Snows likely next week despite stubborn model uncertainty
Friday, January 24, 2014
The hemispheric circulation pattern is changing next week, but the details are still uncertain. One source of uncertainty is coming from the much hyped polar vortex as it currently has split into two pieces. One vortex resides over the Hudson Bay as it has for much of this winter and last summer, while another vortex has settled over Siberia. The cross-polar flow between these airmasses is decreasing, and they are forecast to become isolated from one another by next week. However, the cross-polar flow is expected to increase near the end of next weekend, and the strength and location of this flow determines how much cold air flows from Siberia into Canada and vice versa.
Additionally, the west coast ridge has also been a dominant and long-lasting feature this winter, and models forecast major changes as Pacific energy is predicted to undercut the ridge. Furthermore, phasing of the undercutting energy with the cross-polar flow around next weekend will keep the west coast ridge evolving and uncertainty high in the medium to long range.
In the shorter term, mountain slopes will warm and valley will stay cool as inversions persist through the weekend. There is a dry grazing wave Friday night, but that won’t have much, if any impact on our weather. A far more substantial lobe of cold air rotating around the Hudson Bay vortex may begin dropping temperatures late Sunday, with light snow possible for Monday and Tuesday.
Forecast uncertainty then increases as another cold wave is forecast to drop down from the north and phase with Pacific energy undercutting the west coast ridge midweek. I’d like to emphasize the timing of the Pacific energy undercutting the west coast ridge is uncertain since the feature has been so dominant this entire winter, but it seems likely to happen. Furthermore, there are additional waves of energy forecast to rotate down from the north through Thursday, and if the west coast ridge undercutting eventually happens as predicted, we should remain in cool and moist northwest flow with accumulating snows, likely significant, through much of the week.
A major wave is then forecast to move through this undercutting flow around next weekend and will likely keep snows going. But the forecast for then will evolve as there is so much uncertainty midweek.
Nice weather interrupted by a small storm around Thursday and then lots of uncertainty
Sunday, January 19, 2014
Beautiful sunny and dry weather will persist through Wednesday as a large and stable west coast ridge dominates our weather, though a grazing wave in northwest flow will knock temperatures back a bit on Monday. A small Pacific storm will interact with the ridge early in the workweek and the result of that interaction as well as the effects of another impulse dropping down the east side of the west coast ridge from the north will determine our weather for Thursday.
I don’t expect much precipitation from this scenario as the strong west coast ridge minimizes impacts from the Pacific storm. Cooler temperatures and perhaps only light snow with minimal accumulations are expected on Thursday before current forecasts cut off this storm from the mean flow and leave it over California to our south and west.
There has been and continues to be a large amount of uncertainty in the forecast for next weekend and beyond. It appears that all models want to change the hemispheric pattern and either undercut or break down the west coast ridge. Numerical models often struggle with pattern changes like this, and the uncertainty with next weeks forecast has persisted longer than normal. At this point, there is no use guessing what our weather may be until more stability emerges in the solutions not only between models but also within models.
Snow hangs through most of Tuesday
Monday, January 13, 2014
The Steamboat ski area reported 8” mid and 10” up top at 5am this morning, with about 2” of that coming overnight. Additionally, another 2.5” has fallen between 5am and 9am and it is currently lightly snowing.
The storm yesterday disappointed as a stabilizing and warming airmass not only stopped the snowfall that I expected to continue, but allowed winds to rake the ski area. By 1pm yesterday, much of the upper mountain had wind affected snow and skiing was not that great.
Another subtle wave in moist northwest flow passes over the area tonight, increasing snowfall again. The atmosphere should gradually cool through tomorrow afternoon keeping light snow showers going on the hill even as the valleys see some sun. I would expect 4-8” to be reported in the Tuesday morning report and 1-4” on the Wednesday morning report, all of which will occur during the day Tuesday.
The snows then stop for an extended period as the atmosphere warms and dries as the west coast ridge builds over our area. A grazing cool and dry wave to our northeast on Thursday will knock temperatures down a bit, but it appears the ridge and its associated warm and dry weather will continue through most of next weekend. Mountain slopes will substantially warm, though valleys will be on the cool side as temperature inversions reform and persist.
Storm about 4 hour late, but it’s here now
Sunday, January 12, 2014
Snows did not start until almost report time this morning, about 4 hours later than I had been anticipating. However, the Steamboat magic DID occur as scheduled, with 6” of snow falling between 5am and 9am. Temperatures at Storm Peak Lab fell from about 21F to the current 9F during this time while winds have increased from the northwest and currently average about 28mph with gusts to 45mph up top.
We are currently in moist northwest flow that is now expected to last through much of Tuesday, though snow amounts will be minimal by the end of that day. Since we have already received 7” of snow at mid as of 11am, and I expect periods of moderate to heavy snow to continue through today and especially this evening, I would expect a report tomorrow morning between 10” and 20”. This is consistent with yesterdays forecast of 6”-12” if the 4”-8” I expected by this mornings report is shifted to Monday mornings report.
Snow will continue through Monday with varying intensities, producing another 4-8” by Tuesday morning. Then, snow showers are expected to continue on the hill Tuesday as a trailing wave passes over the area, even as the valleys see some sun. Only 1-4” of new snow is expected during the day Tuesday as the airmass stabilizes and dries.
The west coast ridge is expected to build over our area in earnest on Wednesday, interrupted by a grazing cool and dry wave to our northeast on Thursday. It appears the ridge and its associated warm and dry weather will continue through most of next weekend, keeping mountain slopes warm but valleys cold as temperature inversions reform and persist. Model disagreements by the end of next weekend create uncertainty in the longer range forecast.
Heavy snows begin again around midnight and last through Monday
Saturday, January 11, 2014
Another 9” of snow was reported at mid and top this morning, and skies have partially cleared and temperatures have warmed. The last trough in this very impressive storm cycle arrives around midnight tonight, leading to falling temperatures and moderate to heavy snows. I still expect 4-8” for the morning report, but I expect some Steamboat magic during the morning hours, with lighter but still sometimes moderate snow continuing through Monday as additional impulses of energy periodically increase snowfall rates. I’m raising my initial 4-8” by Monday morning to 6-12”, with still an additional 3-6” during the day and overnight Monday that will be reported Tuesday morning.
Snow showers may hang on for some of Tuesday on the hill, even as the valleys see some sun by the afternoon. The atmosphere then warms and dries as the west coast ridge bring gorgeous weather to our area, though a dry and grazing wave will cool temperatures a bit for Thursday and may bring some high clouds.
We should have a stretch of continuing beautiful days as the ridge is currently forecast to dominate our weather through the early part of the next workweek. Models then struggle with how energy from the Pacific interacts with the ridge, so the forecast for midweek will have to wait until models resolve their differences.
