wxsniss

You and others nailed the fronto signals. We were also posting soundings with great crosshair / snowgrowth potential. But the dual low issue and definite (and ultimately correct) trends to emphasize the easternmost surface low, along with the new downtrends on RAP/HRRR, were not easy to ignore. I think only after we were seeing the strong radar returns off NJ entering LI that I posted ~10pm was there some evidence the s/w was enough to overcome the further east surface low. Some cool anatomy of that band from 6z NAM 5-7am:

Interim measurement ~10am near Brookline Village, still getting moderate so anticipate we end up 10-12

Yeah it was a tricky storm to forecast. The Euro/RGEM/NAM also slipped down yesterday evening as emphasis on the easternmost low increased, giving some credence to the HRRR/RAP downtrends. The big driver of 6+ amounts despite the dominance of the easternmost low was that nearly stationary 700 mb frontogenic band overnight, and while there was evidence for it (CoastalWx's posts yesterday), no guidance had it stationary for so many hours with significant minima north and south. Had this system consolidated a surface low closer to the vorticity emerging from Virginia, with better conveyor mechanics, totals would have been more uniform and higher across the board.

Nothing better than enjoying this winter wonderland with my one year old... sheer magic. Boston metro area (and immediate suburbs including Brookline) probably ends up 10-14" Kudos to all the mets and vets (including myself) who recognized that the quorum of OTS / whiff guidance was discordant with synoptics. And yes, Tip has a knack for starting long-range threads that materialize as big events.

Heaviest rates I’ve seen since that 1-3am Dec 17 2020 WAA band I don’t recall a 700 frontogenesis process sustained over so many hours over Boston like this

Hope you can see this Jerry! Heavy snow in this band, gotta be at least 1”/hr

Was about to ask… you’re right under that great early band you had forecasted, stretching all the way to North Haven. Mesos look great for your area, 6-10 seems in reach. Moderate here, everything whitened in less than an hour

6z NAM back to widespread 6-10 eastern SNE! Continues theme of dominant eastern low that itself positions more west No wonder ensembles had so much spread depicting this surface low position.

First flakes in Brookline MA Nice band setting up Hartford to South shore

east SLP appears to be taking over on schedule:

Would not be bad considering people were talking whiff early in the week. Reaches maturity off Nova Scotia. One aspect that could still surprise is duration in eastern SNE depending on how the west->east transfer unfolds.

0z vs. 18z/12z Euro continues theme of slightly faster west -> east low transfer while being a bit more robust for eastern SNE

Good to have you back, Will Yeah 4z RAP and HRRR runs stopped the bleeding, and associated with later west --> east SLP handoff. I posted the robust radar returns off NJ above. I think that's a sign of earlier/better west SLP development, but hard to say it's kind of in between the 2 low centers. In any case, it's appearing 1-2 hours earlier than progged.

Next 3 hours are pivotal resolving this 2-headed coastal 0z 12k/3k NAM actually does not have the west head In next 2-3 hours, HRRR has west head decay, east head dominates and drives the rest of the show

4z RAP stopped the bleeding This stuff off NJ coast is ~1-2 hours earlier than shown on NAM... any earlier or more robust western low development helps us...

This activity off NJ not depicted on NAM until 2-3 hours later. Let's see how this progresses.

Wave spacing... has this been an issue before this season?

Yep, though I’d weigh mesos increasingly inside 24hrs. RGEM and GFS held. NAM RAP HRRR increasingly favor the eastern low. GFS also did shift in favor of eastern low, but end result was same as 18z. I’d do more upstream real-time analysis of that eastern low but I’m mobile.

Supports Box forecast map… light / mid / dark green: 6-8 / 8-10 / 10-12

0z RGEM looks better…

Yeah just didn't like the trend, and thinking about rest of SNE... for us specifically, that runaway convection is precluding 10+

Yeah 3k NAM not as bad, prolonged event in east

Ugh not liking the trend on 0z NAM... eastern low takes over earlier. Still decent hit on eSNE but much less than possible.