Major Winter Storm With Heavy Rain, Flooding, High Winds And Severe T'Storms Late Week/Weekend (Thur-Sat, Jan 9-11th) Update #4

(7:15PM - 1/9/20) A complex scenario is expected to unfold across the region in the coming days, with a few disturbances and then a main storm system expected to push across the region. During this period all of the following will be possible across the state... Snow, sleet, ice, heavy rain, flooding, high winds and severe t'storms. This post will be directed towards the heavy rain, flooding, high wind and severe t'storm aspect. For information regarding the snow, sleet and freezing rain aspect...please read the update at the following link: https://www.illinoisstormchasers.com/forecasts/major-winter-storm-with-snow-sleet-ice-and-high-winds-this-weekend-fri-sat-jan-10-11th-update-6

Thursday morning-Friday morning...
A lead disturbance moved across the region today, bringing with it scattered showers and high winds that impacted much of the state. Rainfall amounts were on the light side, generally a trace to under 0.25" across the state. Wind gusts topped out in the 25-45mph range across much of the state.

​Additional isolated to scattered showers will be possible across Northern Illinois tonight, however the main focus will be further south. Areas of rain are expected to develop this evening, and spread across much of Central and Southern Illinois tonight through Friday morning. Rainfall totals for these areas during this time could reach upwards of 1-2".

​Friday afternoon-Saturday evening...
As a second disturbance and the main storm system eject out through the region, more organized, widespread and heavier rain and isolated t'storms will develop and spread across the state from Friday afternoon into Saturday afternoon. Training of heavy rainfall is likely for a time across the heart of the state. With a strong storm system, strong jet stream, and ample Gulf moisture advecting in from the south...An axis of high rainfall totals is expected across the region. Rainfall totals during this period will likely range from 1-4" across much of the state. Lingering scattered showers may continue across portions of Eastern and Southern Illinois Saturday evening into Saturday night.

High winds are also likely for much of the state Friday evening through Saturday night. Wind gusts of 25-45mph are likely across much of the state during this time, with the potential for isolated higher wind gusts 45-55mph possible for some areas.

There will also be a severe t'storm threat across Southern Illinois Friday evening into Saturday afternoon. With the aforementioned strong storm system moving through and associated dynamics, unseasonably warm temperatures, high moisture levels for this time of year, and some instability in place....A lower end severe t'storm threat is likely. A broken line of t'storms will likely sweep across Southern Illinois during this time-frame. Given the environment expected to be in place, an isolated severe t'storm threat will exist... With damaging winds will be the main threat, though an isolated tornado cannot be ruled.

Final overall rainfall totals during this multi-day period will likely range from 2-5" across much of the state, with isolated totals in excess of 5" possible across Southwest and Central Illinois. Given the expected high rainfall totals over a relatively short period of time and training of heavy activity, widespread low to moderate flood potential exists across much of the state. Isolated high flood potential is possible across the heart of the state.

Below are the TAM flood, high wind and severe t'storm forecasts for this period.

​JP

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