why is the central u.s. not a good air mass source region?
447609
Air masses are often formed in regions of low relief and calm wind that prevents turbulent mixing that allows the air to take on the conditions of the surface over which it forms.
233922
Warm fronts (lows, low pressure) ride over the top of cold fonts (highs, high pressure).  The winds are going in different directions and can spawn tornadoes.  Also, the water vapor in the warm front air cools as it gains altitude and produces rain.  If there is a lot of turbulence, the water can freeze into droplets of ice which keep going up and down and around in the turbulence produced by the interaction of these air masses.  This produces hailstones.\n\nWarm air is light and laden with water vapor.\nCold air is dryer usually, and always heavier than warm air.\n\nSo you got some different kinds of weather there.\n\nHuge masses of warm, water laden air are found in hurricanes.  The water is in huge, towering masses of clouds.\n\nIn the northern hemisphere, warm air masses (lows) spin counterclockwise.  Cold air masses (highs) spin clockwise.\n\nWarm air comes mostly from the south, cold air from the north.  However, air masses are steered by the Jet Stream also.  Maybe your next topic.\n\nHurricanes have the lowest pressure of all (low barometer reading).
915955
You have probably noticed that the jet stream, cold fronts, and that sort of weather all moves across the U.S. from west to east. What is happening is that New York, even though it is on the coast, is getting its weather from air masses that have come across thousands of miles of land, so the effect of being near the ocean is minimal. \n\nThis is only the case in big weather events such as fronts. On days where not much is going on, I suspect that the land/sea breeze dominates the daily temperatures and makes it fairly mild.
543373
We have air around us. The atmosphere has high preasure and low preasure. When the high preasure area turns into low preasure, the air moves from high preasure area towards the low preasure. This movement of air from one area to another causes the wind. \n\nIt has nothing to do with clouds. The faster the low preasure area is formed, depends on whether you have clouds, or thunderstorms. Low preasure areas causes rain. This is why normally you have winds before the rain.
47849
It has to do with moisture saturation.  Big tall clouds have this unlike the thin high cirrus clouds.
345696
Central and mountain.
80711
I lived there five years, and I don't remember a single one. I hear that higher elevation deters tornado formation. Once, a hurricane plowed through the whole state and did some damage to Boone and the surrounding area, so maybe that counts.
818992
Cool - you seem to have really interesting weather.\n\nYes, if there is a 1000 foot difference between you & the town 7 miles away you will certainly experience different weather in some situations - and typing in your zip code for an online forecast generally will not help - to my knowledge the type of meso and micro scale effects you mention are not included in any of them. You really have to learn how your local weather differs from that at surrounding areas (which are forecast for) for specific situations.\n\nFor example, when the temperature is near the dewpoint with storm systems affecting your region, the cloud base in town can be below 1000 feet and below you. There are many orographic effects on the microscale - mountain-valley breezes, and the extra elevation can in certain situations cause showers to occur over you but not them. After a cool & clear night, you may become warm quicker than the town does - cool air persisting in the valleys longer after sunrise - then they'll become quite a bit warmer than you during afternoon.\n\nThough the NWS attempted to place the doppler radars at locations for the best overall coverage, some mountain locations still cause problems. The base reflectivity images you typically see when you look at a "radar map" are obtained using a beam tilted .5° above horizontal. If the precipitation is occurring primarily below that or there is an intervening mountain, you may get a small or no signal. That is much more common with snow rather than rain showers because low & rather thin clouds can sometimes produce them. Raindrops generally need a much greater vertical distance for the water droplets to combine and become large enough to fall out of the cloud. Ice crystals can float around horizontally much more and do that.\n\nSo there are many possibilities, but I would have to know exactly where you are to say anything specific.\n\nI saw something cool visiting Clingman's Dome in Tennessee one September. It was a sunny day, but on the road to the summit there was a large low area in amongst the mountains over which a cumulus cloud had formed. Became cloudy for a few minutes as we passed by then was sunny again. On the way back down a few hours later, the cloud was still there. There were a few small cumulus clouds here & threre occasionally, but some orographic circulation evidently caused that cloud to form & persist much of the day. Was a warm day - I am guessing a little over 80° even at the summit.
882564
It's the air flow from west to east in the U.S.
639
The fog that develops in the Central Valley is called Radiation Fog. The page listed 1st as a source states:\n\n"Climatologically important conditions for radiation-fog development in the Central Valley include cool 1600 LST surface temperatures, moisture availability as reflected by 1600 LST dewpoint temperatures, early evening surface cooling trends, the rapidity with which mean relative humidity reaches 90%, and the presence of cool, dry air aloft (700–500 hPa)."\n\nGo to this page:\nhttp://www.islandnet.com/~see/weather/almanac/arc2002/alm02sep.htm\nand find the header "Radiaton Fog" about 1/3 down the page to see a very nice explanation of how Radiation fog forms.
