All posts by Jim Woodmencey

Watching the Sky for Thunderstorms

Mountain Weather Blog


Meteorologist Jim Woodmencey
(Note: The content in this post first appeared in the MountainWeather column in the Jackson Hole News & Guide on July 6th, 2016).
 July begins the heart of the “Thunderstorm Season” in the Rockies. It is also the peak of the tourist season, climbing, backpacking, & baseball seasons, etc. etc. . That means more people will be outdoors enjoying the weather, and potentially getting caught in thunderstorms.
In this post I will describe how thunderstorms work, and what to watch for when you are outside during the day. Those telltale signs that dangerous thunderstorms may be developing. I will follow this post with a subsequent one on lightning safety.
Moist and Unstable Air
Most of us would probably describe a “typical summer day” as: Clear blue skies in the morning, followed by some puffy cumulus clouds in the afternoon, and maybe a chance of some afternoon thunderstorms.
How big or ominous those cumulus clouds become will depend on two things:
1) How much moisture is in the air. 2) How unstable the air is.
That clear blue sky that you see in the morning actually contains some moisture, in the form of invisible water vapor. As the day goes on, and the ground heats up, the air begins to rise. As the warmer air rises higher into the atmosphere it encounters colder temperatures, and the invisible water vapor condenses into visible water droplets.
If the air keeps rising, cooling, and condensing, then water droplets start to gather together, and clouds appear.
Relative humidity (RH) is one way to measure how moist the atmosphere is. For thunderstorm development, it can still be very dry in the lower levels of the atmosphere, with low RH. But at the same time, high RH may exist in the upper levels of the atmosphere, which is enough to perk up thunderstorms once there is enough instability.
How unstable the atmosphere is will depend on the difference in temperature between the ground and the upper levels, like up around 20 to 25,000-feet. The bigger the difference in temperature, the more unstable the air is, that is, it must be warmer down low and colder up high to be unstable. Think, “hot air rises”, that’s instability.
If the air isn’t rising, or if temperatures aren’t very cold aloft, or the atmosphere is staying bone dry up through 25,000-feet, then all we see is clear blue skies, all day.
Be Observant
There are a few things to keep an eye on to determine if those little white puffy clouds are going to develop into full-blown thunderstorms on any given day. Watch the sky for these signs of impending thunderstorms:

1) The first puffs of cumulus appear before noontime.
2) The individual cumulus clouds start gathering together and growing vertically.
3) The base of the cloud gets darker, indicating the clouds are growing taller.
4) Taller clouds, darker bases and more of the sky covered by those clouds, the greater the potential for heavy rainfall, hail, and/or strong gusty downdraft winds. And of course, lightning.
However, don’t be lulled into thinking that clouds and thunderstorms can only develop during the afternoon hours. There are many days that don’t fit this “typical” summertime thunderstorm scenario.
Thundertorm Enhancers
Storm systems, otherwise known as low-pressure systems, will periodically roll across the Rockies in the summer, and these will add additional moisture & instability to the atmosphere.
Often associated with a low-pressure system, is a “cold front”. Cold fronts produce more lift and give a boost to the instability. Some of the more potent and violent thunderstorms we see are directly related to the passage of a cold front.
The last thing to be aware of is, the “summer monsoon”. In brief, the Desert Southwest Monsoon is a seasonal wind flow pattern that brings very moist and unstable air up from central Mexico, across the Four-Corners Region, and sometimes that monsoon moisture gets circulated as far north as Northwest Wyoming.
Thunderstorms associated with the monsoon are some of the most random that we will see in the summer, and can occur any time of the day or night.
Whenever you experience a thunderstorm in the middle of the night or just after sunrise – when the afternoon heating is not really a factor– it is very likely that a storm system, a cold front, or the monsoon is triggering the thunderstorm activity.
Keeping an eye on thunderstorm development is of paramount importance to anyone who is spending the day outside. If the clouds develop into lightning-producing thunderstorms, then you are at risk of being injured or killed by a lightning strike; whether you are climbing the Grand, playing a around of golf, fishing the river, or out on the lake or ball field.
Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for almost 25 years.

