"Snowmageddon" Arrives Tonight

Submitted by TheCloudBoy t3_119gukq in newhampshire

Based on some recent requests from users in this sub, here's the updated snowfall map for tonight/tomorrow's storm! Avoid some of the other junk floating around on social media that's lazily drawn or what limited (also junk) information comes from your phone app. Trust me, it's absolute trash.

Snow amounts have been adjusted slightly higher in the northern portions of the Upper Valley and the Lakes Region, where confidence is high in the heavy snow band (snow rates of 1"/hour) setting up overnight. To the south, warm air will transition from wet snow to heavy sleet, the combination of which will drastically cut down snow totals anywhere south of Claremont/Boscawen/Farmington.

The majority of snow and sleet from round 1 is done before sunrise Thursday, though light snow, sleet, and freezing rain will persist through midday. If you're a school administrator, workplace manager, etc., plan on road conditions remaining degraded Thursday, though this will vary drastically across the state.

Colorblind folks: I am working on a more friendly color scale that's also legible for you, I'll have an update for our next storm

https://preview.redd.it/87zl1tt2ktja1.png?width=1920&format=png&auto=webp&v=enabled&s=279cec1d6a03441c802ac00aa336e0b3db6d3480

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kitchinsink t1_j9m6lon wrote

We love you cloud boy.

I am curious, these totals seem a little light on the south (not complaining just trying to have a discussion to learn more about how people forecast), based on some of the newer models. Do you use convecting models?

I ask, because I noticed HRRR and NAM 3k started to eke south, putting even Portsmouth in the firing line, while models like the GFS and regular 'ol NAM seemed to keep that sharp line somewhere above the southern NH border. There was a pretty solid difference.

Anyway thanks for this :)

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TheCloudBoy OP t1_j9mg3ia wrote

Replying to kitchinsink (#1,928,885)

So this is a very good question, it's clear (and good that) you're aware of different model guidance and the trends. Here's my rational for the Seacoast/SE NH when making the map, excuse the numbered list and lengthy thought process!

  1. I do use high-resolution guidance, sometimes called "convection-allowing" models. This naming draws ire from many mets given all models account for convection in one sense or another. Lower-res global models parameterize it whereas short-range guidance have the horizontal & vertical resolution to explicitly resolve convective processes. We won't get into hydrostatic v. non-hydrostatic solvers, but that's important too.
  2. The slight southerly trend from 18Z yesterday to 18Z today is certainly of interest. It's important to utilize both positive snow depth change (PSDC) & static or dynamic snow ratio data for this forecast. The current 18Z suite (at 10:1 static ratios) has 7-10" through all of southern NH, but the PSDC is barely 3" and closer to my map.
  3. Why this difference and my map much lower then? I've closely inspected soundings and it's clear that the above-freezing warm nose makes it to Concord for several hours, keeping precip in/south of there sleet. In addition, the snow growth anywhere south of Laconia is atrocious, with the strongest lift well below the dendritic growth zone (DGZ). So even if we stay barely below freezing above our heads, snowflakes grow poorly and may even be partially melted, aiding to lower accumulations at the ground when its not sleeting. The PSDC maps illustrate this beautifully.
  4. The general rule of thumb is for every inch of liquid, 3" of sleet adds up (3":1"). The average liquid expected south & east of Concord is about 0.70". Let's assume at minimum 30-40% of the precip tonight is sleet and the rest averages to an abysmal 7-8":1" snow-liquid ratio. At most, you're looking at 1-3" of sleet/wet snow slop!
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redditthrower888999 t1_j9mgicc wrote

Wow only 1-2” for my area? I’d like to take the over on that bet but this winter has been real bad for snow accumulation in southern nh.

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totalimmortal_ t1_j9mi9ht wrote

I do not doubt you at all and appreciate your accuracy, but genuinely curious behind the “why” of your comment of the information from our phone app is trash. Are the sources behind Apple’s Weather app not accurate or trusted and would you recommend a different App?

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MrEtrain t1_j9mjefn wrote

I live in the Upper Valley and we seem to always end up with slightly lower totals than very nearby (Lebanon/Hanover area). Assume it’s due to being east of the Greens and in a river valley, but you have a pretty detailed, small zone carved out in this area and wonder what you see that leads to this specific location/wrinkle. Otherwise appreciate the work! Guess we’ll see how it all pans out pretty soon- looks like a lot of snow in a hurry.

