Winter Weather comes to Wyoming this weekend. With a relatively large and cold Low pressure system moving into the Rockies on Saturday, then hanging out over the Central Rockies Sunday into Monday. This will create an “upslope” flow pattern against the Continental Divide.

Initially, the Tetons will pick up a little new snowfall, as that weather system approaches from the West, perhaps a total of 4 to 6 inches at higher elevations, which is more than the models depicted below are forecasting.

Looks like the Wyoming Range, south of the Jackson Hole area will do best on the West side of the Divide, maybe picking up a foot of new snow.

Mountain Ranges along and East of the Continental Divide, the Wind River Range and Absaroka Mountains could see a foot or so of snow at higher elevations through Monday morning.

Posted by meteorologist Jim Woodmencey

(Note: This article first appeared in the August 29, 2018 Issue of the JH News & Guide.)

It has almost become a tradition in this column to talk about the coming winter’s weather, before summer is over. You might ask, why so early and who cares, it is only the last week of August?  Local skiers and snowboarders care, because in September the price of a season pass usually goes up.

Getting some inside scoop on what kind of winter we are going to have might affect whether or not you pull-the-trigger and buy the pass. If the long-range outlook portends a snowy winter ahead, that might provide the extra assurance that your money will be well spent.

I’m not really sure about the psychology involved there, but I do know that most snow enthusiasts want me to say, “We are going to have a huge winter!”

You’ll have to read on to get the real answer.

Climate Prediction Center

The Climate Prediction Center, or “CPC”, is a division of the National Weather Service, whose job is to look way ahead at weather patterns and trends, for the next 10 days, out to 12 months from now.

The CPC’s seasonal forecasts look at the expected departure from normal of temperature and precipitation across the United States, broken down into three-month periods. The forecast for the meteorological winter would include December, January, and February.

The CPC’s latest experimental Two-Class prediction for December 2018 through February 2019, issued on August 16th of this year, calls for between a 55 and 60 percent chance of warmer than normal temperatures over western Wyoming. Which, by the way, was similar to the prediction for last winter, 2017-18. Temperatures last winter did end up warmer than average.

For precipitation, the CPC gave western Wyoming equal chances for an above normal, below normal or normal winter in 2018-19. Not much assurance going on there, but not exactly bad news for snow enthusiasts.

Last winter the CPC gave us a little better than an even chance (50 to 55-percent chance) of above normal precipitation. We ended up with a little more than average snowfall in the mountains last winter, below normal snowfall in town, but above normal precipitation.

El Nino- La Nina

Long-range forecasts are also predicting there will be a 60 to 70 percent chance of an El Nino developing this fall and winter. What exactly does that mean?

El Nino is one phase of ENSO, the El Nino Southern Oscillation. This oscillation reflects the changes in sea-surface temperatures in the Equatorial Pacific. During an El Nino phase, ocean temperatures are warmer than normal, during a La Nina phase, ocean temperatures are cooler than normal.

When temperatures are normal, it is called a “Neutral” condition. Since last winter and through this summer we have been stuck in “neutral”.

Typically, during Northern Hemisphere winters, an El Nino brings warm and dry conditions across the Pacific Northwest and Northern Rockies. At the same time, it brings wetter and cooler winters to California and the Southwest United States.

La Nina winters are supposed to bring cooler and wetter conditions to the Pacific Northwest and the northern Rockies. While, California and the Southwest usually remain drier and milder.

This year’s El Nino forecast does line up pretty well with the precipitation pattern shown in the CPC forecast maps. Unfortunately, that may not be very good assurance of a big snow year for us. We’ll have to wait and see how strong that El Nino becomes, and how it affects weather patterns across the northern Pacific.

Another Indicator

The 2019 Old Farmer’s Almanac doesn’t officially come out until September 4th, 2018. However, I got a peak at their map that depicts the expected winter’s weather across the United States. The map shows most of the Pacific Northwest and northern Rockies under, “mild, snowy” conditions for this coming winter.

Key word there, of course, is “snowy”.

If you like the almanac’s forecast, then take-that-to-the-bank, and make sure you have enough money in your account to buy that season pass!

Jim is the chief meteorologist at mountainweather.com and has forecasted weather in Jackson Hole and the Teton Range for the past 25 years.

In previous posts, I have talked about how thunderstorms develop and also how to make better use of weather forecasts, before you head outside in the summer.

In this week’s post, I will talk about how lightning can hurt you, and some things you can do to protect yourself, if you happen to get caught outdoors in a thunderstorm, with nowhere to hide.

Some Lightning Stats

So far in 2018, there have been 15 people killed by lightning in the United States. Last year the total number of fatalities was 16. The year before that, 2016, was the deadliest year in the last 10, with 40 lightning deaths. The average number of lightning fatalities per year in the U.S. for the last 10 years is 27 people.

Interestingly, that number is nearly identical to the average number of avalanche fatalities per year in the United States, over the last 10 winters, an average of 26 people died in avalanches each year.

