Most blizzards, as you’d expect, happen from December to February—that’s meteorological winter, and peak snow season. But when they happen outside that timeframe, it’s actually more common to get them in spring than in the fall.

They also learned that these winter thunderstorms, although rare, occur most often in the central United States, Great Lakes, the east coast of the U.S. and Canada, and northern Canada during the winter and spring.

When: Blizzards occur during a county’s cold season which is usually anytime between late fall and early spring. If you live in the northern states you will more impacted by blizzards than some of the southern states.

Snow storms are usually caused by rising moist air within an extratropical cyclone (low pressure area. The cyclone forces a relatively warm, moist air mass up and over a cold air mass. These produce the heaviest snowfalls, sometimes many feet deep in a single storm.

The storm-generating maritime polar Pacific air mass is active from northern California to Alaska, especially in the winter, when its mild, wet air reflects the North Pacific temperature anomalies.

There are four categories for air masses: arctic, tropical, polar and equatorial.

Maritime polar (mP): Cool and moist. They usually bring cloudy, damp weather to the USA. Maritime polar air masses form over the northern Atlantic and the northern Pacific oceans. As they move eastward, moisture evaporates into the air, making the air mass more like a maritime tropical air mass.

Continental tropical air masses

Five air masses affect the United States during the course of a typical year: continental polar, continental arctic, continental tropical, maritime polar, and maritime tropical. Continental air masses are characterized by dry air near the surface while maritime air masses are moist.

Arctic air masses

Cold air is always heavier than an equal volume of hot air. “Air” is actually a mixture of several gases. Because cold air is heavier than warm air, an advancing cold front cuts under the warmer air that it is displacing, forcing it aloft.

Cold air sinks. Sinking air compresses and heats. As air sinks, air pressure at the surface is raised. Cold air holds less moisture than warm.

The reason fr this is when air gets heated up it expands and becomes less dense than the air surrounding it also the distance between the molecules increases. So the less dense air floats in the much denser air just like ice floats on water as ice is less dense than water.

Cold air is more dense, therefore it has a higher pressure. Warm air is less dense and has a lower pressure associated with it. Remember, heat is less dense than cold air so the warm air will rise.

According to Boyle’s Law – for a given pressure, the density of a gas varies inversely with the temperature – cold air is denser than warm air and so creates a greater force. This is because water vapour is a relatively light gas compared with oxygen and nitrogen – the main constituents of air.

Actually, water pressure is generally stronger than air pressure. If you pumped the air pressure up enough (like you do when you pump air into a bike tire), then the air pressure may become stronger than standard water pressure.

Since cold air is more dense than warm air… cold air masses are associated with lower pressure at a given height in upper levels of the atmosphere (think of the atmosphere being compressed).

Generally high pressure means fair weather, and low pressure means rain.

Warm air rises, creating a low pressure zone; cool air sinks, creating a high pressure zone. Air that moves horizontally between high and low pressure zones makes wind. The greater the pressure difference between the pressure zones the faster the wind moves. Convection in the atmosphere creates the planet’s weather.

Well, high pressure is associated with sinking air, and low pressure is associated with rising air. Air is moving away from the high pressure center at the surface (or “diverging”) so as a result, air from above must sink to take its place.

Because air is lifted instead of being pressed down, the movement of a cold front through a warm front is usually called a low-pressure system. Low-pressure systems often cause severe rainfall or thunderstorms. Warm fronts usually show up on the tail end of precipitation and fog.

Low-pressure systems are associated with clouds and precipitation that minimize temperature changes throughout the day, whereas high-pressure systems normally associate with dry weather and mostly clear skies with larger diurnal temperature changes due to greater radiation at night and greater sunshine during the day.

Low-pressure areas are places where the atmosphere is relatively thin. Winds blow inward toward these areas. This causes air to rise, producing clouds and condensation. Low-pressure areas tend to be well-organized storms.

A low pressure system has lower pressure at its center than the areas around it. Winds blow towards the low pressure, and the air rises in the atmosphere where they meet. As the air rises, the water vapor within it condenses, forming clouds and often precipitation. Winds blow away from high pressure.

An area of higher pressure, H, is called a high-pressure system and generally has a denser air mass where air temperature is cool. These systems often bring warmer temperatures and dry weather. The lower concentration of molecules causes lower air pressure in these areas.

The pressure of a given amount of gas is directly proportional to the temperature at a given volume. When the temperature of a system goes up, the pressure also goes up, and vice versa. The relationship between pressure and temperature of a gas is stated by the Gay-Lussac’s law.

If you decrease the air temperature the pressure is going to increase. The relationship between the two is that air temperature changes the air pressure. When the temperature cools, the molecules slow down and they do not move and bump into each other. This causes a decrease in air pressure.

This can be easily understood by visualising the particles of gas in the container moving with a greater energy when the temperature is increased. This means that they have more collisions with each other and the sides of the container and hence the pressure is increased.