Romeoville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

159
FXUS63 KDVN 201926
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
226 PM CDT Sun Jul 20 2025

.KEY MESSAGES...

- Hot and humid conditions will settle across the area by mid-
  week. The probability of heat headlines being needed is high.

- The weather pattern looks to turn very active again late this
  week and over the weekend. The ring of fire may be over the
  area again with the potential for nocturnal storm complexes
  along with the risk for heavy rainfall.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 225 PM CDT Sun Jul 20 2025

The nocturnal storm complex has pushed the effective boundary into
far northern Missouri and central Illinois. Weak downward motion
across eastern Iowa and northern Illinois should limit any diurnal
convection through sunset. Closer to the boundary, isolated to
scattered (20-35%) coverage of showers and storms is possible
through sunset.

Tonight the effective boundary in northern Missouri should be the
focus for new nocturnal storm development. With the tropical
connection to the Gulf much weaker than 24 hours ago and the ground
much drier than further north, any heavy rainfall should be very
localized with the ground being able to soak it up.

On Monday, lingering rain across the far south will continue through
mid-morning before ending. With downward motion occurring in the
atmosphere, the prospects of having any diurnal convection develop
during the afternoon is not promising. However, I cannot rule out
the development of a couple of rogue diurnal convective cells. If
this scenario occurs, areal coverage would be 2 percent at best.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 225 PM CDT Sun Jul 20 2025

Monday night
Assessment...low (<20 percent) confidence of rain occurring

Monday evening will be dependent upon whether or not any diurnal
convection develops Monday afternoon. The model consensus develops a
20 percent chance of late afternoon/evening storms south of I-80. If
no diurnal convection develops Monday afternoon, then the overnight
hours will be completely dry.

Tuesday through Thursday
Assessment...very high (>90%) confidence of hot and humid conditions

The heat dome across the Plains will build into the area for the
Tuesday through Thursday time frame. Anomaly data indicates that
PWATS are minimally 2.5 standard deviations above normal signaling a
high probability for dew points in the mid 70s across the area.
Based on data from the various global models, the probability of
heat indices exceeding 100 degrees is very high and that heat
headlines will eventually be needed during this time frame.

The global models are attempting to start breaking down the heat
dome on Thursday and bring an upper level disturbance into the area.
The model consensus depicts this with a 20-30% chance of afternoon
storms. Given the energy potential that will have built up into the
atmosphere the previous several days, if these storms develop, they
would have the potential to be strong.

Thursday night through Sunday
Assessment...low to medium (20-50%) confidence on organized storm
systems

The global models break down and push the heat dome to the south and
west late this week and over the weekend. At the same time a weak
zonal to northwest flow is developing on the north side of the heat
dome. Such a scenario would place the area in the organized storm
complex track around the edge of the heat dome and along with it the
potential for heavy rainfall.

The model consensus is depicting this with 20-30% chances each day
for rain with the nocturnal/morning time frames favored.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1232 PM CDT Sun Jul 20 2025

Nocturnal convection has pushed the effective boundary to near
the IA/MO border. Any diurnal convection is expected to be
isolated through 00z/21 with the probability of a TAF site being
impacted at 10 or less. After 00z/21 a new round of nocturnal
convection will develop in northern Missouri and move east. Main
impact to eastern Iowa and northern Illinois is the development
of fairly widespread MVFR conditions that would last through
15z/21 before slowly lifting.

&&

.HYDROLOGY...
Issued at 1232 PM CDT Sun Jul 20 2025

What has changed...

New flood warnings have been issued for the English River at
Kalona and for the North Skunk River near Sigourney.

Discussion...

As expected additional bands of 1-3 inches of rainfall with
locally higher amounts fell across parts of eastern Iowa and
Illinois. These bands were generally a bit south of the previous
days heavy rain bands.

Both the Iowa River at Marengo and English River at Kalona will
be going into minor flood. The North Skunk River near Sigourney
will minimally go into minor flood but has roughly a 1 in 3
chance of hitting moderate flood stage. It will take about
another 1-1.5 days to get a better accounting of the runoff in
the North Skunk River basin as to whether or not a low end
moderate flood will be realized near Sigourney.

Precipitation over the next 24 hours will be isolated to
scattered and much further south than the previous two rounds of
heavy rainfall. The tropical connection to the Gulf is still
present but much weaker than 24 hours ago. Thus any heavy
rainfall will be much more localized than the previous two
days.

After tonight and Monday the heat dome will build into the area
which will result in little if any rain Monday night through
Thursday. This time period should allow most rivers to crest and
then be on the downward trend for late this week and into the
weekend. Area river levels are expected to remain above to much
above normal through the end of July.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...08
HYDROLOGY...08