Given both the pattern that remains over the Lower 48 and the suggestion that the AO and NAO will remain well into negative territory through pretty much the remainder of March, potentially extending into April now, suggests spring is a long way off.I showed the AO ensemble in my European post earlier and it’s astounding how deeply negative it goes. Now this means there’s a lot of arctic air down through the mid-latitudes and so there is no true nation-wide warmth looming.

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Sure you’ll get warming as we’ll see in the Desert Southwest with Phoenix rising into the 90s but while warmth builds in the Southwest, so cold, late season arctic air dives into the East. There is no sprawling countrywide ridge and with the NAO favouring negative, so the block stands firm up towards Greenland, which means you’ve got troughs wanting to drop into the Central and Eastern parts of the country. That strong negative with the AO means the cold which dives in is likely to be arctic origin, so well below normal temperatures can be expected.

This end game pattern is very fascinating when you look at the contrast between this year and last year. Remember back to last year not only for the United States but here in the UK. Both sides of the Atlantic not only experienced abnormal March warmth but it was record-breaking with Scotland experiencing three straight record-breaking warm days. Winter was very mild across the US while it was warmer than normal here in the UK also. The trend was for a positive NAO/AO and with the March warm outbreak both AO and NAO are opposite to this same period last year. Very strongly positive.

Both from the Plains to East Coast and in the UK, soils were much DRIER than normal which likely helped boost heights within those twin highs to LATE SPRING levels and for the US, it was more like early summer never mind spring as temperatures day after day surpassed 80 degrees throughout the Midwest, even nearing 90 degrees in Michigan.

Not this year. Cold and snow is dominant and likely to bring the coldest March in 10 to 20 years for the US, certainly from the Plains east and for us here in Europe. I believe the current spell or indeed the month of March overall could well be coldest for March in 30 years from Scandinavia to Germany across to Ireland.

So, strongly negative AO and NAO means more cold shots through the remainder of this month, like the one coming into the East over the next few days, will mean a need to pay attention along the East Coast as this setup is favourable for development.

More later!

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Tags: arctic oscillation, cold US spring, NAO/AO usa, north atlantic oscillation, us spring weather, us weather