Flash Flood Warning 7, NWS Chicago, IL

922 
WGUS73 KLOT 180035
FFSLOT

Flash Flood Statement
National Weather Service Chicago/Romeoville
735 PM CDT Sun May 17 2020

ILC031-043-091-097-197-INC089-180315-
/O.CON.KLOT.FF.W.0007.000000T0000Z-200518T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lake IL-Will IL-Kankakee IL-DuPage IL-Cook IL-Lake IN-
735 PM CDT Sun May 17 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1015 PM CDT FOR
SOUTHERN LAKE...WILL...KANKAKEE...DUPAGE...COOK AND LAKE COUNTIES...

At 730 PM CDT, Doppler radar indicated a band of torrential rain 
extending from Chicago south to just east of Kankakee. This band is 
moving east around 25 mph and is producing one to two and a half 
inches of rain in less than an hour. The extremely heavy rainfall 
will lead to potentially significant flash flooding of creeks, 
streams, rivers, and low lying areas. Many roads will be flooded and 
impassable. 

HAZARD...Life threatening flash flooding. Heavy rain producing flash 
         flooding.

SOURCE...Radar indicated.

IMPACT...Life threatening flash flooding of creeks and streams, 
         urban areas, highways, streets and underpasses.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, urban areas, highways, streets and underpasses as
well as other drainage areas and low lying spots.

&&

LAT...LON 4235 8783 4223 8781 4206 8767 4185 8761
      4171 8753 4167 8747 4168 8743 4164 8742
      4162 8723 4117 8746 4117 8753 4114 8753
      4108 8769 4101 8824 4214 8824 4237 8795

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...1-3 INCHES IN 1 HOUR

$$

IZZI

525 
WGUS73 KLOT 180207
FFSLOT

Flash Flood Statement
National Weather Service Chicago/Romeoville
907 PM CDT Sun May 17 2020

ILC031-043-091-097-197-INC089-180315-
/O.CON.KLOT.FF.W.0007.000000T0000Z-200518T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lake IL-Will IL-Kankakee IL-DuPage IL-Cook IL-Lake IN-
907 PM CDT Sun May 17 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1015 PM CDT FOR
SOUTHERN LAKE...WILL...KANKAKEE...DUPAGE...COOK AND LAKE COUNTIES...

At 905 PM CDT, law enforcement, media and public reports indicate 
significant flash flooding is ongoing throughout the much of the 
Chicago metro southward through Kankakee County. This includes rapid 
rises on rivers, creeks and streams in addition to flooding of many 
roadways. Road closures are common. Though the heavy rain has ended, 
additional runoff will continue to result in flash flooding through 
late this evening. With the onset of darkness, flooded roadways will 
become more difficult to recognize. Avoid travel through tonight.

HAZARD...Life threatening flash flooding. Heavy rain producing flash 
         flooding.

SOURCE...Several reports across the warned area.

IMPACT...Life threatening flash flooding of creeks and streams, 
         urban areas, highways, streets and underpasses.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, urban areas, highways, streets and underpasses as
well as other drainage areas and low lying spots.

&&

LAT...LON 4235 8783 4223 8781 4206 8767 4185 8761
      4171 8753 4167 8747 4168 8743 4164 8742
      4162 8723 4117 8746 4117 8753 4114 8753
      4108 8769 4101 8824 4214 8824 4237 8795

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Kluber

327 
WGUS73 KLOT 180313
FFSLOT

Flash Flood Statement
National Weather Service Chicago/Romeoville
1013 PM CDT Sun May 17 2020

ILC031-043-091-097-197-INC089-180320-
/O.EXP.KLOT.FF.W.0007.000000T0000Z-200518T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lake IL-Will IL-Kankakee IL-DuPage IL-Cook IL-Lake IN-
1013 PM CDT Sun May 17 2020

...THE FLASH FLOOD WARNING FOR SOUTHERN LAKE...WILL...KANKAKEE...
DUPAGE...COOK AND LAKE COUNTIES WILL EXPIRE AT 1015 PM CDT...

Widespread flooding, some significant, will continue through 
tonight. However, with little additional rain expected tonight, the 
flash flood risk has diminished. The Flash Flood Warning has been 
replaced by an Areal Flood Warning through Monday morning as impacts 
from road closures and elevated rivers, creeks and streams are 
expected to continue.

