Romeoville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

022
FXUS63 KDVN 142309
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
609 PM CDT Wed May 14 2025

.KEY MESSAGES...

- There is a slight chance (15-30%) of isolated showers and
  storms across northern IL this afternoon into the early
  evening. Brief heavy rain and lightning are the main threats
  in the strongest cells.

- A conditional threat for severe storms (level 2 of 5) remains
  Thursday afternoon and early evening across northwest and north
  central IL.

- Humid and breezy conditions with near record warmth Thursday,
  with most locations hitting 90 degrees or higher.

- Active weather returns early next week, with widespread
  beneficial rain possible.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 220 PM CDT Wed May 14 2025

Early afternoon water vapor imagery shows a weak upper low
rotating across eastern MN and western WI with another stronger
upper low upstream centered over northwest WY. Thunderstorms
have developed in western SD in the diffluent flow aloft and in
western WI and eastern MN. At the surface, an area of low
pressure was seen near KLBF in NE, with a warm front extending
east into northern MO. Temperatures at 2pm, were mainly in the
low 80s, with dewpoints in the upper 50s.

Late Afternoon/Evening...building instability and steepening low
level lapse rates may allow for a few isolated showers and
storms to form in northern IL. No severe weather is expected,
but any cells that form will be slow moving bringing heavy rain.
Any activity will quickly dissipate after sunset.

Tonight...the aforementioned warm front will lift north across
eastern IA, northeast MO, and northwest IL. Several CAMs,
including the 12z HRRR, 12z HREF, and 00z MPAS ensemble run
develop a wing of elevated showers and isolated storms
overnight and have maintained slight chance PoPs for this. Steep
mid-level lapse rates over 8C/Km and deep layer shear just over
30kts may support small hail in the strongest cells.
Temperatures overnight will be mild, only dropping into the
upper 60s/low 70s which is what our normal highs are for the
middle of May!

Thursday...a very warm and humid day is expected and our 1st 90
degree day of the year for most locations is likely. 850mb temps
are progged to reach 19-20C, which is close to the daily max per
SPC climatology and in the top 30 soundings for the month of May
for the entire DVN sounding records dating back to Feb 1995.
Other than some cloud debris from early morning activity, deep
mixing up to 850mb should allow for drier dewpoint mix down
keeping heat indices below advisory levels. Have raised highs a
degree or two resulting in near record to record highs for some
in the low 90s. See climate section below. An interesting note
is that the RAP/HRRR runs today are even warmer than current
forecast. Also, I discounted the 12z NAM/NAMNest with its moist
bias showing 71-74 degree dewpoints advecting in tomorrow which
then shows the more aggressive solutions for convection in the
afternoon. A less humid airmass will advect into the CWA late
Thursday, with dewpoints crashing into the upper 40s/low 50s.

Severe Potential

There remains a conditional risk for severe weather during the
late afternoon and evening. IF the capping inversion breaks
between 850-700mb, then severe storms would be possible, with
all hazards in play (many models show loaded gun soundings
tomorrow afternoon along the Hwy 20 corridor). The area to watch
in our CWA for any convective initiation would be north of Hwy
30 in a narrow window between 3 and 7 pm. Forcing increases just
to our north and east ahead of the dryline early evening, so
there is a possibility we may not see any activity at all (most
CAM solutions show this scenario). We will definitely need to be
watch observational and satellite trends tomorrow.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 220 PM CDT Wed May 14 2025

Friday...closed upper low over MN will track east towards Lake
Superior, while another shortwave trough moves east over the central
Plains. A weak surface low will ride along a cold front from
eastern KS into northern MO keeping the 60+ degree dewpoints and
any subsequent severe risk to our southeast. Behind the front,
deep mixing up to 800mb and a strong pressure gradient will
bring gusty westerly winds over 30 mph at times in the
afternoon. Some BUFR soundings even show some near advisory
level winds could be possible with 45kt winds at the top of the
mixed layer for later shifts to monitor. Afternoon highs to top
out in the low to mid 80s.

This Weekend...broad upper level ridge across the central CONUS to
bring us dry and pleasant conditions with comfortable humidity.
Forecast highs are in the 70s and lows in the upper 40s/low 50s.

Early Next Week...a digging western CONUS longwave trough to track
into the central Plains, setting the stage for more active weather.
A favorable thermodynamic and kinematic setup for severe weather is
expected Monday night through Tuesday just to our west with CSU ML
guidance highlighting western IA and western MO under a Slight Risk.
Further details on this will be made available in later forecasts.
In addition, NBM/ECE/GEFS 24-hr rainfall probabilities greater
than 0.50" are in the 50-70% range at this time, which would be
great news for some much needed rain for the CWA.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 604 PM CDT Wed May 14 2025

VFR conditions will prevail through much of the TAF period, with
the chance for MVFR cigs around 1500-2500 ft moving in between
10-15z. There will be a chance for showers/storms moving through
tonight, but have been left out of the TAFs, as confidence
remains low and chances are 20% or less largely. Aside from
that, the main concern will be the winds. We will start out
southeasterly around 10 KTs and remain as such through the
night. Around 12z, winds will start to shift southerly to
southwesterly and increase in speed. Gusts upwards to 25-30 KTs
will be possible by 18z. More chances for showers and storms are
possible after 18z, but confidence remains low on the potential.

&&

.CLIMATE...
Issued at 220 PM CDT Wed May 14 2025

Record High Temperatures:

May 15:
KBRL: 93 / 1944
KCID: 94 / 1941
KDBQ: 90 / 1944
KMLI: 91 / 1941

Record Warm Low Temperatures:

May 15:
KDBQ: 67 / 2001
KMLI: 69 / 2001

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Gross
LONG TERM...Gross
AVIATION...Gunkel
CLIMATE...Gross