Couple nights ago, but it was weird enough that I had to write it down, which I hardly ever do.

I was shopping at a supermarket at night, with terrible weather outside. Pitch black, howling wind and rain, real tornado weather. Trying to use my phone to look up something when I started to hear ominous creaks and pops from the roof. An employee comes on the staticky intercom to tell everyone to proceed calmly to the back area of the store, which of course triggers a near-panic. As we're all hustling to the back, the ongoing safety announcement sloooowly winds down in speed and pitch before everything kicks over to generator power. I'm one of the first to reach the back doors when I realize I left my phone behind on a shelf. Surely there's time to reach it?

Just as I reach my phone, the generator dies and everything is near-dark apart from a handful of emergency lights. The creaks and groans increase, then a huge tearing sound. It's not a tornado -- it's some giant horrible Cloverfield/Lovecraft/War of the Worlds monster ripping a hole in the back wall. A two-story greenish blob heaves into view with searching tentacles. Dozens of them catapult forward in long arcs and strike people, the rest flee in panic. I notice that each tentacle strike transforms the victim into a smaller creature, a couch-sized blob with a crazy happy expression. As they see people fleeing around them towards the front of the store, they toss smaller arced tentacles forward at angles to grab them. As they inch forward they start merging together like the T-1000. Real Mr. Frundles/The Thing vibes. The only chance was to hide behind stuff while they herded past/over you towards the front.

It kind of morphed from there into driving around outside in the daytime through a The Mist/Godzilla/Cloverfield pastiche, but that zombie arcing tentacle monster bit was really unsettling and I've got no idea where it came from.