is sufficient for severe weather, the veering winds
ahead of the front and modest mid-level lapse rates suggest that
forcing along the front and deeper instability may be a
limiting factor. That said, still think an isolated strong to
severe storm is possible Sunday afternoon, mainly across
northwest IL, with damaging winds being the primary threat.

Regardless, thunderstorm coverage is expected to wane with
eastward extent as the front outruns the upper trough and better
instability. However, showers will prevail through Sunday
evening before tapering overnight though most should be rain-free
by midnight Sunday night. Otherwise, expect clearing skies with
lows in the mid-50s heading into Monday.

Yack

Monday through Friday:

The upper-level low will shift into the western Great Lakes on
Monday. As it does, an embedded impulse rotating around it`s
southern periphery is slatted to foster a period of scattered
afternoon showers and thunderstorms as it tracks across southern
WI and northern IL during peak heating on Monday. Low-level
moisture is not expected to be overly impressive as this impulse
tracks overhead (dewpoints only around 50). However, steepening
low to mid-level lapse rates during peak afternoon heating beneath
of a pool of unseasonably cold temperatures aloft (500 mb temps
of -18 to -20C) look to support ample destabilization (MLCAPE
values of 500 to 800 j/Kg) supportive of thunderstorm chances. We
will have to also keep an eye on the potential for a few stronger
storms capable of producing strong gusty winds across far
northern IL given what looks to be rather well sheared
environment. This threat should wane quickly early Monday evening.

Even outside of the shower and storm chances Monday afternoon,
conditions look to be rather breezy during the day, with WSW to
west winds gusting up to 30 mph. Thereafter, a deamplifying mid-
level ridge is expected to cross the region for the second half of
next week. Accordingly, this will support a period of drier and
warmer weather. Thus, after a cooler start to the work week, with
highs in the low to mid 70s, temperatures are expected to rebound
back into the 80s mid to late week away from any lake cooling.
Shower and some thunderstorm chances may then return to close out
next work week.

KJB

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 104 PM CDT Sat Jun 7 2025

Key Messages:

- 4-7 SM HZ expected today due to wildfire smoke

- Period of SHRA expected late this afternoon through the
  evening, greatest coverage at MDW/GYY with associated VSBY
  reductions.

- 30% chance of TSRA with a cold front Sunday afternoon

Lingering smoke from wildfires in Canada has once again brought
down visibilities across portions of the area to the 4-7 SM
range. For now opted to cover this with 6SM HZ but brief dips to
MVFR VSBYs will be possible through the afternoon.

Scattered shower development is expected this afternoon along
and south of a warm front currently draped near a Dixon to
Joliet to Valparaiso line. This activity will then gradually
lift east northeast into the Chicago area terminals (and
possibly RFD) late afternoon/early evening as a trailing wave
currently over Iowa and Missouri moves over the region. While
showers will be possible areawide, the greatest coverage is
expected south of I-88 (MDW/GYY). Any showers that develop will
be capable of localized heavy downpours leading to VSBY
reductions as low as 1-2SM. For now have maintained MVFR VSBYs
in TEMPO groups this evening though an introduction of lower
VSBYs may become warranted with later updates based on radar and
observational trends.

Heading into the overnight hours, east to southeast winds will
turn light and variable in the wake of the afternoon/evening
showers. If cloud cover manages to clear out fast enough, there
is a low chance for BR/patchy FG toward RFD during the pre-dawn
hours early Sunday morning. Opted to hold off on a formal
mention for now due to lower confidence.

After daybreak winds will increase out of the southwest ahead
of an approaching cold front which will serve as the focus for
thunderstorm development Sunday afternoon. Will account for
this with PROB30s at ORD/MDW at 20-21Z.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002-
     INZ010-INZ011.

LM...None.

&&

$$

Visit us at weather.gov/chicago