high risk

It's being run every hour in parallel, but COD is only displaying a few cycles. It's in its final stability test; if no problems occur in the next 2+ weeks, HRRRv4 will replace HRRRv3 in operations on May 26. Tons of good information here: https://www.emc.ncep.noaa.gov/users/meg/rapv5_hrrrv4/

Saturday could be a particularly interesting day. Taking the GFS verbatim, you'd have a strong trough axis sweeping through at 'peak heating' with strong lift and very cold temps aloft.... Graupel showers on May 9??

The SPC outlook discussion is spot on. Forcing is strong, but the soundings look very meh. Best chance of severe will definitely be further south (as suggested by EJ), where temps will be warmer, giving some hope of modest cape, but it's pretty iffy there too. For those north of DC like me, I'll be happy with thunder: NAM nest looks great for that, but it's a bit of an outlier, with several other CAMS not showing good reflectivity signals north of 66 (VA) and 50 (MD).

Indeed! check out the 12z NAM nest for Sunday afternoon.

While it looks like we'll hopefully avoid some of the nastier scenarios being depicted by various guidance in recent days, I don't think it's worthy of a 'meh' either. We'll still have a 60+ knot low level jet, some very strong lift from multiple sources including upper difluence, and impressive PW values, and even hi-res guidance can often underdo precip in these events. And while it looks to be fairly progressive, there are still some hints of a "round 2" Thursday afternoon in the HRRR and ARW2. Certainly the best chances for big amounts are east of DC, but the chances of really huge totals seem lower now, they're not zero, and we'll still have to deal with issues associated with a heavy event in a short period of time at a minimum.

Yeah, wind profiles look awesome to our west Wednesday night, but instability is negligible. On Thursday, the wind profiles along the I-95 corridor will be decent, but instability again looks to be effectively nada. Agree with EJ that any threat would be flooding. It had been looking like the axis of heavy rain Thursday afternoon would set up just to our east, but the 12z NAM is slower, and a heavy rain threat may set up for DC and points east.

It's worth checking out the overnight runs of the HRRR. All of them have some healthy reflectivity signals for later this afternoon over most of Maryland east of the Potomac. The freezing levels are really low, so if this is right, these would be showers with likely graupel or small hail. It's worth noting that I haven't seen nearly as good of a signal in the other hi-res models, but the HRRR is consistent.....

very reasonable MD issued. a respectable 65/45 at BWI. heating is good - just need to maintain low to mid 40s dew points. It has mixed out to 41 at IAD, but the models have consistently shown a less favorable environment on the west side of DC.

Yeah, that area is going to have trouble with dew points due to downsloping. Upper 40s here. T/Td will be fun to monitor over the next 3 hours.

I'm slightly more bullish about this than you due to the impressive dynamics, but the better solutions say that we're roughly 64/48 just ahead of the storms. If we don't get there, it will definitely be lame.

cape was going to be limited no matter what, but yeah, we need every degree we can get today. At least warm advection is at least somewhat offsetting the lack of sun

yes. The soundings are really cape-starved. The only reason we have a chance is because the dynamics of this system are really impressive. Hail is a concern due to the low freezing levels for sure, but the meager instability argues against seeing widespread larger sizes.

no real change in the 12z guidance. While they differ on coverage/intensity/timing, all CAMs have some amount of convection in our area early to mid afternoon tomorrow. The best signals for coverage and intensity are areas well northeast of here, and the signal within our area is better on the east side of town than on the west. Sfc-based cape isn't great, but there is some in all progs. Soundings support some stronger wind gusts, and I agree with SPC that due to the very cold air aloft and low freezing levels, some hail is possible in any stronger, discrete cells. The MRGL seems to cover the threat well for now.

Slight improvement for Tuesday in the 00z suite. Best chances still appear to be for those further northeast, but both instability and simulated reflectivity improved a bit. Will be tougher to get decent convection the further west you are due to downscoping.

Was just coming in here to post this, but you beat me to it. The forecast soundings look better to our northeast (in the MRGL area) due to it being colder aloft, but there might be a small amount of instability in areas along and east of the Potomac. NAM nest actually has an interesting evolution for Tuesday afternoon.

Significant wind here in North Laurel. A nearby neighborhood has no power, and a colleague who lives a half mile away had a tree go down.

Interesting trade off as the line moves east. It's moving in to way better instability, but the good wind fields are quickly moving off to the east, and the low level flow is veering. Storm-relative helicity will therefore be dropping as the line approaches the DC-Baltimore area, so the tornado threat is decreasing, but the wind threat is likely increasing. That said, despite the decreasing shear, it still could be sufficient for some rotation within the line.

actually, it's quite good. Several discrete cells with a few decent UH tracks. If you want to see a massive bow echo swallowing the entire area, today is not your day.

True, and some of the storms that develop out there will come our way in a few hours, but the CAM simulations also show cells developing locally around midday.

Other than the HRRR, the 00z CAMs across the board are a big step back for the threat.

verbatim, that early morning line has no sfc-based instability to work with and would be non-severe. It's earlier with that round of convection than most other guidance. That run still has some afternoon cells, but it's definitely not showing a widespread severe threat.

Yes, and it then really likes that noon-2pm window. Has a few decent UH tracks.

and likewise. I agree that I'd wait on any hatching up here, but I personally see enough to go up a notch to ENH.

I still have the same thoughts I had last night: QLCS moves through the area during the early-mid morning hours with some discrete cells in the early afternoon. The QLCS will have extreme shear - it's a question of instability, but IF we can get some sfc-based cape (and the chances seem to be going up), you have a threat of widespread wind damage and some tornadoes for sure. The 2nd event will have more instability and reduced shear but still more than enough, and a more "classic" supercell mode would be favored with a legit TOR threat. There are still uncertainties (how much instability for round 1? how much coverage of storms for round 2?), but I think that a 10% TOR threat (and an ENH risk extended north into our area) would be justified in the updated day 2.

Among the CAMs, the NAM nest is by far the best in terms of reflectivity, although its updraft helicity signals are modest. The other CAMs overall aren't as good. But the environment still looks like questionable instability but fantastic low level shear, so we're still very much in the game.