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

1. Colorado Snow
Forecasting
101
Meteorologist Joel Gratz
Photo: Connor Walberg
ActionPhotoSchool.com

2. How this presentation will
help you:
1) Remove mystery of
Colorado weather.
2) Find the most snow.

3. Hi, I’m Joel Gratz.
I grew up in Pennsylvania,
ski raced and instructed,
then moved to Colorado
after college.

4. And I started to
miss powder days due to
inaccurate forecasts.

5. And it made me mad!

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

8. Big Weather
(primary care doctor)
(knee surgeon)

9. Actual Storm Track

10. 16 Day Forecast

11. 15 Day Forecast

12. 14 Day Forecast

13. 13 Day Forecast

14. 12 Day Forecast

15. 11 Day Forecast

16. 10 Day Forecast

17. 9 Day Forecast

18. 8 Day Forecast

19. 7 Day Forecast

20. 6 Day Forecast

21. 5 Day Forecast

22. 4 Day Forecast

23. 3 Day Forecast

24. 2 Day Forecast

25. 1 Day Forecast

26. Actual Storm Track

27. 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

28. How to plan
7-10 days
4-5 days
2-3 days
Toast to
possibilities
Clear your
schedule
Pretend you’re
getting sick

29. Weather is not
magic. It’s
physics.
Forecasts are rarely
perfect, but they are
getting better every year.
Study them, don’t
dismiss them.

30. Long range
forecasts stink!
We cannot reliably
predict snow
accumulations
beyond about two
weeks. Seasonal
outlooks are even worse.

31. Weather happens
when moist air
gets high
1
2
3

32. Where’s the moisture?
Less moisture
(land source)
Lots of moisture
(ocean source)
OK moisture
(ocean + plants)

33. Orographics get air high

34. 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

35. Favorable wind directions
Steamboat
RMNP
Summit Co.
Aspen
Powderhorn
Vail
Crested Butte
Telluride
Silverton
Wolf Creek

36. Breckenridge: NW to N winds
e
or
G
ge
n
Ra
Vail
Pass

37. Vail: Northwest winds
e
or
G
ge
n
Ra
Beaver
Creek
Vail
Vail
Pass

38. Beaver Creek: West winds
e
or
G
ge
n
Ra
Beaver
Creek
Vail
Vail
Pass

39. Telluride: West winds

40. Vail
January 31, 2013

42. http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm

43. Moisture in the air
10F
0F
Temperature >> colder

44. The best snow requires...
• Lots of moisture
• Mountain top temperatures
between about 0-10F
• Not too much wind

45. Wind
directions?
Complicated.
What about
radar?
Nope. There’s a
problem...

46. Jamming the Radar

47. Overshooting the Snow
0.5 deg

48. Denver
Airport
Grand
Mesa
Pueblo
http://www.ncdc.noaa.gov/nexradinv/

49. Steamboat
Vail
Aspen
RMNP
Summit Co.
Crested Butte
Telluride
Wolf Creek
http://www.ncdc.noaa.gov/nexradinv/

50. 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

51. 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

52. Example: Schofield Pass

53. Example: Schofield Pass
2 of 60 storms created
25% of the total season snow

54. Joel Gratz
joel@opensnow.com