Special Weather Statement, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1221 PM CDT Wed Jul 14 2021

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 210 AM CDT Wed Jul 14 2021

All was quiet across eastern Iowa, northwest Illinois and far
northeast Missouri early this morning. Other than an isolated rain
shower over northwest Illinois, skies were largely clear to partly
cloudy thanks to a weak ridge of high pressure overhead.
Temperatures were warm thanks to renewed southerly flow, with
temperatures as of this hour in the upper 60s to low 70s area wide.

Off to the west, showers and storms were ongoing from South Dakota
to Nebraska; fueled by a strong LLJ and shortwave centered over
southeast Montana. Hints of a developing surface low were apparent
on MSAS pressure fall maps across northeast Colorado. These features
will all come together and impact our weather heading into the short
term period.

&&

.SHORT TERM...(Today through Thursday)
ISSUED AT 210 AM CDT Wed Jul 14 2021

[Key Messages]

*Threat for severe thunderstorms today and Thursday as cold front
and shortwave slowly move through the area

*All severe hazards possible including torrential rainfall
which could produce flash flooding

[Discussion]

A busy short term period is expected across all of eastern Iowa,
northwest Illinois, and far northeast Missouri. Showers and storms
currently in place from South Dakota to Nebraska will work their way
east, eventually finding their way to northeast Iowa, southeast
Minnesota and southwest Wisconsin. These should be elevated for the
majority of the duration as they feed off off a fairly potent and
moisture filled eastward moving 30-40 kt LLJ.

These storms are progged by the CAMs to reach that area during the
midday hours (11am-2pm), and should have decent coverage to them as
the LLJ is forecast to not lose too much strength despite the
increasing daytime heating. Storms are likely to impact areas mainly
along and north of the Hwy 20 corridor before eventually moving out
of the area by the mid-afternoon. These could become strong as they
move into an area untapped with some heating and become surface
based, but this threat is likely to remain more into southwest
Wisconsin. This activity should leave an outflow boundary behind
across the area, which will be the focus for additional storm
development during the late afternoon and evening.

While clouds are expected to increase across the area thanks to the
morning convection, they should not pose much of a hindrance to
afternoon/evening development. This is due to the approaching
shortwave in northwest flow aloft, with some pockets of CVA due to
move into the area during this time frame. Forecast soundings show
mid-level lapse rates steepening in response to the approaching
shortwave, and when combined with added convergence from the remnant
outflow boundary, approaching surface front and deepening surface
low moving into Iowa this should be enough to induce late afternoon-
evening storm development.

Think where that outflow boundary sets up will be crucial to where
severe weather is most favored across our area. As is typical in
most of these situations, CAMs are not in good agreement on
placement of the late afternoon/evening formation in the latest runs
due to disagreements on handling of the morning MCS activity. But
there are a couple of potential scenarios:

1) There is a signal in some CAMs that the outflow boundary sets up
around the Hwy 20 to Hwy 30 corridor, in a zone that will be
relatively uninterrupted by morning storms. If this were to hold,
potential would be there w/ the increased convergence of discrete
storms to start (latest runs of the HRRR showing this potential).
Surface instability forecast to climb into 2000-3000 J/kg range with
increasing shear due to the approaching shortwave and LLJ would
favor all severe hazards to start. Eventually, developing storms
would merge and pose more of a damaging wind and torrential rain
threat into the evening hours as cold pool processes take over.

2) With the deepening low pressure to our west, there is an added
option that the leftover outflow boundary gets shunted back north by
strengthening southerly flow near to or just north of the Hwy 20
corridor. This would favor more discrete storms and the favored
tornado/hail threat back into northern and northeast Iowa, with our
area more likely to be impacted by damaging winds and torrential
rain during the late evening. This is the scenario I'm leaning
more towards with this package.

Therefore, much of today's severe threat is deeply tied to the
mesoscale and will likely undergo more changes as the morning
progresses. As of early this morning, the Storm Prediction Center
maintains a Level 3 (enhanced risk) for severe thunderstorms
generally along and north of Hwy 30, with a Level 2 (slight risk)
north of a line from Sigourney IA to Dixon IL.

Eventually, the severe threat should wane overnight as precip
transitions into a more typical MCS setup for the area. Activity
should focus more on the convergence zone of the LLJ and southward
moving cold front, which is forecast to reach the northwest CWA
during the early morning Thursday. The threat will then turn to
torrential rain, as the added convergence of the LLJ/front a
moisture filled PWAT feed from the south focus on the area.

There is good news and bad news. The good news, is that area FINALLY
gets some needed rain. However, it's going to be falling all at once
and quickly, given the deep warm cloud depths and high amount of
moisture. Because the soil is hard and not as permeable due to the
drought conditions, there is likely to be more runoff than not,
making for a higher potential for flash flooding concerns. This is
reflected well in the WPC excessive rainfall outlook, which paints
areas north of I-80 in a Level 2 (slight risk). Given CAM
uncertainty of where the favored convergence zone sets up, decided
against a flash flood watch for the level 2 area at this time.
However, this will be further analyzed later.

Thursday is likely to be a raw day for most of us as the cold front
slowly moves through the area. The persistent LLJ will add
convergence along the front, meaning POPs are going to remain at
"likely" or higher for most of us during the day. Late in the
afternoon, there is potential for a new round of strong and severe
storms, with a focus on I-80 south. The Storm Prediction Center
maintains a Level 1 (marginal risk) for this area in their Day 2
outlook. This will need to be watched closely, as the stronger lift
with the shortwave and jet equatorial entrance region will be
overhead and will work with the front. Debris from earlier activity
is the main thorn in this potential as it could hinder some
development, but think the added lift could fire activity
regardless. All severe hazards will be in play, especially potential
for flash flooding given this area has been hit pretty hard w/
rain in recent weeks.

.LONG TERM...(Thursday Night through Tuesday)
ISSUED AT 210 AM CDT Wed Jul 14 2021

Key messages:

1. Change in pattern to a more quiet weather period.
2. Temperatures in the 80s return for the weekend.

Discussion:

Largescale ridging is forecast to move into the area at the beginning
of the period.  This ridging is forecast to last through the period,
bringer quieter weather with it.  Guidance has one of the NW flow
waves become cutoff south of the area.  This cutoff low may lead to
chances for pops just south of the area.  The placement of this low
could change and with it our chance for precip in the extended.

Friday looks the 'best' day for precip in the extended with the cold
front just south of the area.  While we will be north of the surface
front, a NW flow wave along with the left entrance region of the jet
could be enough for some showers across the area.  QPF looks like
and should not be all that impactful across the area.

From a sensible weather aspect, temperatures are forecast to be in
the 80s with current blend Tds just below 70.  With the corn, these
Tds may be too low.  Summer heat and humidity look to be the main
story next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1214 PM CDT Wed Jul 14 2021

Showers and thunderstorms are ongoing as of 18Z, impacting near
DBQ and MLI. These will continue through 20Z, with a break until
this evening. These storms are bringing along MVFR conditions,
with IFR in some of the heavier storms. Also, some of the storms
this evening can lead to gusts up to 50 KTs and hail. Winds will
stay from the south through tonight and tomorrow morning, with
gust upwards to 20-25 KTs. Again tomorrow, widespread showers and
storms are expected.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

SYNOPSIS...Speck
SHORT TERM...Speck
LONG TERM...Gibbs
AVIATION...Gunkel

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
303 AM CDT Wed Jul 14 2021

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-150815-
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-
303 AM CDT Wed Jul 14 2021

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

The Storm Prediction Center has an enhanced risk for severe
thunderstorms along and north of a Freeport, Illinois to Belle
Plaine, Iowa line. There is a slight risk as far south as a
Mendota, Illinois to Ottumwa, Iowa line.

Super cells and organized bowing segments are likely ahead of a
slow moving cold front, especially in the afternoon and evening.
The main threats will be damaging winds, large hail and isolated
tornadoes. There is the potential for flash flooding especially
where slow moving thunderstorms move repeatedly over the same
areas.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

Thursday, there is a marginal risk for severe storms south of a
Rockford, Illinois to Bloomfield, Iowa line. The main threats will
be strong winds and large hail.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed today and tonight.

