The first big drop in temperatures during autumn can bring some of the most dramatic weather. It may accelerate the leaf colors changing and cut off the growing season, but can also display some of the most unique extreme weather in one part of the country. Cold Canadian air flowing across the warmer Great Lakes can erupt with plumes of heavy snow and waterspouts. Yes, cold air funnels over the water! It’s a right of passage into winter for some and a fascinating show.
The dip of the jet stream this weekend will look like something we could see mid winter. Parts of New York have the best chance to get a winter preview, but the flow over Lake Erie might support some snow showers across Ohio, Pennsylvania, and far western Maryland. The air flowing around a strengthening storm will drag down colder air. Lake Effect Snow is generated by a benchmark of cold air over warm water. The measurement of 13°C (23.4°F) difference between the air at 850 mb (~5,000 Ft above the ground) to the surface water, plus the flow of air over at least a 100 mile fetch of water can generate the cloud plumes and intense bands of precipitation. It isn’t always snow, but often ends up that way.
Great Lakes Water Temps:
Erie and Ontario will be our focus, but I think New York off of Ontario has the best chance to see this weather develop. But Maryland interest with potential snow flakes reaching Garrett County comes off of Lake Erie, so let’s start with that.
Note: Comparing temperatures from the 850mb level to the water temperature can be confusing since numbers aloft are in Celsius but the surface is measure in Fahrenheit. But the measure of a 13 degree difference between those levels is Celsius, which converts to a 23.4 degree Fahrenheit difference.
Looking at the lake water temperature, and quick math would compare Ontario’s 50s to only freezing ( low 30s F or around 0°C ‘aloft’ needed to get the Lake Effect Machine going. The surface air can be in the 30s (even above freezing) and support snow falling from colder clouds to reach the ground.
A closer look at these expected conditions for each lake below. Notice the wind flow and compare to the forecast temperatures aloft and at the surface for 8 AM Sunday morning when conditions will be most supportive.
Erie:
Should showers develop, some could reach western Maryland and the surface temperatures will be cold enough to support any snow falling, making it to the ground.
*If showers do develop off of Lake Erie, there is support for them to cross into the ridges of western Maryland’s Garrett County with snow.
Ontario:
This region has the best chance to experience snow and cold air funnels.
Waterspouts:
Not exactly a tornado on the water, but a funnel of wind churning over warm water is more common than you might imagine. The formation of fair weather waterspouts work on the same dynamics as Lake Effect snow, the temperature difference of 13°C (23.4°F) difference between lake water and air at around 5,000 Ft aloft. The Great Lakes have a first look in the fall, but even cold air reaching south Florida can make it common on The Gulf of Mexico mid winter. They have wind speeds lower than tornadoes and almost always stay over the water.
There is a forecast system in place that does short range modeling based on Szilagyi Waterspout Nomogram. This expands on the temperature contrast needed for Lake Effect Snow incorporating the cloud depth and wind speed as well. In fact, faster winds cut down on the watersouts. In this case, less it more. Less wind can generate more cold air funnels.
The Great Lakes Waterspout Forecast Model was taken down overnight for maintenance in anticipation of this event. When it is back online I will share the products which extend up to 48 hours in advance. For more information about the Waterspout Nomogram, here is the link from the Meteorological Service of Canada research in 2009.
Check back for frequent updates and any images of these events this weekend.
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