Understanding Your Weather Prognosis

Mountain Weather Blog

Meteorologist Jim Woodmencey
(Note: Content in this post first appeared in the MountainWeather column in the Jackson Hole News & Guide June 8, 2016)
Sometimes, the forecast can be confusing or misleading, especially when it comes to understanding the “probability of precipitation. In this week’s column I will explain what those percentages really mean, by way of analogy.
Weather Doctor
Being a meteorologist is a lot like being a doctor, except that my patient is the atmosphere. That patient shows up in my office everyday with a different set of symptoms and ailments. My task is to analyze what is wrong with my patient.
I begin my assessment by looking at satellite and radar images, along with a host of weather maps and observations to get some baseline information. Kind of like the nurse taking your vitals and patient history.
Next, I try and diagnose the problem (or problems) the atmosphere might be presenting to me. I look for the obvious signs and symptoms first. Some days they may be so obvious that the diagnosis is relatively simple. For instance, if it is already pouring rain and thunder-storming outside, then the forecast will be easy, “rain and thunderstorms today”.
That would be kind of like a real patient walking into the doctor’s office with an open fracture of the lower leg. The diagnosis is easy, “your leg is broken”.
Most days though, my patient’s condition requires further diagnosis and testing, as I’m sure it is with many doctor’s patients. Whenever the complaints and symptoms are quite subtle or perhaps very complicated, then an accurate diagnosis becomes more difficult. The same is true with the weather.
Initially, I might say, “I think it might rain today”. The doctor might say, “I think you might have a tumor”.
That’s when the doctor sends you for the blood tests, the x-rays, the MRI’s, the colonoscopies (ugh!), or whatever other tests are necessary to help make a better diagnosis of your problem and how to treat it. That is when I head to the computer models, to help guide me towards making a decision about what the weather is going to do.
Sometimes, the final prognosis, meteorologically or medically, is more of a guess. An educated guess, based on your training, experience and how often you have seen these same conditions.
Probability
The doctor might tell me that after surgery, that I might have a 50/50 chance of surviving.  Like the doctor’s prognosis, weather forecasts are also an expression of uncertainty. Probability of precipitation may be the most looked-at part of any weather forecast, but I imagine it is also the least understood.
Probability in a forecast is usually expressed in percent, 30-percent chance of showers, a 60-percent chance of thunderstorms, etc. etc. But what does that really mean?
Probability of precipitation is an expression of two factors: Confidence and Area.
How confident is the forecaster, or the computer model, that precipitation could actually occur, and over how much of the forecast area will it occur, if it does.
Case1: The forecaster is very confident, 100-percent, that measurable precipitation will occur, but it may not occur everywhere within the forecast area, such as Teton County, as an example. That might generate a 50% probability of precipitation (PoP).
Case 2: The forecaster’s confidence that measurable rain will occur is not that high, say 50-percent confidence, but if it does rain, it would rain over the entire forecast area. That would also generate a 50-percent PoP.
The problem is, you don’t know which case was used for the forecast. Which doesn’t really make this any less confusing or misleading, does it?
Given that, I would say that the best way to interpret these examples is to say: “There is a 50-percent chance that precipitation could occur at any point within the forecast area, during the forecast time period”.  
A “50-percent chance of rain” does not mean that it will rain over half of the time period, or over half the forecast area. Which is a common misinterpretation of PoP.
The table compares the percentages to the uncertain terms and the alternate descriptors used in most forecasts, to give you a reference to work from when making decisions about what that forecast really means.
Remember, the forecast is just guidance, like your doctors advice. In some cases, it may or may not rain, and you may or may not die.
Note: My apologies to any doctors reading this, I did not mean to imply that weather forecasting was as easy as brain surgery.
  
Probability of Precipitation
Probability
“Uncertain” Term
Alternate Description
10 to 20 %
Slight Chance
Isolated
30 % to 50 %
Chance
Scattered
60 % to 70 %
Likely or Possible
Widespread or Numerous
80 % to 100 %
No terms used, forecast just reads: “Rain”, “Snow”, “Thunderstorms”, etc.
Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for nearly 25 years.

