Flooding in Iowa, May 1 to 31, 2019

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1234 AM CDT Wed May 1 2019

...06z AVIATION UPDATE...

.UPDATE...
Issued at 924 PM CDT Tue Apr 30 2019

Have updated the flash flood watch to trim the northern tier of
counties, that were north of the main axis of heavy rainfall
earlier today. This area will likely be on the periphery of another
round of rain currently lifting northeast out of northern MO into
southeast Iowa and overnight QPF should be less than a quarter
inch. Will keep the remainder of the watch going for now, with
a remaining low threat over mainly southeast Iowa and west
central MO, where heavier rain occurred today. Operational and
high res models still show rainfall in this area of .25 to perhaps
.75 possible overnight into Wednesday morning.

&&

.SYNOPSIS...
Issued at 323 PM CDT Tue Apr 30 2019

In similar fashion to yesterday, yet another shortwave and
attendant rain shield is seen exiting in the afternoon
toward the Ohio Valley. This brought another round of moderate
to heavy rainfall of 0.5 to 1.5+ inches to areas along and
especially south of I-80, with the heaviest in a swath from
Keosauqua, IA to Galva, IL. While rain rates haven't been
particularly impressive, the rainfall is occurring on very
saturated ground and leading to additional flooding and isolated
flash flooding. Warm front is situated near the I-70 corridor
in MO extending to weak lobes of low pressure over eastern KS
into OK. Low pressure organizing in the Plains will lift
northeast along with the warm front bringing the threat
for additional showers and storms over the next 12-18+ hours.

&&

.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 323 PM CDT Tue Apr 30 2019

Forecast focus on chances for more heavy rain and low risk of
severe storms, both appear to be focusing mainly across our
south.

Obs/trends support general model consensus of low pressure
consolidating in the Plains attendant to an ejecting shortwave
and right upper jet entrance region. The low and warm front
would then translate northeast across portions of the region
later tonight into Wed AM, accompanied by additional showers
and chance of storms and potential for more moderate to locally
heavy rain. Have gone with an average of 0.3 to 0.75 inches
of additional rain through Wed AM, with the heaviest focusing
south of Quad Cities as it looks right now. With these areas
having already seen moderate to heavy rain today and being very
saturated, it won't take much additional rain to lead to
additional flooding and flash flooding issues even though the
rates may again not be impressive. Thus, the flash flood watch
will remain in effect. Considerable uncertainty does exist with
additional rainfall amounts, as surface based convection on warm
front could interrupt robust WAA and theta-e advection impacting
location/magnitude of additional rains and focusing heaviest
rainfall amounts south of the area. Severe weather risk appears
very low across the south, with unfavorable timing of warm front
and stabilizing boundary layer likely negating any damaging wind
potential. Isolated marginal severe hail may once again be the
main threat. Temperatures look to be fairly steady if not rise a
bit late tonight.

Wednesday will see rain chances decreasing during the morning.
Still a small chance of a shower or weak storm in the afternoon
far south/east ahead of weak cool front. Otherwise, clouds
giving way to a few peeks of sunshine and warmer temperatures in
the upper 50s to upper 60s.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 323 PM CDT Tue Apr 30 2019

Wednesday night and Thursday, 12Z Tuesday model runs indicate that
rain will continue to fall over the region Wednesday night and
Thursday. The amount of rain depends on how far a surface boundary
remains to our south. GFS/ECMWF models are in good agreement in
placing this boundary over southwestern Missouri northeast across
central Illinois and into Michigan. On Thursday morning, an upper
level trof will approach the region with a surface wave developing
on this boundary which will move northeast. Significant rain is
possible over the southeastern part of the forecast area with
precipitable water values ranging between 1.0 to 1.3 inches. High
temperatures on Thursday will be in the upper 50s across the north
with mid 60s over the south.

Friday through Sunday, A shortwave ridge aloft will bring a reprieve
from the unsettled weather with surface high pressure building into
the region. Most of the area will be mainly dry with high
temperatures approaching 70 degrees. However, another upper level
trof will approach the region Sunday evening which could produce
scattered showers or perhaps a thunderstorm.  Areal coverage of
these storms should be limited. Low temperatures will be in the mid
40s to low 50s.

Early next week, Forecast confidence is low. The model blend suggest
the unsettled pattern will continue, but there are differences on
where the active zone sets up. High temperatues will be in the
60s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1228 AM CDT Wed May 1 2019

Stratiform rain band starting to move east of the TAF sites. but
in it's wake will linger IFR to LIFR conditions into Wed morning
wiht low CIGs, and VSBYs reduced by fog and drizzle. Strong east
to northeast sfc wind wake low surge with gusts up to 35 KTS will
affect the TAF sites through 1 to 2 AM at the longest, before
backing more northerly to 5-12 KTs into Wed morning. Some of the
sctrd shower activity now acrs northwestern IA, may get into the
VCNTY of CID and DBQ from 5 to 8 AM Wed morning. Otherwise some
improvement in CIGs rising through the MVFR realm through Wed
afternoon, and possibly a bout of VFR Wed evening. Then more sctrd
showers possibly moving in from the south and getting into the
VCNTY of BRL toward the end of the TAF cycle.   ..12..

