Grasshopper’s Weekly North America Forecast, Thursday Feb 15th – Another Deep Week Lined Up for the Sierras, Southern Cascades and Central Rockies

February 16th, 2024
Perfect conditions in Snowbird on Feb 11th.There is more snow on the way, this week’s forecast favouring resorts in the US resorts. Photo: Snowbird

 Mountainwath | The Grasshopper

Written Thursday morning 15th February (Pacific Time)

We’ve got another active seven-day period ahead, favouring resorts in the Sierras, Southern Cascades and the central Rockies. Today and tomorrow, a frontal band will leave a deep band of powder across these very areas, followed by another top-up this weekend from a weaker, mild and moist system, which will see wet stuff mixed in at low elevations near the Coast.

Monday through Wednesday, the Sierras will go super-deep thanks to a strong Pacific storm pushing up into the Coast. Temperatures will trend cooler over this period, banishing any wet stuff to pre-history, with the central-southern Rockies also receiving another decent load.

Snowfall accumulations (cm) for the next 7-days. Note, snow depths are calculated using the Kuchera Ratio, which uses is a linear function of the warmest temperature in the lower half of the atmosphere. Compared to the traditional 10:1 ratio, the Kuchera is likely more accurate. Source: ECMWF, WeatherBELL 

Thursday Feb 15th & Friday Feb 16th

Today and tomorrow will see a band of powder being laid down over central areas, from the southern Cascades to the Rockies south of the Canadian border, down through Utah and Colorado.

This storm system, which has already brought 20-40cm to the northern Cascades and Sierras, is a rather complex system, but is mainly comprised of a near-stationary front marking the boundary between a freezing and drier Arctic airmass to the north, and a warmer, more humid Pacific airmass to the south.

The heaviest falls will be within the Pacific airmass, as that’s where all the moisture is, with 25-50cm+ likely in Oregon, southern Idaho & Montana, Wyoming, and northern Utah & Colorado, adding to the already massive totals these areas have seen in recent days. Although areas just north of this will see lighter falls in the 5-15cm range, it will be high quality stuff.

Snowfalls will eventually clear during Friday, first in the north, then elsewhere late in the day, although they’ll hang on in Colorado into early Saturday, while the cold airmass pushes southwards and warms.

Snowfall accumulation (cm) for Thursday & Friday (PT). Note: the Kuchera ratio is used here too. Source: ECMWF, WeatherBELL

Saturday Feb 17th & Sunday Feb 18th

This weekend, the action continues across central areas as a Pacific front slowly pushes eastwards over the area, bringing a mild and moist southerly flow. The front will first get things started in the Cascades and Sierras early Saturday, before pushing inland to Idaho and Utah Saturday night, then Montana, Wyoming and Colorado Sunday morning as things start to clear in the Sierras and Cascades.

The biggest totals are expected in northern California and southern Oregon, with up to 15-25cm expected around the Tahoe resorts, while 15cm or less is expected elsewhere. However, the snow will be of the denser variety, and rain will be mixed in at low elevations especially in the Cascades and Sierras.

Snowfall accumulation (cm) for Saturday & Sunday (PT). Note: the old-school ratio of 10:1 is used here so values maybe underdone. Source: ECMWF, WeatherBELL

Monday Feb 19th to Wednesday Feb 21st

Come Monday morning the next storm will be well underway in the Sierras and southern Cascades, having arrived in the dead of the night. There’ll be heavy to very-heavy falls, but again this storm will be borne out of a system bringing strong, mild and moist southerlies, so some wet stuff is expected for low elevations, although temperatures will trend cooler during this three-day period as the main low centre pushes into the Pacific Coastline.

During Monday and Tuesday, the storm will spread mostly light falls northwards into the BC Coast Mountains, and inland to the northern and central Rockies as far south as Utah and northern Colorado. Some areas of the central Rockies, such as the Smoky Mountains, Tetons and northern Wasatch will pick up moderate falls, possibly even heavy.

Another surge in the storm from late on Tuesday, this time a little cooler, will see the Sierras receiving another heavy dump of just good ol’ snow lasting through the first half of Wednesday. This extra surge will also benefit the central-southern Rockies during Wednesday, Utah likely taking the cake with moderate-heavy falls, while moderate falls are likely in Wyoming and Colorado.

Snowfall accumulation (cm) for Monday through Wednesday (PT). Note: the old-school ratio of 10:1 is used here so values maybe underdone. Source: ECMWF, WeatherBELL

Extended Outlook

After a quiet end to the working week, things look to ramp up again next weekend, starting in the north as storms look to roll down south over the following days, with a trend towards colder temperatures. Overall, it looks to be an unsettled week and big totals could be expected, especially along the Pacific Crest and in the northern & central Rockies.

7-day pressure anomalies starting next Thursday afternoon the 2nd February (PT) showing an overall unsettled period. Temperatures are also expected to trend colder, so it’s all lining up for deep powder. Source: ECMWF, WeatherBELL

That’s all from me today. Have a great week, see you next Thursday.