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

Concern about radiation particles being carried across the Pacific and into the western U.S. from Japan has become a popular topic.

Despite assurances that radiation amounts will be very low by the time any of that makes it to the West Coast, the flow in the upper levels of the atmosphere is setting up to bring whatever is being emitted over Japan during the course of the next week, directly towards the West Coast.

In the short term, most of the radiation that is already in the atmosphere will be carried over the Aleutian Islands of western Alaska. The rest of Alaska should be missed, as the flow abruptly turns to the southeast across the Gulf of Alaska and gets involved in the Low pressure center that is sitting just off the West Coast.

Top map shows the jet stream position (at 300mb or ~ 30,000-ft.) on Saturday morning March 19.
The middle map shows the wind speeds and flow at 700mb ~ 10,000-ft., which is more representative of the level at which any radiation in the atmosphere would fall out with precipitation.

Strongest winds point at the far western tip of Aleutians, then turn southeast and decrease considerably before turning eastward into the southern half of California.

The bottom map shows the forecasted jet stream position position by the end of next week, which may be more of a concern as the flow straightens out into more of a direct pipeline from west to east across the Pacific.

Not surprisingly, skiers have already inquired about what this radiation might mean for our weather as we go into Spring. “Does it mean more snow or less snow? Or, will it melt the snow that is already on the ground?”

I don’t really know much about the effects of radiation particles in the atmosphere. They are not like volcanic eruptions and their particles, which can actually enhance snowfall by adding more ice nuclei to the atmosphere. It is my understanding that radiation particles attach to dust particles that already exist in the air, and then fallout with precipitation, along with the dust particles.

Even if a nuclear cloud did enhance snowfall, would you really want to rush out and ski that?

Technically, it wouldn’t create a Nuclear Winter, since Spring begins Sunday, March 20, 2011 at 5:30 p.m.

A Nuclear Spring, maybe.

Text by Jim Woodmencey, meteorologist
Graphics from IPS Meteostar, LEADS On-Line