Severe Thunderstorm Warning 97, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1229 PM CDT Fri Apr 17 2026

.KEY MESSAGES...

- A strong storm system will bring the threat for severe storms
  once again to our area this afternoon and evening. SPC
  continues to highlight nearly our entire area in an Enhanced
  Risk (level 3 of 5) for severe weather.

- Much cooler conditions are expected this weekend. Unseasonably cool
  temperatures in the 30s Saturday night and Sunday night will
  bring the potential for frost/freeze, especially in our north.

- Area rivers are on the rise from the recent rounds of heavy
  rain, and heavy rainfall later today may push them even
  higher. Refer to the hydro section below for more details.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 306 AM CDT Fri Apr 17 2026

Our active period of severe weather this week concludes today as yet
another strong storm system approaches the area this afternoon and
evening. An upper-level longwave trough over the northwestern CONUS
will continue to translate eastward today, along with a southern
stream impulse that will lift over our region this afternoon from
the southern Great Plains. A warm/humid air mass will build over the
area today, characterized by high temperatures warming to the upper
70s/lower 80s and dew points in the mid/upper 60s, should provide
ample destabilization, with the 17.00z HREF ensemble mean progging
SBCAPE values around 2500 to 3500 J/kg this afternoon before
thunderstorm initiation. To the west, behind the approaching trough,
is a surface cold front that will also approach the area this
afternoon and act as a secondary mechanism for thunderstorm
initiation. Storms are progged to fire off along the pre-frontal
trough first approximately along the Mississippi River, with storms
initially more discrete in nature. Given steep mid-level lapse
rates, ample low-level SRH, and STP values around 2 to 4, large hail
and strong tornadoes will be the primary hazards with these initial
storms. The second area of convective initiation, along the cold
front slightly farther west, will also occur this afternoon, so
we're talking about two distinct areas of storm initiation. Now,
while the storms that are progged to develop along the cold front
will initially be discrete, they should grow upscale quickly into a
QLCS, becoming more of a damaging wind threat. This line of storms
should sweep through the area quickly once they grow upscale. SPC
continues to highlight nearly our entire CWA within an Enhanced Risk
(level 3 of 5) for severe weather today. Prior to the storms, gusty
southerly winds will also be in place, with gusts around 40 mph.

As mentioned, all hazards are possible with today's severe weather
threat, with a few strong tornadoes and significantly strong
damaging winds becoming the main threats. Even after the storms
develop into the QLCS late this afternoon into the early evening,
the tornado threat doesn't appear to go away entirely as 0-3 km
layer shear magnitudes appear strong enough along and north of
Interstate 80 (35+ knots) to support mesovortex genesis if
there are any northeastward surges/bowing segments to take
advantage of the low-level shear.

One other hazard that can't be ruled out is flash flooding, thanks
to Pwat values in the 1 to 1.5 inch range, along with wet antecedent
conditions. If storms can train over the same area, particularly
once the QLCS develops, then flash flooding is a possibility, and
there remains a Slight Risk (level 2 of 4) for flash flooding,
mainly for areas along and south of a Sigourney, IA to Dubuque, IA
line.

Eventually, severe storms will wane or move off to the east late
this evening as the cold front sweeps through the area. Dry
conditions should return by sunrise Saturday, with low temperatures
falling to the lower 30s along the I-380 corridor to near 40s over
west-central Illinois.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 306 AM CDT Fri Apr 17 2026

Much colder air will continue to move into the area for the weekend
as a northwest flow pattern develops aloft. An area of high pressure
will build into the area Saturday night, which could set up our
first bout of frost/freeze conditions during the growing season.
There does appear to be a mid-level trough sweeping through the area
Saturday night, which could result in some cloud cover that could
keep our temperatures from falling too much, limiting our
frost/freeze potential. Despite this, the NBM probabilities of
freezing temperatures Saturday night are still around 50-80% along
and north of Interstate 80. Another night of frost/freeze conditions
are possible Sunday night as well, with similar exceedance
probabilities for freezing temperatures.

