Persistent snows through Monday
Thursday, February 6, 2014
The Steamboat ski area reported 1” mid / 2” top early this morning, and the 11am update had an additional 1” mid / 2” top falling between 5am and 11am. We currently have cold air near the surface being overrun by northwest flow contained within a moist and relatively warm branch of the polar jet. Forecast snow amounts will be tricky as two different physical processes compete. Generally, a warming airmass in the mid-levels is not conducive for significant snow accumulations as the warming increases stability and decreases relative humidity. However, this relatively warm airmass is being lifted over the cold air entrenched in the Yampa Valley, and this extra ingredient means light snow accumulations will continue. I might expect a 3-6” report by tomorrow morning.
Continued light snow should occur through Friday before an embedded wave races by to our north Friday night. This will bring some cooling to the atmosphere, increasing snowfall rates through early Saturday before the atmosphere warms again earlier in the day, likely ending snowfall for a very brief period. Snow accumulations may be in the 4-8” range by Saturday morning.
Atmospheric temperatures are then forecast to hold mostly steady through Sunday even as valleys likely warm above freezing on that day. Light snow should redevelop by Saturday afternoon and persist Sunday before another stronger wave passes over the area late Sunday or early Monday. Probably another 3-6” by Sunday morning, and 8-16” spread between the Monday and Tuesday morning reports. The timing of the Sunday night/Monday wave will be refined in later model runs and will determine whether significant snows occur early enough to be included in the Monday morning report.
Snows will likely end for a short time sometime on Tuesday before another embedded wave in the persistent northwest flow will repeat the above pattern midweek.
Snows ongoing for the next week, and likely beyond
Tuesday, February 4, 2014
Snows are forecast to continue for the next week, and long term models indicate an active pattern for much of February will follow this week’s accumulations.
The Steamboat ski area reported 2” / 3” at mid/top this morning which fell during the day Monday and made yesterday’s skiing excellent. As of 11am, the updated report has an additional 1” / 7” (!!) at mid/top, so I expect continued great skiing today.
Snows will decrease by tomorrow morning after another 3-6” falls mostly this afternoon and into the overnight hours, leaving a 3-6” report at mid and a 8-12” report at the summit by Wednesday morning. Very cold air from Siberia captured in cross polar flow splits as it flows across Canada creating a broad zonal (east-west oriented) flow that keeps what is forecast to be an active polar jet stream near us. There may be little or no breaks in the snow as persistent light to moderate snowfall is projected to continue over our area Thursday, with 2-5” of snow forecast for Friday morning.
Lighter snowfall will continue early Friday before a well defined wave in moist and cool northwest flow increases snowfall rates by later in the day. This wave will bring a cold front with increased snowfall though the area early Saturday before snows taper off through the day and end by the evening. The timing of this cold front will determine when most of the snow falls, but I would expect 6-12” when both Saturday and Sunday morning reports are added.
Snowfall will pick up again Sunday as another wave embedded within the northwest oriented polar jet approaches. Cool air arrives later Sunday increasing snowfall rates further, and snowfall is expected to become heavy by Sunday night or Monday morning, and persist until Tuesday morning. We should do quite well from this pattern, seeing around 8-16” reported when both Monday and Tuesday’s reports are added.
Long term models keep a zonal polar jet with embedded disturbances over or near our area through at least mid-February keeping an active and more or less snowy pattern throughout.
Cold and snowy week as Siberian air flows into North America by the weekend
Sunday, February 2, 2014
After a beautiful day today, a couple of complex storm systems will affect our area this workweek and this weekend. Another very cold wave rotating around the Hudson Bay vortex will force the low currently just off the northern California coast to drop southeastward along the coast today and then westward along the Old Mexico border Monday. We may see some snow showers during the day tomorrow as the upper level flow backs to the southwest, moving moisture and warmer temperatures into our area.
I don’t expect much accumulations from this until the very cold wave mentioned above approaches our area early Tuesday. Temperatures should fall through the day and snow increase as the very light winds turn to our favored northwest direction. Even though wind speeds will be low, I expect signficant accumulations by Wednesday morning as the snow will be of very low density - maybe as much as 6-12”.
