wxsniss

What an ugly game... love the AB tweet Doubt my 3-6" call for metro Boston round 1 verified, certainly not in city proper, saw 1.2" 7:16pm KBOS 0z GFS wasn’t bad at all, better than 18z. Tenuous potential but it’s still there.

0z NAM maybe a slight tick east vs. 18z but still a good hit for eSNE, really nails outer Cape... and so close to a much bigger hit 24+ hours away... no further clarity or definite trend re: round 2 at this point

Precarious setup and a tough forecast. It may very well capture too far east or regress to the diffuse weaker solutions, but I wouldn't nail the coffin from just a single 18z Euro run, especially after the entire 12z suite was showing a bigger hit.

As if hearing all the discussion turning to "round 2", 18z NAM goes ballistic colder and heavier tonight

Agree, complex and precarious. Something in how the vortmaxes are handled and how the different lows consolidate made multiple members of 12z suite jump... we're now seeing SLP to 970s by 9z-12z Tues (deepest and closest we've seen yet) on NAM/RGEM/Euro, whereas in general prior guidance has shown a meandering occluded 980s low. The WAA tonight has gotten most of the attention, but real powder keg potential for eastern areas comes Mon night-Tues. It's precarious and guidance is just catching on. What regions benefit most, I'm still uncertain. eastern SNE / NH / ME I think have best shot. And for those who are considering now "just hours before go-time", the more relevant and distinct process of surface low consolidation and ULL capture is > 24 hours away.

Yeah re: B word was wondering that too... 12z RGEM/12kNAM/Euro for Tues are not far off if low gets captured, deepens, and loops off CC as shown. To add to this potential, note that we are now seeing SLP continue to deepen into 970s (whereas on earlier guidance it was a meandering occluded 980s) Still up in the air where this happens (> 24 hours away), and I think eastern half SNE up into eNH/ME all have potential

Boom 6z-12z Tues For eastern SNE, disproportionate attention has been on "round 1", which is really just the first part of a prolonged 2ndary transfer... All about consolidating a dominant 2ndary low which on current guidance is a vorticity mess before 0z Tues As posted pre-Euro above, I anticipate solutions today will converge on a bigger impact after 0z Tues, the far bigger potential for eastern SNE than "round 1"

Happy Birthday Jerry! A real pain forecast, less because of rain-snow issues and more because of complex evolution. Great disco everyone. Some thoughts: Likely oversimplified, but the way I view this entire system of "round 1", "round 2", and in between, is a stretched out and messy secondary coastal transfer. What we're calling "round 1" is still part of WAA associated with the primary low over the Lakes. Yes, 2ndary surface reflections start to pop up by 0z Mon (when the round 1 thump is well underway in SNE and mixing already nearing BOS), but 850 winds are still from the south going all the way back to ~ Michigan. For eastern SNE, IMO the bigger potential snow will be impacts of an eventually dominant 2ndary coastal Monday night - Tues. Powderkeg potential that is not spoiled by round 1. How that develops has been a mess, with multiple pieces of vorticity circling around the ULL, hence multiple surface lows appearing to pop up and bobble back and forth over 24 hours between 0z Mon - 0z Tues. Whichever of these multiple lows dominates will determine how hard we (eastern SNE) get hit by its CCB after 0z Tues in "round 2". Remember this "round 2", even though we are considering it part of the same storm, is still over 24 hours out. I think the baroclinic zone remains closer to the coast and we see bigger impact solutions of a CCB lock in through today. As for a forecast? Easier to separate the different storm parts, and the bigger total numbers of all rounds put together could appear to disappoint if we have 12 hours of lighter rain in between. For the Boston metro area, I'm thinking: 3-6 in round 1, maybe 4-8 in far western burbs... then another 4-8 in round 2 (though I'm much less confident of this for reasons above and its > 24 hours away)... for an event total 7-14. Obviously biggest bust potential is in the CCB round 2 where this could even bust too low if one of the multiple surface lows dominates sooner and closer. Awesome start to met winter!