LAT...LON 4235 8783 4223 8781 4206 8767 4185 8761
      4171 8753 4167 8747 4168 8743 4164 8742
      4162 8723 4117 8746 4117 8753 4114 8753
      4108 8769 4101 8824 4214 8824 4237 8795

$$

Kluber

Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
438 PM CDT Sun May 17 2020

.MESOSCALE DISCUSSION...
438 PM CDT

Corridors of showers and embedded storms have consolidated into a
more single broad area from the Chicago metro down Interstate 55.
Some of this convection is deeper than what we've seen so far
today, especially from Livingston County southward where there has
been colder cloud tops and more lightning concentration. The mode
has been more quasi-linear with occasional lower-topped
supercells within that. One of these looks like it may have
produced a tornado southwest of Decatur in the NWS Central
Illinois CWA.

The effective warm frontal zone is draped near Interstate 80
across the Chicago metro and far northwest Indiana. As cells have
crossed this transition zone where effective storm relative
helicity is closer to 200 m2/s2 (though probably still not
entirely realized) we have seen occasional brief rotation that
has been shallow in depth. Probably will continue seeing some of
that and will have to watch if any deeper storms can reach that
far north. The broader area though of primary concern is looking
to be east of I-55 and south of I-80 where some clearing and
breaks in constant showers have allowed temperatures to warm to
69-72 and boosted 0-3 km mlCAPE to near 100 J/kg per latest RAP
analysis. As the broken line area of convection moves east through
this area through 7-8 p.m., will need to watch for brief
tornadoes. Some of these again could be from discrete/semi-
discrete low-topped supercells or from more quasi-linear behavior
that is most favored just to the north of any northeastward
surges/mini bows.

MTF

&&

.PREVIOUS MESOSCALE DISCUSSION...
1131 AM CDT

...The threat for heavy rainfall leading to flash flooding--some
potentially significant--and a risk for a few brief tornadoes
exists this afternoon and evening...

Late-morning moisture channel imagery depicts a remarkably wound-
up shortwave spiraling across west-central Iowa with a clear wing
of increasing upper-level mass divergence within the diverging
mid-level warm conveyor belts. Associated robust warm advection
and increasing jet forcing continues to support the development of
widespread light to moderate rainfall across the region. The
ongoing precipitation has resulted in generally one half to 1.5
inch rainfall amounts since last evening, with some localized 2+
amounts noted across parts of Ford and Iroquois counties. This
precipitation likely has nearly or completely saturated the sub-
surface after Thursday night's flash flood event, and this is
corroborated by reports of runoff and minor flooding on roadways
in the light stratiform precipitation.

As the aforementioned low approaches our longitude this afternoon,
expect to see a quick uptick in upper jet support in conjunction
with a developing coupled jet as noted on regional cross sections.
The attendant ageostrophic mass response is extremely deep,
through nearly the entire depth of the troposphere, indicating
robust vertical motions for precipitation production. ILX's
morning sounding sampled 1.63" PWATs which have likely only
increased since then. Instability remains one of the wild cards
today, with a lack of higher MLCAPE values potentially limiting
the truly extreme rainfall rates. That said, warm cloud depths
are forecast to increase to around 11 kft, not surprising given
the near-record or record territory PWATs, supporting efficient
warm rain and collision-coalescence processes. Have already seen
this manifested in innocuous-looking rain showers this morning
dropping visibilities to under 1 mile indicative of lots of small
drops. Based on recent mesoanalysis showing a gradual increase in
instability and additional GLM flashes showing up, expect a
gradual uptick in heavier convective cores into the afternoon.

Mean cloud-bearing winds (850-300mb) may remain oriented with
just a hint of an easterly component today which *should* help
keep some forward progression of developing thunderstorms going.
That said, the threat for very heavy rainfall over a short period
over soils that can't handle any additional water will likely
result in flash flooding. Would like to think that some of the 7"+
amounts being forecast by recent runs of the HRRR are a bit
overdone given the lack of more appreciable instability. That
said, we've grown concerned enough in the development of a
potentially significant flash flood threat that we earlier
coordinated a "moderate" Excessive Rainfall Outlook upgrade with
the WPC. Thanks WPC, MKX, IWX, ILX, and DVN for the collaboration
this morning. The main window of concern here is roughly 2 - 8 PM
or so. No changes to the Flash Flood Watch have been made this
morning, although the depending on the western bounds of a narrow
swath of higher rainfall amounts, a westward expansion to include
Lee, Ogle, Winnebago, and Boone counties can't be ruled out.