Current forecasts have this Hudson bay wave mixing with some newly arrived Siberian air and briefly cutting off from the main flow over the Washington / Oregon area by Thursday. The end result is the bitterly cold temperatures on Wednesday will moderate a bit as the flow once again backs to the west and warms. But snows are unlikely to take more than a brief break as bits of energy ejecting from this spinning low to our northest will keep showers going.
Models then have Pacific energy phasing with this spinning storm creating a powerful storm that is currently forecast to move over our area late in the workweek or early in the weekend. Very substantial accumulations are expected before current iterations of the models then indicate a hemispheric pattern change to warmer and more zonal (east-west oriented) flow.
Monster accumulations stay just south while light snowfall persists in Steamboat through Saturday
Friday, January 31, 2014
Two waves in the Pacific branch of the polar jet stream stayed further south than I expected yesterday, with the first wave overnight yesterday giving big snows to Winter Park and Loveland, and the second wave during the day yesterday and overnight last night giving big snows to the rest of the I70 corridor and the Aspen areas. Clearly disappointing for us, and in hindsight, I should have placed greater emphasis on both the fact that Steamboat tends not to do well with predominantly westerly flow and models consistently had the best energy just to our south.
Furthermore, the wave for today also will affect the areas south of us the most so only light snow is expected this afternoon and tonight. However, a another arctic wave rotating around the persistent Hudson Bay vortex will begin cooling temperatures tonight and turn the flow to the northwest keeping light snowfall going through most of Saturday. This snow should of much lighter density as the heavy riming that occurred in yesterdays storm will be absent. I would expect 1-4” both on the Saturday and Sunday morning report, with most if not all of the snow in the Sunday morning report occurring before midnight Saturday.
Sunday should be a nice day with a cold start and the sun will make an appearance, especially in the afternoon. The low that I originally thought would stay south of us will affect our area on Monday with light snowfall as the warm and moist southwesterly flow ahead of the storm overruns the cold arctic airmass left by Saturday’s wave.
Additionally, another arctic wave rotating around the Hudson Bay vortex will force the California low westward and turn our flow to the northwest Tuesday evening, increasing very light and dry snowfall. Wind speeds stay very low as they decrease behind the departing low to our south, and that will limit accumulations Tuesday and Tuesday night. At this point, I would guess 1-4” on both Tuesday and Wednesday morning, with light snow showers and minimal accumulations continuing through day Wednesday.
Another small break on Thursday before the Siberian vortex splits and cross polar flow brings another round of bitterly cold air across the North Pole and into western Canada. There is a fair bit of uncertainty with respect to the interaction of this arctic airmass and the polar jet carrying mild and moist Pacific air, but an active pattern, especially for the west coast is likely for next weekend.
Forecast for heavy snows still on track
Wednesday, January 29, 2014
Clouds have overspread the region in stable flow this morning. The storm cycle is forecast to begin later this afternoon as cooler air associated with a cold wave dropping down the west side of the Hudson Bay vortex interacts with the Pineapple Express mentioned in my last blog. Light snowfall will give way to heavy snowfall around midnight that will persist through at least Thursday, creating 5-10” by the Thursday morning report and 8-16” by the Friday morning report, with some Steamboat Magic occurring between report time and opening time.
Current model trends have us in a break during the morning Friday as the first storm moves east of our area. Another Pacific wave in the Pineapple Express is forecast to slam into the northern California coast early Thursday, and this may affect our weather later Friday. Models are struggling with the northward extent of this second more southerly wave, and that will determine if heavy snows continue Friday afternoon and through the night.
If the Pacific wave stays far enough north, heavy snows will continue through the night Friday, producing another 6-12” by the Saturday morning report. Only light accumulations are expected by Saturday morning if the wave stays south of us.
During the weekend, the polar jet stream is forecast to buckle and drop a storm into southern California, backing our flow further to the southwest and eventually ending snows by late in the weekend as the storm stays south of Colorado.
The weather for next week is looking seasonably cool with only light snow expected for a few days around midweek as cold waves continue to rotate around the Hudson Bay vortex. It appears the cross polar flow mentioned in my earlier blogs will allow very cold air from Siberia to enter the North American continent around next weekend. Another storm cycle may develop if this air is far enough west to weaken a rebounding west coast ridge and allow more Pacific energy to undercut it.