Yep... though in March, this event was the "first child" of winter storms for many of us in SNE.

For sure... I couldn't find 24-hour snowfall maps (vs. total snowfall that is hard to distinguish from preceding Fri-Sat event) to capture how (badly) Euro and others did days before. The consensus Friday was that Sunday would be a snow-to-rain mess for most of SNE. I mean, look at this... 72 hour (!) prog of 12z Euro... and ironically, the GFS Friday for the same time:

Some post-storm analysis of guidance... nothing really groundbreaking here, we all had a sense the mesos did excellent on this I thought a visual summary of the guidance history could supplement our anecdotal / tired recollection. Major caveat is that this uses only a 10:1 snowfall map. I considered using qpf but I did not think that the captured end result we care about as well (e.g. R/S lines which played a factor), and I do not have a qpf map other than the digital accumulation maps. Also, not sure why but PivotalWeather shreds the 12k NAM 6z/18z runs. As you can see: • Mesos were indeed excellent. 12k NAM / Euro may have been the best in the final 12 hours. • 12k / 3k NAM had the best jack zone of the pike region. Euro / RGEM was always too far south. • GFS was terrible. Way too dry throughout. Completely useless. • ECMWF characteristically made slow incremental changes in the same direction towards the best solution. • RGEM was first to latch on to widespread double digits. Not redeeming a terrible performance most of the season.

Yeah I was gonna say he will go back to update the 708am measurement later this afternoon... So so frustrating Saw this on weather.gov, 10.6 at Logan... wonder if it’s been updated somewhere... not on the PNS... and who knows anymore, Deer Island, Logan...

It sure does. I was gonna write up a post-analysis and assess my forecast map later today. RGEM (inside 12 hours? I'll check), NAM, RPM (last 2 runs), HRRR (when it was within range) crushed an event for once. Even Euro was way too conservative in its 12z/18z runs just before onset, though it had a pretty good distribution. GFS was a disaster even on Sun 18z and only had a clue once the event was already underway Mon 0z... but I correct myself, it's purpose is only for under 6 hour guidance.

Shit obs. And by the book, they do not wipe before each measurement. Technically not even the "airport"... that poster earlier said ground crews at Logan were reported foot+

I guess our KBOS measurement woes have not resolved...? ...Suffolk County... South Boston 15.5 918 AM 3/04 Trained Spotter Dorchester 15.5 720 AM 3/04 Ham Radio Chelsea 14.0 815 AM 3/04 Ham Radio Jamacia Plain 13.2 800 AM 3/04 Co-Op Observer Boston 13.0 925 AM 3/04 General Public East Boston 12.1 705 AM 3/04 General Public Logan AP 9.8 708 AM 3/04 Airport

NAM had this as well last night... residual lift ~ 750 mb moving through until about 10am Nice ongoing activity and I'm pretty sure Logan cracks 10"... having stuck my neck out to so many co-workers (with the same forecast map I posted here yesterday + local details), I care about final numbers at Logan and perception more than I might otherwise

Yeah this dessert band really ramped up for Boston, Logan should break 10" for sure... the band further west by Worcester has ramped up a bit as well so we may benefit from that too

Agree I get annoyed the media gets a hold of these prelim maps to summarize the storm

How frequently do you guys clear with each snowfall measurement? And do we know if Logan does? Compaction with this heavy wet stuff is gonna cut down on snow depth

And to think most of that 12 was in 5 hours ~2am-7am... Based on those PNS numbers, you would think Logan should be > 10"...

Yeah NAM last night was too aggressive pushing the mix line to south shore... HRRR / RAP / Euro / RGEM were excellent and pretty steady on this aspect

...Suffolk County... South Boston 13.5 549 AM 3/04 Ham Radio Chelsea 11.0 519 AM 3/04 Ham Radio East Boston 9.7 505 AM 3/04 General Public

Weenies that make forecasts to lots of co-workers care lol