Today, Wednesday June 22nd is the first full day of Summer 2011. With this change of season comes a new format for the Jackson Hole Forecast on www.mountainweather.com

This is the first major revision of the forecast format in several years, and hopefully it makes for an easier to use and more visual experience.

Take some time to get oriented to the new layout. There is all of the same information you are used to getting, but now it is also displayed in a graphical format.

Mountain temps and ridgetop wind forecasts now go out 5 days instead of only three. The thunderstorm and lightning forecast also goes out 5 days. In the winter, that will be replaced with the snowfall forecast, which will also go out 5 days.

Sunrise/sunset times are now listed for the next 5-days, so you can track when the days start getting shorter! (Ugh)

The only thing missing right now from the old version, is the moon phases. We are still working on how to best fit that info on the page.

There is a printable version from the website that includes everything down to the 3-Day Weather Forecast Description. This is free to print and display at you place of business for visitors to read. (Saving your employees countless time not having to answer the question, “what’s the weather going to do?”).

The e-mail version of the forecast, which includes all the forecast information you see on the web, plus a detailed weather discussion and extended outlook written each weekday morning by meteorologist Jim Woodmencey and sent out to your e-mail address (that discussion does not appear on the website). The e-mail version will still be available to those customers who currently subscribe.

For more information about receiving the e-mail version, or any questions or comments you may have on the new format of the forecast, feel free to e-mail me or call at:

jim@mountainweather.com

307-739-9282

JH Forecast by meteorologist Jim Woodmencey

New layout created by AJ Best of Gliffen Designs in Jackson, WY

There’s an old saying about the seasons in Jackson Hole, “We get nine months of winter and three months of bad skiing”. Which would apply to most ski towns in the Rocky Mountains and the Western U.S. this year.

Fact of the matter is, the first snowfall in the Teton Mountains came back on September 10, 2010, and it is now June 19, 2011, and still snowing at the higher elevations today. There is still about 10-feet of snow on the ground above 9500-feet in the Tetons, which means there might be more like only 1 or 2 months of bad skiing this year. (Current snowdepth map for the Central Rockies).

Spring Ends

The Summer Season officially begins on Tuesday, June 21^st If all goes well, temperatures will crack 70 degrees by Tuesday afternoon, something that has only happened a handful of times this spring in Jackson. And, as if someone flipped a switch, it looks like the first week of summer will be warm and dry, with highs remaining in the 70’s all week.

Normal high temperatures for this time of year would be mid 70’s. The record high in Jackson on the Summer Solstice is 90 degrees, set back in 1994.

This June so far, we have seen cooler than normal temps most days. There was that one weekend when we almost hit 80 degrees (June 5 & 6). But then it snowed in town on June 9^th and the high was only 50 degrees (record cold max temp for that date). And it looks like it will be another well above normal precip month, as well.

So, while we never really had a fall or a spring season, we can at least hope for a few weeks of summer this year.

The Solstice

The exact time of the Summer Solstice on Tuesday June 21, 2011 is 11:16 AM MDT. This is when the sun will be directly over the Tropic of Cancer at 23.5 degrees North latitude.

The Solstice also marks the longest day of the year in the Northern Hemisphere. But the days don’t start getting shorter for about another two weeks, as the sunrise/sunset times do not change much around the Solstice.

We will have almost 16 hours of daylight in Jackson the rest of the month — not including twilight — compared to less than 9 hours around the Winter Solstice in December.
The graphic below shows the change in the tilt of the earth and its orientation to the sun, which is responsible for the seasonal changes we normally see. As you can see, in the summer, the northern hemisphere is tilted towards the sun.
So, when the sun finally does appear from behind all the clouds, it will be as high in the sky as it gets around here, about 70 degrees above the horizon at noontime.

text by meteorologist Jim Woodmencey

This week I will highlight all the various sources of snowpack, water, and flood reports available via the internet so that you can stay on top of the run-off conditions this Spring. Most of these sources of information can be found on the www.mountainweather.com site, with a little poking around. Information specific the Jackson Hole region will be highlighted, but links to snow, water, and flood information for the rest of the U.S. are also included.

