About ESAC

Our Mission:
To provide quality avalanche and snowpack information to local and visiting backcountry users in the Eastern Sierra Nevada with the goal of helping them make better decisions while travelling in avalanche terrain.


The Eastern Sierra Avalanche Center has a staff of three full-time forecasters - profiled below.
For general information, please email 

Doug Lewis
Lead Forecaster


As a lover of all things snow and citizen of the world, I have been working in the Avalanche Forecasting and Snow Safety Field for over almost 20 years with my first introduction to Snow Science as an intern with the Park City Ski Patrol at 16. Since then I have built on that experience in some of the most avalanche prone regions throughout the world, including: Alaska, Colorado, Utah, Chile, Canada, New Zealand (most recently The Remarkables). I am excited to have this opportunity to share my passion for snow with kindred spirits and to be a part of the Eastern Sierra backcountry community. 
Josh Feinberg


Josh moved out to the Eastern Sierra for a winter in 2002 to try out Ski Patrolling, and can’t seem to leave.  Discovering and exploring the winter backcountry soon became a passion as he learned to link more than 2 turns together on those floppy hippy skis with broken heal bindings.  Over the years he’s learned to respect the snow thru experience and education.  He’s had the privilege of being part of the Mammoth Mountain Ski Patrol team for a dozen years, and it is now his fifth year as part of the Eastern Sierra Avalanche Center’s forecasting team.  He spends summers working for the Forest Service’s Forest Inventory and Analysis program, hugging trees with measuring tapes and collecting data on forest health all over central California.

Clancy Nelson


Clancy grew up in Mammoth with skis on his feet ski racing on both nordic and alpine teams. He began teaching skiing at the age of 12. He studied environmental science and philosophy at Whittier College and Claremont Graduate School before returning to the east side to work for the Inyo National Forest as a backcountry ranger and trail crew leader during the summer. After spending a season on Mammoth Mountain Ski Patrol Clancy decided to ski the Sierra backcountry and study our local snow full time. Clancy has been an observer for ESAC, working closely with forecasters and tracking weather and snowpack trends, which he has been recording since 2008. He has been certified though the AIARE Level 3 (now Pro 2) program, is a certified AIARE avalanche course instructor, and has training in winter weather forecasting through AAI. Clancy has also started coursework to become an AMGA ski guide. 


The Friends of Eastern Sierra Avalanche Center is a 501(c)3 non-profit organization dedicated to raising funds to ensure staffing for the operation of the avalanche center each year. The organization is overseen by a volunteer Board of Directors, outlined below.  For general information, please email office@esavalanche.org.

Nate Greenberg

Nate Greenberg has called the Eastside his home since 2000. Drawn here by the acess to amazing terrain and quality of skiing, he has spend a considerable amount of time exploring the snowy Sierra. Nate is AAA Level III trained and has worked as a NOLS instructor for climbing and mountaineering. A former competitive telemark skier, Nate now enjoys getting into the backcountry with friends and exploring the endless terrain of the Eastern Sierra.

As his day-job, Nate is the IT Director for Mono County, and as the co-author of Backcountry Skiing California's Eastern Skierra, Nate's interest is in disseminating quality information to the general public. As a result, Nate spends a great deal of time on the Center's website, and helps coordinate the overall operations of the Center.


Scott Quirsfeld
Vice President

Over the past 18 years Scott has been working in the outdoor industry, starting as a rock climbing instructor, part time Ski Patroller and a PSIA certified Ski Instructor. After a winter in New Zealand, Scott moved from Taos, NM to Mammoth in order to pursue longer winters. He has been a Pro Patroller for Mammoth and a passionate Eastern Sierra backcountry skier since 1998.

Scott earned an Engineering degree at The Ohio State University and immediately relocated to the Rockies where he earned an Emergency Medical Technician degree from the University of New Mexico. Since moving to Mammoth he has earned the following certifications: National Avalanche School phases I & II, Avalanche Blaster’s license, AAA Level III, AUNAC Artillery Gunner, Avalanche Rescue Dog Handler. He has continued to challenge himself and fellow patrollers by organizing avalanche rescue scenarios and training new patrollers at Mammoth. He is currently recognized by Recco, Dynastar/Lange, and Hestra as a representative.
When Scott is not working, you can find him backcountry skiing, ski mountaineering, or ski touring with his dogs all over the Eastern Sierra.  