Neither of these stats takes into account how many people are injured by lightning or avalanches. Those numbers are much higher. For lightning, it is estimated that around 250 people a year sustain injuries.

Based on the current population of the United States, the National Weather Service has calculated that your odds of being stuck by lightning in a given year, resulting in injury or death, is more than one in a million. (To be exact, the odds are 1 in 1,171,000).

The odds of you being struck by lightning in your lifetime, if you live to 80 years old, are somewhat less than one in 15,000. (Precise odds: 1 in 14,600).

Of all outdoor activities, fishing leads the nation in lightning fatalities. Soccer typically leads the way as the most dangerous sport.

How to be Safe

A single lightning bolt generates up to around 100 million volts of electricity, for a split second. During that split second, the temperature of a lightning bolt can reach 54,000-degrees Fahrenheit, or about five times hotter than the temperature of the sun.

There are a few ways that the electrical energy and heat from lightning hurt you: 1) Direct strike, 2) Conduction, 3) Side-flash and 4) Ground currents. Direct hits and conduction only account for about 20-percent of all lightning casualties. Side-flash accounts for about 30-percent and ground currents account for the other 50-percent.

There is not much we can do to protect ourselves from a direct hit, that’d just be really bad luck. Conduction is something we can protect ourselves from, by not being near any metal or graphite objects (that fishing rod) or standing in water. Side-flash injuries are not as avoidable, as any bolt that hits nearby will generate some heat and electricity.

Think of a lightning bolt like a hand grenade, a standard U.S. Army grenade has a kill radius of around 25 feet and a casualty (injury) radius of roughly 50-feet. So, to play it safe out on the battlefield, spread your troops out. That way, if someone does go down after the explosion, others in the group can give aid.

Same thing goes when you are outside, hiking in the mountains, for instance. Spread the members of your party out, 25 to 50 feet when lightning is nearby.

Feet Together

While ground current kills or injures the most people every year, it is perhaps the easiest to protect ourselves from. If you find yourself outside in the heat of battle, with lightning striking nearby, then stand with both feet together.

When a bolt hits nearby, the ground current radiates out in all directions and travels through the ground. If your feet are apart, the current can go up one leg, through your body and then exit out the other leg. Taking the path of least resistance for the electricity.

By keeping your feet together at all times, you might take a bump from the ground current, but your vital organs will be spared, hopefully.

Sitting Indian-style (can I say that these days?), with your legs crossed is also acceptable. However, lying down in a tent is not, as too many different parts of your body are contacting the ground. And by the way, that camp pad does not insulate you from ground currents.

As far as spreading out goes, you and your tent mate might want to “ro-sham-bo” to see who gets to go stand outside, 50 feet away, during the height of the thunderstorm.

Heeding some of this advice might just prevent you from becoming a lightning statistic.

(This content first appeared in the Jackson Hole News & Guide, August 1, 2018)

Posted August 10, 2018 by meteorologist Jim Woodmencey

If you woke up this Saturday morning in the Town of Jackson to the pitter-patter of rain, you might have been as surprised as I was. Seeing as there was no mention of any chance of showers in the forecast, for the previous three days! No showers were even mentioned in the forecast for Jackson in the forecast issued just a few hours before,. Precipitation probability in the mountains was only 8% this morning!!

Models Missed it

I went back and looked at several different computer models and none of them had any precip here for Saturday morning. One of the highest resolution models ran just 6 hours previous to the passing showers. Like the one below. Image is for total precip between 6:00 am and 9:00 am Saturday. (Click for a loop).

Very perplexing when in this day and age weather forecasts are supposed to be getting better, more sophisticated and are running at very high resolutions. But, every once in a while things like this, on this small a scale, can fall through the cracks and be missed, even by the best computer models.

Real Images

The reality is in the images below, from the Infra-Red Satellite and a screenshot from the Teton Pass webcam.

The Only Indicator

If you have read this far, I will hit you with some more technical stuff about why the showers occurred and what the computer models missed.

There was some high level moisture (500mb), loosely connected to monsoon moisture near the Four-Corners. That moisture was scheduled to move over eastern Idaho and NW Wyoming in the models on Saturday morning. There was also enough instability in the atmosphere, which was not  being generated by afternoon heating, thus confirming the likelihood of monsoon moisture.

There was one weather forecast product that I used when I was making my own forecasts for Jackson that showed this pretty clearly, with enough RH around 500mb and instability in the morning hours (12Z is 6:00 a.m. MDT).
See the Time-Height Cross Section product below, generated for Jackson, WY from Univ. of Utah.

Somehow, the computer models did not have the ability to put these pieces together and at least generate a forecast that had some chance of showers. Oh well, so much for weather science getting better. As I like to say, especially during baseball season, “Mother Nature always gets to bat last!”

Posted July 28, 2018 by meteorologist Jim Woodmencey.

