North America on the long term 16th Feb

4th-8th March

Mild troughing for the Northeast US and the Southern California region. A SE Ridge is persistent in this period, together with a strong +AO and a +NAO. A very strong Aleutian Ridge is in progress as well, per EC Monthly.

9th-13th March

Western US troughing in this period is anchored by a SE Ridge and strong Aleutian ridging, together with a strong +NAO.

14th-18th March

The Western US troughing declines, but the Aleutian ridge and Eastern US ridging are still in place playing into a +NAO-esque Atlantic.

19th-23rd March

Troughing returns to the PNW/BC and the Sierras, again anchored by the Aleutian high and increased Eastern ridging,

24th-28th March

The trend of troughing for the Northwestern US down to Tahoe continues, with the Eastern ridging and Aleutian High still present.

Climate Drivers

The Arctic Oscillation remains in very strong positive territory. This has been assisting snowfall particularly in the Northwestern US, and in British Columbia and Alberta.

The MJO is expected to be briefly within the Phase 7-8 region, which may explain a slight tilt towards the Eastern US in terms of systems, and a slowing down of the snowy pattern for the PNW/BC region. But the +AO will ensure that this will probably not eventuate to much snowfall for the Eastern US. This favourability if you can even call it that, will slow down as we go into March, with the Western US expected to be the big winner of March again.

We see little activity in the stratosphere of consequence that may weaken the strong stratospheric and also tropospheric vortex. GFS notes some hints towards neutrality at the surface, but given the stratospheric base state I would suggest that the +AO theme that has been going on since the start of this year will continue.

The atmospheric momentum budgets show less positive deposits in the tropics after the spike in January, that had little consequence in terms of changing the pattern.

The positive deposits between approx 40N-60N and the negative deposits at approx 15N-35N have reestablished, which is essentially a consolidation of the status quo. A strong Atlantic (+NAO) will continue, the PNW will continue to be favoured in general and the Eastern US will be less favourable for snowfall.

Verification

So this has been a hard year for those involved in seasonal forecasts. Here are the predictions I made:

  1. The Interior of the East Coast on the Appalachians and further west is set to have a better than average snowfall season. The East Coastal regions are set to have a mostly average season.
  2. California is set to have a largely below average season. It won’t be absolutely abysmal though, with potentially improving conditions later in the season.
  3. The Southwest of US is set to have a largely average season, with New Mexico doing better than Arizona.
  4. Utah is set to have an average season. Which tends to be pretty good anyway.
  5. Colorado is set to have a mildly above average snowfall season.
  6. The Canadian/Northern US Rockies are set to have a mildly above average season.
  7. The PNW Coastal mountains are set to have a mildly below average season, but I can see them having a better early-mid season compared to California.
  8. The Central Interior US from the Great Plains to the Midwest to the Tennessee Valley is expected to have an above average season for snowfall and deep cold at times.

Per SNOTEL, other NOAA sources, and Rutgers Snow Lab:

  1. The Eastern US had a below average season, not an average one. Better than some others though.
  2. California did have a below average season. So I got that right. We might see some improvements in the next little while, but not as fast as I expected.
  3. I got the Southwest pretty well too, slightly above average in NM, and somewhat below average in AZ.
  4. I got Utah pretty well, perhaps doing a little better than expected.
  5. Colorado went pretty well for my verification.
  6. I got this pretty well for the interior PNW/BC Rockies.
  7. PNW/BC Coast started slow (compared to a decent start for California IIRC), but came out better than I thought originally, with a very good second half of the season.
  8. I did reasonably well in the Great Plains, it was more average in the Midwest, and failed further towards the south. The Central US ultimately didn’t get the strong levels of snow and cold I predicted for this season.

So I did well across most of the Western US, underestimated the PNW Coast a fair bit, and overestimated the Central and Eastern parts of the US in terms of snowfall.

I had expected troughing over the Central North America, instead it angled towards the Northwest, with ridging through the Eastern US.

As always, lessons to be learned, to improve for next season.

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. 

Thanks again for reading this 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. I appreciate everyone who has taken the time to read the blog over the season, I will see you next year.

3 thoughts on “North America on the long term 16th Feb

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