That's the title of a special weather statement issued by the Buffalo office of the National Weather Service this evening, and here is the technical discussion from earlier which gives the background for the lake-effect snow warning that they correctly issued this afternoon in the midst of a tricky meteorological situation. The details of the lake-atmosphere setup, as they note in the discussion, are virtually unprecedented in the known record; this is the earliest in the autumn they've ever issued such a warning!

Tom Niziol, who wrote this evening's statement and is the meteorologist-in-charge of that office, and the staff there really know their lake-effect stuff, and although they're very experienced with the phenomenon and have seen some real doozies, such as the epic December 2001 snow blitz, I'm sure this is one they'll be talking about for awhile!

The current bizarre weather pattern brought tropical moisture surging all the way to Alaska and has now resulted in an equally anomalous (for this early in the season) wintry blast down into the lower 48, with a number of locations near the Great Lakes receiving their record earliest accumulation of snow.

The term "lake-effect" refers to precipitation which occurs when cold air passes over relatively warm water, and the water adds heat and moisture to the lower atmosphere.

A distinguishing characteristic of lake-effect precipitation is that it would not occur without the presence of the lake over which the air is passing. Precipitation that would be falling anyway but is enhanced is called, well, you guessed it: "lake-enhanced."

The bodies of water most known for the phenomenon are the Great Lakes, but it can occur downwind of other lakes such as the Great Salt Lake in Utah. "Bay-effect" and "ocean-effect" snow can occur by the same process, and precipitation induced or enhanced by bodies of water is not limited to the U.S.

Lake-effect precipitation can be in the form of rain, but is most commonly associated with snow, which can take the form of extremely intense squalls (even thundersnow like tonight). Although it is typically "showery" in nature rather than having the broad shields of steady precipitation associated with other winter storms, when a band is persistent over the same location the snow in that localized area can be steady and heavy, and the accumulations can really add up.

This event is notable because it's so early in the season, the lake water is so warm, the snow is so wet and heavy (not only in intensity but also in weight), and the leaves are still on the trees. If you're in the Buffalo area and your power is not out, post a comment and let us know what it's like there ... ditto for anyone else in the Great Lakes region who had snow!

UPDATE FRIDAY 5PM ET: Well, this is one Friday the 13th that won't soon be forgotten in Buffalo! After posting my entry last night, what was shown on that radar image above just kept going and going and going, and things got out of hand. No matter what the situation, one key requirement for extreme lake-effect accumulations is that the squall band must persist sufficiently long in the same location.

Thank goodness we won't have multiple days of multiple feet of snow falling like what led to the 81.6 inches in late December 2001, but what fell so far this time -- including the official 22.6" at the airport -- has been enough to create havoc because of the heavy, wet nature of the snow rather than the drier, fluffier kind usually seen with winter lake-effect events, and the fact that leaves were still on the trees.

Dr. Forbes did some calculations, and for a more typical December lake-effect snowstorm with a 25:1 snow-to-liquid-equivalent ratio, 22.6 inches of snow would weigh 4.7 pounds per square foot.

However, for relatively wet lake-effect snow like during this event, which had approximately a 10" snow to 1" liquid ratio, 22.6 inches of wet snow weighs 11.75 pounds per square foot!

Also in regard to the 22.6", that's no slouch, even by Buffalo standards: per the graphic below, which contains info dug up by Tom Moore, TWC's resident lake-effect guru, it's Buffalo's 6th greatest 24-hour accumulation on record.

And quite a legacy is left: it truly is as if a hurricane swept through and blew slews of trees down, or to use a winter precipitation analogy, the impacts from this event are more typical of a severe ice storm. As evidenced by some of the comments posted below, it's nothing short of a disaster.

UPDATE SATURDAY 1PM ET: It's been quite a couple of days in the Buffalo area, and as Jim Cantore reported live from Amherst this morning, the recovery is proceeding but it's a challenge due to all the trees down and ongoing power outages. From the latest Buffalo Storm Update on the National Grid website: "Field assessment reports from across the region are confirming that our network has experienced a level of damage that is unprecedented for Western New York."

Even shoveling the snow is not easy because of the weight of it.

Speaking of which, with all the climatological data and observations in, as best as I can tell the ratio of snow to liquid equivalent for the Buffalo snowstorm was closer to 12:1 than 10:1, but that's still 9.8 pounds per square foot, which is a lot of weight per unit area and much more than for a dry powdery snow with a 25:1 ratio!

More than half the snow -- a foot -- fell in a four-hour period from 1am - 5am on Friday, with 8" falling in two hours between 2am and 4am.

And this excerpt from the observation just before 3am Friday is one to remember:

KBUF 130653Z 00000KT SNINCR 4/14 1/4SM +TSSN FQT LTG

Translation: 2:53am ET, winds totally calm, snow increased 4" in the past hour for a total of 14", 1/4 statute mile visibility in heavy thundersnow, with frequent lightning!