North America on the long term 9th Feb

Hello all, this is unfortunately the last long term outlook of the season for North America. I started pumping out the forecasts both seasonal and long term from October last year, and as the forecast period enters into March, when the snowfall season winds down, this means my season also winds down. Thank you so much to all those who have been following all season, hope you enjoy my final forecast through to Mid-Late March in the Climate Driver section.

27 Feb-2 Mar

A initial front on EC Monthly pushes moderate snowfall over the Sierra Nevada over the 27th and 28th, pushing into Utah and Colorado, and Wyoming later on. Behind this front, light-moderate snowfall in a deeper Low system brings snowfall to the PNW region on March the 1st, and moves down into CO, UT, AZ and NM on the 2nd of March as moderate snowfall, before easing on the 3rd of March.

3-5 March

A system brings moderate-heavy snowfall to the PNW and BC on the 3rd. This snowfall should push down to Tahoe and the Inland PNW on the 4th slowly easing, before it hits CO/UT on the 5th and moves out into the Plains.

5-6 March

EC Monthly shows another system hitting BC and PNW with moderate snowfall, hitting on the 5th, and then moving East on the 6th and fading away.

8-11 March

EC Monthly shows the Pacific jetstream slamming into BC and the PNW, and just continuing plunging snowfall into the mountains there for about four days with moderate-heavy snowfall, easing further inland.

Climate Drivers

  • From about now until the 16/17 Feb, we should see a +EAMT produced pattern. The jet starts extended according to the graphic I posted earlier on the 12th. We are currently in a -EAMT, so the extension impacts start within days of the start of the +EAMT period. The PNA impacts should start to be felt from the 18th or so, and continue for a 10 day period. This should push the Aleutian ridge more into the -EPO domain, more so than the NWP forecast IMO. This would probably move more of a ridge into the +PNA territory, which I think will start to happen around the 20-22 Feb, as we give a moment for the pattern to change and move. This should be the end of the very good period for California and further inland in the Rockies, that we have seen recently. There is still around 10 more days to this pattern however, I still think there are plenty of options for snowfall in the Western US to make Spring very worth while.
  • EPS shows a big fat low developing around the 16th, descending over the Mongolian ranges and into the Himalayas, fully disturbing the +EAMT by the 18th. This will weaken the push of the ridge into the -EPO domain, but I still think it should be further West than it is in this chart. The messy low situation on the West Coast is probably going to be maintained, so we need that low off Labrador to move further southwest in longer term runs. That would further allow the gradient curated -NAO (via the MSLP level Low over Siberia). This is indicating that the processes that curate the cold stable Siberian High are starting to break down or otherwise known as the beginning of the end for winter. However I do believe there is still plenty of room for more ridging in Siberia, it is just winter is starting to lose it’s feet. Don’t dismiss winter for Eastern North America yet though, as the breakdown of this winter stability can curate some unstable patterns that generate big winter storms.
  • Overall I think the Western US will do well over the next 15 days and potentially beyond, but so will the Eastern US will still see the conveyor belt of storms behind it, on the 12th, 16th and 20th pretty roughly. The last week of February is the “peak” of this particular period for the Eastern US, but I see no reason to discount potential for winter storms in the first two weeks of March. But after then, I think we are pretty much out for the Eastern US (no random 12″ early April storms, as one would expect). The next three weeks from now are what we are looking for. I think it is a pretty good indicator to see plenty of options, into the reality that tropical forcing in particular is driving a lot of this pattern. There is a potential for a nice snowfall period to finish off the season for the Western US in Mid March, working with our cyclical timetable.

FT is currently increasing, which is an indicating of poleward propagation of +FT anomalies, but I wouldn’t be surprised with a bit more of a jump, although I would prefer the WWB a bit further to the West for maximum +FT effect. These are improving signals, but it isn’t like there isn’t already an abundance of westerly momentum in the atmosphere anyway. This has been part of the reason that the West Coast has been doing so well recently. The synoptic pattern in the Pacific has been weirdly Nina like, with an Aleutian ridge, so that springs up an -PNA, and add in extra westerly momentum and you have a great pattern. The +EAMT that should impact later in month also means that if we get a long enough jetstream extension, the Sierra Nevada or further up into the PNW depending on the jet’s location, would receive more snowfall, on top of that produced by the current pattern. But inevitably downstream it will reap more benefits for the East.

The MJO is currently in Phase 7/8 heading towards Phase 1 in the latter stages of February, with a fairly strong amplitude on EPS, and a far stronger one on the GEFS model. They both indicate a strong pattern favouring snowfall for the Eastern US, in terms of tropical forcing. Later on in Mid-Late March, we start to see the MJO on the longer range models head into Phase 3/4, which starts to support snowfall for the Western US, hence my comments earlier about that period.

The Arctic Oscillation is forecast by the EC Weeklies to become negative around the 17/18 Feb, and remain deep in the negative AO phase until it rises back up to positive around the 6/7 March. This further supports the argument that the Eastern US receives a good snowfall period from the 15th-20th to about the 5th-10th of March. Then afterwards we may see a few more big storms for the West Coast in Mid March.

Finally, the last bit of the season, where I take a look at how my seasonal forecast roughly went. Here is the SNOTEL observations chart, courtesy of the US Dept of Agriculture.

My forecast as it was in November, and the results as of Feb 5 (I know it’s early, but there shouldn’t be too many major changes at this stage in the season): I forecast California to have an above average snowfall season. This forecast went relatively well

I forecast Colorado/Utah/NM/AZ to have an average, maybe even slightly above average snowfall season This worked for UT/CO, but I didn’t foresee the poor season reported in most of NM & AZ

I forecast the PNW and BC to have a below average snowfall season. They actually did much better than I thought they would.

I forecast the Eastern US (New England and Mid Atlantic) to have a moderately-strongly above average snowfall season, particularly in December and February February isn’t over, but all and all this season didn’t go very well for those in the Eastern US, we may see a bit of a late bloomer, but the season wasn’t as good as I saw it to be.

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. Thanks again for reading these forecasts all season, and I look forward to doing it all again next season.

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