high risk

The Kuchera daylight ratios show us getting 37 straight hours of darkness.

Clarification needed: the 12z soundings do not make it into the 12z HRRR. They’ll be used in the 13z cycle (which of course only runs 18 hours out…..)

That's awesome! But this really isn't about pulling in mild air from the ocean. It's a question of where the thermal boundary sets up at the start of the day and how quickly it moves southeast. The snowiest models move it quickly away, while the other solutions keep it close by, and we lose some QPF to a mix, before the cold air finally wins out during the afternoon.

1.5" in southern Howard County

I think that's really generous, but we'll see......

Looking at the RAP with Kuchera ratios for a snow event is like eating an entire stick of butter when you want a modest snack and then washing it down with a glass of canola oil.

It's driven by lower-atmosphere temperatures. It's great at chopping amounts in marginal temperature environments, and the premise that SLRs will be better than 10:1 in cold environments has some truth, but it's not as simple as colder=better SLR, so it goes nuts when the air mass is cold.

Thank you. The Kuchera drives me nuts. It always feels like this is 10:1 and this is the same case with Kuchera:

I'm in the "00Z NAM at f84 looks closer to the 18Z Euro at f90" camp.

Up to 6" here in southern Howard County, with moderate snow falling under this good band.

You should have just said that you were looking at the NAM (which is 2 hours slower than most other guidance).

It actually matches the HRRR (and several other models quite well), although I'd lean towards the latter parts of those time periods. The NAMs have a clear bias towards too slow of an onset in precipitation, and that is true whether it's summer convection or a winter storm.

Yeah, by hour 96, the 00Z cycle handled the shortwave over Montana quite differently than the previous 2 cycles.

Note that this run does not include any of the 00Z model runs, and no NBM snow product contains any Canadian data. No NBM product at all contains any UKMET data.

Agreed. In areas that stay all snow, a blend of the Ferrier product and the Kuchera product might work pretty well.

When looking at 3k NAM output, it's worth looking at the Ferrier snow accumulation product. This one is connected directly to the model microphysics, so it knows exactly what the model is doing with the falling precipitation. It can actually run a bit low for areas that stay all snow, but it's terrific at sorting out where the model thinks that the sleet will be mixing or other interference to pure snow accumulation.

The 3k is a far superior model.

00Z HRRR does *NOT* have the 00Z raob data. Edit: to be clear, this cycle can never have them, as its start time is too early

The NAM tends to do funky things with placement of coastal lows and such, but once it has the synoptics nailed, there is no better model for identifying warm layers in warm advection events and dry slots. The question, though, is whether it has nailed the synoptic details for this system. It's probably slightly early to think with confidence that it has, but it shouldn't be immediately tossed onto the garbage heap. The 3km version, though, is FAR superior to the 12 km.

10:1 is always underdone in a cold storm, but Kuchera tends to run really high. Splitting the difference makes sense in areas that will stay all snow.

I'm trying to make sense of these WB maps. It appears that they are NOT forecasts of precip type right at the particular time. The label says "6 hr QPF by type (in.)", and legend below notes that it's liquid equivalent. But since there is no way to plot amounts of each type on a single map when precip types varies during a 6h period, we have to figure out what they're doing. The GFS does not parse amounts by type, so my guess is that WB does some sort of internal tallying by using hourly precip type data and hourly QPF, and they plot whichever type is the highest over the previous 6h, but that's admittedly an assumption. Regardless, no one should interpret this map as "it's sleeting or freezing rain at 18Z over most of the area."

It's really an EMC question, but you nailed it. The HiResW FV3 can in some ways be considered a hi-res GFS, but the GFS has been tuned a fair amount in recent years, with none of those upgrades making it into the HiResW FV3.

I've never seen this much attention paid to the timing of availability of a NAM run 2.5 days out from an event..... Everyone needs to remember that the model almost always runs at the exact speed it does every other day. Dissemination of the data via various platforms and then generation and loading of graphics at the various display sites is what has almost all of the variability.

MAYBE in 2026.

I'll spare everyone the NBM history, but right now, the winter suite at this range actually uses all ECMWF and GEFS ensemble members, along with 10 SREF ARW members and the GFS. We're now coming into the range where it will start using the NAM Nest and HiRes Window FV3.