high risk

I was surprised by the box, given no MD and the fact that we're cooling post-sunset. But the parameters on the SPC mesoanalysis look pretty good.

While the location of the max is jumping around (as it often does), the last several consecutive HRRR runs all have a 2-4" max somewhere in north-central or northern Maryland.

That NAM3 run thinks that most of the convection will die before reaching Delaware - it has a few scattered cells moving across the state much later tonight. It's not an unreasonable solution that convection will not be widespread at the unfavorable time of day. That said, there are other CAMs that generate enough forcing ahead of the front to compensate for the limited late-night instability, and they have more widespread and heavier rain in eastern areas later tonight.

I'm mostly on board with the severe threat, although the coverage of storms during the severe "window" (roughly 21z to 02z) will be limited. Might transition to more of a flash flood threat later in the evening.

I didn't pay close attention to guidance yesterday, and the potential for Sunday to not be so nice of a day really snuck up on me.

What's happening now in the PHL-TTN corridor this evening would have been us with a slightly further west and slower track for Ida.

I'll say this: there seems to be some agreement that this line to our west will sweep through in a few hours. The HRRR hodographs are garbage, but even though the 18z NAM Nest weakens the shear, it keeps the sfc winds more backed, and I can't rule out a TOR or two if that solution ends up correct.

The HRRR has another nice convective band moving through early this evening, but low-level winds are progged to significantly veer by then, so I'm not buying much of a TOR threat unless those forecasted wind profiles are really off.

Any school system on the east side of the Potomac that didn't dismiss early made a mistake today. The Annapolis tornado hit right around dismissal time.

The only event I can recall is the April 27-28, 2011 event when we were under a tornado watch here for over 20 straight hours. But that was an instance of SPC continually reissuing the box. I can't recall an event with two separate events (with a break in between) requiring tornado watches on the same day before.

18z IAD special rob has a 0-1 km helicity of 261 !!!

It's broad, but I would be erring on the side of extreme caution today if I were at LWX.

That cell just east of Waldorf looks great!

Spot on. At the least, they'd have to be sending kids home in torrential rain if they didn't alter the dismissal time.

DCA now 81/73 with a southeast wind. BWI is 79/75 with an east wind. We may not get the 2000 CAPE values that some guidance was showing yesterday, but it certainly seems like sufficient instability will be in place, at least along and east of the I-95 corridor.

Tornado watch coming soon.

Howard County schools closing 3 hours early. SPC Mesoanalysis shows that we have work to do in terms of instability along the I-95 corridor to ramp up the threat. The likely earlier arrival of the forcing will give less time for heating, but I'm absolutely not ready to lower the threat yet.

That would be good. My worries are that some schools will end up under tornado warnings, and they usually bring the kids to interior hallways, and that kind of crowding is not what we want during a pandemic......

School systems would be very wise to have an early dismissal at noon. It would be bad to potentially have to get kids home while there are active tornado warnings.

I don't like that the 00z HRRR run brings the TOR threat into our area by mid-afternoon Wednesday instead of late afternoon. Do not want kids on school buses as tornado warnings are issued.

Yes, most guidance had a modest chunk of the huge predicted rainfalls for PA occurring tonight.

You may be on to something here. I wasn't worrying too much about the late night threat due to what I thought would be a lack of instability, but even though it's somewhat of an outlier, the HRRR has a modest shear/instability combo here towards morning.

I'm WAY more worried about the TOR potential in the DC-Baltimore corridor than I am about flooding. That said, I think it's worth noting that while the major flooding potential is going to be in PA/WV/western MD tomorrow, there will absolutely be potential for FLASH flooding in the DC-Baltimore region. It's going to be a roughly 6 hour period late tomorrow with several bands of convection (with potential for TORs) that will have torrential rainfall. I can certainly see some localized 3-4" totals that will create major problems for the evening rush hour. Things will be worse if the warm advection rain later tonight ends up overperforming, which is always a possibility in this type of environment.

But that's not what the guidance shows. There is a lot of consensus that much of the area along and southeast of an IAD-FDK line will stay mostly dry tomorrow until the convection rolls in during the mid to late afternoon.

Interesting to see whether SPC will add a 10% TOR contour in the upcoming day 2 outlook. There is probably just enough uncertainty in the exact area to draw a 10 to make them wait until tomorrow to better define a higher threat area, but the setup as currently progged may support greater than a 5% TOR outlook. If you're looking for TORs, you can't ask for much more in this setup than what's currently shown: a dry slot keeping us dry through a big chunk of Wednesday, allowing surface heating to maximize instability ahead of strong forcing and strengthening wind fields at the right time of day.