Winter Storm Types and Formation

Overview

This lecture covers the different types of winter storms, their formation, precipitation types, notable examples, impacts, and mitigation strategies.

Winter storms involve heavy snow, blowing snow, and/or dangerous wind chills.
Blizzards feature blowing snow and strong winds, causing very low visibility.
Ice storms involve at least 1/4 inch of ice accumulation on exposed surfaces.
Lake effect storms form when cold, dry air passes over large bodies of water, producing heavy snow near the Great Lakes.
Snow squalls are brief, intense snowfalls with strong gusty winds.

Winter storms need cold air (below freezing near the ground), lift (rising air), and moisture.
Lift is typically provided by orographic (mountain) or frontal mechanisms.
Winter precipitation commonly begins as snow in the clouds and changes type depending on air layers encountered during descent.

Rain: Snow melts in a thick warm layer and remains rain to the ground.
Freezing rain: Rain freezes upon contact with surfaces at or below freezing.
Sleet: Partially melted snow refreezes before reaching the ground, forming icy pellets.
Snow: Falls as snow when air remains below freezing from cloud to ground.

Snow flurries: Light, brief snow with little or no accumulation.
Snow showers: Intermittent, somewhat heavier snow, possible accumulation.
Snow squalls: Intense, brief snow with gusty winds, significant accumulation possible.
Blowing snow: Wind-driven snow causing reduced visibility and drifting, may occur even without new snowfall.
Blizzard: Blowing/falling snow, winds >35 mph, visibility ≤1/4 mile for at least 3 hours.

Nor'easters: Powerful winter storms along the US East Coast, thrive on cold air and moisture, can produce hurricane-force winds.
Bomb cyclone: Rapidly strengthening storm with quick pressure drops, causing extreme winds and conditions.
2021 Texas Freeze: Severe storm with extreme cold, power grid failure, 240 deaths, and major damage.
Polar vortex and jet stream: Polar vortex is contained by the polar jet stream; warming weakens the jet stream, allowing cold air to move south.

Insulate water pipes and keep faucets dripping to prevent freezing.
Maintain roofs, insulate homes, caulk/weatherstrip doors/windows, and clear gutters.
Stock up on non-perishable food and keep emergency supplies in cars.
Dress warmly and stay dry; prepare vehicles for winter conditions.

Blizzard — Storm with blowing snow, winds >35 mph, visibility ≤1/4 mile for ≥3 hours.
Ice storm — ≥1/4 inch ice accumulation on exposed surfaces.
Lake effect storm — Heavy snow from cold air over warm lake water.
Snow squall — Brief, intense snowfall with strong winds.
Nor'easter — Major coastal storm with strong northeast winds and heavy precipitation.
Bomb cyclone — Rapidly intensifying low-pressure winter storm.
Polar vortex — Region of cold air in the stratosphere near the poles.
Jet stream — Fast-flowing air currents that confine weather patterns.