The Early Winter Outlook

Mountain Weather Blog

Meteorologist Jim Woodmencey
It seems like weather predictions for the coming winter are beginning earlier and earlier every year. They used to come out in early October, then it was September, now they are appearing in mid-August.
The early release of the Old Farmer’s Almanac hit the major media a couple weeks ago. You can buy it in stores beginning this week. Or, if you have to write a column about it, like me, you could buy the pre-release digital copy.
It seems odd to me to be previewing the winter, when I haven’t even had the chance to review the summer. After all, fall doesn’t officially begin for another three weeks. But, here we go!
Outlooks Galore
The various Farmer’s Almanacs are just one way to get a leg-up on what the winter might be like. The Climate Prediction Center, a division of NOAA and the National Weather Service is another source.
El Nino has dominated the weather limelight this summer, and certainly the current and predicted state of the El Nino weighs heavily in the long-range outlooks for this winter. You can get updated on what I wrote recently about El Nino by searching the archives on the JH News and Guide website, or on my mountainweather blog page.
The short story is, it looks like the current El Nino will continue through the winter and early spring. NOAA expects it to become stronger and peak in November or December.  Previous strong El Nino events have brought above average snowfall to the Sierras and the Southwest United States.
NOAA-CPC
I analyzed all of the long-range outlooks from the Climate Prediction Center (CPC) for the winter months, broken down into three overlapping three-month categories, namely: November-December-January, December-January-February, and January-February-March. I also compared what is known as their “Three-Class” version and their new experimental, and as yet “unofficial”, “Two-Class” version of these outlooks. I like the new 2-class version, because it is simpler and less ambiguous than the 3-class version.
Basically, the 2-class version establishes what is “normal”, or average, by using historic weather data from 1981-2010. They pick out the coldest and the driest 15 years, and the warmest and the wettest 15 years.  From there, forecasters then estimate which regions of the country they believe will be well above or below these averages and assign probabilities.
For instance, a 60-percent probability that it will be warmer than normal, means there is a 40-percent probability temperatures could be below normal. If they are unsure, then it is a coin-flip, 50/50 chances of being above or below, or what they call EC “Equal Chances”.
Suffice it to say; no matter how you slice it, all versions of the CPC outlooks are bleak for the Northern Rockies. The overall picture they are painting for our area is for warmer than normal temperatures and below normal precipitation from November through March. However, the probabilities of that happening are generally around 60-percent. Doesn’t that give us a 40-percent chance of it going the other way, colder and snowier? Think positive!
Farmer’s
When I opened up my digital version of the Old Farmer’s Almanac, the familiar yellow-jacketed almanac you’ll see in Stone Drug or in your favorite grocery store this week, I found that it doesn’t do us any favors either. Their big color map of the U.S. has all of Idaho, Utah, western Montana, western Wyoming and western Colorado categorized as, “Mild and Dry”.
This almanac’s forecast has the Cascades of Washington, Oregon, and northern California under, “Cold and Snowy”. Should I pack my bags for Mt Baker or Mt. Hood? Not so fast.
In the 2016 edition of the Farmer’s Almanac, the orange and green-jacketed almanac, they are calling for, “Very Snowy and Typical Winter Cold” for Montana, Wyoming, and Colorado. Bingo! Let’s run with that forecast, it sounds so much better than the doom and gloom of all the others.
Caveat Emptor
Buyer beware! These are long-range outlooks, which I would liken to reading a fairy tale. Good or bad, it does not necessarily mean the predictions will come true.
Computer models generate much of what goes into these forecasts. I work with computer models everyday, and I can tell you that there are plenty of days that the models can’t get it right, for just 24-hours into the future. Naturally, I am a little skeptical of any model that predicts weather conditions 3 to 6 months into the future.
Take a deep breath, don’t worry, be happy, it will get cold this winter and it will snow. Some winters are better than others, and I would never write this one off before the first snowflake has even had a chance to fall.
NOAA Climate Prediction Center Three-Month Outlooks
Three-Month Period
Temperature
Precipitation
NOV-DEC-JAN
55% above
55% below
DEC-JAN-FEB
60% above
65% below
JAN-FEB-MAR
50% above
60% below
Probabilities from the new Experimental “Unofficial” Two-class Climate Outlooks
Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for almost 25 years.

Hyper-El Nino may be Over-hyped

Mountain Weather Blog
Meteorologist Jim Woodmencey


(Note: The article in this post was originally published in the Jackson Hole News and Guide on August 19, 2015).
The comments and questions are starting to come more often now, about the current El Nino and how it will affect our winter. I blame the bigger media outlets for creating this hype, by attaching monikers to their headlines like: “Super El Nino”, “Strongest El Nino Ever”, and my personal favorite, “The Great Godzilla of an El Nino”.

