Severe Thunderstorm Warning 88, NWS Chicago, IL

482 
WWUS53 KLOT 232025
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
325 PM CDT Mon Aug 23 2021

ILC103-141-232035-
/O.EXP.KLOT.SV.W.0088.000000T0000Z-210823T2030Z/
Lee IL-Ogle IL-
325 PM CDT Mon Aug 23 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN LEE AND
SOUTHWESTERN OGLE COUNTIES WILL EXPIRE AT 330 PM CDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However gusty
winds and heavy rain are still possible with this thunderstorm.

LAT...LON 4190 8963 4196 8957 4191 8938 4176 8951
      4185 8963
TIME...MOT...LOC 2025Z 299DEG 15KT 4183 8944 

$$

RATZER

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
302 PM CDT Mon Aug 23 2021

.SHORT TERM...

Coming shortly.

&&

.LONG TERM...
301 PM CDT

Wednesday through Monday...

A persistent pattern of heat and humidity may finally break early
next week, but until then the mid to upper 90s heat indices will
linger into the weekend, with actual highs in the upper 80s to lower
90s.  Relatively weak southerly flow for most of the period may
allow for lakeside cooling on some afternoons. The best bet for
significant onshore cooling winds comes on Thursday following the
passage of a weak frontal zone late Wednesday.

In this type of pattern with an upper ridge to our south and quasi-
zonal flow across the northern CONUS, heat headlines and afternoon
convection are usually the two competing questions.  This certainly
will be true on Wednesday ahead of the approaching frontal zone. The
latest guidance suggests we might be very close to but just below
thresholds for a heat advisory, and additional uncertainty is
provided by the influence of possible convection along the surface
boundary.

Precip chances will remain elevated, though for now still in the
chance category, as the front pushes into the area late Wednesday,
stalls Wednesday night, then begins to lift back north on Thursday
as a warm front extending eastward from a surface low moving from
the Southern Plains toward Lake Superior.  North of this front on
Thursday is also where the cooler easterly flow off the lake would
develop.

By late in the week and into the weekend, heat and humidity persist
but precip chances presently look lower with the lack of additional
shortwaves or low-level boundaries to provide a focus for lift.
Models then suggest a more significant cold front will move through
late Sunday and usher in cooler conditions to start next week, but
there is considerable uncertainty that far out in such a weakly
forced pattern.

Lenning

&&

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

Aviation Weather Concerns: Primary concern will be possible early
morning showers and thunderstorms Tuesday morning, with a second
round possible late Tuesday afternoon.

An area of thunderstorms west of I-39 this morning kicked off a line
of showers that is now dying out south and east of I-80, but a few
showers may linger into the late afternoon, especially in my
southern counties. IFR to LIFR CIGs/VIS from this morning have
lifted or dissipated to VFR conditions, which will remain VFR
throughout the rest of Monday into Monday evening. Overall wind flow
is from the south to southwest, with a few locations gusting to
around 16 kt. Overall flow will remain from the south through
Tuesday afternoon.

A short-wave and associated convection is expected Tuesday morning,
bringing showers and thunderstorms, and some MVFR visibilities and
ceilings. Model guidance is a bit scattered in location and timing,
but enough of a hint exists, and has existed for the past couple of
days that we believe convection will occur, most likely between 10
and 15Z on Tuesday. Presently conditions do not appear to be severe,
but some gusty winds and heavy rainfall is possible with these
storms. After this area of convection moves out late morning
Tuesday, there is a possibility for a second wave of convection
occurring around 00Z Tuesday evening, but only a few models have
indicated this possibility, so did not reflect this second wave of
convection in my TAFs. If it occurs it could be as early as 23Z, and
last into Tuesday evening.

BKL

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&

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Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
1153 AM CDT Mon Aug 23 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-241700-
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-
1153 AM CDT Mon Aug 23 2021 /1253 PM EDT Mon Aug 23 2021/

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

.DAY ONE...This Afternoon and Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk.
  Limited Flooding Risk.
  Limited Excessive Heat Risk.

DISCUSSION...

A few isolated thunderstorms are possible this afternoon near and
west of I-39. Additional thunderstorms may develop over the area
overnight, posing a threat for gusty winds. Heavy downpours may
cause ponding on some roads.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday and Wednesday...
  Limited Thunderstorm Risk.
  Limited to Excessive Heat Risk.
Thursday through Sunday...
  Limited Thunderstorm Risk.
  Limited Excessive Heat Risk.

DISCUSSION:

Hot and humid conditions are expected through at least Wednesday
with heat indices over 100 possible Tuesday and Wednesday.
Periodic thunderstorms will occur as well, though many hours will
stay dry.

.SPOTTER INFORMATION STATEMENT...

  Spotter activation will not be necessary through tonight.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the east and southeast at 10 to 20 mph.

LMZ740>745-241700-
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-
1153 AM CDT Mon Aug 23 2021

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...This Afternoon and Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday through Sunday...
  Limited Thunderstorm Risk.

Castro

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Special Weather Statement
National Weather Service Chicago/Romeoville
252 PM CDT Mon Aug 23 2021

ILZ008-010-232030-
Ogle IL-Lee IL-
252 PM CDT Mon Aug 23 2021

...A strong thunderstorm will impact portions of western Lee and
southwestern Ogle Counties through 330 PM CDT...

At 252 PM CDT, Doppler radar was tracking a strong thunderstorm near
Dixon, moving southeast at 30 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Dixon, Polo, Lost Nation, Grand Detour, Nelson, Harmon, Woodland
Shores, Eldena, Woosung and Nachusa.

Including the following interstate...
 I-88 between mile markers 45 and 60.

This includes...  Sauk Valley College.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4200 8961 4188 8930 4165 8948 4176 8963
      4193 8963 4193 8967
TIME...MOT...LOC 1952Z 305DEG 24KT 4188 8959

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

LENNING