Snowpack

There are two ways to look at the snowpack that remains in the mountains and how it compares to average. One is the Snow Water Equivalent (SWE), and the other is Total Precipitation.
(from the JH Information page go to “Snowpack Information”, which takes you to this page…
Snow-Precipitation Update).

Both SWE and Total Precipitation numbers are shown for the various river drainages in Wyoming. For the rest of the Western U.S., scroll down to the bottom of the Skier’s Page and click on the Western U.S. Snotel map to generate similar data or reports.

SWE shows the percent of average snow water that still exists, as of this date. Most of these numbers are extremely high, because normally by this time of year we are losing snow, or in some locations most of the snowpackdown to next to nothing or is already completely gone.

In the Snake River Drainage, SWE is at 232% of average for this time of year.

This year, the snowpack has declined very little since mid-April (when it reached its peak) at the higher elevations. Even mid-elevation snowpack is way more than what it normally is at the end of May. And it looks like we won’t lose much through the Memorial Day Weekend. As a matter of fact at higher elevations we’ll likely be gaining some snow!

Snowdepths at JHMR May 26: Rendezvous Bowl = 159 in. & Mid-mountain = 97 in.
Snowdepths at JHMR April 3: Rendezvous Bowl = 142 in. & Mid-mountain = 108 in.

Precipitation totals for the water year (which begins October 1^st) are perhaps a better gauge of how much water we have had this winter, used, in combination with how much water is actually in the snowpack that has yet to melt.

Snowdepths in the Tetons, around Togwotee Pass and Yellowstone Park between 8000 and 9500-feet are still between 75 and 150 inches (@ 6 to 12 feet deep!).

In the Snake River Drainage, Year-to-date Total Precipitation is at 130% of average.

Water Content of that remaining snow in the surrounding mountain ranges is between 30 and 50 inches.

Water

Reservoirs and streams are already pretty full in most places across Wyoming and Idaho, with still some room left for more water from run-off in Jackson Lake and Palisades. This info can also be found on the JH Information page.

Another way to look at the stored water is the Surface Water Supply Index (SWSI), which is a combination of water in reservoirs and the forecast run-off. For Wyoming, these number are very high, which simply means we are very wet. (See SWSI Map).

Flooding

The National Weather Service’s Hydrological Prediction Service keeps track of river levels and makes forecasts for flooding potential. There is also a lot of information available about river flows and flood forecasts for eastern Idaho & Wyoming on the JH Information page, or nationally from the River Forecast Center website.

Text by Meteorologist Jim Woodmencey

Wet snow and mud slides in May are not an unusual occurrence, especially after a big winter’s snowfall that is followed by a very wet spring. Bare ground or a snowpack that is being saturated with water due to melting snow become well lubricated and poised to move downhill.

Big landslide and snowslide events have been responsible for closing roads around the Yellowstone and Jackson Hole area this May.

On Sylvan Pass in Yellowstone Park a cycle of wet slab avalanches blocked the highway with avalanche debris up to15 feet deep on May 11th, 2011. While I am still in the process of investigating all the details of the snowpack and weather leading up to this event, it seems that the sequence of events that provoked these slides goes something like what is described below.

Avalanche Weather

Rain and warm temperatures at the beginning of April were followed immediately by colder temperatures, forming hard crusts up to around the 10,000-ft. elevation. That was followed by heavy snowfall the second, third, and into the fourth week of April. Temperatures then warmed in early May, reaching a peak around 50 without refreezing overnight at the end of the week, with more wet snow and rain May 6th to 8^th. All that new snow from April & early May was warming and it is likely that free water was able to percolate down to the rain-crust layer that formed in early April, providing a well lubricated sliding surface for the avalanches to run on.

(See more Spring avalanche photos from around the Tetons at Bridger-Teton Avalanche Center site by starting here: Snowpack Summaries with avalanche photos

Landslide Weather

As far as the landslide down in the Snake River Canyon, this is the second major slide in the canyon this spring. An earlier slide on the opposite side of the river did not affect the highway and was given little attention. The one that occurred this past weekend (May 14^th and 15^th), was also likely provoked by the weather this spring.

