Wednesday, January 11, 2017
Another wave in the Pineapple Express phases with cool air traveling southward from western Canada and moves over the Steamboat Springs area this afternoon. Some dry air has unexpectedly worked in behind a weak wave last night, delaying the moderate to heavy snow showers until cooler temperatures arrive later today. Furthermore, the cooler air won’t be as cool as earlier forecast, further decreasing the originally forecast snowfall for overnight. The end result is I now expect a much lower 4-8” on the Thursday morning report.
Meanwhile, a splitting weather system crosses the West Coast on Thursday. Most of the energy forms a closed low that waffles off the coast of southern California through Saturday, with southwesterly flow ahead of the storm warming our temperatures during the day Thursday. Waves of energy in the northern part of the split will periodically enhance snowfall through Saturday morning as they pass near our area.
Right now, models indicate the best snow to occur from Thursday afternoon through Friday morning. Snow total will be dependent on the evolution of this closed low and the poorly resolved waves in the northern portion of the split, but another 4-8” of dense snow is possible by Friday morning. Snows should taper off during Friday before ending by Saturday morning, leaving another 1-4” of snow for the Saturday morning report.
While dry air lurks to our north through the weekend, the closed low off the southern California is forecast to slowly move northeast across the southern Great Basin on Sunday and Monday, keeping at least clouds over the area. Keeping in mind these closed lows are notoriously difficult to predict due to nebulous upper air forcing, dry air is expected to finally reach northern Colorado around Tuesday.
There are model differences with the next storm as the persistent Bering Sea ridge migrates to East Asia and allows cold air from Siberia to pour into the Pacific and energize the jet stream. But models generally have another surge of Pacific moisture moving over our area by later Wednesday or Thursday that brings precipitation back to our region.
Monday, January 9, 2017
Pieces of a massive Gulf of Alaska storm will move over the Steamboat Springs area over the work week, phasing with some cool air rotating down from western Canada tonight and Wednesday night leading to impressive snowfall accumulations of of over two to three feet in generally windy westerly flow.
As of noon on Monday, mountain-top temperatures have begun to cool as an ill-defined cool front moves through from the west. This should turn any rain or rain/snow mix in the Yampa Valley to all snow this evening, with moderate to heavy snows occurring overnight in the valley and on the hill. There may be 8 to 16 inches of snow on the Tuesday morning report, with the snow becoming less dense and fluffier toward the morning.
Snows will decrease but not end during the day Tuesday under warming temperatures, leaving another 4-8” on the Wednesday morning report as temperatures cool a bit overnight.
Another strong wave in the Pineapple Express passes through on Wednesday and Thursday and again phases with cool air moving southward from western Canada around Wednesday afternoon or evening. The air is colder than on Tuesday, and this is forecast to bring more wind and moderate to heavy snows on the hill and down to the valley floor, leaving another 10 to 20 inches the Thursday morning report.
The European ECMWF was the winner from the last forecast, bringing a splitting system into the West Coast near the end of the work week. This system has moved north from the previous forecast, and we are on the northern edge of precipitation from this warm system later Thursday, Friday and into Saturday morning.
Dry air is forecast to overtake the area later Saturday, marking an end to this impressive storm cycle. A wave moving westward across the Gulf of Alaska early in the weekend will bring some cooler air and at least clouds for Sunday. Some brief clearing is forecast for early Monday before snow showers are again in the forecast for later in the day or overnight, followed by a mostly precipitation-free work week as a flat ridge moves over the West.
Friday, January 6, 2017
Behind the last storm and ahead of the next one, tonight will see very cold nighttime temperatures followed by a cold and sunny Saturday morning, with possible clouds later in the day.
Yet again, a strong Gulf of Alaska storm forms over the weekend. Strong southwesterly flow ahead of the storm forms the so-called Pineapple Express as it reaches back to the old Hawaii system left over from several storms ago and moves the remains eastward over a broad ridge that forms over the western U.S ahead of the storm.
Though we will see snows on hill Saturday night and Sunday, and precipitation will start out as snow in the valley, the much warmer temperatures under the ridge as well as the copious incoming moisture may lead to a rain event in the Yampa Valley from Sunday night through Monday afternoon or night.
On the mountain, there may be an inch or two on the Sunday morning report, with another 2-4” during the day and again overnight leading to a 4-8” Monday morning report.
Temperatures look to cool by later Monday or early Tuesday as a cool front passes through, changing the rain to snow in the valley and turning on the snow-machine in cooler and still windy, wet northwest flow. Accumulations could easily be in the 8-16” range or more by Tuesday morning depending upon timing of the cool front.
