OceanStWx

Well that CC is getting chewed up a bit as it moves into central NH.

The snow starts sooner thank you think, but so does the sleet.

Not a bad eyeball there, current motion has it about 1 hour 45 min. I think a good chunk of our warnings are going tits up.

As the rain/snow line creeps ever close to my backyard, I can hang my hat on the Airport Weather Warning I issued for MHT. At 2342z, I issued one saying that snow will mix with or change to sleet/freezing rain as early as 02z. The 201z SPECI reported PL. Honestly remarkably well modeled and well behaved mixing line.

-PLSN in the 201z SPECI

It's subtle but you can see it on CC. It's about splitting the peninsula in half, pushing through Chebeague now. And on BOX's radar that CC line is steady on the march north. The high is just in a bad position to hold it off. You don't want the ridge axis east of the mountains.

I wouldn't worry about that until 11 pm or midnight. So I think 5-6" is still doable.

Our heaviest precip really shouldn't be until we're approaching midnight, so I'm not too worried about this initial band. If eastern PA isn't lighting up in 2ish hours then we can start sounding the alarms up here.

Guidance is insistent that the slot fills in. You can see moisture peeling back in the more northerly direction on WV (jet is WSW/ENE, but moisture is moving more NE), but that may be too late for many as wetbulbs continue to creep.

Here's a look at the GFS depiction of forcing as precip starts before this event winding down and the next one coming in. I think notably the jet streak is weaker, so you would anticipate the forcing to be weaker as well. But look at the orientation of the jet. It's subtle, but it's there. It's both farther north, and more east/west axis. This should produce a more uniform initial thump of snow than this current event. This suggests to me something a few inches less than what is out there right now, and shifted north closer to the Canadian border.

I mean, yes, but I was also on my couch.

I'm on, but swing shift, so mostly just keeping the forecast in the lane.

I know, but I loathe missing a category of storm. There's a big difference between 8 and 18 inches.

They obviously correctly picked up on the right forcing mechanism. I kind of shook off the HRRR forecasts over double digits for me, but it kept nagging me how consistent the mesos were.

And I'm trying to tease out why we're going to miss low on the forecast, especially with totals in a relatively narrow band that are pushing some real deal snowstorm numbers. This time yesterday was just moving from a 6-8" event to 8-12" for portions of the area, and some are going to end up 15-18".

I was on the sidelines for this one, but my forecast went from less than 1" to probably 10ish by the time I measure when I get home.

This event really seems to have the hallmarks of a lateral quasi-stationary (think parallel) band transitioning to a pivot. The orientation of that departing equatorward jet streak was definitely more SW/NE than WNW/ESE, which tends to promote that parallel band riding along storm track. That's what I think it pumping our highest totals up over a foot, pushing 18", vs a more uniform 6-10" followed by the pivot.

125+ kt at 500 mb and 140+ kt at 250 mb. Not bad.

I have 4.5 seasons of snowfall at my current location, and January 2023 (20.3") has now moved into 3rd biggest month behind Decembers 2019 (25.3") and 2020 (25.5"), edging out January 2022 today. I know March 2018 was bigger (something on the order of 30+) but I didn't have a full season there so I didn't start tracking until the next winter.

Congrats Dendrite!

One thing I noticed on modeling while chasing the kids around this weekend was the trend towards a more robust poleward exit region later in the event (i.e. today). Initially forcing looked mostly equatorward entrance, a classic WAA thump scenario. But by now the dominant forcing was from the exit region of the next approaching jet streak. That is a class mechanism to get the banding to pivot and involve the cold conveyor.

Now I was mostly scrolling on my phone with beer, but it seemed like the HRRR extended ranges were onto the extent of snow. Maybe a hair too cold (snow band was displaced a little south of where it actually snowed the heaviest today), but overall was sniffing out this cold conveyor location at 12z yesterday.

Given the last storm had the mixing hanging right on Route 2, and now this one follows up so closely before trees shed anything, this was about as easy as we'll ever have it knowing outages are coming.