Later in February and early march, the influence of the sub-tropical jet stream driving short bursts of "warmth" becomes stronger. The Polar jet which drives the winter pattern often bounces back and forth as the southern branch shows flashes of dominance. Both jet streams can blend together as troughs become deeper in the middle of the continent. Waves travel along the jet stream which develop into deep circulations at the surface and aloft inside the large scale trough. These waves can deepen rapidly causing rapidly rising temperatures and heavy rainfall.
Four components are coming together for a potential big flooding event because of this active jet stream:
1) Rising temperatures: Temperatures will make a run at 50
2) Heavy snow cover: Only 7 other winters since the late 1930s have had at least 13" of snow cover this late in the winter: 2008 (15"), 2007 (17"), 1993 (21"), 1987 (13"), 1984 (13"), 1960 (13") and 1954 (13")
3) Strong winds
4) Steady rainfall of at least 1/2" over 13" of snow cover
Snow water equivalent is greater than 3" in many locations:
How often has all FOUR of these components come together this late in the winter?
NOT SINCE 1938 WHEN SNOW DEPTH RECORDS BEGAN AT HOPKINS AIRPORT
River levels will need to be monitored Friday and Saturday especially the Huron, Chagrin, Black and Grand Rivers. All should be well above flood stage Friday.
River Flooding Level website here for updated information
Milan could see the worst flooding according to Wednesday morning river forecasts: