Ah yes, nothing screams “SPRING” like a classic retrograding ridge that shifts into Greenland and the Hudson Bay in the Spring months after the previous winter season! We see with strong support from ensembles how the ridging expands across Canada from Greenland, along with ridging across British Columbia into the Pacific NW that produces below average heights across the U.S. east of the Rockies.

Lets put this block into perspective, since it’s actually going to be quite anomalous for this time of year! Taking the NAO index and all numerical weather models shown with this graphic, believe it or not but they’ve drastically underestimated the degree of this block. We actually are going to see, which is happening currently, a blocking ridge over 5 standard deviations! Below this graphic is the trend of the EPS forecast utilizing all members (51). What’s pretty remarkable is the utter miss and underestimation of the block!

Now it probably shouldn’t come as a big shock to see this development, especially after a major sudden stratospheric warming event from February (remember that?!), which research shows that we see resulting effects “bleed” several weeks and even more than a month after a major warming event that lingers in the troposphere. This high-latitude blocking certainly isn’t a coincidence, and has ties to that event.

Lastly, what this means is widespread below average temperatures across the lower 48 as we head into early May and with that an active pattern, especially east of the Midwest. For instance, the CFS weekly shows average to above average precipitation for areas basically east of the Rockies and especially the East Coast, which makes sense given the persistent troughiness. This does look to have some lasting power, with a more transient pattern looking to take hold as we approach closer toward early-mid May. So for now, if you’re expecting more of the summer-like previews, well you’re going to have to wait because that’ll be certainly stymied for the time-being, but the actual season of Summer truly isn’t far behind!