1. Mountain Weather

2. Weather
Weather: the exact atmospheric conditions over a short period of time
The main components of weather:
Temperature
Pressure
Wind
Humidity
These elements continuously interact in a very complex process. Though scientists understand individual interactions very well, in practice there are too many variables for accurate predictions (even by the world’s most powerful computers)
Temp
Barometric pressure
Humidity
Wind

3. Temperature
Daily Variation: Usually lowest in morning and highest in afternoon. This is when local winds are at their strongest.
Higher Elevation -> Lower Temperature (lapse rate)
3°F/1000 feet moist
5°F/1000 feet dry
Temperature Inversions: Check the forecast, it might be cloudy down here but clear up high and warmer!
Check point forecast: Go to NWS site and use map to find hiking place, click on that point.
Temp
Barometric pressure
Humidity
Wind

4. Pressure Atmospheric pressure is the weight of the air above you
Higher Elevation (less air) Lower Pressure
Low pressure systems
Rotate counter-clockwise
Usually associated with bad weather
Winds from S or SW
High pressure systems
Rotate clockwise
Usually associated with good weather
Winds from N or E
Temp
Barometric pressure
Humidity
Wind

5. Humidity Humidity is the amount of water in the air.
When air gets pushed up it cools, increasing the humidity until clouds form and then precipitation occurs.
Thunder clouds
Tall, vertical clouds
Dark streaks or sections
Temp
Barometric pressure
Humidity
Wind

6. Wind Jetstream Prevailing winds Localized winds
High altitude winds from west to east
Tend to move weather systems
Prevailing winds
Winds produced by weather systems.
Usually because of differences in pressure
Localized winds
Variations do to local features that obstruct the prevailing winds
Using wind to forecast: With your back to the wind-Low pressure on your Left. Backing wind (wind direction changing in a counter-clockwise manner) means approaching Low.
Temp
Barometric pressure
Humidity
Wind

7. Wind Chill Wind makes it colder.
Promotes evaporation, which makes it colder still
Temp
Barometric pressure
Humidity
Wind

8. Northwest Weather Almost all of our weather systems move west to east
Occasionally, one sneaks down from Canada but that’s more so in the Okanogans on the east side
Prevailing winds
S-SW winds mean a low is off the coast
N winds means a high is off the coast
E winds means high pressure in Eastern Washington is pushing over the mountains
Temp
Barometric pressure
Humidity
Wind

9. Northwest Mountain Weather
Rain Shadow
Rain Forest
Chinook winds
When in doubt about the weather– go east
Temp
Barometric pressure
Humidity
Wind

10. Predicting weather
Monitor your altimeter: If your altimeter is showing higher elevations that means the pressure is falling.

11. Monitor the clouds:
High cirrus or “mares tails” signal an approaching front. As the clouds get thicker and lower the front is getting closer.

12. Halo around the sun There may be no clouds but a halo around the sun also signals approaching cloudy weather.

13. Lenticular clouds
These clouds tell you the wind is very strong up high.

14. Lightning
Due to our maritime climate and PNW weather patterns, lightning in the mountains does not occur that often.
None-the-less, do NOT underestimate the hazard
Learn to recognize approaching thunderstorms.
Learn what to do if you get caught
Temp
Barometric pressure
Humidity
Wind

15. Recognize the Signs
Vertical development of clouds

18. Recognize the Signs The sound of thunder or sight of lightning
Thunder clouds moving in
Hail falling
Hair standing on end
Buzzing or humming sounds
Sparks or shocks from static when you touch stuff.
Temp
Barometric pressure
Humidity
Wind

19. Avoidance Measures Don’t leave home without a forecast
If lightning is expected, start early and be off the mountain by noon
Get off the mountain before it’s too late
Gauge a storm’s movement and act in a timely fashion (Count the seconds from seeing lightning to hearing thunder. Five seconds is one mile.)
If your hair stands up or metal objects hum, act immediately!
Temp
Barometric pressure
Humidity
Wind

20. What to do if Caught Get off summits and ridges
Don’t be the tallest thing around (or near it)
Avoid moist areas, small caves, and depressions
Crouch to make yourself small, but don’t lie flat
Get on an insulating pad or pack(?)
Get rid of large metal objects (ice axe)
Temp
Barometric pressure
Humidity
Wind

21. Be Prepared Take gear appropriate for the forecast
Take extra gear appropriate for season
Drink water and eat plenty of food
Allow extra time in bad weather
Don’t be afraid to call it off or head east
Temp
Barometric pressure
Humidity
Wind