A steady and sometimes powerful Westerly flow brought the bulk of the snowfall between Wednesday January 18^th and Saturday January 21^st , 2012. Storm totals for the entire 7-day period from last Monday morning, January 16^th thru this Monday January 23^rd 2012 were pretty impressive, with around two feet of snow falling in the valley and over 4 feet of snow in the mountains around Jackson Hole. That snow contained over 2 inches of water at lower elevations and more than 4 inches of water at higher elevations.

Getting a big dump of snow like that is not without its problems though, and hats off to the WYDOT crew for being on top of it and keeping things safe on Teton Pass during a busy avalanche cycle. (See some photos below from Jamie Yount, Avalanche Forecaster for WYDOT). And good job also to the local area ski patrols for doing the same, not an easy task when you are dealing with that much snow and that much wind in a relatively short amount of time.
As much as we all were yearning (and maybe a little crazy!) for fresh powder, patience is a valuable virtue when the mountains are rocking and rolling like they were.

Photos from Left to Right…Glory Bowl Crown. Bottom of Glory at Road. Beaver Slide debris on West side of Teton Pass. (All Courtesy of Jamie Yount, WYDOT).

Snowfall Numbers

Basically our snowpack doubled in less than a week, going from a settled snowdepth in the valley of around 16 inches last Monday to 37 inches this Monday. Mountains did the same, growing from around 40 inches to 80 inches tall.

Snowfall numbers and comparisons below for the Rendezvous Bowl Study Plot at the Jackson Hole Mountain Resort.

Numbers from the Teton Pass Study Plot that WYDOT uses, on the West side of the Pass had 48 inches of snow for the storm through Sunday morning (but some of that settled well before they could go measure it) and a whopping 5.40 inches of water!

Snow in Other Areas

Best swath of snow with this moist Westerly flow was from the Cascades of Washington, across the mountains of Idaho and into Western Wyoming. Big Winner was Mt. Baker in Northwest Washington where they reported 95 inches of snow in the last 10 days and a settled snow depth of 166 inches, looking like the deepest in the lower 48 U.S. right now.
Brundage Mountain near McCall, Idaho reported 40 inches of snow this past week and they now have a settled snow depth of 72 inches.
Significant snow also fell in Utah and Colorado’s mountains, but not nearly as much as the aforementioned areas, but enough to cause avalanche problems down that way also. Since everywhere snow fell, it fell on a weak existing snowpack.
Oddly, there were parts of central Idaho and Southwest Montana’s mountains that got significantly less snow. There were some mountain areas that got short-changed by this moist Westerly flow (For example: Sun Valley got way less snow than Brundage Mountain & Bridger Bowl got way less snow than Montana SnowBowl). That was probably due to some downsloping effects as moisture was lifted over mountain ranges to the west and then created a “dry-hole” to the leeward, unable to lift over the next adjacent range in time to dump out more snow. Best I can do to explain that for now without further investigation.
To be honest, I hardly gave these places a thought until after the fact, mainly because I was too busy keeping up with measuring snow fall around Jackson and then analyzing and calculating what was coming for the next 2 or 3 days. It was an exhausting week of forecasting for sure!

Posted by Jim Woodmencey, meteorologist

We haven’t really seen much change in the weather pattern over the Western United States over the last 8-weeks, with the exception the New Year’s Weekend storm. But, it finally, it looks like we’ll see some changes beginning next week. First indications that a strong Westerly flow will develop from the eastern Pacific across the Northwest U.S. and the northern Rockies.

A series of weather disturbances will be moving through this developing Westerly flow, with a Low pressure center hanging around the British Columbia Coast helping to supply colder air, and segments of strong jet stream cycling right overhead, should all add up to being a good longer-term snow producer, from the Cascades to the Northern Rockies.

Over the last 8 weeks we’ve seen a relatively dry weather pattern, most of the time the jet stream was way to the north in Canada, or it was split, or we were under a dry Northerly flow. None of which was very good for producing more than a few brief shots of snow.

Current Jet Stream Map

Finally, it looks like this developing weather pattern could persist for a period of 7 days or more. As it looks right now, we should see some snow beginning Monday & Tuesday of next week, and then the potential for heavier snowfall coming by the end of next week. With snow continuing through the following weekend (Jan. 21/22).

