How To Forecast Your Next Powder Day

How to forecast you next Joel Gratz | March 4, 2010 Powder Day REI Boulder

Your thoughts on weather forecasts? Colorado vs. ______? Joel Gratz | Meadow Mountain, CO | 2009-03-11

What do you want? JoelJoel Gratz | Steamboat, CO CO | 2009-03-11 Gratz | Meadow Mountain, | 2009-04-01

ColoradoPowderForecast.com... my meteorological destiny? Joel Gratz | Meadow Mountain, CO | 2009-03-11

GOAL Forecast Track Observe weather’s affect on snow Joel Gratz | Meadow Mountain, CO | 2009-03-11

please please please please (remember) orographics orographics orographics orographics orographics orographics orographics orographics orographics orographics Joel Gratz | Meadow Mountain, CO | 2009-03-11

Forecast Joel Gratz | Meadow Mountain, CO | 2009-03-11

WEATHER 101: Weather happens

WEATHER 101: Weather happens “Weather happens” when moist air gets high.

WEATHER 101: Weather happens “Weather happens” when moist air gets high. 1. Moist air rises.

WEATHER 101: Weather happens “Weather happens” when moist air gets high. 1. Moist air rises. 2. Less pressure = air expands = cools. (air pressure decreases as you go up)

WEATHER 101: Weather happens “Weather happens” when moist air gets high. 1. Moist air rises. 2. Less pressure = air expands = cools. (air pressure decreases as you go up) 3. Water vapor (gas) condenses into water drops (liquid) = a cloud forms.

WEATHER 101: Weather happens “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high.

WEATHER 101: Finding Moisture It depends on the path of the storm. Storms from the west and southwest bring the most (heaviest) snow. Little moisture (land source) OK moisture Lots of moisture (ocean + plants) (ocean source) http://www.virtualsources.com/Countries/North%20America%20Countries/us-map.gif

WEATHER 101: Finding Moisture Water Vapor Satellite Image, 3:45am on Fri, Jan 22, 2010 Lots of moisture (ocean source)

WEATHER 101: Finding Moisture Water Vapor Satellite Image, 12:00:pm on Thu, Mar 4, 2010

WEATHER 101: Weather happens “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high. “Weather happens” when moist air gets high.

WEATHER 101: Five ways to get high

WEATHER 101: Five ways to get high C is for convection.

WEATHER 101: Five ways to get high C is for convection. L is for low pressure.

WEATHER 101: Five ways to get high C is for convection. L is for low pressure. O is for orographic.

WEATHER 101: Five ways to get high C is for convection. L is for low pressure. O is for orographic. U is for undercut.

WEATHER 101: Five ways to get high C is for convection. L is for low pressure. O is for orographic. U is for undercut. D is for dynamic.

WEATHER 101: Five ways to get high O is for orographic.

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Flattops Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Flattops Grand Mesa Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Flattops Grand Elk Mesa Mtns Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Flattops Grand Elk Mesa Mtns N&S San Juans Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Flattops Grand Elk Mesa Mtns N&S San Juans East San Juans Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Flattops Grand Elk Mesa Mtns Sangre de N&S Christo San Juans East San Juans Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Precipitation is Elevation ph ic! ro gra ro is fo O Park Range Indian Peaks / RMNP Flattops Grand Elk Mesa Mtns Sangre de N&S Christo San Juans East San Juans Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: The upslope wind direction East RMNP North Steamboat Northwest Summit Co. Powderhorn Vail West Aspen Crested Butte Southwest Telluride Silverton Wolf Creek

WEATHER 101: Storm position STORM IS CLOSE STORM IS FAR AWAY O is for orographic. O is for orographic. L is for low pressure. C is for convection. D is for dynamic. C is for convection.

WEATHER 101: Who cares? Forecast Fri 3/5 5am L

WEATHER 101: Storm position STORM IS CLOSE STORM IS FAR AWAY O is for orographic. O is for orographic. L is for low pressure. C is for convection. D is for dynamic. C is for convection.

SNOW in CO: The upslope wind direction Forecast Fri 3/5 5am

SNOW in CO: Strong cold front = hrs of heavy snow Forecast Fri 3/5 2am Vail

SNOW in CO: The upslope wind direction Forecast Fri 3/5 2pm

Total Snow: 5pm Thursday to 5pm Friday Vail

Total Snow: 5pm Thursday to 5pm Friday Liquid 1) 0.40-0.60” Vail

Total Snow: 5pm Thursday to 5pm Friday Liquid 1) 0.40-0.60” 1” Liquid 2) = 17” Snow Vail

Total Snow: 5pm Thursday to 5pm Friday Liquid 1) 0.40-0.60” 1” Liquid 2) = 17” Snow Vail Snow 3) 5-10”

FORECAST

FORECAST Few hours of heavy snow Thursday night (dynamics...storm is close)

FORECAST Few hours of heavy snow Thursday night (dynamics...storm is close) On-and-off snow Friday (orographics & convection...storm is far)

Forecast for 16 days?

