Unrated tornado, Maquoketa Caves Sp, Iowa, April 17, 2026

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

.KEY MESSAGES...

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

- A flood watch has been issued for much of the area through
  tonight for the potential of excessive rainfall with the final
  round of storms this afternoon/tonight. Soils across the area
  are saturated north of I-80 and very moist south of I-80.

- 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 1252 PM CDT Fri Apr 17 2026

Convective initiation has occurred across eastern Iowa. The
individual discrete cells will rapidly grow upscale into one or
more broken lines ahead of the cold front.

The atmosphere is becoming increasingly moist so the storms will
have plenty of fuel to produce heavy rainfall. The axis for the
heavier rain is somewhat narrow but rainfall amounts of an inch
in an hour will be possible with the stronger storms. Where
storms linger or repeat over the same areas, rainfall amounts
of 2 to 3 inches in a short time will be possible.

The pre-frontal line(s) of storms look to push east of the
Mississippi in the 6-8 PM time frame with the cold front
arriving during the mid to late evening hours. Very short range
models which had been pointing to a solid line of storms with
the front are now trending toward a scattered to broken line
with not much thunder associated with it. This 'may' be an
indication the convective allowing models are struggling with
the overall forcing from the upper level system.

The bulk of the rain looks to end across the area by midnight
but scattered rain showers along and immediately behind the
front will linger past midnight. However, the overall trend will
be decreasing areal coverage from west to east after midnight.

&&

.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 1136 AM CDT Thu Apr 16 2026

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...Flood Watch through late tonight for IAZ040>042-052>054-
     064>068-077-078-088-089-099.
IL...Flood Watch through late tonight for ILZ001-002-007-009-
     015>018-024>026-034-035.
MO...Flood Watch through late tonight for MOZ010.

&&

SHORT TERM...08
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