Whenever we have thunderstorms that are not caused strictly by afternoon heating,  there is usually another root cause. Most commonly, thunderstorms that form overnight or in the early morning hours in the Rockies are a result of a low pressure center or cold front passing overhead, or monsoon moisture.

This morning, Tuesday July 17th, 2018, Jackson Hole experienced some early morning thunderstorm activity that was due to an upper level Trof of Low-pressure moving across Eastern Idaho and Northwestern Wyoming.

There were no fronts or obvious surface Low-pressure centers marked on the Surface map over eastern Idaho or far western Wyoming. (See map below).

The Trof was barely detectable on the upper level weather maps, that is, it was not a big, obvious wave. However, it did have two things going for it that the computer models did predict very well: 1) High level moisture. 2) Positive Vorticity Advection or PVA. (PVA is a technical term for an area of spin that causes upward motion. In other words, it creates more instability in the atmosphere. Sometimes referred to as a “short-wave”.)

The PVA shown was most likely responsible for perking up these early morning thunderstorms, which produced moderate amounts of lightning and brief heavy rain in a very concentrated area.

Last map below shows the predicted high level moisture in the early morning hours on July 17th. Relative Humidity greater than 90% over Teton Co. Idaho & Wyoming, which is where the Vorticity was headed and where the line of thunderstorms developed.

Finally, the photo below is from the Teton Pass webcam, showing storm as it was passing over Jackson Hole.

Post by: meteorologist Jim Woodmencey
17-JULY-2018

In this week’s post I will talk a little bit about how to prepare yourself each day to avoid being surprised by thunderstorms. And if for some reason you do get caught out during a thunderstorm, some tips on what to do.

Weather Check

Your first order of business each day, should be to check the weather forecast. That will to give you some idea about what to expect. In particular, check the probability of precipitation, and also if any thunderstorms are mentioned in that forecast.

On the Jackson Hole Forecast page of mountainweather.com you will see daily weather icons, as well as in the textual description for each day, showing the percent chance of precipitation. Below that text, “Precipitation Probability” is also listed for the mountains, which often times will be a little higher than for the valley.

A “Lightning Activity” forecast is given each day, listed as: None, Low, Moderate, or High. The activity rating will depend on the likelihood of thunderstorms and how strong those thunderstorms are expected to be. Further down the page this info for the mountains is displayed in a graph format.

A high probability of precipitation, greater than 60-percent, in combination with moderate or high lightning activity, should perk-up your interest and be cause for concern that day.

That said, even a low chance of thunderstorms or lightning activity warrants some vigilance of your surroundings. That is, keep an eye on the sky for building cumulus clouds.

Activity Check

The next thing you should do, whenever there is any mention of thunderstorms in the forecast, is to assess the activity you plan on engaging in. Will you be hiking or biking up to a ridgetop, going over a pass or saddle? Will you be travelling across large areas of open terrain? Will you be on a lake or river?  All of the above put you in areas of high exposure to lightning.

Fishing and boating are high exposure activities in a medium that is a really good conductor of electricity, water. Of all the outdoor activities, fishing accounts for the highest percentage of lightning fatalities in the United States.

Are you going to be on a baseball or soccer field? These are wide expanses of open terrain that leave you highly vulnerable to lightning strikes.

Also, assess how much time and what time of day you expect to be in any of these vulnerable positions?

Safety Check

A thunderstorm does NOT have to be directly over you to throw a bolt of lightning your way. It does NOT have to be raining first, before you should seek shelter. Although, most people never think about seeking shelter until either one or the other of these is happening.

Another Trivia bit: The most dangerous time for a fatal lightning strike, is before the thunderstorm is directly overhead.

When you do seek shelter, buildings or vehicles are the safest places to be. A picnic shelter, baseball dugout, or under a rock overhang are NOT safe places. Why? Because:

1) The picnic shelter is an un-grounded structure that will not fully disperse the electrical charge.

2) Same with the dugout, which may also have a chain-link fence that can conduct the electricity, so at least don’t hang onto the fence!

3) Under the rock overhang, your body is filling in the space between the roof of the overhang and the ground, making it easier for electrical currents running through the rock to close that gap, directly through you!

Postpone or Go Home

No matter what the weather forecast, or how you interpreted it, as your mom used to say, “better to be safe than sorry”. In this case, better to turn around, cancel your plans, of just go home early than to be fried by lightning.

In the mountains at least, I have learned to not let my goals interfere with my decision making. I keep re-assessing the weather, but when clouds are building and as soon as I can hear thunder, I don’t want to be in a vulnerable location to wait it out, I am looking to retreat.

Lightning can be marvelous to watch, but it can also be quite frightening, kind of like being too close to the fireworks. I will write more about thunderstorms and lightning safety in future columns this summer. Have a happy and safe Fourth of July.

Posted by meteorologist Jim Woodmencey

Some of the content of this post first appeared in the Mountain Weather column in the Jackson Hole News & Guide on July 4th, 2018