Forrest Cross

Forrest Cross has been visiting the Eastern Sierra for almost 15 years and has lived here for the last 10 years. One of the main reasons he lives here is for the endless backcountry skiing opportunities during the winter months. For the last 20 years he has been backcountry skiing in the mountains of Northern California and the Sierra. He has completed a level 2 AIARE course and has taught avalanche awareness to guides for Outdoor Adventures at UC Davis. When not playing in the hills, Forrest works as an engineer for the Mammoth Community Water District and helps monitor all the runoff that the winter snows produce. Forrest enjoys being involved with ESAC and helping to spread the word of avalanche safety in the Eastern Sierra. As Membership Director he keeps tabs on membership numbers and maintains the member email list-serve.

Howie Schwartz

Howie Schwartz is an AMGA/IFMGA certified ski and mountain guide based in Big Pine, California. Howie guides skiing and mountain climbing trips year round in the Sierra Nevada, the Alps, Alaska and other destinations. He is an instructor/examiner for the American Mountain Guides Association and is on the AMGA Technical Committee. He was a founding member of the American Institute for Avalanche Research and Education and leads AIARE level 1-3 avalanche courses. Howie also trains AIARE instructors. Howie’s skiing relationship with the Sierra started in the spring of 1996 on a basecamp ski trip near Virginia Lakes. Since that time, this love affair has all but ruined his otherwise productive professional life. Howie has still not figured out what “Sierra Cement” is, but he has heard some can be found up near Lake Tahoe.

Allan Pietrasanta

It was almost 25 years ago that Allan Pietrasanta realized the need for an easier to use, more protective case for his Pieps avalanche beacon. The standard yellow thin cloth bag and shoestring necklace just wasn’t cutting it, so he created high-tech padded pouches that he was able to use in trade for payment to complete one the first avalanche courses taught in Mammoth. While the beacon case project helped increase his avalanche awareness, it was also the roots of a sewing manufacturing company, ABCOM/Buttermilk Mountain Works, that Allan owned and operated for over two decades in Bishop. Allan has left ski tracks in the High Sierra and other mountain ranges of the world, and continues to celebrate the joys of backcountry skiing and its contributions to world piste. He combines his interest in business, his past experience as a mountain guide and early Board member of the American Mountain Guides Association to help ensure a bright future for ESAC.


Joani Lynch

Joani has spent the better part of her career in at Mammoth Mountain Ski Area. A specialist in Public Relations, Lynch quickly rose through the ranks of the marketing department and is now Senior Director of Brand Marketing. In her current role she is responsible for developing and implementing integrated marketing communications plans and directing all communication efforts on behalf of Mammoth Mountain and its ancillary businesses. She oversees a team of 15 diverse staff members with expertise in their fields including public relations, social media, advertising, creative services and content creation. She also acts as resort spokesperson with live television experience on KTLA, Weather Channel and more.

An outdoor enthusiast, Joani enjoys skiing, snowboarding, Nordic skiing, mountain biking and exploring the Eastern Sierra with her husband and two daughters. Joani is involved in a number of community organizations and sits on the Board of Directors for Protect Our Winters.


Walter Rosenthal
President in memoriam

Walter Rosenthal was the Snow and Avalanche Analyst for Mammoth Mountain, a remote sensing expert for the U.S. Army Cold Regions Research and Engineering Laboratory and a researcher at the Institute of Computational Earth System Science, University of California, Santa Barbara. He specialized in remote sensing of snow and snowpack processes related to sintering and avalanches. As a private consultant he provided operational subresolution snow mapping algorithms and programs to the U.S. Army Cold Regions Research and Engineering Laboratory from 1995 through 2002. Both the Army and the National Weather Service’s National Operational Hydrologic Remote Sensing Center employ his algorithms and are expanding their use to daily operational snow cover maps over North America.

Walter tragically lost his life while trying to save the lives of others in 2006. He was a vital force in the development of the Center and is dearly missed.

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