Forecast Jet Stream map for Jan. 20

Jet stream maps courtesy of IPS MeteoStar

Still A Ways Away…
Granted, this is still almost a week away, but at least the computer models and the longer range outlooks are giving us some hope for pulling out a decent January, snowfall-wise. (See the precipitation outlook maps below).

You can read and view more extended forecast and outlook info at www.mountainweather.com by going to the NWS Discussions & Outlooks Page.

6 to 10 Day Precipitation Outlook Map

8 to 14 Day Precipitation Outlook Map

Text by meteorologist Jim Woodmencey

Maps from IPS MeteoStar’s LEADS Online
and NOAA

The Winter Season officially begins Wednesday December 21st, 2011 at 10:30 pm MST. As we enter the Fourth Quarter of the Month of December, I know quite a few people in the Mountain West are wishing for snow, but please remember, I am not the Tim Tebow of meteorologists!

I’d like us to finish strong in December and come out ahead with a lot of fresh powder, but we’ll probably fall short of most people’s expectations.
The good news is, the weather pattern we’ve been locked into most of the month of December is showing signs of changing and the jet stream across the Pacific looks like it will begin directing some weather systems and some moisture across the Pacific Northwest & Northern Rockies on a more regular basis.
We’ve been in a split flow, with moisture getting directed north into Alaska & Canada most of the month, and also south across the Southwest U.S. (See jet stream map from 12/20/11).

DECEMBER 20, 2011 Jet Stream Map
Courtesy of IPS MeteoStar

Looking much better even as we head into the week between Christmas and New Years.
(See jet stream map for Christmas Night below). Much more of a Westerly flow across the Gulf of Alaska, and that is what we want to see. It’s not quite the Super Bowl of weather situations, but it should get us back on track with more frequent snowstorms and salvage the season after a somewhat dismal start.

DECEMBER 25, 2011 Forecast Jet stream Map
Courtesy of IPS MeteoStar

More to come…….

Posted by meteorologist Jim Woodmencey
Maps from LEADS, IPS MeteoStar

A fair mount of excitement was generated earlier this fall when word got out that we were going to continue with a “La Nina” again this winter. However, not all La Nina’s are created equal and this year’s La Nina is weaker than last years. Map comparing area of cold Sea Surface Temps (SST) around the Equatorial Pacific that defines a La Nina, below.

La Nina/ El Nino Review: La Nina means colder than normal SST’s in the Equatorial Pacific, and El Nino means warmer than normal SST’s. La Nina’s usually keep the Northwest U.S. wet in winter and the Southwest U.S. dry. El Nino’s usually have the opposite effect.

By now you may have noticed a difference between the amount of snow and the frequency of snowstorms that we’ve had this season so far, compared to the way we started last season with a bang in late October. The Winter of 2011-12 is not off to the same start as last winter, and that is consistent across the entire Western U.S.

Pre-season snowfall, October & November 2011, was actually still a little above average in Jackson Hole, but nowhere near the amounts seen pre-season in 2010. (See graph below left).

The biggest difference though between this time last year and right now is seen in the settled snowdepths at ski areas throughout the West. Snowdepths are much lower than they were in early December 2010. (See graph above, right)

Here in Jackson Hole I suspect most folks naturally expected a repeat of the “700 inch” snowfall winter we had last year during that “La Nina”. Obviously the possibility of that wish coming true dwindles with each passing day without new snow. Again…..not all La Nina’s are created equal!

While a La Nina winter usually means that we will see above normal snowfall in the mountains (true for most Pacific Northwest and Northern Rockies mountain locations), it does not define how or when that snow will be delivered.

Part of that is controlled by where a Ridge of High pressure sets up in the Pacific and where the main storm track sets up to bring Pacific moisture inland. Last year most of the winter the High was set up perfectly and storms rolled across Pacific Northwest, Sierras, Northern & Central Rockies almost continuously. (Red line on Map).

This year the Ridge of High pressure, so far, as caused the storm track to take a more northern route up into Alaska. That has prevented the continuous train of Pacific moisture from coming directly across the Western U.S. (White line on Map).