It makes me want to throw-up when I read these headlines, especially since nothing extraordinary is actually happening yet.
To help squelch some of the hype, by way of plain-old scientific explanation, in this week’s column I am going to tell you what El Nino is, what the current and forecasted state of the El Nino is, and what affects this El Nino might have on weather patterns this winter. In particular, what it might mean for snowfall in Jackson Hole.
El Nino Defined
El Nino is not a monster storm, nor is it a series of monster storms that guarantee copious amounts of snow. I will guarantee you though, that every single major weather event that happens between now and next spring will be blamed on El Nino.
El Nino is part of a larger phenomenon that has to do with the Sea Surface Temperature (SST) in the equatorial Pacific, collectively known as “ENSO”, or the El Nino Southern Oscillation.
ENSO comes in three different flavors: 1) El Nino, when SSTs are warmer than average. 2) La Nina, when SSTs are cooler than average. 3) Neutral (No-Nino), when SSTs are near average.
The strength of an ENSO event is measured by how much warmer or cooler those SST’s are getting, and how far across the Equatorial Pacific they are spreading. This in turn creates differences in pressure across the Equatorial Pacific. Sometimes, in the case of an El Nino, a complete reversal of the normal wind flow pattern may occur.
Ocean temperatures down near the equator are relatively warm to start with, but during an El Nino they may get 1 or 2 degrees warmer. This creates more thunderstorm activity over the ocean, and the effects of that extend up into the upper atmospheric circulation, as well.  And voila, we have a disruption of the “normal” atmospheric circulation, which translates to a change in the weather patterns both north and south of the Equator.
El Nino 2015
I don’t know if you remember back to May of 2014, but NOAA scientists then were predicting that a “Super El Nino” would develop for the fall and winter of 2014-15. That never materialized. El Nino conditions (warmer SSTs) never showed up until March of 2015, too late to disrupt winter weather patterns in the northern Pacific.
May-June-July 2015 average SSTs warmed up to 1-degree (Celsius) above the average in some portions of the ocean. Winds were not reversing yet, but they were slowing down, and more convection was noted; that is, more thunderstorms were showing up on the satellite photos.
All of that has led NOAA forecasters to predict: “This El Nino will peak in the late fall/Early winter with 3-month average SSTs near or exceeding 2-degrees C above normal. IF this forecast comes true, it will place the 2015 event among the strongest El Ninos in the historical record (1950-2015).”
The strongest El Nino winters on record were 1997-98, which peaked at 2.3 –degrees above normal, and 1982-83, which peaked at 2.1 degrees above normal, for their three month average SSTs in November-December-January.
What’s Expected?
If this does develop into an El Nino of those proportions, then what should we expect to happen? Usually during El Nino winters the jet stream, or storm track, tends to dip further south in the Northern Pacific, moving over California and the Southwestern United States, then cruising across the Southeastern U.S., keeping those locations wetter than normal in winter.
In both 1997-98 and 1982-83 the Sierra Nevada Mountains in California had huge winter snowfalls, both were attributed to the strong El Nino.
The Pacific Northwest and northern Rockies are a bit too far north of the storm track during strong El Nino’s to reap the same benefits. The opposite though is true during strong La Nina winters, when the storm track usually does favor the Pacific Northwest and Jackson Hole, and leaves California and the Southwest dry.
In Jackson, during the strongest El Nino Winter of 1997-98 we had average snowfall in town and just above average snowfall in the mountains. In the El Nino Winter of 1982-83, we had below average snowfall, both in town and in the mountains.
When I take into account all the El Nino years, weak & strong, it’s a 50/50 proposition for Jackson Hole. Half the El Ninos ended up with above normal snowfall around here, half had below normal snowfall.
Given all that info, I wouldn’t get too hyped-up about this “Giangundous El Nino 2015” just yet for Jackson Hole, it might make for a bigger snowfall winter here or it might not. Unless you live in Tahoe, then it’s going to be HUGE, for sure, dude!
Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Range for almost 25 years.

