For nearly 30 years I lived in the Quad Cities and never once did I see or hear of what happened today. On the south side of the metro a rare “river effect snow” occurred that resulted in a narrow but intense plume of significant snow.
Below you can see the set-up that created the situation. The most important contributor was the 20 mile stretch of the Mississippi River that runs west to east from Muscatine to the Quad Cities. (That’s different than most other parts of the river where the water runs north to south from Minnesota to the Gulf of Mexico). Due to the recent mild conditions that stretch of the river was open and free of ice.
Today a perfect west to northwest surface flow ran across that fetch of the river. It delivered cold air over the relatively warm waters. That picked up moisture from the river and seeded the atmosphere downstream. The warm moist air was lifted and the ensuing condensation developed the localized snow plume that impacted a small sections of Rock Island and Henry Counties. That included a small part of the Quad City metro area south of the Mississippi.
Another factor which may have contributed to the snow plume are factories along that stretch of the Mississippi that produce industrial exhaust plumes. We see them all the time in the in the winter when the warmth of the factory exhaust hits the cold air resulting in a giant condensation or steam cloud you can see for miles. This too could have contributed to the overall seeding process.
Once the snow got going, it rapidly intensified early Friday. After reports of near whiteout conditions the NWS in the north side of the metro where it was not snowing put out this statement regarding the phenomena.
In the discussion above you can see where the forecaster noted he could see the plume well on radar. Here’s a screen grab I took during the event Friday morning. It’s roughly 10-20 miles wide and 25 miles long.
One of my long time chasing buddies Kholby Martin of Galesburg got in on what was happening to the north and went out to document the rare occurrence. He took this shot of the heavy snow near Orion just south of the Quad Cities.
He then sent this ground truth image showing the snow had stacked up to a fluffy 2″ in a short time. Outside of the plume to the north and south not even a flake was falling.
To be honest, this is one of the most unique weather events I have ever heard of in and around the Quad Cities where I’ve researched the records (in depth) going back to the 1800′s. It’s extreme events like this that fuels my interest in meteorology. Mighty interesting stuff that may not happen again for decades! Roll weather…TS