Snow History in JH

If you look at it statistically, in Jackson Hole the mountains have an above average snowfall 70% of the time during a La Nina year. Last Winter’s La Nina was strong to moderate, more like 2007-08. This year’s La Nina is weaker, more like 2000-01. Both of those winter’s saw above average snowfall at the end of the season tally, but when the snow came was decidedly different.

Even if you look closely at the snowfall distribution at Jackson Hole (9500-ft. Rendezvous Bowl Study Plot) from last winter (2010-11) most of the snow came pre-season and post-season. The mid-winter snowfall was just average, December thru February.

(See Graph 1).

Outlook For Winter 2011-12

While La Nina conditions are still expected to continue thru the northern hemisphere winter, although it may take a little longer for the weather pattern to finally change for the better (snowier).

Right now it looks like there may be a more significant shift of that Ridge currently parked out in the Pacific, and subsequently see the storm track starighten out again across the Pacific by about the time we get to the Winter Solstice (Dec. 21).

Below are the 3-Month Outlook Maps for January-March 2012, and the signature is still that of a La Nina, colder and wetter Pacific Northwest and Northern Rockies. Note that the line of above average precip do not extend as far south into the Sierras and Utah/Colorado like it did last year. (“EC” means Equal Chances of above or below average).

Obviously we didn’t see the pre-season snowfall that we had last year, and it’s unlikely we would ever duplicate the unbelievable post-season snowfall amounts that we saw last winter/spring. However, it would make sense to see a bigger mid-season snow than we had last year, and still make the Winter of 2011-12 come out above average.

This Blog entry was adapted from a presentation given by meteorologist Jim Woodmencey at the Avalanche Awareness Night in Jackson, WY on December 1, 2011.

Usually by around Halloween skiers start thinking more about winter than they are about fall sports. If you remember last year at this time the Northern Rockies were already blanketed with 2 to 3 feet of snow between October 23 & 26, 2010 and people were backcountry skiing like it was early December.

Yesterday I took a mountain bike ride (while thinking about skiing!) with Chris Harder who told me he had skied “25-short” in Grand Teton National Park, to the valley floor, on October 28, 2010. What a difference a year makes.

This year, on October 25 & 26 the Central Rockies of Colorado got the big early season dump with 10 to 15 inches in 24 hours and more than 2 feet total in some locations this week. That storm extended from Wolf Creek in the Southwestern part of the Colorado Rockies all the way across the State to Eldora just outside of Rocky Mountain National Park in the northeastern part. (Map below shows snow depths as of Oct. 28, 2011 in Wyoming & Colorado)

Also, parts of the Northeastern U.S. have already had some pre-Halloween snowfall, from the Catskills of New York to the mountains of Vermont and New Hampshire (pronounced “New Hampsha”). They got good snow this past week also, albeit less than 10 inches in most places. The other area that was getting heavy snowfall this week was the mountains of British Columbia and into the Canadian Rockies.

Some skiers in the U.S. Northern Rockies might already be saying where’s ours? With all the hype about it being another “La Nina Winter” I think people expect a repeat of 2010-11. And while we may end up with an above normal snowfall winter again in Jackson Hole, the distribution of that snowfall may not necessarily be identical to last year, nor as continuous like it was from late October to late May!!. It’s already different than it was last year going into this winter.

Keep in mind as we go through the next 6 months, that no two La Nina’s are created equal.

Keeping Track of Who Has the Snow

If you are planning ski trips this winter you can keep track of where the snow is, across the entire USA and southern Canada by going to www.mountainweather.com and getting on the Skier’s Page under the “Additional Mountain Weather” drop-down menu.

Here you will find links to ski areas throughout the US, with a concentration of links and more information for western U.S. ski areas. Also links to the latest Avalanche Advisories are midway down the page, for the backcountry skier.

At the bottom of the page is where you’ll find snowfall and snowdepth info in more detail. (An example of the National Snow Depth map is shown below).

There is also a link in the Quicklinks box in the upper right hand corner of the Skier’s Page that will take you to the National Snow Analyses page that is updated daily by NOAA.

If you are a real snow-nerd, you can keep up with everything from snow depths, to snow-water equivalent, to sublimation throughout the early season and over the course of this winter.

Posted by meteorologist Jim Woodmencey
October 29, 2011

It has arrived, the first snow of the season, and it is only Oct. 6^th. An unusually cold Low pressure system covering most of the Western U.S. with a huge counter-clockwise circulation around it, brought snow this morning to the valley floor in Jackson Hole. Generally about 2 inches in the valley, with maybe 6 inches at higher elevations, but not too much more than that at this point (end of day Thursday). But before it is done later Friday, there might be 10 or 12 inches at higher elevations in the Tetons.

This time of year the most popular question I get asked is, “What kind of winter do you think we’ll have?” My standard response is, “Snowy!”

Temperature Map below for December-January-February

The Lightning Detection system I spoke of in the last MountainWeather Blog is now up and running and working pretty well. “Live” lightning strike data is now available for Jackson Hole and it can be viewed by going to mountainweather.com and clicking on the Lightning Map under the Jackson Hole drop down menu. Or, just click this link: Lightning Map.

Sample Map from this past Thursday Night’s Thunderstorms, before they hit Jackson.

Reading the Maps

If you open another browser page along side this one, I will guide you through how to read and interpret these maps. Once you have the Lightning Strike Map page open, you will find two maps on this page………. Along with local satellite and radar map sat the bottom.

The top map is a “static” map or a “screenshot” that is zoomed out to 63 miles from the center. The white rings are in miles from the center, and the center of the map is right over the top of Snow King Mountain, just above the Town of Jackson. The large red ring is the 50-mile mark, out from center.

The lower map, further down the page, is an “active” map that goes out to 180 miles from center. It has some user controls that allow you to zoom even further out, to have a look beyond 300 miles. What you see out that far though is unreliable. From the testing done over the last month or so, I have found the useful range of this instrument to be between 120 and 150 miles. Beyond that, the accuracy of strike placement and detection of all strikes is inconsistent. This system has been working really well tracking the location of strikes and thunderstorm intensity within a 60 to 75 mile radius.

The symbols on these two maps are roughly the same. Big red dot is a recent negative ground strike and big orange dot is a recent positive ground strike. Most important difference between the two is the positive ground strikes are much more powerful, and are usually the strikes that kill people or start fires.

The + and – symbols are in-cloud lightning flashes, either between two clouds or within a single cell. These bolts are not striking the ground, but they may be an early indication that a thunderstorm is developing.

All of these symbols become smaller dots on the map after a minute and a half (90 seconds). The small dots are old strikes, both ground and in-cloud.

When a cluster of strikes occur in the same vicinity the TRAC system kicks in (Thunderstorm Ranging and Acquisition) and analyzes the thunderstorm and tracks its progress and intensity. These will appear as green, yellow, or red circles on the map indicating the approximate location of the thunderstorm and its strength, weak, moderate, or strong thunderstorms, depending on how much lightning they are producing.

Alert and Warning System

Right now, Snow King Mountain uses this information to make decisions about when to stop loading the summit chairlift. The software used with this sensor has an alarm system built in that is pre-set to 50 miles (thus the red ring on the map). Whenever lightning is detected anywhere within this 50 mile radius, an e-mail alert is sent out to the chairlift operations workers at Snow King. In this alert message the bearing (compass direction from town, the strength of the storm and whether it is intensifying or not, are all indicated in the message.

Like I said before, this sensor and these maps in no way assure that you will be magically protected from lightning strikes. It does provide you with a useful tool that can increase your ability to take some action to avoid dangerous lightning that might be approaching.

Special thanks to Snow King Mountain fro throwing some money at this project to see if it would work, and to Adam Shankland and his crew at Snow King for helping with the installation and adjustments this past month, one time with thunderstorms knocking at the door!

Also a big thanks to AJ Best of Gliffen Designs for doing all the programming and networking work that had to be done to be able to publish these maps “live’ on the internet.

Feel free to contact me if you would like more information about this sensor, or the alert system.