Regarding the severe potential: the risk for a few brief tornadoes
continues this afternoon as diurnal gains in at least modest
instability are realized. These are always hard events to message
and forecast since it seems like either these low-topped
supercells seem extremely fickle when it comes to ingesting more
buoyant near-surface instability. ILX's morning sounding sampled
38 kts of 0-2 km bulk shear and 212 m2/s2 SRH in that layer, with
similar values expected into parts of our area which would support
a conditional tornado threat given 0-3 km MLCAPE values forecast
to push north of 100 J/kg given sufficient low-level hodograph
turning. Currently think the main threat area may remain relegated
to near and south of I-80 and roughly east of a Pontiac to Morris
line during the roughly 2 PM - 7 PM timeframe.

Updated products have been transmitted.

Carlaw

&&

.LONG TERM...
228 PM CDT

Monday through Saturday...

Lakeshore Flooding: The slower motion of the low and the track over
northern Illinois may delay the onset of lakeshore flooding
concerns, with lingering uncertainties with just how the north
wind shift will evolve given this storm's slow motion. There
remains decent uncertainty in the start time, with a small low
track change resulting in a significant chance in wind speeds on
the north side of the low, but we continue to favor the main
window for impacts due to increasing wave action and surge later
tonight into Monday for the Illinois shore, and a bit later across
Indiana.

No major changes to the extended forecast here from the overnight
shift. With the upper low still centered across east central
Illinois, we will still have some showers ongoing into Monday and
Monday evening, though we should see some easing of these as the
upper low is now progged to slowly dip south toward the Ohio
Valley. As this occurs additional moisture via wrap around theta-e
advection will spread back across northeast Illinois and
northwest Indiana on Tuesday, leading to a continuation of rain
showers, clouds, and cooler northeast winds across the area.

The upper low will only slowly migrate south and east through the
Ohio Valley Wednesday-Friday, will eventually lose its grip on
the region. High pressure across the upper Great Lakes will
maintain northeast winds, and thus the mid-late week period will
feature gradual warming -- again with continued cooling near the
lake.

Upstream ridging will eventually win out and lead to more warming
for the weekend with deep upper troughing across the west. Southwest
flow will provide the warmth and bit more mugginess but also steer
some upper level energy this direction as well which could trigger
some diurnally favored showers or storms, especially the latter half
of the upcoming weekend.

KMD/Carlaw

&&

.AVIATION...
For the 18Z TAFs...

Main concerns through the TAF period

 *Ongoing rain showers through the day, moderate to heavy at
  times
 *Thunder potential this afternoon with isolated strong wind gust
  under any stronger storms
 *Wind direction trends this afternoon and overnight
 *Low cigs and vis overnight into early Monday

Showers will continue through this evening increasing in coverage
and intensity through this afternoon. MVFR to occasional IFR
vis/cigs are possible with the stronger showers. There is some
question as to the overall thunder potential this afternoon. This
will be highly dependent on how unstable the atmosphere can get
into this afternoon. If sufficient instability is able to lift
north toward the terminals, any of the more robust showers will
have an increased thunder potential early this afternoon. Strong
wind gusts are also possible with any of the stronger storms. Have
bumped up this time generally from the 19Z-23Z period for
ORD/MDW.

Another concern for overnight into early Monday morning is the
potential for fog/low cig development. As the center of the low
moves overhead, winds will become light. This combined with
increased moisture in the low levels could result in cigs and vis
quickly drop to near LIFR. Have maintained 1SM vis for the
current TAF period but could foresee even lower vis occurring,
mainly between 10-13Z period. Will continue to monitor trends for
later updates.

Heading into the day tomorrow there is the potential for the
occasional light shower on the back side of the departing closed
low with cigs gradually improving through the day. Winds will
begin to pick up by late morning out of the northeast.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Flash Flood Watch...ILZ005-ILZ006-ILZ011-ILZ012-ILZ013-ILZ019-
     ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-
     ILZ105-ILZ106-ILZ107-ILZ108 until 1 AM Monday.

     Lakeshore Flood Advisory...ILZ006-ILZ103 until 4 PM Tuesday.

     Lakeshore Flood Advisory...ILZ104...1 AM Monday to 4 PM Tuesday.

IN...Flash Flood Watch...INZ001-INZ002-INZ010-INZ011-INZ019 until 1
     AM Monday.

     Lakeshore Flood Advisory...INZ001-INZ002...7 AM Monday to 4 PM
     Tuesday.

LM...Small Craft Advisory...Winthrop Harbor to Northerly Is. until 4 PM Tuesday.

     Dense Fog Advisory...LMZ742 until 7 AM Monday.

&&

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Hazardous Weather Outlook...CORRECTED
National Weather Service Chicago/Romeoville IL
335 PM CDT Sun May 17 2020

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-182015-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
335 PM CDT Sun May 17 2020 /435 PM EDT Sun May 17 2020/

This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.