Snow in July in theTetons

Mountain Weather Blog
Meteorologist Jim Woodmencey

An unusually cold Low pressure system for late July moved across the Northern Rockies on Monday, July 27th, 2015 , bringing with it  a dramatic drop in temperatures, and snow to the higher elevations of the Teton Range in western Wyoming, as well as some strong, gusty winds.

SNOW
Snow was observed at the top of Teton Pass Monday evening, at an elevation of just over 8400-ft. Snow was on the ground down to around the 9500-ft. elevation on Tuesday morning in the Tetons. It is not especially unusual in the higher Tetons to have snow in July, however, to see it on the mountains to such a low elevation this time of year it is. Last summer it snowed down to about the same elevations in late August. So, we are a month earlier this year!

WIND
There were some strong gusty winds with that front, hitting 70 mph at the Lower Saddle (11,610-ft.), 54 mph on top of the JH Tram (10, 318-ft.), and 49 mph over on Lava Mountain near Togwotee Pass (10, 430-ft.).
The Jackson Hole Airport experienced wind gusts of 30 to 40+ mph between noontime and  3:00 pm. They maxed out with a 43 mph gust.

TEMPS
Temperatures dropped over 20 degrees in the valley as the front passed in the afternoon, going from a highs in the mid to upper 60’s around noontime to the mid to upper 40’s by 3:00 pm.

The low temp at the JH Airport Tuesday got down to 30-degrees. In town it was mid 30’s and not really threatening the record low of 31 degrees for July 28th, set back in 1940. The record low for July 29th is 27 degrees, and I have foretasted a low near 30 for Wednesday morning.

In the mountains temps went from a high near 70 degrees at 10,000-ft. on Sunday afternoon to highs in the upper 50’s at noontime Monday, then the temperature plummeted to near 30 degrees by 3:00 pm Monday afternoon. A 40-degree drop in about 24-hours!

At one point Monday evening at the Lower Saddle of the Grand Teton, the temperature was 25 degrees and the wind was blowing steady at almost 40 mph, causing the windchill factor to make it feel like 7 degrees. Yes, seven!

Summary of Weather Events around Jackson Hole & the Teton Mountains for July 27th, 2015.      

Post by Meteorologist Jim Woodmencey

July 15,2015 Thunderstorms

Mountain Weather Blog
Meteorologist Jim Woodmencey

We were underneath a Southwesterly flow this week in western Wyoming out ahead of a Trof of Low-pressure that was over the western US. That kept a decent supply of moist and unstable air overhead that produced late day thunderstorms on Monday, none on Tuesday, and then as that Trof got closer, some rain showers & thunderstorms on Wednesday.

The crescendo of activity was Wednesday evening in Jackson Hole as the cold air aloft within that Trof crossed into western WY, acting just like a cold front passing through. Combine that with the best heating of the day, and good lifting in a Westerly flow over the Tetons, and away ya go!

Some Weather Highlights from Wednesday:

  • Between 0.19 & 0.26 inches of rainfall in town.
  • Some pea sized hail.
  • Wind Gust at the Lower Saddle of 76 mph (at 11,610-ft. elevation).

There was also a decent amount of lightning along the Teton Range, and a few good strikes near town, as well.  Below are some images of weather maps during the height of the activity on Wednesday.

Radar with lightning overlay. Jackson is yellow dot. Yellow circle highlights the whole thunderstorm complex.

Satellite and lightning strikes, yellow arrow upper level wind direction.
Image courtesy of MeteoStar

Infra-red satellite image at 5;30 pm MDT

What can we blame this winter’s weather on?

