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Colorado Snow
Forecasting
101
Meteorologist Joel Gratz

Photo: Connor Walberg
ActionPhotoSchool.com
How this presentation will
help you:
1) Remove mystery of
Colorado weather.
2) Find the most snow.
Hi, I’m Joel Gratz.
I grew up in Pennsylvania,
ski raced and instructed,
then moved to Colorado
after college.
And I started to
miss powder days due to
inaccurate forecasts.
And it made me mad!
So I learned how to forecast in
Colorado, and started to share.
Dec 2007

28 people email list

2008-2009

500 people emai...
Big Weather
(primary care doctor)

(knee surgeon)
Actual Storm Track
16 Day Forecast
15 Day Forecast
14 Day Forecast
13 Day Forecast
12 Day Forecast
11 Day Forecast
10 Day Forecast
9 Day Forecast
8 Day Forecast
7 Day Forecast
6 Day Forecast
5 Day Forecast
4 Day Forecast
3 Day Forecast
2 Day Forecast
1 Day Forecast
Actual Storm Track
When to trust the forecast
10 days
+ storm or no storm
+ cold, hot, dry, moist
3-5 days
+ details becoming clearer
1-2 day...
How to plan

7-10 days

4-5 days

2-3 days

Toast to
possibilities

Clear your
schedule

Pretend you’re
getting sick
Weather is not
magic. It’s
physics.
Forecasts are rarely
perfect, but they are
getting better every year.
Study them, don’...
Long range
forecasts stink!
We cannot reliably
predict snow
accumulations
beyond about two
weeks. Seasonal
outlooks are ev...
Weather happens
when moist air
gets high

1

2

3
Where’s the moisture?
Less moisture
(land source)

Lots of moisture
(ocean source)

OK moisture
(ocean + plants)
Orographics get air high
Mountains = Precipitation
Indian Peaks /
RMNP

Park Range
Flattops
Gore

Ten Mile &
Mosquito

Grand
Mesa
Elk
Mtns

N&S
San...
Favorable wind directions
Steamboat
RMNP

Summit Co.

Aspen

Powderhorn

Vail
Crested Butte

Telluride
Silverton
Wolf Cree...
Breckenridge: NW to N winds

e
or

G
ge

n
Ra
Vail
Pass
Vail: Northwest winds

e
or

G
ge

n
Ra

Beaver
Creek

Vail
Vail
Pass
Beaver Creek: West winds

e
or

G
ge

n
Ra

Beaver
Creek

Vail
Vail
Pass
Telluride: West winds
Vail
January 31, 2013
http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm
Moisture in the air

10F

0F

Temperature >> colder
The best snow requires...
• Lots of moisture
• Mountain top temperatures
between about 0-10F

• Not too much wind
Wind
directions?
Complicated.
What about
radar?
Nope. There’s a
problem...
Jamming the Radar
Overshooting the Snow

0.5 deg
Denver
Airport

Grand
Mesa

Pueblo

http://www.ncdc.noaa.gov/nexradinv/
Steamboat

Vail
Aspen

RMNP
Summit Co.

Crested Butte
Telluride
Wolf Creek

http://www.ncdc.noaa.gov/nexradinv/
Colorado is a state of
extremes
The difference between a wet
year and a dry year can come
down to the presence or absence
o...
Colorado is a state of
extremes
More than half of the total annual
precipitation falls in only 20% of
the days when precip...
Example: Schofield Pass
Example: Schofield Pass
2 of 60 storms created
25% of the total season snow
Joel Gratz
joel@opensnow.com
Colorado snow forecasting 101
Colorado snow forecasting 101
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Colorado snow forecasting 101

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Slides often used by meteorologist Joel Gratz in his presentations about Colorado snowfall.

