Colorado SnowForecasting101

Photo: Connor Walberg ActionPhotoSchool.com

Meteorologist Joel Gratz

1) Remove mystery ofColorado weather.

How this presentation will help you:

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!

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

So I learned how to forecast in Colorado, and started to share.

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 days+ details are as clear as possible

How to plan

7-10 days 4-5 days 2-3 daysToast to

possibilitiesClear yourschedule

Pretend you’regetting sick

Weather is not magic. It’s physics.

Forecasts are rarely perfect, but they are getting better every year. Study them, don’t dismiss them.

Long range forecasts stink!

We cannot reliably predict snow accumulationsbeyond about two weeks. Seasonal outlooks are even worse.

Weather happens when moist air

gets high

1 2 3

Where’s the moisture?

Lots of moisture(ocean source)

Less moisture(land source)

OK moisture(ocean + plants)

Orographics get air high

Mountains = Precipitation

Indian Peaks / RMNP

Sangre deChristo

Park Range

Flattops

GrandMesa

ElkMtns

EastSan Juans

N&SSan Juans

Sawatch

Gore

Ten Mile &Mosquito

Favorable wind directions

Wolf Creek

Silverton

Telluride

Powderhorn Crested Butte

AspenVail

Summit Co.

SteamboatRMNP

Breckenridge: NW to N winds

Gore Range

VailPass

Vail: Northwest winds

BeaverCreek

Vail

Gore Range

VailPass

Beaver Creek: West winds

Vail

Gore Range

VailPass

BeaverCreek

Telluride: West winds

VailJanuary 31, 2013

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

Moi

stur

e in

the

air

Temperature >> colder

10F 0F

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

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

Denver Airport

PuebloGrandMesa

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

RMNP

Steamboat

Telluride

Wolf Creek

Aspen

Vail

Summit Co.

Crested Butte

Colorado is a state of extremes

Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

The difference between a wet year and a dry year can come down to the presence or absence of just a few major storms.

Colorado is a state of extremes

Joe Ramey, National Weather Service Grand Juntion, Slide #8 2009-2010 Winter Outlook for Colorado

More than half of the total annual precipitation falls in only 20% of the days when precipitation occurs.

Example: Schofield Pass

Example: Schofield Pass

2 of 60 storms created

25% of the total season snow

Joel Gratzjoel@opensnow.com