Overly saturated ground from melting snow from an above normal winter snowpack, compounded by much above normal precipitation in April and early May, further saturated the soil, and is what likely set that soil in motion. I would defer to the geologists to further explain what exactly is going on with the soil and rock strata down there in the Snake River Range. (see quote below). But without a doubt, excess water on the ground this spring contributed to the movement.

(See more about this landslide and more photos on Jim Stanford’s site at JHunderground.com).

Note: Wally Ulrich, Wyoming State Geologist, just sent along this explanation of the geology in the Snake River Canyon area to me (May 19, 2011):

“The stratigraphy is filled with clay layers and the overthrust has bent and folded layers onto complex structures. Erosion exposes the dipping folded structures. Resistant layers act as boundaries, water as lubrication & gravity energy.
Tilted beds and a dipping anticline contribute to the present landslide.”

May 1997 vs. May 2011 Landslide

You may recall that there was a similar large landslide in the Snake River Canyon back in May of 1997, almost to the day, on May 18^th.

I thought it would be interesting to look at the weather in the Winter & Spring of 1996-97 and 2010-11, to help explain how it may have contributed to setting these landslides in motion.

While both years had way above normal snowpack going into the spring….. April-May 1997 and April-May 2011 had completely different weather conditions.

April & early May 1997 was drier and warmer than normal (below normal precipitation, above normal temps). The week prior to the May 18, 1997 landslide we were had highs in the 70’s in Jackson, and one day with just over ¼ inch of rainfall between May 16 & 17.

April & early May 2011 was wetter and cooler than normal (way above normal precipitation and below normal temperatures). The week prior to the May 15, 2011 landslide we had only seen a few days that got over 60 degrees in Jackson, but we had almost 2 inches of rainfall. That on top of about 3 inches of rainfall in the month of April 2011.

Forecasting vs. Backcasting

The important thing to keep in mind with both wet snow avalanche and landslide events of this magnitude is, that they are both extremely hard to forecast for. It is easy to “backcast” after they occur and point to specific weather that likely caused the massive failures, but beforehand, it is purely speculation that they could occur. And certainly pin-pointing exactly where they might occur is even more difficult.

Text by Meteorologist Jim Woodmencey

Photo of Avalanche in Yellowstone courtesy of NPS and Brad Ross

Photo of Landslide in Snake River Canyon from Steve Owens

With precipitation records being broken in many parts of the country this past April, and severe weather events that included devastating tornadoes in the Midwest and Plains, flooding along the Mississippi and many other rivers, all in all it was a wet and wild April to behold.

Map of Total Precipitation amounts across the US for the Month of April

It probably comes as no surprise then that April 2011 was wetter than normal in Jackson Hole, as well.

As a matter of fact it will probably go down as the “wettest” April on record here. While I do not have the “official” numbers yet from the US Forest Service’s manually read climate station, I do have the numbers from the automated weather station that is located right next to the official climate station instrument shelter.

Jackson, WY Weather Stats for April 2011

· Total precipitation for the Month of April 2011 was just over 3 inches.

· Average April precipitation is 1.12 inches

· Record precipitation is (was!) 2.66 inches (April 1963)

· Average High temperature in April 2011 was 45 degrees, normal high is 52.

· Average Low temperature in April 2011 was 28 degrees, normal low is 25.

· Average Mean temperature in April 2011 was 36.5 degrees, normal mean is 38.5

· The warmest temp we had in April 2011 was 59 degrees on April 2^nd .

· The coldest temp we had was 15 degrees on April 23^rd.

Cool and Soggy Start to May

The Month of May started out quite wet also, nearly reaching our average precipitation for the month in the first 10 days of the month. The automated rain gauge recorded 1.80 inches through May 10^th. The average precip in Jackson in May is 1.88 inches. May, by the way, is normally the wettest month of the year, on average.

According to the thermometer at the weather station, we’ve only had one day so far in 2011 that has topped 60 degrees (Cinco de Mayo).

All that will be changing this week, with drier weather, more sunshine, and temperatures getting into the 60’s………for more than just one day!