&&

.HYDROLOGY...
Issued at 1030 PM CDT Tue Apr 30 2019

Today's axis of rainfall of a half inch or more was roughly south
of a line from Sigourney through DeWitt to Freeport, with heaviest
amounts mainly south of I-80. Radar estimates showed the heaviest
totals of 1 to 2 inches or more concentrated along and south of an
axis from Fairfield to Kewanee. With saturated soils from heavy
heavy rainfall over the past several days, runoff has contributed
to further flooding along tributary rivers and exacerbated on-
going major flooding along the Mississippi River.

Latest indications suggest there will be one more round of mainly
light to moderate rain, lifting northeast across northeast
Missouri, southeast Iowa into west central Illinois through
midnight, with rainfall totals in the range of a quarter to near
three quarters of an inch. Additional showers will be possible
toward morning with a weaker wave lifting E-NE out of Nebraska,
but heavy rain is not likely with this round. Most of Wednesday
then looks dry.

On the Mississippi River: Major flooding is on-going at all sites
except Gregory Landing, where Moderate flooding is occurring.
Latest river forecasts, updated this afternoon and maintained
this evening, have made significant upward adjustments to crests,
especially from the Rock Island downstream. Upstream, the crest
appears to be reaching Fulton and minor downward adjustments to
crests were noted at Comanche and Le Claire.

At Rock Island, LD 15, the forecast crest was adjusted in an
update this afternoon to 22.4 feet, occurring Wednesday night. This
would be just shy of the record crest of 22.63 feet from July
1993. Further downstream, forecasts this afternoon and this
evening, adjusted for the runoff now the system and anticipated
rainfall tonight have resulted in earlier crests, which in many
locations were significantly higher than forecasts from just
this morning. However, none at this time were approaching record
stages.

On the tributaries:

In the Rock River basin, Major flooding is now expected at Moline
Wednesday, while Moderate flooding is forecast upstream at
Joslin. The Green River was also showing a rapid response with
Moderate flooding occurring this evening and is expected to reach
Major flooding Wednesday afternoon.

On the Iowa tributaries: Moderate flooding is occurring at
DeWitt, where levels are expected to crest Wednesday. Moderate
flooding is also expected on the Iowa River at Oakville, Skunk
River at Augusta and St Francisville of the Des Moines River.

The La Moine River at Colmar has been rising rapidly over the past
6 hours and is expected to crest just into Moderate flood stage on
Wednesday.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flash Flood Watch through this afternoon for Des Moines-Henry IA-
     Jefferson-Lee-Louisa-Muscatine-Scott-Van Buren-Washington.

IL...Flash Flood Watch through this afternoon for Bureau-Hancock-
     Henderson-Henry IL-McDonough-Mercer-Putnam-Rock Island-
     Warren-Whiteside.

MO...Flash Flood Watch through this afternoon for Clark-Scotland.

&&

UPDATE...Sheets
SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...Kuhl
AVIATION...12
HYDROLOGY...Sheets

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
355 PM CDT Tue Apr 30 2019

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-012100-
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-
355 PM CDT Tue Apr 30 2019

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...LATE THIS AFTERNOON AND TONIGHT

Additional showers and a few thunderstorms are expected across
the outlook area tonight. The main threat associated with these
thunderstorms will be heavy rain, lightning and small hail.
There is low risk of an isolated severe storm south of I-80
tonight, with the primary threat marginal severe hail.

There is a flash flooding threat tonight. The best chance for
flash flooding looks to be along and south of a line from Iowa
City to Clinton to Milledgeville. A flash flood watch is in effect
for this area through the Wednesday morning.

Moderate to major flooding will continue along the Mississippi
River and other tributary rivers. Please see the latest Flood
Statements and Flood Warnings for details.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Thunderstorms are expected to exit the Illinois side of the
Outlook area off to the east by late Wednesday morning. These
storms are not anticipated to be severe, but may produce locally
heavy rain adding to flooding potential.

More rain with embedded thunderstorms and moderate rainfall
amounts may move across portions of the Outlook Area from late
Wednesday night and Thursday. This activity may aggravate ongoing
flooding situations. The potential for severe storms on Thursday is
low.

Moderate to major flooding will continue along the Mississippi
River. Some tributary rivers will also be in flood. Please see
the latest Flood Statements and Flood Warnings for details.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated tonight. Any reports of
flooding would be appreciated.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
703 PM CDT TUE APR 30 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0702 PM     HEAVY RAIN       1 NW DAVENPORT          41.56N 90.61W
04/30/2019  M1.11 INCH       SCOTT              IA   TRAINED SPOTTER

            12 HOUR TOTAL

&&

DC