Special Weather Statement, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1241 AM CDT Wed Aug 29 2018

...AVIATION UPDATE...

.UPDATE...
Issued at 914 PM CDT Tue Aug 28 2018

Based on radar trends, the risk of heavy rain has shifted to the
southern half of the area. Thus the flash flood watch has been
cancelled along and north of a line from Iowa, Johnson, Cedar,
Clinton, and Carroll counties.

The severe risk remains across the area, generally south of a line
from North English, IA to Milledgeville, IL.

&&

.SYNOPSIS...
Issued at 103 PM CDT Tue Aug 28 2018

Early this afternoon, an outflow boundary was slowly drifting
south across the CWA. Showers and thunderstorms began to form
along this boundary. Aloft a typical flash flooding pattern was
setup with broad southwest flow from at least H85 to H5. This
brought bountiful moisture into the area, especially. To the west
a H5 wave was located across NE and SD. This setup will continue
to lead to showers and thunderstorms across the area through
overnight and will serve as the main forecast problem in the
extended.

&&

.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 103 PM CDT Tue Aug 28 2018

This afternoon: Current convection appears to still be elevated at
this time. These cores have been popping then dropping. With broad
southwest flow through the area, any wave through the flow is
leading to storms. Couple this with outflow boundaries and you
have the main driver for this afternoons storms. Hires guidance
has been less than stellar in placement of storms as the mesoscale
nature of the forcing is hard to grasp. That said, current
analysis of the environment suggests that there is a wave located
across SW IA that will continue to force storms this afternoon.
The elevated nature of these storms suggest that the main threat
from them will be small hail and heavy rain. This heavy rain may
act to prime the atmosphere for tonights main event, leading to a
flash flood event. At the least, this rain is across areas where
it is badly needed.

This evening: Main threat for severe looks to be tied to the main
wave across NE/SD and associated cold front. Stationary boundary
is expected to become active this afternoon and sweep towards the
east. With an unstable warm sector and sufficient moisture return,
the atmosphere is expected to recharge before this comes through.
Deep layer shear with the wave is forecast to be 40 to 50 kts.
O-3km shear from 00z to 06z is forecast to be near 40 knots nearly
perpendicular to the line. 0-1km shear of 20 to 25 knots. This
shear is perfect for a well defined QLCS with an embedded tornado
threat. There is also a threat for 70 mph wind gusts with any
mesovort that develops. Timing of this line is expected to affect
the area from 6pm in the west to near midnight in the east. Hires
guidance suggests that this line will mature across our CWA and
then weaken as it enters our eastern neighbors CWA.

Also tonight, with high PWATs flash flooding looks possible across
the CWA. As a result will keep the watch going through 12Z
tomorrow.

Tomorrow: Quiet beautiful day. Highs in the 70s with dew points in
the 50s.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 151 PM CDT Tue Aug 28 2018

Slight changes to the long term were made this period with overall
pattern unchanged. No main changes to the superblend were made.
Quiet weather with below average temperatures Wednesday and
Thursday. Then the chance for rain and storms return for the end
of the week. With this expect the return of humidity and heat as
well. It does not appear that the heat will be as high as this
last weekend, more like average temps.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1238 AM CDT Wed Aug 29 2018

MVFR/VFR conditions associated with a convective complex will
slowly deteriorate to more widespread MVFR/IFR conditions through
12z/29. After 12z/29 conditions will slowly improve to VFR as high
pressure slowly builds into the Midwest.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flash Flood Watch until 7 AM CDT this morning for Des Moines-
     Henry IA-Jefferson-Keokuk-Lee-Louisa-Muscatine-Scott-Van
     Buren-Washington.

IL...Flash Flood Watch until 7 AM CDT this morning for Bureau-Hancock-
     Henderson-Henry IL-McDonough-Mercer-Putnam-Rock Island-
     Warren-Whiteside.

MO...Flash Flood Watch until 7 AM CDT this morning for Clark-Scotland.

&&

UPDATE...08
SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...08

Hazardous Weather Outlook...UPDATED
National Weather Service Quad Cities IA IL
923 AM CDT Tue Aug 28 2018

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-291430-
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-
923 AM CDT Tue Aug 28 2018

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

A Heat Advisory is in effect for the counties approximately along
and south of a line from Sterling, Illinois to the Quad Cities to
Washington, Iowa. In this area, peak heat indices are forecast
near 100 F.

