(8:00PM – Thursday, September 26th, 2024) Thursday night update on the remnants of Hurricane Helene, which will spiral through the region over the next several days, through late this weekend. Interaction with an upper level low in the region will lead to both pieces jointly bringing periods of rain and a period of high winds to portions of the state during this timeframe.
Update…
•With this update, only minor placement changes were needed on the flood threat/rainfall forecast.
•With this update, only minor placement changes were needed on the high wind forecast.
Timing…
•Thursday Evening – Sunday Evening, September 26-29th.
Location…
•Much of Illinois.
Impacts…
•Periods of rain can be expected across the state from this evening through Sunday evening.
•Of note will be a period of organized and heavy rainfall across Southern Illinois from tonight through Friday night.
•Event rainfall totals across Southern Illinois will range from 1.00-5.00″. Localized higher rainfall totals are possible. Localized to widespread flooding will be likely.
•A period of high winds will occur across a large portion of the state from early Friday morning through early Saturday morning. During this time, wind gusts of 40-60MPH will be likely across a large portion of the state. Locally higher wind gusts will be possible.
Discussion…
•As the remnants of Hurricane Helene spiral through the region, interaction will occur with an upper level low sitting in the region. As this interaction between both pieces happens, a fujiwhara effect will occur, as well as phasing. These two pieces will jointly lead to periods of rainfall across the state over a multi-day period, including a period of heavy rainfall maximized across Southern Illinois from tonight through Friday night. While drought conditions are in place across Southern Illinois, the expected heavy rainfall amounts in a short period of time will lead to localized to widespread flooding issues. In additional to the rainfall aspect, a period of high winds can be expected across a large portion of the state from early Friday morning through early Saturday morning.