Special Weather Statement
National Weather Service Quad Cities IA/IL
1215 PM CDT Wed Jul 14 2021

ILC085-IAC045-061-097-105-141745-
Jo Daviess-Jackson-Dubuque-Jones-Clinton-
1215 PM CDT Wed Jul 14 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT WESTERN JO DAVIESS...
JACKSON...DUBUQUE...NORTHEASTERN JONES AND NORTHERN CLINTON COUNTIES
UNTIL 1245 PM CDT...

At 1214 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Balltown to near Lost Nation.
Movement was east at 30 mph.

Wind gusts up to 50 mph and pea size hail are possible with these
storms.

Locations impacted include...
Dubuque, Clinton, Maquoketa, Galena, Asbury, Bellevue, Epworth, East
Dubuque, Peosta, Preston, Delmar, Lost Nation, Andrew, Charlotte, La
Motte, Menominee, Rickardsville, Sherrill, Welton and Monmouth.

Torrential rainfall is also occurring with these storms. Minor
flooding of low lying areas, creeks, streams and urban areas is
possible. If you encounter water over a roadway, do not drive through
it.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4265 9074 4263 9070 4259 9069 4254 9064
      4251 9064 4251 9040 4184 9030 4184 9085
      4265 9098 4265 9090 4268 9090
TIME...MOT...LOC 1714Z 259DEG 25KT 4266 9091 4193 9079

DC

Special Weather Statement
National Weather Service Quad Cities IA/IL
107 PM CDT Wed Jul 14 2021

ILC073-131-161-IAC045-163-141845-
Rock Island-Mercer-Henry-Scott-Clinton-
107 PM CDT Wed Jul 14 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT EASTERN ROCK ISLAND...
NORTH CENTRAL MERCER...NORTHWESTERN HENRY...SCOTT AND SOUTHEASTERN
CLINTON COUNTIES UNTIL 145 PM CDT...

At 107 PM CDT, radar indicated strong thunderstorms were located
along a line extending from Reynolds to near Donahue. Movement was
northeast at 45 mph.

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

Locations impacted include...
Davenport, Moline, Rock Island, Bettendorf, Clinton, East Moline,
Silvis, Eldridge, DeWitt, Colona, Milan, Camanche, Le Claire, Coal
Valley, Hampton, Port Byron, Walcott, Blue Grass, Buffalo and
Andalusia.

This includes the following highways...
 Interstate 74 in Iowa between mile markers 1 and 5.
 Interstate 80 in Iowa between mile markers 287 and 306.
 Interstate 80 in Illinois between mile markers 1 and 12.
 Interstate 74 in Illinois between mile markers 1 and 15.
 Interstate 88 between mile markers 1 and 2.
 Interstate 280 between mile markers 1 and 18.

Torrential rainfall is also occurring with these storms. Minor
flooding of low lying areas, creeks, streams and urban areas is
possible. If you encounter water over a roadway, do not drive through
it.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4143 9029 4191 9031 4177 9074 4123 9078
TIME...MOT...LOC 1807Z 236DEG 37KT 4130 9068 4165 9071

Uttech

Special Weather Statement
National Weather Service Quad Cities IA/IL
113 PM CDT Wed Jul 14 2021

ILC015-085-161-177-195-IAC045-097-163-141845-
Rock Island-Whiteside-Jo
Daviess-Carroll-Stephenson-Jackson-Scott-Clinton-
113 PM CDT Wed Jul 14 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHEASTERN ROCK
ISLAND...NORTHERN WHITESIDE...JO DAVIESS...CARROLL...STEPHENSON...
SOUTHEASTERN JACKSON...NORTHEASTERN SCOTT AND EASTERN CLINTON
COUNTIES UNTIL 145 PM CDT...

At 113 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Apple River to near Clinton.
Movement was east at 35 mph.

Wind gusts up to 50 mph and pea size hail are possible with these
storms.

Locations impacted include...
Clinton, Freeport, Sterling, Rock Falls, Morrison, Mount Carroll,
DeWitt, Camanche, Fulton, Savanna, Lena, Stockton, Lanark, Warren,
Garden Plain, Milledgeville, Preston, Fairhaven, Albany and Hanover.

This includes Interstate 88 between mile markers 26 and 44.