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TheCloudBoy OP t1_j9mm52q wrote

Replying to [deleted] (#1,930,576)

Ahh maybe not a bad call if you're up and about before sunrise! The margins are going to be razor thin in York County between steady sleet and not a ton of snow and heavy snow that adds up over 6" there. If you're south of Wells, I think you're fine regardless

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ScottieWP t1_j9mmesk wrote

You remind me of Space City Weather, which was my go to in Houston. No nonsense forecasts with the data to back it up, and in such a way that us laymen can understand it. Keep up the good work!

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TheCloudBoy OP t1_j9mnn4h wrote

Replying to MrEtrain (#1,930,368)

So that featured I drew into the grids was intentionally done in each forecast for this event based on meteorologist experience (a combo of going to school at Lyndon State and forecasting for the area for numerous years). The reason behind that swath of lower totals stems from SE winds forced over the Kinsman-Cannon Range & Garfield Ridge, which is called downsloping. This dries out & warms the environment locally, which is more hostile to adding up precipitation there in those regimes.

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FaustusC t1_j9mo9eq wrote

In one day I've heard everything from 5-8 now 1-3. I officially no longer care.

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TheCloudBoy OP t1_j9mp3su wrote

Replying to totalimmortal_ (#1,930,231)

A good question! Your phone app is using some deterministic model or a "hodge-podge" of gridded products to deliver your forecast, all of which are likely low-resolution and a single forecast.

You immediately run into problems with that approach because we live in a state with many climates (which requires high resolution data), models have biases as they're run deeper into a forecast period, and single model forecasts don't show potential uncertainty like what I've been doing here the past few days.

The company I work for is developing a solution to this issue, I'll recommend whichever app takes our data in the future :)

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Scubakim13 t1_j9mpx5b wrote

my husband told his co-workers about Cloud Boy. The fan following is growing. Thanks for updates!!!

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l337quaker t1_j9mqf3k wrote

I'm curious, CloudBoy, what's your take on New England Weather Guy on Facebook (if you're familiar him.) He's usually much better than the various apps and news stations for accuracy.

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kitchinsink t1_j9mvyfx wrote

Replying to TheCloudBoy (#1,929,997)

Thank you for the detailed response. I appreciate it! I really need to get better at reading soundings. I can pick out favorable tornado conditions, but that's about it.

Also, I thoroughly enjoy the weather, especially the nuances of forecasting, but unfortunately went the engineering route so now it's just an interest. Still, always learning!

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Ok_Low_1287 t1_j9mwnpk wrote

Why does that band in Littleton get only 4-8?

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lubelle12 t1_j9mxzla wrote

Do you know what travel will be like in Nashua around 7:30 am?

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theshwa10210 t1_j9n1wkk wrote

>Claremont/Boscawen/Farmington.

One of these things is not like the other

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paraplegic_T_Rex t1_j9n54ei wrote

I’ve already got 2-3 inches in Londonderry. The predictions aren’t looking great so far.

Edit: I stand corrected. We never got much more accumulation. All hail Cloud Boy!

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ShireSkiBum t1_j9n7wsg wrote

Mt washing might get 2ft plus. Refill is finally here. mind if i cross post to icecoast? They'd love you over there.

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Different_Ad7655 t1_j9ngc8n wrote

Just a regular run of the mill February storm lol. Not even a Big punching nawth eastuh. Good solid snow more concrete and compact the father south you go hear nothing like sleet on top of snow. Hey banks easily for snow plows, sticks where you put it

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FMAB-EarthBender t1_j9nvrxu wrote

Replying to lubelle12 (#1,932,003)

I can tell you my kids school called and gave a 2 hour delay for today, usually they do that because of busses and if they can function enough on the roads as well as if kids wud be freezing waiting at busstops.

But it doesn't seem like it's to bad rn and it's almost 4am as I'm commenting.

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gmcgath t1_j9o7rva wrote

"Snowmageddon" was a bust. I'll go back to real weather forecasts, thank you.

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movdqa t1_j9o8ruf wrote

I went out to shovel last night and there were about 2 inches but it was moderately heavy though not super-wet. Apple Weather says we got 3.7 inches so far withanother 4+ to go and I'm about to head out to do some shoveling just to see what it's like. This doesn't seem very bad so far in southern NH. I haven't seen any WMUR clips yet but they should have them up within the next hour.

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movdqa t1_j9ocac6 wrote

Replying to movdqa (#1,936,570)

Just back in and about 4 inches but it was annoying as there was sleet, ice and moderately heavy snow. I'm inside for a cup of coffee and to do some chores and then back outside. I am going to clear a roof that we have that has been prone to leaks in the past.