Jim Woodmencey

Meteorologist

307-739-9282

It was one year ago today, July 21^st , 2010 when a series of thunderstorms pounded the Grand Teton with an abundance of lightning, injuring 17 people, and causing the death of one other climber when he was knocked off the mountain. The amazing story of this incident and the ensuing rescue of the victims have been retold in this week’s issue of Sports Illustrated magazine, in an article by writer Brad Wieners. A link to that article on-line can be found here:

July 18, 2011 Sports Illustrated: Countdown to Tragedy, by Brad Wieners

During the summer months in the mountains, lightning is probably the greatest weather hazard we face when recreating. You don’t have to be climbing the Grand Teton (with a backpack full of metal objects, no less) to be struck. Even though the Grand is the absolute highest point around and your odds are considerably increased, it is also possible to be struck by lightning in the valley, on the baseball or soccer field, out on the lake or the golf course, as well.

It has been an ongoing challenge of mine to educate as many people as possible on the subject of “Thunderstorms and Lightning Safety”, and I will outline at the end of this article the most important things to watch for when you are outdoors this summer.

Lightning Detection System

I have also been working on a project to install a Lightning Detection System for the local area. This has been a cooperative effort between MountainWeather and Snow King Mountain to provide an early warning of approaching thunderstorms, and their dangerous lightning.

This project was originally conceived to help make the summer operations at Snow King a little safer. Although, you must keep in mind, this is a lightning detection system, not a lightning prediction system. It is only capable of plotting strikes that have already occurred.

Just before the Fourth of July Weekend, Adam Shankland of Snow King, AJ Best of Gliffen Design (my IT guy), and myself installed the instrument at the top of Snow King. Since then we have been able to test, re-configure, and retest the system over the several days of thunderstorms that we have experienced over the course of the last few weeks. It seems now like it is working well enough that I am almost ready to put the lightning map on the website and make it available to the public on the mountainweather.com website (it will be under the Jackson Hole drop down menu).

This instrument can detect lightning strikes out to a radial distance of approximately 200 miles, less in some directions and further in other directions. This variability is due to the complex mountainous terrain that surrounds us here in western Wyoming.

Not only will this instrument detect dangerous ground strikes, but it will also detect in-cloud lightning bolts, which often are the first indication of lightning activity in thunderstorm clouds. All of this information gets plotted on a scaled map, with distant rings out to a radius of 300 miles.

When this information gets linked on the mountainweather.com website I will make an announcement here on the MountainWeather Blog (and on Facebook). At that time I will let you know how to interpret the information, what its limitations are, and how to best utilize the map. There will also be an opportunity to receive e-mail warnings from this system (for a small monthly fee), so that you can receive fair warning when lightning is in the area, even if you can’t see it or hear it. That will be handy for those times when you are actually outdoors and not glued to the lightning map on the computer!

While this project in no way assures that you or your property will be magically protected from lightning strikes, it does however provide you with another tool to perhaps increase your ability to avoid dangerous lightning. More on this project soon….

Thunderstorms & Lightning Safety

· The earlier in the day clouds start building; the earlier in the day thunderstorms can occur.

· The more cumulus cloud there are covering the sky, the better the chances of developing larger and more dangerous thunderstorms.

· The taller the cumulus clouds are, the more likely they will produce a thunderstorm.

· The darker the base of the thunderstorm, the taller the thunderstorm is, and the more likely it is to produce a heavy downpour of rain and/or hail. Very dark bases over a very broad area indicate potentially more violent thunderstorms, with strong wind gusts or even tornadoes.

· The “scattered sheep” or “fair weather” cumulus type clouds never develop vertically very much.
Their bases stay white all day, rather than turning gray, and they do not pose a threat.

· Prime time for thunderstorm development is mid-afternoon to early evening (2 p.m. to 7 p.m.). Nocturnal (nighttime) thunderstorms are usually the result of a storm system or a cold front passing. Or, they may be related to “monsoon” moisture coming up from the south, usually in July & August.

Lightning

· Get away from metal objects, including fences, hardware or machinery, chairlifts, golf clubs, etc.

· Never stand under a lone tree. Being in a grove of trees of similar height is a better option.

· Get off the ridgetops, get out of open fields, get out of the water!
Swimming or boating is also very dangerous during thunderstorms.