Thunderstorms are expected area wide today. Some of these storms
could be severe with the main threats being damaging winds, heavy
rain and isolated tornadoes. Large hail is a secondary threat. A
flash flood watch is in effect across the area through 7 am
Wednesday.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Periods of thunderstorms are possible late Thursday through
Monday. It is too early to determine the potential for severe
weather.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is likely from 2 PM to 10 PM today.

Special Weather Statement
National Weather Service Quad Cities IA IL
1130 PM CDT Tue Aug 28 2018

IAZ089-098-099-ILZ025-026-034-035-MOZ009-010-290630-
Des Moines-Van Buren-Lee-Henderson-Warren-Hancock-McDonough-
Scotland-Clark-
Including the cities of Burlington, Keosauqua, Fort Madison,
Oquawka, Monmouth, Carthage, Macomb, Memphis, and Kahoka
1130 PM CDT Tue Aug 28 2018

...Thunderstorms With Heavy Rain Continue Overnight..

Heavy rain will continue into the early morning hours, mainly
south of a line from Memphis Missouri, through Burlington Iowa
and Monmouth Illinois. Additional rainfall amounts of an inch or
two are possible over much of this area. Expect ponding water on
roads and minor street flooding. Do not drive through water
covered roads, which can be especially dangerous at night.

Storms will also produce cloud to ground lightning and possibly
isolated wind gusts up to 40 mph.

RP Kinney

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1136 PM CDT TUE AUG 28 2018

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

0950 PM     HEAVY RAIN       2 WSW YARMOUTH          41.02N 91.35W
08/28/2018  M5.10 INCH       DES MOINES         IA   TRAINED SPOTTER

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1139 PM CDT TUE AUG 28 2018

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

0930 PM     TSTM WND DMG     3 E COLMAR              40.35N 90.83W
08/28/2018                   MCDONOUGH          IL   TRAINED SPOTTER

            TREE AND POWER LINE DOWN.

&&

UTTECH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1141 PM CDT TUE AUG 28 2018

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

1140 PM     HEAVY RAIN       CANTRIL                 40.64N 92.07W
08/28/2018  M3.40 INCH       VAN BUREN          IA   TRAINED SPOTTER

            STORM TOTAL PAST 12 HOURS.

&&

UTTECH

Special Weather Statement
National Weather Service Quad Cities IA/IL
126 AM CDT WED AUG 29 2018

ILC109-290715-
McDonough-
126 AM CDT WED AUG 29 2018

...A THUNDERSTORM PRODUCING HEAVY RAIN WILL AFFECT SOUTHERN MCDONOUGH
COUNTY UNTIL 215 AM CDT...

At 123 AM CDT, radar indicated a thunderstorm with heavy rain was
located near Colmar, or 14 miles southwest of Macomb, moving east at
40 mph.

Areal flooding is possible, including ponding of water in low lying
areas and flooding near creeks and streams. In addition, winds in
excess of 30 mph are possible.

Locations impacted include...
Industry, Adair, Fandon, Colmar, Plymouth and Pennington Point.

Torrential rainfall is also occurring with the thunderstorm with
heavy rain, and may cause localized flooding. Do not drive your
vehicle through flooded roadways.

Minor flooding is possible. If you are driving and encounter a
flooded roadway, Turn around, don't drown. Most flood deaths occur in
vehicles.

LAT...LON 4029 9091 4038 9091 4046 9045 4028 9045
TIME...MOT...LOC 0623Z 254DEG 35KT 4030 9083

Uttech

Special Weather Statement
National Weather Service Quad Cities IA/IL
221 AM CDT WED AUG 29 2018

ILC067-290800-
Hancock-
221 AM CDT WED AUG 29 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHERN HANCOCK COUNTY
UNTIL 300 AM CDT...

At 220 AM CDT, radar indicated strong thunderstorms were located
along a line extending from near Kahoka to near Canton to 6 miles
northwest of Palmyra. Movement was east at 45 mph.

Winds in excess of 40 mph are possible with these storms.

Locations impacted include...
Augusta, Bowen, West Point, Denver, Tioga and Stillwell.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 4021 9151 4027 9149 4031 9097 4019 9094
TIME...MOT...LOC 0720Z 255DEG 38KT 4035 9177 4015 9161 3986 9161

Uttech