Colorado Climate: How would you describe it? Overall -- semi-arid with precip gradually increasing as you go eastward into Kansas and Nebraska -- dry winters,

Colorado Climate: How Colorado Climate: How would you describe it?would you describe it?Overall -- semi-arid with precip gradually Overall -- semi-arid with precip gradually

increasing as you go eastward into Kansas and increasing as you go eastward into Kansas and Nebraska -- dry winters, wetter springs and Nebraska -- dry winters, wetter springs and summer, highly changeable weather, often summer, highly changeable weather, often

windy, and some occasional monstrous windy, and some occasional monstrous thunderstorms with damaging hail.thunderstorms with damaging hail.

--provided by --provided by Nolan Nolan DoeskenDoesken, Colorado , Colorado Climate CenterClimate Center

AgendaAgenda

A. TopographyA. Topography

B. Local Influences on WeatherB. Local Influences on Weather

C. Upslope and DownslopeC. Upslope and Downslope

A. TopographyA. Topography

Colorado lies astride the Colorado lies astride the highest mountains of the highest mountains of the Continental DivideContinental Divide

Mountain ranges extend Mountain ranges extend North and South through North and South through the middle of the statethe middle of the state

The average elevation is The average elevation is 6800 feet, the highest 6800 feet, the highest State in the UnionState in the Union

Eastern plainsEastern plains

B. Local Influences on WeatherB. Local Influences on Weather

North Facing Slopes vs South Facing North Facing Slopes vs South Facing

1. 1. North Facing SlopesNorth Facing Slopes Wetter so they support cool, wet spruce forestsWetter so they support cool, wet spruce forests Support GlaciersSupport Glaciers

2. South Facing Slopes2. South Facing Slopes Arid; host aspen and poplar treesArid; host aspen and poplar trees

The difference between sun and shade may be as The difference between sun and shade may be as great as 22-28 degrees C or 40-50 degrees F.great as 22-28 degrees C or 40-50 degrees F.

North vs South Facing SlopesNorth vs South Facing Slopes

More Local Influences on WeatherMore Local Influences on Weather

3. The Continental Divide3. The Continental Divide

Our weather must climb and Our weather must climb and crest crest the divide.the divide.

Eastern slopes are characterized by Eastern slopes are characterized by much drier climates than areas only much drier climates than areas only a few kilometers on the Western a few kilometers on the Western side of the divide.side of the divide.

Local Influences…Local Influences…

4. Latitude4. Latitude

Latitude affects the angle with which the Latitude affects the angle with which the sun’s rays hit the Earth. The farther from sun’s rays hit the Earth. The farther from the equator, the sun’s rays impact the the equator, the sun’s rays impact the Earth at increasingly shallow angles. Earth at increasingly shallow angles.

With the northern latitude of the Rockies With the northern latitude of the Rockies in excess of 50 degrees North our in excess of 50 degrees North our sunlight never comes from directly sunlight never comes from directly overhead.overhead.

Even more Local Influences..Even more Local Influences..

5. Altitude5. Altitude

As you climb in elevation, the air pressure As you climb in elevation, the air pressure decreases. Thinner atmospheres are less decreases. Thinner atmospheres are less capable of holding heat, resulting in a gradual capable of holding heat, resulting in a gradual drop in temperature.drop in temperature.

For every 300 meters climbed the average drop For every 300 meters climbed the average drop in temperature will be 1.5-3.0 degrees C.in temperature will be 1.5-3.0 degrees C.

Wind increases with altitude Wind increases with altitude

As an average, a climb of 30 meters (100 feet) As an average, a climb of 30 meters (100 feet) delays spring by one day!delays spring by one day!

C. Upslope vs DownslopeC. Upslope vs Downslope

Upslope Flow – Air that flows toward Upslope Flow – Air that flows toward higher terrain, and is forced to rise. In higher terrain, and is forced to rise. In Denver, wind from the East.Denver, wind from the East.

– Bring an increase in clouds and often rain or Bring an increase in clouds and often rain or snow to Denversnow to Denver

– Dry weather will hold west of the Continental Dry weather will hold west of the Continental DivideDivide

Downslope (Chinook) – winds from the Downslope (Chinook) – winds from the West; typically warm and dry.West; typically warm and dry.

UpslopeUpslope

DownslopeDownslope