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Colorado snow forecasting 101

  1. 1. Colorado Snow Forecasting 101 Meteorologist Joel Gratz Photo: Connor Walberg ActionPhotoSchool.com
  2. 2. How this presentation will help you: 1) Remove mystery of Colorado weather. 2) Find the most snow.
  3. 3. Hi, I’m Joel Gratz. I grew up in Pennsylvania, ski raced and instructed, then moved to Colorado after college.
  4. 4. And I started to miss powder days due to inaccurate forecasts.
  5. 5. And it made me mad!
  6. 6. So I learned how to forecast in Colorado, and started to share. Dec 2007 28 people email list 2008-2009 500 people email list 2009-2010 245,000 pageviews 2010-2011 1,315,000 pageviews 2011-2012 3,330,000 pageviews 2012-2013 12,000,000 pageviews
  7. 7. Big Weather (primary care doctor) (knee surgeon)
  8. 8. Actual Storm Track
  9. 9. 16 Day Forecast
  10. 10. 15 Day Forecast
  11. 11. 14 Day Forecast
  12. 12. 13 Day Forecast
  13. 13. 12 Day Forecast
  14. 14. 11 Day Forecast
  15. 15. 10 Day Forecast
  16. 16. 9 Day Forecast
  17. 17. 8 Day Forecast
  18. 18. 7 Day Forecast
  19. 19. 6 Day Forecast
  20. 20. 5 Day Forecast
  21. 21. 4 Day Forecast
  22. 22. 3 Day Forecast
  23. 23. 2 Day Forecast
  24. 24. 1 Day Forecast
  25. 25. Actual Storm Track
  26. 26. When to trust the forecast 10 days + storm or no storm + cold, hot, dry, moist 3-5 days + details becoming clearer 1-2 days + details are as clear as possible
  27. 27. How to plan 7-10 days 4-5 days 2-3 days Toast to possibilities Clear your schedule Pretend you’re getting sick
  28. 28. Weather is not magic. It’s physics. Forecasts are rarely perfect, but they are getting better every year. Study them, don’t dismiss them.
  29. 29. Long range forecasts stink! We cannot reliably predict snow accumulations beyond about two weeks. Seasonal outlooks are even worse.
  30. 30. Weather happens when moist air gets high 1 2 3
  31. 31. Where’s the moisture? Less moisture (land source) Lots of moisture (ocean source) OK moisture (ocean + plants)
  32. 32. Orographics get air high
  33. 33. Mountains = Precipitation Indian Peaks / RMNP Park Range Flattops Gore Ten Mile & Mosquito Grand Mesa Elk Mtns N&S San Juans Sawatch Sangre de Christo East San Juans
  34. 34. Favorable wind directions Steamboat RMNP Summit Co. Aspen Powderhorn Vail Crested Butte Telluride Silverton Wolf Creek
  35. 35. Breckenridge: NW to N winds e or G ge n Ra Vail Pass
  36. 36. Vail: Northwest winds e or G ge n Ra Beaver Creek Vail Vail Pass
  37. 37. Beaver Creek: West winds e or G ge n Ra Beaver Creek Vail Vail Pass
  38. 38. Telluride: West winds
  39. 39. Vail January 31, 2013
  40. 40. http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm
  41. 41. Moisture in the air 10F 0F Temperature >> colder
  42. 42. The best snow requires... • Lots of moisture • Mountain top temperatures between about 0-10F • Not too much wind
  43. 43. Wind directions? Complicated. What about radar? Nope. There’s a problem...
  44. 44. Jamming the Radar
  45. 45. Overshooting the Snow 0.5 deg
  46. 46. Denver Airport Grand Mesa Pueblo http://www.ncdc.noaa.gov/nexradinv/
  47. 47. Steamboat Vail Aspen RMNP Summit Co. Crested Butte Telluride Wolf Creek http://www.ncdc.noaa.gov/nexradinv/
  48. 48. Colorado is a state of extremes 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
  49. 49. Colorado is 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
  50. 50. Example: Schofield Pass
  51. 51. Example: Schofield Pass 2 of 60 storms created 25% of the total season snow
  52. 52. Joel Gratz joel@opensnow.com

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