985665
The primary reason why we don't get many tornadoes in the New York area is the influence of the cooler Atlantic Ocean.  Cooler air nearer the coast acts as a stablizing influence and takes some of the zap out of tornado producing thunderstorms.  While there are exceptions, usually as strong cold fronts approach the coast they weaken and these fronts are often responsible for the heaviest thunderstorm activity.\n\nAs far as earthquakes go, we do not live near the edge of continental plates where there are more earthquakes of stronger magnitude, but just because we haven't experienced a big earthquake in New York in our lifetime, doesn't mean that it cannot happen.  Actually there is a fault that runs under 125th St. in Manhattan.  There are several others in Westchester County.  Some geologists have discovered that there is evidence that there have been some pretty big earthquakes in the New York area in the past, they just don't happen very frequently.  Not all major earthquakes happen near and along where different continental plates come together.
474726
You have gravity holding down air at lower elevations due to the mass of the Earth. The higher you rise, the less gas there is contained in the atmosphere (but you probably already know this). As you have less mass and more vacuums in higher altitudes, the need to fill the vacuum becomes much greater. The water starts to fill here and other water tends to coagulate around these base droplets. You eventually find groups of water together that tend to vary based on temperature.
1117649
several things are at work:\n\n1) the mass of the trees & coal in any area is comparatively insignificant when contrasted against the mass of the earth\n\n2) conservation of matter (which roughly translates in this instance to conservation of mass): the involved processes are not nuclear in nature\n\nfor instance, a pound of coal is taken from the Black Mesa, AZ and burned in New York, NY.  in New York, it leaves behind 0.8 ounces of Mercury, 1.2 ounces of carbon black and 0.5 ounces of material retained in the formation of ash: 13.5 ounces were converted to components of exhaust gases -- commonly, carbon dioxide and water.\n\nNow imagine the total mass of the earth is 2000 tons and the average density is 4 g/cm^3 (just over 249.71 lbs/cu ft): the average radius of the earth would then be very slightly less than 15.638 feet (roughly 27,680,013 cu ins).\n\n\nWithout going into the slight deformation of our oblate spheroid, and imagining the pound of coal had an average density of 1.5 g/cm^3, the extracted coal had a volume of roughly 18.453 cu ins.\n\nThe distance those 18+ cu ins were moved amounts to just under 93 inches along a great circle route describing a 1179.07-inch circumference (almost 28.387 deg).\n\nObviously, this is going to have negligible effect on the mass of the overall body, even with it rotating at 1/4 deg per minute (1 revolution per 24 hours). \n\nthese gases disperse, and are usually absorbed by various organisms.  however, some of these gases are further converted (for instance, lightning can separate water and other compounds into their constituent atoms, and provide the energy for reforming other compounds such as ozone).\n\nfor those unfamiliar with it, ozone is the triatomic form of oxygen (which is why i get a kick out of ads like the one for the "ionic breeze" that "converts ozone to oxygen")\n\nthe point is that the masses of the constituent elements never changed: they were simply redistributed -- arguably, in a way that mitigates against the creation of even a very slightly unbalanced condition.
163797
In the midwest, the mountains to the west and the Gulf of Mexico to the south produce the layers of cool, dry air and warm, moist air, these coditions are favorable for tornado formation. These conditions happen much less often toward the coasts. Tornados aren't uncommon on the east coast though. In fact, areas hit hard with hurricanes(Gulf Coast) have tornado outbreaks too because the hurricanes produce apt conditions for formation.
1149050
The predominant wind patterns are from the Ocean to land. The water is relatively cold off the shores of all California due to the Japan current. The energy to create storms that move inland are not there. Storms brought in from the East are often dissappated by the high mountain ranges along the California shore, in OC, as little as 10 miles away. The tremendous, fast uprise of wet air moving west dumps the water in the mountains and leaves little to effect the California shore. Due to the Gulf Stream in the Atlantic, East Coast storms are much more dangerous and prevalent. The Great Planes have storms generated by massive cold 'bubbles' of artic air hitting the moist air from the Gulf or Atlantic...California is not positioned to have these effects...we have Earthquakes and threat of Tsunamis instead.
538503
Because the air is less dense the higher the altitude, there are less molecules available to retain heat. Therefore the heat of the sun dissipates more readily.
1029587
Previous answers are crap. Air pressure is less up in the mountains, so the air there is less dense. When you are at the beach, you have all of the air from the beach to the top of the atmposphere above you. This air has weight, and pushes down on you. This is the same idea as the pressure at deep parts of the ocean being very high. Because air is compressable, the air at the beach is made more dense because of the weight of the air above it. In the mountains, you have less air above you (most of the air is below you), and so the air pressure is less. This means the air is less dense, and so it is "thin".