high risk

Even if we lower the dew points, it's the lapse rates that are driving the huge instability. Some sort of remnant EML appears likely to advect into our area overnight Thursday - there is really good, continued model agreement this evening about that. (Toss the GFS/HiResW FV3 which are known to underdo lapse rates.) The impressive lapse rates will allow some sort of MCS to survive into our area early Friday and then enhance whatever severe threat exists Friday afternoon. I'm still not totally sold on a trigger (yeah, a leftover boundary from a morning MCS could help a lot), and we might have some downsloping subsidence to suppress convection, but the shear/instability profile would favor splitting supercells with a wind and very large hail threat if any storms can form. (The tornado shear profile shown in the forecast sounding above is not supported in this evening's guidance which generally shows more westerly surface winds.)

Strong signal across all global ensembles for a cooler than average Memorial Day weekend.

Any MCS early Saturday would likely be elevated and therefore unlikely to have any SVR threat. It’s just so difficult to get severe here outside of the period of peak heating.

The NAM is doing its usual thing with too high dewpoints, BUT it is forecasting very steep lapse rates for Friday which might be real and would certainly contribute to higher CAPE and a legit large hail threat. As noted, however, triggers look to be minimal right now, but a high-impact isolated cell or two still seems possible.

Friday is certainly interesting. To start, several models show some sort of early morning MCS. The NAM in particular has some steep lapse rates, which likely explains the signals for big hail. I'm not sure what the trigger would be for afternoon storms to form and take advantage of some positive factors, but it's definitely worth tracking.

The HRRR has shown this for several cycles, and the evening CAM suite continues the trend. That said, while they seems to be spot on in terms of location and timing, actual coverage so far appears to be less than progged.

I will admit that I don't trust it, but there was a pretty clear signal in the 12Z CAMs for heavy rain to break out on the east side of DC and over to the Eastern Shore during the mid evening hours.

Yeah, the CAMs this evening look more like the earlier globals with decent rains from the Bay to all points west. Still not as good of a consistent signal for the Eastern Shore, but it does seem like even those areas should eventually do at least ok (later Tuesday into Wednesday??).

Fri/Sat is definitely worth watching, but there is a lot of disagreement on whether we get decent height falls or if they're focused more north of here. Any modest height falls would probably bring a severe threat, given the good moisture in place and good wind fields.

People on the east side of the Potomac are going to truly hate the morning hi-res runs.

Notable speed-up in the overnight and morning guidance with the arrival of the rain: initial shower bands may arrive before the dinner hour on Monday.

Still a pretty good signal in the evening CAMs for at least scattered convection Tuesday afternoon for those mainly north of the DC Beltway

The problem is that the upper low now looks to cut off further west, so Sunday is probably now a warm day with convection that the GFS is likely not resolving well. That said, it could very well end as an event with winners and losers instead of everyone getting some love.

Really nice supercell in western Maryland this afternoon.

Looking great for a big soaking later in the weekend into at least early next week. Note that there is a separate thread for this event.

There is a bit of a signal for the highest amounts being north of here, but all 3 global ensemble means are 2"+ for most of this subforum, and 2 out of 3 have 2+" for the entire subforum. And it's spread out over multiple days instead of being some convective deluge that can't sink in. This looks a much-needed huge win for our region.

Full-blown, massive cave.

In particular, the GEFS made a huge move towards the other guidance.

Latest HRRR initializes it well and does try to bring it into Montgomery/Loudoun before weakening. It actually shows lapse rates increasing a bit, generating some elevated CAPE, so perhaps it *could* hold together further east than initially thought.

I'm calling it a night before waiting for the 00Z suite, but it's worth noting today that the Euro and AI-Euro both have the weekend trough cutting off and hanging around for a while and giving us a much-needed multi-day rain event. It seems to have some ensemble support. The GFS/GEFS, prior to the overnight runs, are very progressive with the trough and want nothing to do with the Euro idea.

The slightly slower solution ended up verifying, and we do have a MRGL along and east of I-95 for this afternoon. There is actually some good model agreement that a broken line of thunderstorms will form around 2pm very close to I-95 in Maryland and extend at least a bit south of DC on the Virginia side. Looks like there will be some instability, but deep layer shear looks slightly weaker than it did in earlier progs, so a MRGL seems to be the right call (but a few wind reports are certainly possible, especially further east).

Yeah, widespread heavy convection Friday night (as depicted on that one NAM Nest run) just doesn't seem likely, although there could be a few good downpours for some lucky areas. After that, I'm glad to see some ensemble agreement for a strong trough passage the following weekend, but I don't like seeing the prolonged signal for northwest flow after that.

If the NAM Nest and HiResW ARW2 are correct, there would be a MRGL and eventually perhaps a SLGT for Saturday along and east of I-95, but they seem to be outliers with their slower timing and higher dew points (driving good instability with modest deep layer shear). Since slow timing and overmoistening are clear biases of both systems, it's unfortunately tough to buy their solution. At this point, I just hope to cash in on some heavier showers Friday evening and overnight.

The EML will definitely be there, but the impact of an EML can be significantly lessened if you're dealing with a stable surface layer. You're all spot on that every hour earlier that convection arrives makes a huge difference here. Let's look at the HRRR temperatures, since it's the warmest model. Here is peak heating time: That's plenty warm for the Shenandoah Valley and across most of northern VA, but it's much cooler across central MD, and other guidance seems to be in agreement. Not sure that earlier arrival will help as much for areas east of the Potomac as we think. The HRRR brings convection racing west to east generally north of I-66, and the reflectivity looks super cool, but the forecast soundings in advance are not awesome: Thunder? With those lapse rates generating a good amount of elevated CAPE, you betcha. Shear is super. But that very stable surface layer is going to make it incredibly difficult to get wind down to the ground. And despite the good lapse rates to promote hail, the freezing level is quite high, so the stones would likely melt before reaching the surface. But perhaps the overall speed of the MCS (or whatever you want to call it) will drive some better gusts than this sounding might imply. As mentioned earlier, the dynamics (500 height falls are nice!) are super. As the outlook implies, the highest threat is definitely further west and northwest with lowering threats the farther east one goes.

Simulated radars look really interesting, but the soundings suggest that the convection will be elevated due to early evening cooling and therefore have limited SVR potential. That said, the dynamics are really strong, so this is certainly worth a look.