Mountain Weather Blog

Meteorologist Jim Woodmencey
Almost everyone probably agrees that we had a weird winter, not just here in Jackson Hole, but across the entire United States. Characterized by warmer and drier than normal conditions in the Western United States and Alaska, contrasted by unusually cold and record breaking snow in the Eastern United States.
Even though the Winter of 2014-15 is behind us, people are still asking, “Why was our winter so weird? What caused it to be so warm and dry?” More to the point, what can we blame that on?
In this week’s column I will attempt to explain the phenomena that affected our winter’s weather and why weather patterns were so disrupted across the U.S.
Name Blame
Anytime we experience unusual weather we like to blame it on something. It makes it easier if we can blame it on something with a catchy nickname, like “El Nino” or “La Nina”. We couldn’t do that this year, as the sea-surface temperatures in the Equatorial Pacific remained neutral until very late in the winter season.
If it wasn’t El Nino, then what was it? Besides El Nino, there are a number of other ocean and atmospheric interactions that can alter the “normal” weather patterns.
One possible explanation is the Pacific Decadal Oscillation or PDO, which has to do with sea-surface temperatures in the northern part of the Pacific Ocean.
The PDO usually runs on a 20 to 30 year cycle of either warmer or colder than normal. Back in the 1990’s and early 2000’s it was in a warm phase. Then, there was a marked trend of cooling temps in the north Pacific between 2007 and 2013. By early 2014 the ocean was warming again, reaching a peak in December and January 2014-15, and temps were still above normal by a couple degrees through March 2015.
I thought maybe we could blame this past winter’s weather pattern disruption on the PDO.
Then I came across a study done by the Atmospheric Science Department at the University of Washington. They described a slightly different phenomenon, which one of their climate scientists, Nick Bond, called, “The Blob”.
“The Blob” sounds more like science fiction than it does science, however, the more technical name for it is the North Pacific Mode (NPM). The NPM is similar, but a separate phenomena to the PDO. In short, the NPM (aka the Blob) is a large area of very warm ocean temperatures that extend up along the West Coast and across the Gulf of Alaska in a horseshoe pattern. That warm water also extends down into the sea 300 feet deep.
According to their recent paper published by the American Geophysical Union, the University of Washington scientists found that “The Blob’s” origins are related to, “a persistent high-pressure ridge that caused a calmer ocean during the past two winters, so less heat was lost to cold air above. The warmer temperatures we see now aren’t due to more heating, but less winter cooling.”
In other words, the ocean never cooled down this past fall and winter, like it usually does, and high-pressure stayed put, creating a blocking pattern in the Pacific that would not go away.
Blocking Highs
When big, tall, warm ridges of high-pressure form in the atmosphere they tend to persist, and that is exactly what occurred this winter. That big ridge essentially cut the western U.S. off from the flow of Pacific moisture and left us in a warmer and drier weather regime, with only a few brief storm periods.
Those big ridges in the atmosphere are like a standing wave in a river, usually caused by a big boulder that disrupts the normal flow. Just downstream of that big, tall wave is a big eddy, or trough. That is what the eastern U.S. was under most of last winter, a large, cold trough of Low-pressure. And what did we name that weather monster? The “Polar Vortex”. Not a new concept, just a catchier name.
This standing wave weather pattern –ridge to the west and trough to the east- was hard to break, and persisted for much of January, February, and March 2015.  Coincidentally, when the “Blob” was at its peak.
The next time somebody asks you why this past winter was so weird; you can tell them it was “The Blob”. Let’s just hope the Pacific Ocean continues to cool and we don’t have to endure watching “The Blob 2” next winter.
Posy by Jim Woodmencey
 
(Note: This post is re-printed from the original article that appeared in the Jackson Hole News & Guide’s Mountain Weather Column in April 2015. )

Jackson Hole’s Winter 2014-15 Reviewed

Mountain Weather Blog
Meteorologist Jim Woodmencey

This winter began pretty much the same way it ended, with people thinking about mowing their lawns. Those thoughts were squashed at both ends with abrupt changes from warm and sunny to cold and snowy.

In this week’s column I will review the winter season and see how it stacked up against the historic records. In brief, I am sure everyone would agree it was warm and relatively dry. But here are all the details to put it in perspective, from beginning to bitter end.

