high risk

Regarding the “failed” morning MCS, guidance overnight showed that the far southern flank might ignite after 8 or 9 am this morning in northern MD. A few showers are now indeed breaking out, so there is clearly at least some forcing. Model solutions vary between just isolated weak showers and actual robust storms, so I’m unsure how the next few hours will play out, but we clearly do have some sort of forcing mechanism.

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.