A quieter weather pattern will persist into early next week as a
broad upper ridge remains in place through the central US. A larger
trough begins to take shape across the western US into the latter
portion of the week. Therefore, some warming and a move toward some
smaller precipitation chances (20-40%) start to return to the area
by Thursday with a larger storm system potentially nearing the
region for Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1225 PM CDT Fri Apr 17 2026

Convective initiation has begun over eastern Iowa with surface
winds gusting to 30 knots. Very short range models indicate
rapid upscale growth of TSRA through 00z/18. Discrete TSRA cells
will grow upscale into a line that congeals along the
Mississippi River by 00z/18. Based on forecast soundings,
probability is high for wind gusts over 50 knots with the
discrete cells and as the line forms. By 06z/18 the cold front
will have swept through the area with widespread MVFR conditions
and winds gusting up to 25 knots.

&&

.HYDROLOGY...
Issued at 312 AM CDT Fri Apr 17 2026

What has changed...

River flood warnings have been issued for the Rock River from
Como down to the mouth.

River flood warnings have been issued for the lower Iowa River
at Wapello and Oakville along with the Cedar River near
Conesville.

River flood warnings are now in effect for the Mississippi River
from Muscatine down through Burlington and for Gregory Landing.

A river flood watch has been issued for the Mississippi River at
Dubuque.

Discussion...

Over the past five days, multiple rounds of heavy rain have
impacted eastern Iowa, northern Illinois and southern Wisconsin.
Rainfall amounts have run from 2 to 5 inches of rain; much of
this rain has been north of Highway 30.

Another round of heavy rain is forecast this afternoon and
evening with amounts running from a half inch to around 1.5
inches. With area soils running from moist to near saturation,
this additional rainfall will quickly run off into area
waterways resulting in new or increased river flooding along
with the potential for flash flooding.

Much of this rain is forecast to fall across southeast Iowa,
west central Illinois and into northern Illinois. River basins
impacted would be the Rock, lower Iowa, Skunk, Des Moines and La
Moine.

Rock River...

Based on overall river forecasts and another round of heavy rain
expected today, confidence is high (>80%) that the entire
length of the Rock River will reach flood stage by the weekend
and remain above flood stage into much of next week.

Mississippi River...

Routed flow coming down from the upper Mississippi, Wisconsin,
Rock, Iowa and other tributary rivers will cause general rises
along the length of the Mississippi. Based on the current routed
flow and another round of heavy rain, confidence is high (>80%)
that the Mississippi will reach flood stage from Muscatine down
through Keithsburg and at Gregory Landing. Gladstone and
Burlington are already above flood stage and will see additional
rises as the additional routed flow arrives over the weekend
and into next week.

Iowa Tributary Rivers...

Rivers in eastern Iowa are running high from the rounds of heavy
rain. Flood warnings continue for the lower Wapsipinicon River
near DeWitt and the Iowa River above Coralville near Marengo.
Based on routed flow, the lower Cedar River near Conesville will
go above flood stage over the weekend.

The North Skunk River near Sigourney is forecast to go above
flood stage tonight with general rises expected farther
downstream and on the Skunk River.

&&

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

&&

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

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
323 AM CDT Fri Apr 17 2026

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-180900-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
323 AM CDT Fri Apr 17 2026

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...TODAY AND TONIGHT

An Enhanced Risk (Level 3 of 5) for severe weather remains in
place across the area for this afternoon and evening. Damaging
winds and tornadoes, some possibly strong, are the primary
threats. Localized flash flooding is also possible.

Southerly winds will gust to around 40 mph this afternoon prior to
the severe thunderstorm development.

Area rivers are experiencing flooding. Please see the latest Flood
Statements and Flood Warnings for details.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

Much colder air will bring the potential for frost and freeze
conditions to parts of the area Saturday night and Sunday night.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is likely for this afternoon and evening.

JTS