Torrential rainfall is also occurring with these storms. Minor
flooding of low lying areas, creeks, streams and urban areas is
possible. If you encounter water over a roadway, do not drive through
it.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4250 8943 4220 8951 4220 8969 4193 8969
      4193 8963 4172 8963 4173 9055 4251 9032
TIME...MOT...LOC 1813Z 268DEG 29KT 4250 9004 4187 9026

DC

Special Weather Statement
National Weather Service Quad Cities IA/IL
147 PM CDT Wed Jul 14 2021

ILC011-073-161-195-IAC045-163-141915-
Rock Island-Whiteside-Henry-Bureau-Scott-Clinton-
147 PM CDT Wed Jul 14 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT EASTERN ROCK ISLAND...
WHITESIDE...NORTHERN HENRY...NORTHWESTERN BUREAU...EAST CENTRAL SCOTT
AND SOUTHEASTERN CLINTON COUNTIES UNTIL 215 PM CDT...

At 147 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Garden Plain to near Warner.
Movement was east at 40 mph.

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

Locations impacted include...
Clinton, East Moline, Sterling, Morrison, Silvis, Geneseo, Colona,
Camanche, Le Claire, Coal Valley, Prophetstown, Hampton, Orion, Port
Byron, Erie, Garden Plain, Atkinson, Rapids City, Albany and
Princeton.

This includes the following highways...
 Interstate 80 in Iowa between mile markers 305 and 306.
 Interstate 80 in Illinois between mile markers 1 and 33.
 Interstate 74 in Illinois between mile markers 9 and 22.
 Interstate 88 between mile markers 1 and 39.

Torrential rainfall is also occurring with these storms. Minor
flooding of low lying areas, creeks, streams and urban areas is
possible. If you encounter water over a roadway, do not drive through
it.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4143 8979 4130 9043 4133 9043 4133 9044
      4182 9035 4189 8970
TIME...MOT...LOC 1847Z 253DEG 37KT 4184 9009 4138 9027

Uttech

Special Weather Statement
National Weather Service Quad Cities IA/IL
203 PM CDT Wed Jul 14 2021

ILC015-177-141945-
Carroll-Stephenson-
203 PM CDT Wed Jul 14 2021

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN CARROLL AND
SOUTHERN STEPHENSON COUNTIES UNTIL 245 PM CDT...

At 203 PM CDT, a strong thunderstorm was located near Pearl City, or
9 miles northeast of Mount Carroll, moving east at 30 mph.

Winds in excess of 40 mph are possible with this storm.

Locations impacted include...
Freeport, Pearl City, Shannon, German Valley, Ridott, Loran,
Winneshiek, Albertus Airport, Bolton and Stephenson  County
Fairgrounds.

Torrential rainfall is also occurring with this storm. Minor flooding
of low lying areas, creeks, streams and urban areas is possible. If
you encounter water over a roadway, do not drive through it.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4220 8969 4212 8969 4212 8992 4230 8992
      4237 8940 4220 8940
TIME...MOT...LOC 1903Z 260DEG 27KT 4220 8985

Uttech

Special Weather Statement
National Weather Service Quad Cities IA/IL
217 PM CDT Wed Jul 14 2021

ILC011-073-195-141945-
Whiteside-Henry-Bureau-
217 PM CDT Wed Jul 14 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT WHITESIDE...
NORTHEASTERN HENRY AND NORTHWESTERN BUREAU COUNTIES UNTIL 245 PM
CDT...

At 217 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Emerson to Cambridge. Movement was
east at 40 mph.

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

Locations impacted include...
Sterling, Rock Falls, Morrison, Cambridge, Geneseo, Prophetstown,
Erie, Walnut, Atkinson, Sheffield, Annawan, Tampico, Lyndon,
Hooppole, Deer Grove, Emerson, Fenton, Yorktown, Round Grove and
Manlius.

This includes the following highways...
 Interstate 80 in Illinois between mile markers 18 and 44.
 Interstate 88 between mile markers 21 and 44.

Torrential rainfall is also occurring with these storms. Minor
flooding of low lying areas, creeks, streams and urban areas is
possible. If you encounter water over a roadway, do not drive through
it.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4135 8972 4129 9026 4184 9000 4191 8963
      4159 8963 4158 8955
TIME...MOT...LOC 1917Z 262DEG 33KT 4184 8984 4132 9018

Uttech