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!

For where?!

A combination of factors sadly, including laziness/incompetence, inexperience, and sub-par data delivered to end users such as yourself!

Whoa, I appreciate that and remain humbled! Can you give me any hints to which workplace this is haha?

My forecast is admittedly aggressive for locations south of NH-101, but the warm nose and poorly placed lift are slated to create widespread sleet and poorly formed snowflakes through midday Thursday.

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 :)

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.

Who had 5-8" for your location (which I assume is south of NH-101)?

I don’t stress unless it’s in the 8+ range. Or if it’s all coming down at once.

I love NEWG on Facebook - and (as per usual) the comments section is gold.

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.

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

It will be mostly cloudy for the majority of the day, though there will be more sunshine towards sunset!

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.

He’s spot on for the Concord area. It’s 5:30 AM over here and so far he’s good

Everyone busted badly north of Concord, in fact much worse than me. Good luck finding one that was right.

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".