At this point, snows are forecast to taper off later Tuesday before another strong wave in the Pineapple Express passes through on Wednesday and Thursday and partially phases with cool air moving southward from western Canada. This is forecast to bring more wind and moderate to heavy snows down to the valley floor and again, significant snowfall totals are expected by Thursday afternoon.
There is model disagreement for the end of the work week, with the European ECMWF bringing a splitting system into the West Coast that stays mostly south of us, while the American GFS keeps that system consolidated as it moves it over our area, beginning snows again by Friday.
Tuesday, January 3, 2017
The cold front discussed in the Sunday forecast is now forecast to consolidate and stretch further west, keeping moderate to heavy snows over the Steamboat Springs area through at least early Thursday and necessitating this update.
Several waves of energy are forecast to move over northern Colorado this afternoon, and I now expect 5-10” of snow to be reported by Wednesday morning at mid-mountain.
But the real reason for this update is Wednesday, as the stronger front, reinforced with energy dropping southward from central Canada, will force moderate to heavy snows through the day Wednesday and overnight. The ribbon of dry air discussed earlier is now well north of the area and no longer a concern, and I now expect 6-12” during the day Wednesday along with another 6-12” overnight, leading to a Thursday morning report of 1 to 2 feet.
The cold front slowly sags southward during Thursday, and as we lose the forcing associated with the front, snows will diminish. There is model disagreement with respect to how fast the front moves south, with some models tapering off snowfall during the day on Thursday and others waiting until Friday morning.
Regardless, dry air will invade the area by sometime Friday, eventually bringing sunny skies and cold temperatures that will last through Saturday.
Current model forecasts have another strong Gulf of Alaska storm forming over the weekend. Models are forecasting that part of the old Hawaii system left over from a couple of storms ago will mix with the southern end of the Gulf of Alaska storm and move eastward over a broad ridge that forms over the western U.S.
Though we may see some light snow showers on Sunday, the warmer temperatures under the ridge as well as the copious incoming moisture may lead to a rain event in the Yampa Valley, with snow at higher elevations, from Sunday night through Monday night. Temperatures look to cool by Tuesday morning changing the rain to another round of possibly significant accumulating snow.
Those local residents who are considering removing snow loads from their roof may want to act over the weekend. I will still issue the late-week forecast on Thursday or Friday and expect to have a better idea of how next week’s storm will evolve.
Sunday, January 1, 2017
The good news is the bitter cold forecast in the last discussion will likely be warmer and of shorter duration and we should still see snow for much of the work week in the Steamboat Springs area. The bad news (from a forecasting perspective) is there is still considerable uncertainty in the near term among the numerical models, which is unusual since a consensus usually emerges this close to an event.
A strong storm along the Pacific Northwest coast has phased with some bitterly cold air from western Canada originally sourced from Siberia. The storm is forecast to split and elongate to the west and east underneath a ridge of high pressure in the Gulf of Alaska, eventually forming a frontal boundary that encroaches over our area around Monday. The major uncertainty lies with how far west and south energy from this storm propagates in the eastern Pacific.
Models do agree that cold air will move over the region from Monday through early Thursday, though the splitting storm will carry the coldest air to our north and east. The European ECMWF has a reinforcing wave of cold air moving over the area late in the work week while the American GFS keeps more energy in the eastern Pacific, pumping up a flat ridge over the Great Basin and moving copious Pacific moisture inland under warming temperatures.
Light snow should start overnight on New Year’s Day, with up to an inch or two of snow for the Monday morning report, and pick up for a time during the day as cold air invades the area. However, there is no sharp frontal boundary which reduces the likelihood of heavy snow and the mountain-top winds are from the west, which is not an ideal direction for Mt. Werner. But the snow is persistent and lasts through the overnight hours, so I would expect 4-8” of snow by the Tuesday morning report.
Light snow will continue through Tuesday with another 3-6” forecast for Wednesday morning before another push of very cold air moves over the area later Wednesday into Wednesday night. Though the winds veer to a more favorable northwest direction, a ribbon of dry air lurks just to our north so snows should wind down during the day and overnight with another 1-4” expected during Wednesday.
The forecast for Thursday is dependent upon the track of cold air traveling southwestward from western Canada as discussed above. The European ECMWF keeps the end of the work week drier and colder, while the Amercan GFS brings moderate to sometimes heavy snows inland under a warmer Pacific airmass for later Thursday and Friday.
Lot’s of uncertainty, so stay tuned for my late-week weather discussion next Thursday or Friday.