Monday, December 12, 2016
While a storm in the Gulf of Alaska spins in place early this week, some energy moving around the west side of a large eastward moving vortex in south central Canada will keep light snow showers over the Steamboat Springs area overnight.
Tuesday should be precipitation-free before the Gulf of Alaska storm begins moving towards the West Coast. Some energy ejecting from the storm will bring a warm front through the Intermountain West on Wednesday, beginning snow showers by Wednesday afternoon and continuing overnight. The last forecast wrongly minimized the snow amounts from this type of event, and with that in mind I expect 4-8” of dense snowfall by the Thursday morning report.
Temperatures will continue to warm on Thursday as the Gulf of Alaska storm approaches the West Coast, with a large piece of energy crossing central California on Thursday followed by the main storm on Friday. This first piece of energy will carry a lot of Pacific moisture and wind, and begin moderate to sometimes heavy precipitation by Thursday night, with a rain/snow mix possible at the lower elevations.
Concurrently, a large mass of arctic air once again makes its way south across western Canada and partially phases with the main part of the Gulf of Alaska storm, eventually beginning another battle between the airmasses from the Pacific and arctic. The arctic front is expected through the region later on Friday (though timing at this point is uncertain) increasing snowfall rates even further as the snow becomes lighter and fluffier and travel becomes difficult or impossible for a time, before snows end on Saturday.
There are a lot of moving pieces that will likely change in future forecasts, but I expect another round of very significant accumulations possible by Saturday morning, followed by dry and cold temperatures through the rest of the weekend and lasting into early next week.
Thursday, December 8, 2016
The arctic airmass currently entrenched over most of the US will be pushed eastward on Friday as a moist Pacific jet stream slams into the West Coast.
A persistent ridge over the Bering Sea is largely responsible for our current and future weather. Very cold air from Siberia has been shunted over the North Pole by the ridge, bringing the sub-zero temperatures observed this week. Additionally, a moist Pacific jet stream has undercut the Bering Sea ridge and is currently bringing precipitation to the northern half of the West Coast. A battle will ensue between the warm Pacific jet and frigid arctic airmass, with temperatures first warming aloft tonight before the warming makes it’s way to the lower elevations on Friday.
This is a difficult short-term forecast since there will be a lot of moisture around, but Steamboat Springs usually does not do so well when there is warming aloft. In fact, we had our notorious freezing rain event around this time two years ago that also involved warming aloft, and I can’t discount the possibility that there may be some of that again. However, it is relatively rare so I won’t include it in the forecast, but I do expect that snow amounts will be tempered from tonight through Saturday morning while this is occurring. I would expect 2-4” overnight with another 1-3” during the day Friday.
Snow on the mountain and a possible rain-snow mix in the valley will taper off during the day Friday but likely not completely stop before they pick up again by Saturday afternoon as an embedded cool wave in the west-northwest flow moves over northern Colorado by Saturday night.
Snowfall will become moderate to heavy by midnight and continue through the morning hours before substantially decreasing by later in the day and overnight. I would expect 6-12” by the Sunday morning report with another 3-6” during the day, likely making travel conditions quite difficult or even impossible for a time.
Meanwhile, another wave traveling down the east side of the Bering Sea ridge will send more cold air south and west Sunday night, though the still strong Pacific jet stream will keep the coldest air to our north and eventually east. While the westward moving air will invigorate another storm in the Gulf of Alaska, the re-introduction of the relatively dry arctic airmass over our area will keep lighter snow showers off and on from Monday through Wednesday.
There are a lot of moving pieces that will likely change in future forecasts, but by Wednesday night, a piece of the Gulf of Alaska storm is forecast to be carried over our area by the Pacific jet stream and could make Thursday a snowy day with possibly significant accumulations as another round in the battle of the airmasses begins.
Monday, December 5, 2016
Cold air sourced from the North Pole, euphemistically referred to as Big Blue, will invade our area over the next few days making Tuesday, Wednesday and Thursday morning the coldest days of the season so far. A wave in northwest flow is currently crossing the Pacific Northwest coast and will bring bitter cold, wind and some moisture to begin snow again starting Tuesday afternoon and lasting through some of the day Wednesday. Even though the moisture content of the air is modest due to the cold temperatures, 4-8” of very light fluffy snow may be reported on the Wednesday morning mid-mountain ski report.
But temperature may reach as low as the minus teens for Wednesday and Thursday mornings with highs in the single digits for Wednesday. The light snows will end by Wednesday afternoon after another inch or two possible, with peaks of sun in the valley making it feel slightly less cold.
A transient flat ridge follows for Thursday and Friday, bringing welcomed warming and enough wind to scour out the valley inversions and bring temperatures back closer to normal. Though there will be sun during the first part of the day Thursday, there will be enough moisture embedded in the brisk northwest flow to bring the threat of light snow showers back to the region later Thursday.
Hard to define and time waves in a proximate jet stream oriented west-northwest are forecast to pass around or north of the Steamboat Springs area for Friday and Saturday, bringing periods of moderate to heavy snowfall at times and likely leaving significant accumulations over the 2 days.
A break in snowfall is currently timed for Sunday before another grazing wave begins snowfall again by late in the day. In fact, current model simulations have the jet stream close enough to keep the threat of snowfall going for most of the following week. However, small variations in the location of the jet as well as the moisture contained within it make for a rather uncertain forecast with large variations in predicted snowfall likely until a model consensus emerges.
Friday, December 2, 2016
A low to our south and a large storm in the Gulf of Alaska will affect our weather over the next week. The southwest flow from the low to our south has directed moisture and light snow showers over our area that will persist through the night with only an inch or two of accumulations.
Meanwhile, the atmospheric jet stream is currently punching into the Pacific Northwest bringing copious precipitation as energy begins to be ejected from the Gulf of Alaska storm. We may see some very light snow showers on Saturday afternoon and overnight as energy in the southern end of the jet stream grazes northern Colorado.
While the northwest and northern U.S. Rockies will see the bulk of precipitation from this storm, Colorado is tantalizingly close to some action, and the models have been struggling with the proximity of the jet stream over these last few days. What appeared to be a very promising storm a few days ago now looks to deliver more cold than snow early next week after a flat ridge moves over the Steamboat Springs area on Sunday and briefly warms temperatures.
Snow showers should start by early Monday morning as the main part of the storm approaches from the northwest. Snows will generally be light until a strong cold front blasts through the area on Monday, likely accompanied with a burst of snow that quickly ends behind the front.
Very cold air will then invade our area making Tuesday and Wednesday the coldest days of the season so far. There is another wave in northwest flow that looks to bring more snow showers to Colorado on Tuesday and Wednesday, and models are wavering on the exact track, which will likely change as we move closer to the event. Right now, some dry air is forecast to spread over the Steamboat Springs area on Tuesday, keeping snows to our south, before light snow showers visit our area Tuesday night and early Wednesday.
A transient ridge follows for Thursday and Friday, bringing warming that will be most noticeable at the mid and higher elevations as developing inversions keep the valleys chilly. More grazing waves are forecast for Saturday and the following Monday, but I expect the forecast to change as models get a better handle on two features that will likely determine our weather over the next 2 weeks; a sharp ridge over the Bering Sea between Russia and Alaska and cold air from western Canada moving westward that may interact with that ridge as well as possible undercutting energy from Asia.