How does snow form???

Question

How does snow form? Why can't it snow is San Francisco? If San Francisco is too low, What about the other Bay Area cities like San Jose, Gilroy, Fairfield, etc? Can it snow there? Why is it that it snows in Washington DC and not in SF? Aren't they about the same lattitude? If Malibu can get snow sometimes, Can SF or other Bay Area cities get it too? It does get chilly here during the winter, highs are only in the 50's during the day for winter. It does get really cold like 30's and 40s in the morning and nights. Why is there no morning or night snow showers if it is really cold during those times? Why? If it needs to be more inland to snow, San Jose, Gilroy, Santa Clara is more inland than SF.

Answer 1

Snow forms when water vapor is lifted to areas where there are sub-freezing temperatures. Water vapor condenses, and then freezes. The frozen water droplets freeze slowly to construct very unique crystallized shapes. This can only happen at cloud level, and not on the way down to the surface or at the surface. If the water droplets freeze too fast, then you get hail or sleet.

For snow to form, one important factor is to have sub-freezing temperatures at cloud level. The second important factor is to have an abundance of water vapor. The third important factor is to have a mechanism of transfer and lift. If parts of California, or anywhere else in the world, cannot provide any one of these factors, then snow will not form.

Answer 2

actually snow forms when water vapor turns into ice directly w/o turning into water first.

when it goes from water to ice, you get hail.

up around 7 miles high, the temperature is something like -50 degrees.

so snow can form anywhere.

it doesn't snow in san francisco, or anywhere west of the sierras because while snow does form, it melts on the way down and becomes rain.

if you're driven up I-80 in the winter, when there's a storm, you'd know that at some level rain turns into snow, as it gets colder and you get higher.

<<If it needs to be more inland to snow>>

no, it needs to be higher.  like the top of Mt Hamilton or Mt Diablo where you get snow several times every winter.

none of the locations you mentioned are anywhere near high enough.

that said, rarely you do get snow in some of those locations.

more often, but far less than once a year, you get hail.

Answer 3

The sun and water makes it snow.

All weather is driven by the sun, the tilt on our planet’s axis causes us to have seasons and for the weather patterns to change.

When water or air gets warm it rises.  As air gets really high it gets cold and sinks.  Warm air can hold more water vapor then cold air so as moisture filled air rises and cools the water vapor falls out and if it is cold enough it freezes.  If the ground is warm then the water melts on the way down, it can even evaporate before it hits the ground and so go back up into the air.

Large bodies of water have warm water at their surface, because the colder water falls down, that means it has a lot of water ready to evaporate and so storms moving across the water grow and large bodies of water are heat sinks and weather generators.

Arctic air flowing south cools the air, the rising sun in the east causes air to rises and the warm air from the Gulf of Mexico comes in and smashes into that cold air.  This creates a lot of weather.  Terrain deflects it and pulls it around and areas as far away as El Nino off the coast of Peru (in South America) can affect storms in California.  Warm water from the Pacific Ocean crosses the Himalayan Mountains and since the air has to rise to cross the mountains it drops out most of its water vapor.  This makes India a rich water filled land.  It makes the Middle East a dry parched land; small dust storms that starting in the Sahara Desert are pushed across the Atlantic Ocean where they gain warm water and grow into Tropical Storms even into Hurricanes.

Meanwhile warm water filled air from the Pacific is flowing north from the warmer equator and it smashes into the cold air flowing out of Canada.  This causes it to rain a lot in Washington State.  In San Francisco the rain often evaporates on the way down before it reaches the ground and so forms fog.  It won’t snow because the warm water from the Pacific Ocean prevents it.

The moisture filled air from the Pacific that flows east hits the Rocky Mountains, it can’t cross the mountains so it piles up and rises, then it cools and cold air can’t hold as much water vapor.  Therefore it rains out on the California side and on the other side is a desert.  Kansas would be a desert except that warm water from the Gulf of Mexico flows north and hits that cold Arctic air again causing it to fall as rain.

The air is always moving in a circle perpendicular to the ground; but if it gets knocked over and flows parallel to the ground a tornado is formed; which is why Kansas is part of tornado alley.

Those storms coming across the Atlantic can snow in Washington D.C. because they are so strong.  There is so much water vapor that freezes that it can fall and remain cold enough to hit the ground as snow.  This is helped because of that cold arctic air again that is flowing south and the air goes south east because the hot desert causes an eastward air flow since the air can’t get over the Rocky Mountains.  Therefore the weather can be different at the same latitude because of the land and water around it.

The air from the Pacific going north makes sure you don’t get snow in California.  The cold arctic air flowing south gets pushed to the side by the deserts in Utah and Nevada so it can hit Washington D.C. letting it snow.  There is a lot of warm air coming from the Atlantic Ocean and when it hits that cold arctic air it cools and has to drop off all that water.

Weather is a world wide event and influenced by geography and started by the sun.  Without the sun the winds wouldn’t blow.  Yes the air would freeze, but before that the winds would die.

Thunderclouds (http://en.wikipedia.org/wiki/Thunderstor... can tower over 40,000 feet and the air is real cold up there.  The air is rising and falling and taking up water near the land and dropping it when it gets high.  If the storm is over water then it gets more fuel to power it and grows.  If the storm is violent enough then it can push that air around fast and the cold air falls fast and the water vapor with it freezes and can hit the ground as snow, even if the ground is over the freezing point of water.

If it is cold on the ground then the snow can stick, but if the air is dry then it won’t snow.  The Pacific Ocean makes sure it won’t snow over most of California.  But the East Coast has a different geography with the cold air coming south and hitting the warm air over the Atlantic so it has a higher chance to snow on the East Coast.

Notice how a Hurricane hits the coast and then drops in power and falls into a storm, with no water it has no heat source or water source so it runs out of power.

The fog in San Francisco started out as snow that melted on the way down and almost evaporates so it becomes a wet foggy cloud.  The air is warmer higher up over San Francisco than it is over Washington D.C.

The warm water is driving storms so when you are inland the storms start to drop off, the water vapor that makes it that far north is dropped pretty quickly and the Arctic air flowing south makes sure it is cold so snow is more likely the further inland you go in the US.

If the earth revolved backwards then the snow would be more likely to land on San Francisco than on Washington D.C.  The weather engine would be reversed.  Latitude is only one factor in determining the weather, the biggest factor is where your local source of warm water is.

Chicago is the windy city because the cold arctic air hits the warmer air over the Great Lakes and that air circulation starts, the water drives a storm and so wind is the result.  There is more snow in Chicago than in Montana because there is more local warm water and you need the water.

There is a desert in Washington State, so far north because of the barrier of the Rocky Mountains.

Your question was literally all over the map so my answer has to do the same.  The simple answer is the warm Pacific air makes sure it won’t snow over San Francisco, the cold arctic air has a hard time reaching you and most of its water vapor drops out over Oregon and Washington State.  What snow does fall melts on the way down, and can even partially evaporate causing all your fog.

There are morning and night showers, but it is less likely because it is colder so there is less water vapor in the air; therefore less storms.

Large bodies of water are heat sinks so if you leave near one you get a lot of water, and it is warmer.  If you live further inland the air will be cooler so events like snow are more likely.