A very intense and dangerous lake effect snow event will unfold downwind of the Great Lakes, starting tonight and lasting into Wednesday.As the storm system we are dealing with today strengthens and moves off to the northeast, bitterly cold air will rush into the region on southwest winds starting tonight.
With overnight temperatures well into the teens and daytime highs only in the 20s over the next couple of days, the contrast between the air and relatively warm waters of the Great Lakes will be extreme. Current lake temperatures are in the upper 40s, creating a 25-35º temperature difference.
That temperature difference will generate huge amounts of instability, which is the ability for air to move upward rapidly and is a key component of both thunderstorms and lake effect snow. In fact, thunder and lightning are very likely within the lake effect off of both Erie and Ontario.
Lake effect snows will start tonight as a disorganized spray of flurries and squalls to the east of the lakes. With strong winds and rich moisture, this lake effect should extend well inland and some of the higher elevations of southern Cayuga county could get a few inches tonight.
On Tuesday, the bands should consolidate into single, intense bands with snowfall rates well over 3″ per hour. These bands will be to the northeast of the lakes, impacting the general Buffalo and Watertown areas. With gusty winds, blizzard conditions are likely along stretches of both I-81 and I-90. Similar events have shut down both highways and I strongly suspect such closures will be needed again. Travel should be avoided in these areas at all costs through Wednesday morning.
The lake effect will jog south Tuesday night to a similar position as it will have tonight before shooting back north on Wednesday morning. By Wednesday afternoon, the storm should end as winds turn towards the south ahead of the next system.
As is always the case with lake effect snow, this will be a very localized event and huge differences in snow amounts may occur over a very short distance. This snow map is a general guide, but local variation is inevitable.