high risk

not really. Yes, the NAM (and other regional models) will be replaced by a system that is run hourly (like the HRRR), but the new system will be FV3-based. regarding the Monday event, the HRRR is the craziest for central MD and DC, but several other hi-res models show a change to snow on the backside of the system, at least across central MD.

I'm not sure about the EPS, but the GEFS members are run at 25 km resolution, while the ops GFS is 13 km. So yes, that could be making a difference.

Definitely much more dispersive than the previous version of the GEFS.

The previous version of the GEFS was extremely underdispersive, but the new GEFSv12 has way more spread. That was one of the strengths of GEFSv12 noted in the summary presentations on the evaluation web page: https://www.emc.ncep.noaa.gov/users/meg/gefsv12/ (It also helps that 10 additional members were added.) If most members agree something at day 5, that's a much bigger deal in the new version.

This is what happened on 11/15/18. The NAM was one of the coldest models for that event too and was largely dismissed, but it had the right idea of big rates overcoming a very marginal air mass.

The parallel GFS had statistically significant synoptic range improvement over the ops GFS in the medium range over the full course of the retrospective runs. But that certainly doesn't preclude it doing worse on any single event. I wish we were able to run it more than once per day right now.....

Honestly, those details haven't been sorted out yet. It's not an output in the RAP/HRRR (which have actual snow accumulation as an output), although their SLR methodology is documented. The plan is to carry over the RAP/HRRR products into the RRFS (replacing all of the regional models in 2023) and build it into the 2024 GFS/GEFS upgrade.

They do run tend to a bit low (especially when the ground is relatively "warm", but they're so much better than 10:1 maps in any event in marginal thermodynamic environment. I honestly don't blame WB or TT. The problem is that NCEP doesn't generate true snow accumulation output for any models except RAP and HRRR, so it's up to the user to assign and apply an SLR. This is going to be addressed going forward.

In these events with very marginal temperatures, the Tropical Tidbits accumulated positive snow depth change are the best maps to examine. They show what the model believes can actually accumulate on the ground.

Speak for yourself. It basically hits a wall at the Potomac.

00z NAM continues to show a deformation band of snow across the area Saturday.

a quick FYI for our severe friends that the HRRR is now run to 48 hours 4x per day, starting this morning.

You left out the next panel in which it basically wipes out that line as it moves into the metro area..... That said, the HRRR has the same feature, and it keeps it going further east, but the HRRR is warmer in the low levels and keeps it as rain for the metro area.

same here. would have been even more interesting with more sfc heating....

That Mt Holly discussion works very well for most of our area too. Interestingly, progged parameters for early this afternoon have improved, but overall, the CAM simulated reflectivity forecasts for our area have gotten worse. 12z NAM nest stops the bleeding and actually has a nice convective feature and a secondary low center - we'll see if it has the right idea.....

several morning CAMs do show a broken line moving through parts of the area during early Monday afternoon, with a few hours of heating prior to arrival. If that plays out, with several hundred J/kg of CAPE, there is certainly some severe potential.

I've been looking this evening at the Monday threat, and while I'm not too optimistic at our SVR chances, I can't argue with the MRGL. The warm front looks to move through the area by mid-morning taking the steady rain with it. There is a period late Monday morning when the progged hodographs should be outstanding, and several CAMs have a more scattered, somewhat cellular nature to the precip, but instability just isn't there in the CAMs right now. By early afternoon, it *does* appear that we'll get several hundred J/KG of sfc-based CAPE as the dry slot moves overhead and much of the area warms into the mid 60s. Unfortunately, the low-level winds are progged to veer by then, and the hodographs don't look as good. That said, there may be a broken line of convection on the cold front (High-res Window ARW2 really shows this), so some severe threat, especially in the form of wind gusts, will exist if we can achieve the higher (500?) CAPE values. The faster that the warm sfc air overspreads the area Monday, the better the chance of severe. Ultimately, the instability and best low-level shear likely won't overlap (keeping the tornado threat fairly low), but with very strong winds just above the surface, there will be an opportunity for at least a few severe gusts if we can heat up by early afternoon.

very impressive winds here in southern Howard County just after 7pm

I'm guessing wants to see some actual obs/reports before deciding whether to go with a box..... I don't blame them.

With the 1630 upgrade to SLGT, it's time to move discussion of the convective line over to the severe thread.

There is zero doubt that a convective line will move through the region later today. I've been skeptical about the potential for winds to mix down, but given the reports coming out of Ohio, I guess I can't argue with the SLGT.

There is no argument that there will be a strongline of convection later Sunday moving across the area - the radar will look nice. My questions are whether it will have lightning and whether it can produce strong wind gusts. The forecast soundings just don't have enough instability for lightning - stronger wind gusts are a better possibility, although they should stay below severe limits. if instability is greater than progged, some lightning and gusts near the severe threshold would be on the table.

CAMs are very emphatic about a forced line of convection sweeping across the area later Sunday. Mixing down some strong winds to the surface and/or getting some lightning are both on the table although not particularly likely due to very weak instability.

Sunday looks like a really rotten day - still not clear whether we'll have periods of rain or just some occasional drizzle, but low clouds with temps stuck in the 40s seems fairly likely.

getting some huge drops that sound like small hail when hitting the ground with the southern Howard County cell