Mountain Snowpack

While we’d normally be seeing the snowpack shrinking in the mountains this time year, we’ve actually still been accumulating snow, and settled snowdepths above 8,000 feet have held there own the last month or so.

The Tetons, Wasatch and parts of the cntral Colorado Rockies all have plenty of snow remaining in them this spring. See maps below.

Maps of Snow Depth and Snow Water Equivalent (SWE) for WY-UT-CO region.

The settled snow depth at the bottom of Rendezvous Bowl at JHMR (Elevation 9580-ft.) on April 1, 2011 was 142 inches. It was also at 142 inches on May 10, 2011.

Snow depth at the Phillip’s Bench SnoTel site on the east side of Teton Pass (Elevation 8200-ft.) stood at 95 inches on April 1, 2011. It was at 100 inches on May 10, 2011.

There is also 43.70 inches of water still contained in that snow yet to melt.
You can reference all the snowpack info for the U.S. by going to the bottom of the Skier’s Page on mountainweather.com

Direct link: https://www.mountainweather.com/index.php?page=skiers_page

Brace yourself for the run-off that is yet to come!

While on my spring break this past week I had the distinct pleasure to be able to work with some members of the United States Air Force Combat Weather Unit on an avalanche course here in Northwest Wyoming.

Arriving on the heals of one of the biggest winters ever in

Jackson, and still experiencing “full” winter conditions through the last week of April, eight Air Force meteorologists assigned to a special unit at Hurlburt Field in Fort Walton, Florida made the trip to Jackson, WY for seven days of avalanche instruction.

This was a Level I & II avalanche course that was coordinated through the American Avalanche Institute and co-instructed by myself and John Fitzgerald, along with Don Sharaf adding a lecture on Snow Hydrology. The purpose of this course was to teach these guys as much as we could about avalanches and snowpack stability evaluation, skills they need when operating in mountainous regions like the Hindu-Kush in Afghanistan & Pakistan.

The extended winter weather enabled us to experience more January-like snow conditions rather than the spring skiing one might expect this time

of year. While trying to slowly break these guys in from sea level to our altitude, we marched them all over the Teton

Pass and Togwotee Pass areas for seven days in a row. As you would expect from combat ready soldiers, they were up for the task and took on the lack of oxygen with gusto.

By the end of the week they were pushing uphill with heavy packs at over 10,000-ft. as if they were back on the beach running through the sand rather than deep snow.

And deep it was, with new snowfall on several of the days, making for great powder skiing. And settled snowdepths in most place above 9,000-ft. in the mountains exceeding 12 feet, which made digging all the way to the ground an almost impossible task.

The odd thing about this season’s snowdepth is, that it is almost as deep up at Togwotee Pass as it is in the Tetons. Normally, Togwotee might see only half or, two-thirds of what the Tetons have. Not so this year, it’s almost the same across the board.

Temperatures most of the week were way below normal as well, starting the week (over Easter weekend) in the single digits in the morning at 10,000-ft. And ending the week with temps in the teens. On April 29^th I got out of my truck on Togwotee Pass at 13 degrees at 10 a.m. and when I returned at 5 p.m. it had warmed up to 15 degrees! Winds at ridgetop level that day were a steady 30 with gusts to 50. Nice day.

I have to say this was one of the best avalanche courses I have ever been a part of. It was an honor for me to be able to be out in the mountains with fellow meteorologists and share my knowledge of snow and avalanches with them.

It was also an honor to be in the company of such a distinguished and unique group of servicemen. These guys are not just sitting in a weather office staring at a computer, they are deployed to places like Afghanistan and often have to put down the hand-held anemometer and pick up a gun to help defend our freedoms. I thank them for that.

I only wish I could have still been with them this past Sunday evening when news came in that Osama Bin Laden was KIA. I’m sure

that would have been a time!

I salute all you guys for the job you do, and if our paths ever cross again, as I hope they will, I will be the first to buy you all a round at the bar.

Photo of the Team on Top of Glory Peak.

Posted by meteorologist Jim Woodmencey

As blasphemous as it sounds, that’s enough powder for one season. Who isn’t ready for some warm, sunny weather, and some good corn skiing?

