I posted reply with screenshot, but its awaiting approval. I am seeing this in all the major etf's, spy, qqq, iwm.
From Silexx. I don;t see anything odd except Silexx is sing a different int and Div than MM as the puts Ivol are lower than the calls.
Interesting: Below is screen shot from TOS. Each broker seems to have their own derivations for both the Individual IV, as well as the series IV. If your trading is sensitive to this, it may be wise to derive your own. Note: TOS computes a different IV for the CALL VS the PUT for the same strike... This is wrong, but apparently most TOS users are not concerned with accuracy, or they derive their own. (BTW: I compute my own, since I need reliable references). I think most that produce the Term IV, may also have a "home brew" derivation. I prefer the VIX White-paper derivation, primarily due to it being a known reference (as apposed to holding any secret sauce). TOS approximates the VIX White paper method for DTE's of 1 month and more for the Term IV, per my comparisons.
The term structure in IV is nearly accidental. Of much greater effect are known economic and political events whose outcome yet remains uncertain. Option markets take that uncertainty and capitalize it into prices -- which we then mathematically back out as the volatility implied by those prices. Further, these uncertainties can be resolved in seconds (with a headline, for example); it sounds like you've observed this already. In the heat of a fast-moving market, you can see this entire 'volatility surface' change by the minute. If you want to take it a step further, you can plot this by strike, by expiry, and look for the differences week-to-week. It's a great way to write options -- by knowing both where the IV *is*, and where it is *not*.
Not too familiar with the SPY myself, but is this market sentiment showing through by bidding up/down the options? The volume relative to open interest looks off to me, and in a way that's suggestive of short butterflies. Fwiw, I'm usually not a fly guy, but I've left an order open on some each of the last two days (on individual, and big name, stocks) for Friday expiry with the opinion that we stagnate or grind slowly north until monthlies expire. For my part, this would be the forest to what I see in the trees... What's the IV on further ITM / OTM contacts looking like?