Lake effect snow

The weather reports and forecasts (11/18/22) are not at all promising. While the entire Eastern Seaboard looks to become very white over the next several days, Buffalo, New York is getting much of the negativity in the national news services — even to the point of prompting the NFL to move Sunday’s football game out of the danger zone and to Detroit; conveniently upwind from Lake Erie, as opposed to on the lee shore as is Buffalo.

(There have to be some priorities in this life, and while American football may not be anywhere near the top of my personal list, the Bill’s two-game losing streak (after starting 6-1), and their 4th quarter and OT immolation at the hands of surging Minnesota last week, makes many of the Buffalo fans nearly rabid in their enthusiasm for a return to glory this Sunday against the struggling Browns of Cleveland).

Anyway, lake effect snow is actually fairly easy to understand, and is based upon several fundamental rules that affect the weather (click here for an earlier post with additional background information on the climate and how it works):

1) The atmosphere takes on the temperature and moisture conditions of whatever it is over.

2) A warmer air mass can (and will) hold more water vapor than a colder air mass.

3) When a warm, moist air mass cools, the contained water vapor condenses, leading to precipitation.

4) Winds blow from areas of higher pressure to lower pressure.

5) Moving air is directly affected by the “Coriolis Force” — the deviation of the atmosphere from a straight path simply because of the earth’s rotation. Along with giving birth to the various westerly jet streams, the Coriolis effect causes the atmosphere to rotate clockwise around an area of high pressure (in the northern hemisphere), and counterclockwise around a low (leading to hurricanes and tornadoes). This rotation due to Coriolis is reversed south of the equator.

So how does all this lead to five feet of snow in Buffalo between now and kick-off on Sunday morning?

The westerly “Polar Jet” that runs eastward across the northern United States, when at just the right latitude, crosses the Great Lakes. During the winter months, the cold air mass takes on the temperatures of the lakes themselves and heats up. Since the air is now warmer and can hold more water vapor (and is flowing across wide bodies of water), it evaporates much of the liquid and fills with water vapor. There can be a lot of air, and a veritable buttload of vapor!

When the now warm and moist jet stream gets over the bitterly cold lands downwind of the lakes, the air mass cools, the vapor condenses back into the liquid phase, and promptly falls as precipitation. There can be a lot of precipitation!

Some of it builds up as ice on whatever may be on or near the ground. (This is very similar to the “freezing rain” that attacks Portland, Oregon, but that’s for a later post). There can be a lot of ice!

But much of it falls as snow, and there can be a lot of snow!