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Hydrologic Outlook

Hydrologic Outlook
ILC007-031-037-043-053-063-075-089-091-093-097-099-103-105-111-
141-197-201-INC007-073-089-111-127-241015-

Hydrologic Outlook
National Weather Service Chicago IL
507 PM CDT Wed Jun 23 2021 /607 PM EDT Wed Jun 23 2021/

...Risk for Heavy Rainfall and Possible Flooding Increases through
the Weekend...

The region will transition to a period of wet weather beginning
Thursday, with multiple separate rounds of rainfall possible,
including heavy thunderstorms at times. Despite dry weather and
drought conditions across portions of northern Illinois, river
flooding and flash flooding may still be possible. Uncertainty is
high regarding the exact locations of the highest rainfall totals
and the extent of the flood threat.

Rainfall is expected to move into the area on Thursday. Multiple
periods of rain, including heavy rainfall at times, may then occur
through at least a portion of the weekend or into next week. A more
favorable pattern for wet weather will take shape, with the heaviest
rates likely to be associated with thunderstorms. Some locations may
experience several inches of rain over several days. Although
recent rainfall has slightly improved drought conditions for
portions of the area, moderate to extreme drought still exists in
far northern Illinois.

Drought conditions will reduce the threat of flooding, however
rainfall rates in heavy thunderstorms can lead to flash flooding in
dry soil conditions, as well as in heavily urbanized and/or poor
drainage locations. If multiple waves of heavy rainfall were to
occur in the same locations, dry soil moisture conditions could be
overcome and river flooding could occur. Confidence in the exact
location of the the heaviest rainfall remains low at this time, and
rainfall amounts by next week may vary significantly across short
distances.

This outlook means that there is the potential for elevated river
levels and flooding impacts, but the timing, extent, and severity
remain uncertain. Persons with interests along area rivers should
closely monitor the latest forecasts. No additional statements are
expected at this time.

$$

WSL/RC



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