.DAY ONE...Tonight.

Weather hazards expected...

  Significant Flooding Risk.
  Significant Thunderstorm Risk...with an associated:
     Elevated Tornado risk mainly south of I-80.
     Limited damaging wind risk...up to 60 mph.
  Elevated Fog Risk.
  Elevated Lakeshore Flood Risk Illinois shore.

DISCUSSION...

Showers and storms will increase and coverage and intensity
through this afternoon. The ground is saturated and anticipated
swaths of heavy rainfall are therefore expected to result in flash
flooding, some potentially significant, along with renewed river
rises. A threat for severe storms exists this afternoon and
evening, with a potential for damaging wind gusts and and even a
few tornadoes, mainly south of I-80 and east of I-39.

Some dense fog will be possible tonight. In addition, increasing
surge and waves will result in a threat for minor lakeshore
flooding across the Illinois shore.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday and Tuesday...
  Elevated Fog Risk.
  Elevated Lakeshore Flood Risk.
Thursday through Saturday...
  Limited Thunderstorm Risk.

DISCUSSION:

Near record water levels combined with gusty northeast winds,
increased wave action, and developing surge may lead to areas of
lakeshore flooding Monday into Tuesday.

.SPOTTER INFORMATION STATEMENT...

  Spotters may be needed this afternoon and evening.

GENERAL STORM MOTION OF THE DAY:

  Individual storms moving toward the northeast at 30 to 35 mph,
  with the line of storms motion generally toward the east at
  10 to 15 mph.

LMZ740>745-182015-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
335 PM CDT Sun May 17 2020

This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.

.DAY ONE...Tonight.

Weather hazards expected...

  Hazardous conditions for small craft.
  Elevated Thunderstorm Risk...with an associated:
     Limited thunderstorm wind gust risk...up to 45 kts.
  Elevated Fog Risk.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday...
  Hazardous conditions for small craft are likely.
  Elevated Fog Risk.
Tuesday and Wednesday...
  Hazardous conditions for small craft are likely.
Friday and Saturday...
  Limited Thunderstorm Risk.

Carlaw

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
632 PM CDT SUN MAY 17 2020

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

0530 PM     FLASH FLOOD      3 N CAMPUS              41.07N 88.31W
05/17/2020                   LIVINGSTON         IL   FIRE DEPT/RESCUE

            NUMEROUS ROADWAYS CLOSED IN ROUND GROVE
            TOWNSHIP DUE TO FLOODING.

&&

WSL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
636 PM CDT SUN MAY 17 2020

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

0310 PM     TORNADO          2 NW MILLINGTON         41.58N 88.63W
05/17/2020                   LA SALLE           IL   PUBLIC

            PHOTOS AND VIDEO POSTED TO SOCIAL MEDIA SHOW
            BRIEF TORNADO NORTHWEST OF MILLINGTON. TIME
            ESTIMATED BY RADAR.

&&

WSL/MDB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
637 PM CDT SUN MAY 17 2020

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

0615 PM     FLASH FLOOD      PLAINFIELD              41.61N 88.22W
05/17/2020                   WILL               IL   LAW ENFORCEMENT

            PLAINFIELD PD INDICATES VIA SOCIAL MEDIA
            THAT NUMEROUS ROADWAYS ARE FLOODED ACROSS
            THE VILLAGE.

&&

WSL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
638 PM CDT SUN MAY 17 2020

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

0630 PM     FLASH FLOOD      3 NW BOLINGBROOK        41.72N 88.12W
05/17/2020                   WILL               IL   NWS EMPLOYEE

            MULTIPLE VEHICLES STALLED DUE TO FLOODING
            ALONG NAPER BOULEVARD BETWEEN ROYCE ROAD AND
            BAILEY ROAD.

&&

WSL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
639 PM CDT SUN MAY 17 2020

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

0630 PM     FLASH FLOOD      3 SE NAPERVILLE         41.74N 88.12W
05/17/2020                   DUPAGE             IL   NWS EMPLOYEE

            SEVERAL FEET OF WATER ON NAPER BOULEVARD
            NEAR BAILEY ROAD.

&&

WSL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
648 PM CDT SUN MAY 17 2020

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

0640 PM     FLASH FLOOD      1 WSW RIVERSIDE         41.83N 87.83W
05/17/2020                   COOK               IL   LAW ENFORCEMENT

            RIVERSIDE PD REPORTS 1ST AVENUE CLOSED NEAR
            FOREST AVENUE DUE TO A FLOODED UNDERPASS.

&&

WSL