Late Fall

Think back to the first week of November, when temperatures were in the lower 60’s in Jackson, and in the 50’s for the start of the second week of November. The grass was green, the birds were chirping, and no one was thinking of heading south.  Heck, it was 54-degrees on Sunday afternoon November 9th. Then it snowed the next day. Five inches in town, over a foot in the mountains, followed by record cold temperatures for early November. Overnight lows in Jackson got down to 22-below zero on November 16.
So much for mowing the lawn, everyone figured it was “game-on” at that point. Some headed south, others waxed skis.
November snowfall finished strong; with almost triple the normal monthly snowfall in town, 28 inches compared to an average of 10 inches. November was also more than three degrees colder than normal. And it would end up that November was the snowiest month of the season, and the only one with below normal temperatures.
December-January
December was about as close to normal as you can get for snowfall in town, with 19 inches in December 2014, compared to an average of 18 inches. In the mountains, at the bottom of Rendezvous Bowl at JHMR, there was 76 inches of snowfall, normal December snowfall is 79 inches.
December started the trend of warmer temperatures, ending up four degrees warmer than normal. January temps were only one degree above normal, when you compare monthly mean temperatures, that is, the average of the monthly average high and low temps.
February-March
February was the fourth warmest on record in Jackson, with the mean temperature for the month a full eight degrees above normal. Total snowfall in town was only four inches, well below the norm of 12 inches for the month.
February snowfall in the mountains was well below normal also, with 48 inches compared to the average of 67 inches in February.
March was cold for the first few days, then whimpered heavily as we hit a spell of warm and dry weather that lasted from March 6th through March 23rd. That spell peaked when we hit 60-degrees for the first time this year on March 16th. Hardly any snow fell in town, and the grand total for the month was just four inches, less than half the average of nine inches.
The mountains didn’t fair much better, with a total of just 23 inches at Rendezvous Bowl in March. Average March snowfall is 65 inches at that location. Not the grimmest March ever in the mountains, that distinction belongs to March of 1994 with just 16 inches. March of 2007 was another bleak one, with only 18 inches of total snowfall up there in March.
Winter Snow Totals
For the four-month period, December through March, the Town of Jackson had 40 inches of snow or 68-percent of normal, the average is 59 inches. However, if you were to include the snowfall we got in November, that would push the total snowfall to 68 inches. Normal snowfall for the five months is 69 inches. So, that would mean we had a pretty normal “snowfall season”, with 99-percent of our average snowfall for November through March. How about that for a stat!
Same thing was true with the water in that snow, December through March was 74-percent of normal for the four month period. Toss November’s water in there and we were 96-percent of normal precipitation for the five month period.
The mountains received 202 inches for December through March or 68-percent of normal, the average is 295 inches. If you pile November’s snow on top of that, it brings the entire season’s snowfall total up to about 81-percent of normal at JHMR. Once again, November carried us through an otherwise dry winter season.
  
Winter Temps
Temperature-wise this winter we ended up about 4-degrees warmer than normal in Jackson, when you look at the average mean temperature for the four-month period, December through March. The historic average mean winter temperature would be about 21-degrees, this winter we had an average mean temperature of 25-degrees.
That would make the Winter of 2014-15 the sixth warmest winter on record in town. The Winters of 2004-05, 2002-03, 1999-00, 1994-95, and 1952-53 were all warmer than this one, for the four-month period. That is still quite a feat to string together four winter months in a row with above normal mean monthly temperatures.
We should count ourselves lucky, compared to many other areas around the Western United States this winter. Our snowfall was way ahead of everyone else, west of the Mississippi, and temperatures at elevation stayed cold enough to preserve the snow until the end. The Eastern United States was the complete opposite of the West this winter, much colder, and much, much snowier than normal.
Looks like I’ve run out of space, so I will have to save any discussion of “why” this winter was like it was for a future column. For now, get out and enjoy your last licks of the ski season.
(*Note: This blog post originally appeared in the JH News & Guide April 1 2015).
 
Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for more than 20 years.

Big Snow & Blow in the Tetons

Mountain Weather Blog
Meteorologist Jim Woodmencey

Lots of SNOW & wind for Jackson Hole, ski areas and weather instruments around the mountains reporting 20 to 26 inches of new snow from Friday night through Monday morning in the Teton Mountains. 

But, this is not technically a big “storm system”. It is a STORM, and we are getting very stormy weather…..but it is not being generated from a typical low pressure system, or what we would call a storm system.

This is a strong Northwest Flow aloft that is carrying moisture over the top of a Ridge of High pressure that is parked over the Western U.S.


Yes, this is sometimes referred to as a “Dirty Ridge”, when moisture rides over the northern periphery of the Ridge axis and causes some weather, rather than the clear skies we normally experience when directly underneath the Ridge itself (like California is right now).

There is no Trof of Low pressure in the upper atmosphere anywhere nearby. Just a weak surface Low pressure over Montana. 

But this is one of the best ways to produce snow in the Tetons, with a very moist and strong NW flow.

— 700mb map and Satellite photo shows flow and moisture (RH) in that flow.
— Surface Map shows the overall weather pattern with High pressure to south & west of Wyoming, and a stationary front east of the Continental Divide, with warm air to the west of that line and colder air to the east of that line.