Track Joel Gratz | Meadow Mountain, CO | 2009-03-11

SNOW in CO: Jamming the radar

SNOW in CO: Jamming the radar The “magic” of radar is rather useless in the mountains since the beam is often blocked. Snow also doesn’t show up very well on radar. Beam is blocked by the ﬁrst mountain and can’t “see” to the second mountain. 0.5 deg http://www.iconspedia.com/uploads/2058636058.png http://www.drawingcoach.com/image-ﬁles/cartoon_clouds_1.gif http://images3.wikia.nocookie.net/funorb/images/0/06/Radar_Dish.PNG

SNOW in CO: Overshooting The radar can also overshoot the snow if it looks too far away. Radar beam at Steamboat = 16,000ft after starting at 10,000ft from Grand Mesa (GJT radar). Base Elevation + [ tan(0.5) = height / dist from radar ] Beam overshoots most of the snow and you 16,000ft can’t “see” it on radar. 10,600ft 0.5 deg 10,000ft http://images3.wikia.nocookie.net/funorb/images/0/06/Radar_Dish.PNG

SNOW in CO: Jamming & Overshooting The Denver, Pueblo, and Grand Junction radars are often jammed at the low levels, and overshoot the falling snow at higher levels. Steamboat RMNP Denver Radar = 5,400ft Pueblo Radar = 5,300ft Vail Grand Junction Radar = 10,000ft Summit Co. Aspen Telluride Wolf Creek http://www.ncdc.noaa.gov/nexradinv/

SNOW in CO: Satellite Can’t see snow - just the clouds that produce snow. You have to be “ninja” savvy to look at satellite images and see snow.

SNOW in CO: Surface Observations

SNOW in CO: Webcams!

Observe Joel Gratz | Meadow Mountain, CO | 2009-03-11

SNOW in CO: A state of Extremes Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: A state of Extremes • More than half of the total annual precipitation falls in only 20% of the days when precipitation occurs. Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: A state of Extremes • More than half of the total annual precipitation falls in only 20% of the days when precipitation occurs. • The difference between a wet year and a dry year can come down to the presence or absence of just a few major storms. Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: A state of Extremes • More than half of the total annual precipitation falls in only 20% of the days when precipitation occurs. • The difference between a wet year and a dry year can come down to the presence or absence of just a few major storms. • In the arid Western states, “normal weather” is just the average of 30 years of extreme events. Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Continental Snow Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Continental Snow • Dry. 5-10% density, 1” of liquid = 10-20” of snow. Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

SNOW in CO: Continental Snow • Dry. 5-10% density, 1” of liquid = 10-20” of snow. • Less. The 5ft storm is rare. Usually a few inches. Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

Forecast Tricks • Watch the weather every day, and match the forecast to actual conditions. • Read the “Area Forecast Discussion” from the National Weather Service. Available for Boulder (BOU), Pueblo (PUB), and Grand Junction (GJT) areas. http://www.nws.noaa.gov/view/prodsByState.php?state=CO&prodtype=discussion • Understand how the computer model forecast is trending as the storms moves closer. Computers are never exactly correct.

Websites: ColoradoPowderForecast.com FORECAST Moisture: relative humidity at 700mb (10,000ft) www.rap.ucar.edu/weather/model Orographic lift: wind direction and speed at 700mb (10,000ft) www.rap.ucar.edu/weather/model Other lift: C.L.O.U.D. using various maps www.rap.ucar.edu/weather/model CAIC Discussion: Get a “feel” for the weather pattern http://avalanche.state.co.us/ NWS Discussion: Grand Junction, Pueblo, & Boulder http://www.nws.noaa.gov/view/prodsByState.php?state=CO&prodtype=discussion TRACK Surface reports, Radar (very limited), Satellite http://www.rap.ucar.edu/weather/ http://www.nws.noaa.gov/ OBSERVE Snowfall http://www.wcc.nrcs.usda.gov/snow/ Temperature & Moisture by elevation http://mesowest.utah.edu/index.html Cloud Cover http://www.rap.ucar.edu/weather/ Wind Transport http://mesowest.utah.edu/index.html

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How To Forecast Your Next Powder Day

by Joel Gratz on Mar 05, 2010

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How To Forecast Your Next Powder Day — Presentation Transcript