1. Colorado Climate: How would you describe it?
Overall -- semi-arid with precip gradually increasing as you go eastward into Kansas and Nebraska -- dry winters, wetter springs and summer, highly changeable weather, often windy, and some occasional monstrous thunderstorms with damaging hail.
--provided by Nolan Doesken, Colorado Climate Center

2. Agenda A. Topography B. Local Influences on Weather
C. Upslope and Downslope

3. A. Topography
Colorado lies astride the highest mountains of the Continental Divide
Mountain ranges extend North and South through the middle of the state
The average elevation is 6800 feet, the highest State in the Union
Eastern plains

4. B. Local Influences on Weather
North Facing Slopes vs South Facing
1. North Facing Slopes
Wetter so they support cool, wet spruce forests
Support Glaciers
2. South Facing Slopes
Arid; host aspen and poplar trees
The difference between sun and shade may be as great as degrees C or degrees F.

5. North vs South Facing Slopes

6. More Local Influences on Weather
3. The Continental Divide
Our weather must climb and crest the divide.
Eastern slopes are characterized by much drier climates than areas only a few kilometers on the Western side of the divide.

8. Local Influences… 4. Latitude
Latitude affects the angle with which the sun’s rays hit the Earth. The farther from the equator, the sun’s rays impact the Earth at increasingly shallow angles.
With the northern latitude of the Rockies in excess of 50 degrees North our sunlight never comes from directly overhead.

9. Even more Local Influences..
5. Altitude
As you climb in elevation, the air pressure decreases. Thinner atmospheres are less capable of holding heat, resulting in a gradual drop in temperature.
For every 300 meters climbed the average drop in temperature will be degrees C.
Wind increases with altitude
As an average, a climb of 30 meters (100 feet) delays spring by one day!

10. C. Upslope vs Downslope
Upslope Flow – Air that flows toward higher terrain, and is forced to rise. In Denver, wind from the East.
Bring an increase in clouds and often rain or snow to Denver
Dry weather will hold west of the Continental Divide
Downslope (Chinook) – winds from the West; typically warm and dry.

11. Upslope

12. Downslope