Winter comes rumbling in

SNOW Ystone1

by nathan oster

Winter rolled in like a lion this week, bringing significant snowfall and far below average temperatures to towns and cities across the Big Horn Basin.

Chris Jones, a warning coordination meteorologist for the National Weather Service in Riverton, said some snow and cold is to be expected in December.

The snow that blanketed parts of Wyoming and produced the worst snowstorm in South Dakota history in late September and early October was unusual.  And Jones said he might be tempted to say it’s an extreme start to winter — if it weren’t for the relatively mild months of October and November that came between the two storms.

“We spent a good part of that time above normal in terms of temperatures,” said Jones.

That included Monday, when the mercury climbed into the mid 50s.

The high at the Greybull airport was 54, which was recorded at around 1:30 p.m.

By 7:53 p.m., it had dropped by 18 degrees, with a reading of 36 at the airport

When the sun rose Tuesday morning, several inches of snow were on the ground and temps were in the teens in Greybull.

“It can change quickly,” said Jones. “From a high of 54 … I can probably safely say you aren’t going to see 54 for awhile.  It’s not that unusual, though, for there to be a warm day or two ahead of a big storm like this one.  You can see temps anywhere from 15 to 20 degrees above normal when that happens.”

Wind also contributed to chill in the air, as the Greybull airport measured gusts of between 30 to 40 miles per hour starting around 7 p.m. Monday and continuing into Tuesday morning.  Frannie had the most powerful gusts from the storm, with some measured around 50 mphs overnight.

The next seven to 10 days don’t figure to bring much relief, either.

“Cold … that’s the big word of the day,” said Jones. “And it looks like it’s going to stay cold, too.”

Jones said he doesn’t expect much snow to fall in the coming days. Highs in the single digits are forecasted through the weekend.  It may not be until the early part of next week that highs climb into the teens.  The overnight lows during this upcoming stretch figure to be 10 to 20 below 0.

From a bigger picture standpoint, December is notoriously fairly dry in terms of water content.  The climate prediction center, which produces 30- and 90-day precipitation outlooks, called for a better than average chance of above normal precipitation and a trend toward colder than normal temperatures in December.

“That’s looking like a pretty good call at this point,” said Jones. “The first half of the month, other than yesterday and Sunday, is likely to be well below normal, in terms of temperatures.”

Jones said the climate prediction center isn’t suggesting that it will be colder or snowier than normal. “They’re seeing a trend toward average, with no strong ties with the patterns that we are seeing.  They look at temps in the Pacific Ocean, and right now, they’re in a neutral phase, so they aren’t able, with any confidence, to say, ‘Well, that means this,’ or ‘That means that.”

Looking at the last 15 years worth of weather data for Greybull, Jones said the average high for December has been 32 degrees.  The average low during that same stretch has been 8.3 degrees.

The only December since 1998 that produced below normal average temperatures came in 2009.  From Dec. 7 through Dec. 11 of that year, the high ranged from a -2 reading on the 9th to a high of 16 on the 11th.  The lows during that five-day span were -8, -22, -24, -22 and -23.

For the month of December in 2009, the average high was 21 degrees.

Jones said that the way this December is starting, that mark could be in jeopardy.