Corn skiing has nothing to do with making turns on a slope in Nebraska, if there even are any slopes in Nebraska? It’s about the optimal spring skiing condition. It’s about that feel of carving high-speed turns on a butt-smooth backcountry snowfield, which can be just as exhilarating as floating through thigh deep powder in January.

The term “corn snow” comes from the kernels of frozen snow grains that break loose off the surface of the snow when you apply your edges in a turn. These rounded, melt-freeze snow grains, often about the size of corn kernels (thus the name), trickle down the slope ahead of you.

The corn is best when the sun just begins to heat the top quarter-inch of the snow surface. You can carve a turn like you would on a groomed slope at a ski area. Except this condition is happening in the backcountry, on the un-skied, smooth slopes, groomed by Mother Nature. (Photo of spring skiing in Grand Teton National Park).

Weather Makes the Corn Grow

To get good crop of corn in the mountains, several things need to happen in unison. Or else, either the crop won’t grow, or it will become damaged. Sunshine is not the only weather factor corn relies on. Cloud cover and overnight temperature are also critical. Additionally, you cannot have had any recent new snow.

To really know if the weather is “growing” a good crop of corn, pay attention to the recent weather and the forecasted weather. Here’s a corn crop checklist and some explanation for each.

Corn Snow-Weather Checklist

1) No recent new snowfall.

2) A spell of warm and sunny weather.

3) Clear skies overnight, or the last two nights.

4) Below freezing temps in the morning, at all elevations in the mountains.

5) Sunny or Mostly Sunny skies during the day

Details:

1) No new snow: An inch or two of new snow will take a day or two to melt down and re-freeze. Ten inches of new snow may take 5 days to cook down to a good, solid frozen surface.

2) Warm and Sunny: First you need a stretch of warm temperatures and lots of sunshine to melt the snow, and start cooking up the corn. That’s the melt part of the melt-freeze cycle that makes a melt-freeze crust. If you don’t have wet snow on the surface during the day, it just won’t be real corn the next morning. It’ll just be a hideous suncrust. There’s a difference! (Photo of Melt Freeze Grain Cluster)

3) Clear skies overnight: You must have clear skies overnight to let the wet snow consolidate back into a frozen crust of rounded melt-freeze snow grains, all glued together. Even a thin overcast layer of high clouds can cause the snow to not re-freeze completely. This is because the clouds act like a blanket, insulating the snow and holding in the heat. Actually, what is going on is, at night the out-going radiation from the surface of the snow gets re-radiated back to the earth’s surface. As this radiation is reflected back down to earth by the cloud bases, it inhibits a solid freeze.

4) Below Freezing temps: It must get to at least 32 F or 0 C overnight at the elevations you want to ski. If not, the corn won’t last long and you’ll be punching through the crust or leaving deep ruts in the slush.

5) Sunshine during the day: Cloud cover in the daytime can also have a negative effect on the corn by not letting enough sun in to properly melt and loosen the bonds between those melt freeze snow-grains. If the sun isn’t hitting the slope, you’ll end up just skiing a frozen ocean that never softens into good corn snow.

Rule-of -thumb is: If you can’t see any stars before you go to bed, you probably don’t need to bother getting up early the next morning to ski corn.

Timing is Everything

Corn-snow farmers must rise early to hit it just right. East facing slopes will cook first, and after about 9:30 a.m. most spring mornings they are usually done. Due-south facing slopes might last until maybe 10:30 a.m. Southwest facing slopes should be ready around just before noontime.

It’s better to be there on top and have to wait for the corn to go-off, than it is to arrive too late and miss the good stuff. And then experience the embarrassment of leaving behind deep ruts in the wet snow that will take many days to heal back over to a smooth slope. After all, this is all about seeking out a smooth, untracked, snow slope to truly experience the thrill of corn skiing.

