Educational stuff here. check out the 2 links for indicative weather pattern cloud fotos.

http://atmos.es.mq.edu.au/AMOS/weath...2/0123mb01.jpg
fair or static weather, indicitive of Valley winds

http://www.australiansevereweather.s...8/1229jd01.jpg
Dynamic weather, Category Adiabatic,

Dynamic winds;
Note: these are only a few of the types of dynamic winds.The ones I feel are most influential on site doability irreguardless of the time of day....

I. Katabatic Winds



Under the influence of gravity, a shallow mass of cold, dense air slides downhill, resulting in a katabatic wind. This phenomenon is sometimes called cold air drainage.
(Katabatic effect is a local wind blowing outward from an ice cap or elevated area as a result of intense cooling, subsidence and spreading of air.)
This usually occurs in winter over extensive snow-covered plateaus or hills. Adiabatic warming is not enough to heat the parcel of descending air, so that the air is still very cold when it reaches lower elevations.
The best known of these is called the Mistral in Europe, which occurs in the snow-capped Alps. Winds descend downslope into the Rhone Valley of France and along the Mediterranean Coast.
This phenomenon also occurs on the eastern edge of the Rockies, thus inundating such cities as Denver, Boulder, and Colorado Springs with cold air from higher elevations.
Katabatic winds rarely reach speeds of 10 km/hr, but occasionally they can be funneled through narrow valleys, causing winds to reach destructive speeds. The cold air draining off Greenland and Antarctica can reach speeds of up to 100 km/hr.

Adiabatic Cooling and heating:

Adiabatic cooling deals with the cooling of parcels of air as they rise, or are forced up, through the atmosphere. There are three different rates of cooling for air. The first is the ambient atmosphere lapse rate which is the rate that air cools as one goes up in altitude. The second, is the Dry Adiabatic Lapse Rate, -10 degrees/1000m. The third is the Wet Adiabatic Lapse Rate, about -6 degrees/1000m. The last two rates are in reference to a parcel of air that is rising through the atmosphere. The first rate is used to describe the temperature of the surrounding air that the rising air is passing through. The best illustration of adiabatic cooling is as a parcel of air is being forced over a land formation, such as a mountain. Let us take this process step by step with illustrations.

(Sorry, I have to get Micks help on the Illus)


As one can see the temperature difference between the western side and the eastern side of this mountain are considerably different. The western slope receives much more rainfall than the eastern side, making the eastern side much dryer.. This situation is known as a rainshadow. The winds (Chinook winds obviated sometime by Altocumulus Lenticularis clouds) that come down on the eastern side are some of the driest, which can make the land even dryer by evaporating what water is there.

Chinook Winds

Chinook winds develop when relatively stable air is forced over a mountain range, then warms as it compresses on the leeward side of the mountains. Hence, these are dry, hot winds as opposed to katabatic winds.
Chinook winds actually respond more to pulling than to gravity. The air is actually stable, and wishes to return to its pre-mountain stable position on the other side of the range.
In addition, cyclonic and anticyclonic circulation patterns on the lee side of the mountains also acts to pull winds down from the mountain ranges.
Chinook actually means "snow eater" because these winds, when moving over snowy areas, can evaporate up to half a meter of snow in just a few hours. In Germany, these are called foehn winds, and in Argentina they're called zonda winds.
The Santa Ana winds of southern California occur as hot dry air is pushed from a high in the Great Basin over the mountains of southern California, desiccating vegetation and contributing to destructive wildfires

Mountain and Valley Winds in a fair or static weather system

During the day, the slopes of mountain heat up and becomes less dense than air at the same elevation over the valley. Hence, winds tend to flow upslope during the day and these are called valley winds. Because of Funneling through the Valley these low, cool, dense daily winds can easily reach 40mph+ in the spring because of the higher temparature gradient in the lower and upper air levels (Upper is still cold from the winter, Ground is warmer because the higher inclination of the sun).
The reverse situation happens at night. The steep mountain sides cool much faster causing air to become more dense. This causes air to sink and winds then become downslope. These are called mountain winds.

Mountain and Valley Winds, Solar heating and radiational cooling influence local flow in terrain situations
Consider daytime heating of a south-facing slope in the Northern Hemisphere.

Sun heats slope
Air adjacent to slope warms, its density decreases, and attempts to ascend
Near the top, the air rises vertically
It is easier for air to move upslope, rather than rise vertically


At night when raditional cooling occurs on slopes, the cool dense air near the surface descends along the slope (downslope wind)
Where downslope winds accumulate on opposite slopes of the valley, cold air can accumulate on the valley floor

If there is a slope to the valley floor, air can move down (or up) the valley, resulting in a canyon wind.

The effect of solar radiation is dependent on valley orientation
east-west valleys only have one slope significantly heated (the south-facing slope) In the Northern Hemisphere.
north-south valley will have both slopes heated at midday independent of hemisphereical location.

Flow perpendicular to valleys tend to form circular eddies and encourage local flows
Flows parallel to valleys tend to discourage local flows and sweep clean the valley
Flow down the leeward side of mountains, Dynamic, - Fohn (Alps), Chinook (Rockies), Zonda (Andes) winds can result in
Very high windspeeds....100mph+, with clouds (Altocumulus Lenticularis) remaning stationary at the peak wave points above the dewpoint..
End of part one.
Credits to all whove helped me directly or indirectly...
Space. (Tracy Walker)