· If you are on an exposed ridge: sit on an insulated pad or backpack. Be sure you are not in a natural water course, like a gully, these will conduct ground currents when bolts hit nearby.

· Retreat to a building or car, lie down in a dry ditch, or try to lie as low as possible.

· The most dangerous time for a fatal strike is before the thunderstorm is right over you. Lightning usually precedes heavy rainfall. It does not have to be raining to be struck by lightning

Lightning has been known to strike the ground from over 5 miles away!

Note: Ideally, this would be more like a 30/30 Rule. But there aren’t many folks I know who will seek shelter that early, or hang around that long before they go back out. So, 20 minutes is a compromise

Adapted from Reading Weather, by Jim Woodmencey

©2011 MountainWeather

Click here to get a PDF of this to print

We were getting a little bit of moisture from the Desert Southwest Monsoon this week, causing some thunderstorms around the area. And it looks like we may get another surge of that monsoon moisture again this coming week.

If you happen to listen to my forecast rap in the mornings on the radio (KZ95 95.3 FM & KJAX 93.3 FM) you will frequently hear me mention “monsoon moisture”, during the summer months. In this week’s blog entry I’d like to explain exactly what that means.

The term “monsoon” comes from the Arabic word mausim, which means “a season”. It refers to the large-scale wind flow that lasts for a whole season near the Indian Ocean and the Arabian Sea.

A “monsoon”, therefore, is simply a seasonal wind flow pattern. The Desert Southwest Monsoon that occurs in the United States is similar to the Asian Monsoon that affects India and the Himalayas during this same time of year, from July to early September.

The North American version of the monsoon originates over the interior of Mexico, where very moist (i.e. humid), tropical air is converging over the land from the Pacific Ocean to the west and from the Gulf of Mexico to the east. That moisture is then drawn northward by southerly winds over the hot, dry deserts of the Southwest. This causes frequent strong thunderstorms over New Mexico and Arizona.

Often in July and August the monsoon will surge up into Utah and Colorado, causing thunderstorms over the deserts of southern Utah and western Colorado. Some of these thunderstorms create flash flooding situations in the canyon country of the Southwest.

A few times a summer that monsoon moisture will reach as far north as Northwest Wyoming and Southwest Montana, causing thunderstorms here, which are often some of the strongest of the summer season.

The typical weather pattern that sets up in July and August that will bring transport the monsoon moisture this far north is when a thermal Low pressure (dry low pressure caused by heating) develops over southeast California and western Arizona, at the same time High pressure develops over eastern Texas. Then when a Low pressure system or upper level Trof of Low pressure moves into the Northwest U.S., that helps draw that monsoon moisture northward. (See example map below of this weather situation).

Difference in Type of Thunderstorms

Monsoon-related thunderstorms are a little different than the more typical summertime, afternoon thunderstorms that we have engrained in our memory banks. These more typical afternoon thunderstorms are known as “airmass” thunderstorms, which develop due to the convection caused by afternoon heating.

Whenever there is enough moisture and instability in the atmosphere (that varies from day to day) cumulus clouds will develop as the ground gets heated by the sun in the afternoon. These airmass thunderstorms, or garden variety afternoon thunderstorms, will occur between 2:00 PM to 5:00 PM, or sometimes into the early evening hours.

Thunderstorms generated by the monsoon can occur anytime of the day or night. They are more random in nature, kind of like a drive-by shooting, you never quite sure where or when they are going to hit.

This makes for a challenging forecast situation, as the development of thunderstorms is dependent upon whether or not that monsoon moisture gets over your location. Often times we end up on the very northern edge of that moisture here in Jackson Hole, with thunderstorms just south of us.

Monsoon Surge July 5th to 7th, 2011

Last week was a good example of that in action. Tuesday we got a surge, and had thunderstorms in the south end of the valley, but nothing really north of the Airport.

(See the Satellite Imagery in the graphic, click image for loop from Tuesday afternoon.)

On Wednesday, the monsoon moisture retreated a little further south and we had no thunderstorms here. Thursday and early Friday it surged back up and got close, with a few thunderstorms nearby.