This was a marginal
event...but a unique and unusual one. After the winding down of synoptic
snow early on 13th...a huge arctic high pressure pressed southward from
northern Ontario and Quebec and set up a brisk low level north to northeast
flow of arctic air. This
flow had little shear and a rather high inversion (5000 ft) for a NE flow event...enabling some locally heavy lake effect snowbands to develop and move inland along the south shore of Lake Ontario. The heaviest snow fell thru mid afternoon...then the inversion lowered a bit and the activity became narrow finger -type bands just a mile or two wide. Winds veered to east during the night...shifting the activity to the immediate lakeshore from Greece to Hamilton, Ontario. It tapered off Thursday morning and became absorbed in yet another approaching synoptic event.
The heaviest snows
fell within a few miles of the lakeshore from the Rochester area to Oakville
Ontario. 5 to 7 inches was reported from Ontario...Webster...Greece and
Rochester. 4 to 6 fell over Orleans and northern Niagara counties. Less
than an inch fell
south of a Leroy to Batavia to Niagara Falls line.
This type of event often plagues the "Golden Horseshoe" at the west end of Lake Ontario between St. Catherines and Toronto. In fact, the major highway called the Queen Elizabeth Way, or QEW for short has been impacted im major ways a number of times from these types of snowbands. Many forecasters have been caught unaware of this feature because they are busy worrying about the typical large scale weather this type of synoptic scale pattern produces, namely mixed precipitation events. But while everyone is watching a big Low moving north up the Ohio Valley, the arctic High over Quebec develops the east-northeast flow along the long fetch of Lake Ontario and lake effect snow. Because the airmass is very cold with these types of events, the snow is very fluffy and dry so it won't take much to pile up a 6 or 7 inch snowfall. This is the same type of pattern that can produce snow over Cape Cod ("Cod effect") and down Long Island Sound ("Sound Effect").
The MM5 did especially well with this event. Itís rare to receive 6" or more on a pure Lake Ontario event.
This was the sixth significant Lake effect event in less than 3 weeks!