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WellWhatTheHeck_1 t1_j9oewl1 wrote

Replying to TheCloudBoy (#1,930,406)

Well that sucks. I rely on accurate weather predictions for work, and find them to be awfully inaccurate as of late. Figured it was a climate change thing: weather becoming less predictable. But now I see there are other reasons too.

How familiar are you with aviation weather reporting (the TAF to be specific)? They only predict out about 18-24 hours, but should be high-ish quality, right? (I find them to be less useful than they were a decade ago. Not sure if it's just my imagination.)

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AllstarGaming617 t1_j9oftnu wrote

Just measured here in the north side of Nashua and I think we managed to stay just north of the warmth. Measured about 6.5-7 inches. Only switched over to sleet for about an hour around 4am, still snowing now so even if it stays light we’ll end up with around 8 inches if it keeps snowing another couple hours. Some other Nashua residents reporting around 4 inches so I think that line came right through and sat over the middle of Nashua over night.

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TheCloudBoy OP t1_j9og6gw wrote

Replying to AllstarGaming617 (#1,937,456)

If you can fire that report over to the NWS, that will be helpful in illustrating how narrow of a gradient the accumulations are in Nashua. Radar last night showed the band briefly stationary just north of the MA border before it moved east, so your report makes sense. For reference, that band was supposed to be 30-40 miles to your north

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AllstarGaming617 t1_j9ohbcn wrote

Replying to TheCloudBoy (#1,937,525)

How to I do that? Id be glad to. I also just commented on your newest post since I didn’t know if you were still monitoring this one. We have strange weather in Nashua. More often than not it seems as though any major precipitation breaks up over the monadnock region and we end up getting way less than predicted. Last night was an anomaly with the NWS actually hitting the exact total(here on the north side of town.) Its almost always 20-50% less accumulation than predicted.

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danmac1152 t1_j9oi9iw wrote

Well. I live in the area that says 1-2 inches. I got 6.

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starista t1_j9okaqb wrote

What do you suppose tomorrow (Friday) will bring for the Upper Valley?

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TheCloudBoy OP t1_j9okr82 wrote

Replying to AllstarGaming617 (#1,937,686)

Good question! You can submit storm reports to NWS Gray here: https://inws.ncep.noaa.gov/report/. A lot of our weather enters from the west (especially during the summer), so it's not surprising to hear the thought that the Monadnock Region destroys most of your potent weather. I fully expected the warm front to clear the southern half of the state and switch the Merrimack Valley to heavy sleet, swing and a miss.

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wickedpissahdude83 t1_j9os503 wrote

Meteorology is the most over-rated sensationalized gig out there. I have never seen so much self dick sucking as I have than in that industry.

Hey you know, I am just some jack-wagon asshole with a BSME but I can tell you for fucking sure that I can look at a simulation in my industry and know when it doesn't look right and I need to read between the lines and utilize the knowledge that I have and forecast something that conflicts with the sim.

Why the fuck is it so hard for you self dick sucking righteous assholes to do the same thing?

I mean what the fuck guy? I havn't even had my great one xtra xtra yet this morning guy. i mean what the fuck is going on we got my man Tony being cancelled and rogue meteorologists throwing around bunk ass forecasts on reddit while half the liberal twats on here shove their nose so far up your ass.

#DADDYDESANTIS2024

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TheCloudBoy OP t1_j9ou9i7 wrote

Replying to wickedpissahdude83 (#1,939,287)

Ahh a mechanical engineer, you work at any of the companies in Manchester? Well you've gone through a number of the classes I have (thermodynamics, physics, probably fluid dynamics, etc.), so you should understand the complexities in numerical weather prediction and how it can vastly differ from simulations engineers utilize.

The better meteorologists in our field do read between the lines and leverage the basics taught in college, however the issue overnight differs from other scenarios where people just rip a model forecast like lemmings. Coming into this, there was decent confidence probabilistically that the 700 mb warm front clears into NH, so the ensemble blend of forecasts (or simulations) agreeing on this. When it becomes apparent 3-5 hours prior to snow starting that the front won't clear, well you're screwed.

I'm happy to rationally defend my thinking and explain complexities like a competent meteorologist should, but I won't sit here and let my above-average skillset be chalked up to some "dick sucking, righteous asshole".

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wickedpissahdude83 t1_j9oxrjq wrote

Replying to TheCloudBoy (#1,939,572)

What BAE? No thanks. Or any of the other defense contractors with a business model that thrives on tearing the planet apart with sustained war or executives cutting corners that leads to planes falling out of the sky.

joking aside, yes, i understand the volatility with the behavior of the atmosphere you guys are constantly dealing with and how that differs from me running a simulation based on physics that havn't been volatile since Newton was alive.

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