Article and ski photo by Jim Woodmencey, meteorologist

Snow grains photo from Alaska Ice & Snow Research

About the only question remaining for Jackson Hole is, when is winter going to quit?
In the Tetons the first significant snowstorm of the year in the mountains happened on September 10, with about a foot of snow above the 9,000-ft. elevation.
(Photo below left of Ranger Ron Johnson near Paintbrush Divide Sept. 10, 2010)

Here we are April 9th and we just finished a week (Monday thru Friday) that saw an additional 40 inches of snow fall above 9,000-ft.
(Photo below right of Chris Harder & Ray on top of Snow King, April 7, 2011)

If it keeps snowing into May in the mountains,
that’ll be 9 months of winter.

In the Town of Jackson we started accumulating snow in October, and we haven’t really stopped yet. That’s 7 months of winter so far, will it be 8?………read on for more about that later….

SO, HOW BIG WAS THIS WINTER?
Depending on how (and where) you measure your snowfall, the winter of 2010-2011 in Jackson Hole was big, and must be considered in the top three all-time, by almost any measure.

As of this morning (April 9, 2011) there was 155 inches of settled snow at the base of Rendezvous Bowl at JHMR (that’s almost 13 feet deep!). That matches the biggest year for settled snowpack depth on this date, set back in April 1997. (See Table below).

As far as snowfall from October 1 thru April 8, the Winter’s of 1996-97 and 2007-2008 both had more snow than this past winter. Numbers from last winter are thrown in for comparison also.

We are darn close to that magical “600” inches of snowfall for the winter at JHMR. The Raymer Plot read 599 inches this morning. Same date in 2008, it stood at 609 inches.
Why is 600 inches so “magical”. Because that’s 50-FEET of snowfall!

LA NINA
The buzzword this winter was “La Nina”, which began last fall and remained strong through January or February before it showed any signs of weakening. La Nina of course usually means more snow for the Pacific Northwest and Northern Rockies, and that played out in spades this winter.

What’s most unusual about this La Nina is, that it affected areas further south, like the Sierra’s in California and the Wasatch in Utah, and even the central Colorado Rockies did O.K. and had well above normal snowfall winter’s also.

The La Nina is a little weaker now, although we are still feeling her impacts, and she is expected to continue to weaken into June, when we should get back to more normal climatic conditions.
NOTE: That does not mean it is going to snow until June!

You can get all the La Nina, El Nino, & Long Range Forecast info you want by scrolling down the NWS Discussions & Outlooks Page of www.mountainweather.com

A warm Ridge of High pressure that has been building inland over the western U.S. the last 24-hours will get flattened out by a Trof of Low pressure that will be moving across the Northwestern U.S. the next 24-hours.

Very HOT in the Southwestern U.S. on the last day of March 2011……75 in Moab, 79 in Zion, 92 in L.A., 101 in Palm Springs, and hottest was 103 in Death Valley.

Still some clouds coming over the top of that Ridge in a WNW flow over us today, which may cause a few showers over Yellowstone Park and the Teton Mountains, otherwise, just some clouds moving by from time to time today. And warm spring-like temps.

That weather system coming into the Pacific Northwest will bring Jackson Hole some rain on Saturday, by afternoon. A strong cold front will then move through sometime Saturday evening and that will change the rain over to snow at all elevations. Expect dramatically cooler temps by Sunday.

That Low pressure center moves by to the north of us and out into the Dakotas on Sunday. Some moisture remains behind this system in a North to NW flow Sunday & Monday for some light snow.

It now looks like a somewhat moist Westerly flow will be over us Tuesday & Wednesday, with warming temperatures bringing a chance of some valley rain showers and some snow in the mountains.

Text provided by Meteorologist Jim Woodmencey

Graphics by IPS MeteoStar LEADS On-Line

There’s some good news, and some bad news, and some good news again…. about the flow across the Pacific over the next 5 to 7 days.

The first good news is, a Low pressure system this weekend will bring snow Saturday night and Sunday to Jackson Hole.

The bad news is, as we go into the middle and end of next week it looks like a Ridge of High pressure will build over the Western U.S. and Rockies and send storm systems that are lined up out in the Pacific right now to the north of us into Canada and SE Alaska.

The good news about that is….. any radiation that might be in that flow coming across the Pacific from Japan will also get diverted well to the north of Jackson Hole.

Text by Meteorologist Jim Woodmencey
Graphics by IPS MeteoStar, LEADS -OnLine