Jns2183

That's the 3k nam, reg nam, observed The NAM suite’s performance during the Arkansas snowfall event was a case study in systematic failure, characterized by a severe northwest displacement and a critical underestimation of moisture transport. Both the NAM 3km and Parent models shifted the entire storm track 95–110 miles too far northwest, which effectively "erased" the heavy 7.8-inch snow core from Central Arkansas by placing it in a modeled dry slot. While the models were predicting 0.0" for Little Rock and Conway, the actual atmosphere was tapping into a rich Gulf moisture plume that the NAM fundamentally failed to resolve, leading to a massive +7.8-inch error at the storm's most intense point. The root of this "NAM Gap" was a flawed thermal profile that modeled the 850mb "warm nose" much too aggressively and far north of its verified position. By over-amplifying the ridge ahead of the storm, the NAM physics engine incorrectly predicted that dry air would "eat" the incoming precipitation shield, when in reality, the column stayed cold and saturated enough for high-impact snowfall. For those tracking the storm's progression into the Ohio Valley and Northeast, the takeaway is clear: the NAM’s known dry bias and tendency to over-pump warm air can lead to a 100% miss in the transition zone, making a weighted consensus of the HRRR, Euro, and NBM a far more robust strategy for defining the true snow line. Sent from my SM-S731U using Tapatalk

Lessons from Arkansas below. Later I'll do an update for round two and look at Kentucky/Missouri, Ohio Trust the NBM for the most likely total. * Use the HRRR to define exactly where the heavy bands will set up (the "where"). * Keep the Euro in the mix to ensure you aren't being "fooled" by a high-res model (like the NAM) that might be missing a major moisture plume. Sent from my SM-S731U using Tapatalk

Let's see how the NAM handled snow in Arkansas so far First image is snowfall output from NAM 2nd is observed at official stations Take a big look at Little Rock Out of all the models euro preformed best there Almost all pushed mix to far north Different system when it gets up here but at least we have some data Sent from my SM-S731U using Tapatalk

Even better video https://x.com/i/status/2014698738137117002 Sent from my SM-S731U using Tapatalk

Verizon network is once again down Sent from my SM-S731U using Tapatalk

7"/hr https://x.com/i/status/2014722834476466189 Sent from my SM-S731U using Tapatalk

Here Sent from my SM-X210 using Tapatalk

That high being a bully is our friend Sent from my SM-X210 using Tapatalk

This is the sounding for Norman Ok, off the 18z NAM for 21z, a mere 3 hours after initiation. Next image is temperature from weather ballon launched at 21z. Sent from my SM-S731U using Tapatalk

It also seems like it may start much earlier Sent from my SM-S731U using Tapatalk

Here Sent from my SM-S731U using Tapatalk

The HRRR looked amazing Sent from my SM-S731U using Tapatalk

I hope that verifies! It's so bonkers and a perfect encapsulation of CAD Sent from my SM-S731U using Tapatalk

The model outputs a couple days ago started for the south and Missouri valley started Twitter arguments between metrologist so intense it ended up all over the news. I think a prudent thing to do is look who was right tomorrow morning Sent from my SM-S731U using Tapatalk

Also the warm nose can stay negative but still screw enough with snowflake microphysics you end up with ratios well below 10:1 Sent from my SM-S731U using Tapatalk

https://x.com/i/status/2014730518286242198 Sent from my SM-S731U using Tapatalk

There's some approaching 3feet today Sent from my SM-S731U using Tapatalk

There's video going around from that lake effect mega snow band in New York showing what 7" per hour rates are like. Basically like being inside a cloud. Sent from my SM-S731U using Tapatalk

Look at the satellite water vapor images in western Canada. That high is hauling ass down and that might be why Sent from my SM-S731U using Tapatalk

We aren't getting steep lapse rates within the dgz (thunder snow!) that can easily overcome a small dgz, this storm. Our rates are maxed when we get a huge dgz with good accent and lapse rates above it. Compare image used to show this (1st) with that one from the GFS when rates are great. Sent from my SM-S731U using Tapatalk

Great summary Im definitely leaning towards a 50/50 blend right now When we're staring at model snowfall maps for the next storm, you'll often see options like the plain old 10:1 ratio (10 inches of snow per 1 inch of liquid) or the Kuchera method, which a lot of sites use because it's supposed to be smarter. The Kuchera approach looks at the warmest temperature anywhere in the atmospheric column (usually up to about 18,000 feet) and plugs it into a formula to tweak the ratio. If that max temp is really cold (say below about -2°C or 28°F), it can spit out fluffy ratios well above 10:1—sometimes 20:1 or more—while warmer columns drop it down toward 5:1 or even lower to account for denser, wetter snow or partial melting. It's a quick way to adjust totals without needing super detailed soundings, and it often gives higher accumulations than straight 10:1 in cold-air setups.But here's the catch that a lot of amateurs (and even some pros) overlook: Kuchera basically ignores the dendritic growth zone (DGZ), that magic layer between roughly -12°C and -18°C where those big, starry, branching snowflakes form best. Those dendrites trap tons of air and stack up super fluffy (high ratios like 15:1–30:1+), especially when the whole layer stays saturated and deep. Kuchera just keys off the single warmest temp in the column, so it can seriously underestimate snowfall in setups with a nice, cold, deep DGZ even if the column max isn't ultra-frigid, or overestimate in marginal/warm cases. Next time you're comparing maps, check model soundings for how beefy that -12° to -18°C layer looks Sent from my SM-S731U using Tapatalk

My biggest concern is the alignment of when we have truly thick dendritic growth zone to when we have the best omega Sent from my SM-S731U using Tapatalk

Big Jan 96 vibes with the multiple storms and artic cold Sent from my SM-S731U using Tapatalk

Someone made these from 00z model models Sent from my SM-X210 using Tapatalk

After the epic storm drought we've had I think it would take us getting less than 7" for me to feel slightly jibbed. I do think now we end up in the 12"-14" range much more than 16"-18" range it won't affect my enjoyment Sent from my SM-X210 using Tapatalk