— Snowfall forecast map is for Monday morning thru Tuesday morning.
Good snow producer across the northern Rockies. Nothing going on to the south of Idaho or Wyoming with this current flow.

Infra-Red Satellite 0800 MST 05JAN15

700mb or @ 10,000-ft. 0500 MST 05JAN15
Surface Map 0500 MST 05JAN15

Snowfall forecast map 05 to 06 JAN 2015


Posted by meteorologist Jim Woodmencey
05JAN15

Understanding Winter Weather Warnings

Mountain Weather Blog

Meteorologist Jim Woodmencey
This past year, I became what is known as a “Weather Ready Nation (WRN) Ambassador” The WRN program started in 2011 and it partners private meteorologists, like myself, with NOAA and National Weather Service forecasters, to help spread the word and educate people about how to be prepared for hazardous weather conditions.
In this day and age of the Internet, Facebooking, Tweeting, NIXLE alerts, etc. there is virtually no reason we should not all be getting the message when extreme or hazardous weather is on the way.
For instance, on my website mountainweather.com on the Jackson Hole Forecast page, whenever the NWS in Riverton issues any kind of weather alert, advisory, watch or warning for Teton County Wyoming, a red box appears above the forecast.
This box works great for the big stuff, but it becomes a bit annoying when there is an “Alert!” issued for things like: colder temperatures, valley fog, or slick driving conditions. These are things that would be extreme weather events in L.A., but this is Wyoming, and I think we can handle that sort of stuff on a daily basis.
What is more important than an “Alert”, is an “Advisory” or most importantly, a “Watch” or “Warning”, of more severe weather. Weather that might cause a true Wyomingite to take heed.
Here are some links to the “Ready Weather Nation” websites:
Advisories
The National Weather Service will issue Winter Weather “Advisories” to alert the public to weather situations that may present a hazard. “Advisories” are for weather that may cause significant inconvenience or difficulty to travelers.  Although, these weather situations should not be life threatening.
The most common Advisories issued during the winter are:
1) Winter Weather Advisory:  Issued for snow events or when a combination of precipitation is expected, such as: snow, sleet, freezing rain, or blowing snow.
2) Snow Advisory: Issued when snowfall is expected to be between 3 and 6 inches in 24 hours in valley locations. For mountain locations the criteria is for 6 to 12 inches of accumulation within 24 hours.
3) Blowing Snow Advisory:  Issued when wind-driven snow intermittently reduces visibility to ¼ mile or less.
Watches and Warnings
“Watches” and “Warnings” are more serious business than advisories.
Winter Storm Watch means: Be Prepared! The NWS issues these when conditions are favorable for dangerous winter weather to occur. It does not mean it will occur, but you should start making preparations in case it does.
Watches are intended to provide enough lead-time so that people can adjust their schedules. They may be issued up to 48 hours in advance of the event and often will precede a “Warning”. 
Winter Storm Warning means: Take Action!  A warning is issued when a winter storm is imminent or occurring. If you hear a warning, immediately go home or seek shelter until it is safe to travel again. Blizzards, extreme cold and windchill can quickly become deadly outside.
Winter Storm Warnings are usually issued when heavy snow and/or strong wind are possible. Heavy snow means that snowfall is expected to exceed 6 inches per event in the valley. For mountain locations it is 12 inches or more per event.
Blizzard Warnings imply strong winds of 35 mph or greater, cold temperatures, and considerable falling and/or blowing snow that frequently drops visibility to ¼ mile or less. These conditions are expected to last for 3 hours or longer.
While a “Winter Storm Warning” may not necessarily translate into a “big dump” for skiers, it should at least prepare you to be cognizant of bad visibility, and some “western” driving conditions.
Unfortunately, there are times when I feel like we are being “over-warned”, and we run the risk of suffering from the “cry wolf syndrome”. That is, we stop paying attention to the warnings, because they come too often, in the form of alerts or advisories, that may seem like just everyday winter weather here in Jackson Hole. Hopefully this article helps to sort out the most important stuff, and explains some of the lesser weather events we may get alerted to during the winter.
 (This article was re-printed in part from the Mountain Weather Column in the Jackson Hole News & Guide)
Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for over 20 years.