1. Nic Wayand and Ryan Currier

2. Heavy Rain Melting Snow (Less than 25%)

3. “Typical” Storm SNOWFALL RAINFALL RUNOFF No runoff production Elevation Z 1 AREA contributing overland runoff to stream Photo credit: Flickr.com User: Lucas – K Lu Slide by Mark Raleigh RUNOFF

4. Rain-on-Snow Event SNOWFALL RUNOFF Elevation Z 2 Rain-on-Snow event produces Larger AREA contributing overland runoff to stream Warmer Storm (1 week later) Elevation Z 1 ΔZΔZΔZΔZ RAINFALL Photo credit: Flickr.com User: Lucas – K Lu Slide by Mark Raleigh Snowcover exposed to warm, windy weather

6. From Mike Dettinger

7. So what does melt the snow?

8. You need energy to melt snow “Snow” = Ice, liquid water, and air Melting snow requires a phase change from ice to liquid. The phase change breaks bonds. The amount of energy required to break these bonds is called the Latent heat of fusion It takes 334000 Joules to melt 1 kg of ice

9. Sources of energy for the snowpack MELTING Rain Solar Reflected Solar Incident/ Emitted Longwave Thermally Active So SrSr P L in S in L out G ΔE Snow Soil Ground heat Flux Sensible Heat Flux Latent Heat Flux LeLe H

10. Solar Radiation During a clear day Solar Radiation is the primary energy input into a system

11. Terrestrial Radiation Clouds, Trees and anything that has a temperature emits radiation, including you! °F

12. Credit: Dr. J. Lundquist

13. Sensible Heat Flux Think Convection (hair dryer) Warm and windy conditions = larger sensible heat flux www.shutterstock.com

14. Latent Heat Flux Water Vapor Liquid Condensation Latent heat released Heat melts snow! Warm, windy, and HUMID conditions = larger latent heat flux

16. SNOWFALL RAINFALL RUNOFF Photo credit: Flickr.com User: Lucas – K Lu RUNOFF How will Rain-on-snow Floods change in the future? ΔZΔZΔZΔZ