Western North America on the long term 19th Dec

Hello all, welcome to another Western North America on the long term by me, the Snowy Hibbo. Today we are going to be looking at the models, and other forecasting techniques, before viewing the

5-9 January

EC Monthly shows the jetstream slamming into the PNW/Southern BC, bringing a big system, that brings moderate-heavy snowfall to the Coastal and Inland Northwest, as well as Tahoe and Tetons on the 5th. The system stays put on the 6th and 7th, bringing continuing snowfall to the locations above. On the 8th and 9th, the system weakens and brings light snow to Tahoe, UT, WY and parts of CO. GFS hints at the jet hitting the same location on the 4th, which seems to somewhat concur with EC Monthly. The Bering Sea Rule shows that troughing is expected for the Northwest US during the 5-7 Jan period. The Recurring Rossby Wave Train forecast also shows potential for a system around the 4-7 Jan period.

10-13 January

The jetstream blasts California on the 10th, through to the 11th on EC Monthly, bringing heavy snowfall to California’s ski resorts, and light-moderate snowfall further inland in CO, UT, NM, AZ and parts of the Inland Northwest. The system moves east over the 12th and 13th, and brings heavier snowfall for CO, UT, NM and AZ, before moving out by later on the 13th. CFS shows the jetstream hitting the PNW on the 10th, through to late on the 12th, with heavy snowfall for Coastal PNW and light-moderate snowfall for WY, ID and MT.

14-15 January

This system on EC Monthly hits Southern BC, Washington and Northern Idaho on the 14th and 15th, bringing moderate snowfall, before dissipating later on the 15th. CFS shows a system hitting PNW and NoCal on the 13th, and continuing into the 14th, with heavy snowfall for the coast, and light snowfall for the Rockies (UT, CO and Inland Northwest), as the system weakens.

17-18 January

This system on EC Monthly hits Southern BC and the PNW later on the 17th, bringing heavy snowfall, before weakening to lighter falls for Idaho and Interior BC/Alberta. CFS shows a big front, hitting the whole West Coast on the 18th, bringing heavy snowfall to the Coastal Ranges, and mostly light snowfall for UT/CO and the Inland Northwest.

Climate Drivers

The current forecast is for a period favouring the Eastern US from Christmas to the first week of January. The Euro Weeklies (same model as the EC Monthly Control, just the mean of the ensemble) show a potential change of pattern to favour the Western US in the 2nd week of January.

The MJO is currently forecast to be in Phase 7/8 for the next week on EPS, before it weakens to the inner circle.

This will create more favourability for snowfall for the Eastern US for the next week or so. But this influence will have waned by the start of the New Year.

EC and GFS are both forecasting a weakening of the polar vortex, near East Asia. This has interesting, yet complex effects on the East Asian jet. But the bottom line is that this may induce a -AO setup, which would favour the Eastern US.

CFS forecasts a -AO between Christmas and Early January, which favours the East, as the models currently show. Then the pattern goes more neutral, that could help the Western US get more snowfall.

While some sources argue for less snowfall, the pattern shown by the EC Weeklies and CFS shows a change to favourablity for the West Coast. Hopefully more snowfall will come….

Thanks so much for reading. I hoped you enjoyed reading it.

Disclaimer: There is low skill asssociated with using long range model forecasts to find snow systems. All systems you see here will change, as the date gets closer and may not eventuate all together. I don’t give much accuracy to these forecasts, but you can give these a bit of your time and your dreams might come true 😉 I find the chase of these long range snow systems awesome, so come and join me! The climate driver forecasts tend to have a bit more skill than the model forecasts, but certainly don’t put all your money on them. However, climate drivers are an awesome tool to explain the weather around us.

Thanks again for reading this Western North American long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

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