high risk

Line filling in nicely now. Was not, however, expecting to be in an MPD..... The wording, though, clearly favors the Eastern Shore.

It has nicely cooled aloft. This is what I was suggesting earlier that there might be a window for a couple of hours past sunset with a severe threat, as mid-level cooling would compensate for surface cooling. Unfortunately, with the line (or whatever is left of it) not getting into the DC area for a few more hours, I'm just hoping for a rumble or two of thunder at this point.

Yeah, the initial convection moving up from the southwest really didn't have much of an impact. The line to our west will continue to move east, but we'll be dealing with surface cooling when it arrives. That said, there *may* be a window just after dark when cooling aloft compensates for the cooler surface and allow a severe threat to persist into the DC Metro area.

The NAM/NAM Nest solution is our path to severe. The HRRR is not. HRRR initiates convection in southern VA by early afternoon which moves NNE and maybe bring a SVR threat to southern MD and the eastern shore, but it screws most of the DC-Baltimore area on severe and rainfall by killing the line arriving from the west. The NAM idea is to have that initial round of convection be far less widespread and not interrupt the convection arriving from the west.

I don’t hate the end of the 12z NAM Nest run…I’ll say that.

Guidance seems to be converging on better timing for Sunday. Could still be an issue in which widespread clouds and multiple rounds of showers kill instability and any severe threat, but we're in the game for now.

Spot on. Forecasted highs for Thursday and Friday are way too warm.

Did you accidentally stumble in here while looking for the Guam forum???

Yeah, the GFS timing would be terrible; hug the Euro.

Beware the midweek back door cold front! A fair amount of guidance has at least the northern parts of the forum much cooler than the far southern parts Wednesday- Friday.

Thanks for noticing! My forecast was pretty good, except that the storms (while sub-severe) persisted all the way east into the DC Metro area this evening. The CAMs were too quick to really disintegrate the line.

Pretty remarkable CAM agreement on an intense line rolling through the area in the early afternoon tomorrow. (The NAM Nest is a bit later than any other guidance, but it has a notorious slow bias on convective timing.) The reflectivities look amazing, but is there really any severe potential with it in the DC area? The wind fields are amazing, and if we had even 500 j/kg of sfc-based cape, we'd be looking at widespread damaging winds and QLCS tornadoes. But there really isn't any instability shown by any model. Maybe the HRRR squeezes out 50-100 j/kg, but it looks warmer than most other guidance. So, I have to wonder if this will be just a short period of torrential rain followed by stratiform. Before I totally poo-poo the threat, however, it's worth noting that sometimes the incredible shear and overall dynamics can drive severe weather with a forced line in an environment with basically no cape, so I won't rule out a damaging event with an isolated brief pinup, but I don't think that it's likely. The better environment actually establishes itself over northern VA and areas to the north and northwest in the evening hours, as the very cold air aloft arrives, steeping lapse rates. Go look at sfc-based cape fields for the early evening hours. The values aren't awesome, but they're notably higher than during the early afternoon event. Wind fields are still decent, so any cells would likely be supercellular have hail and wind potential. Unfortunately, the upper system arrives just a bit too late, and nighttime sfc cooling with reduce the potential as the evening goes on. The best severe threat with this round will be over eastern WV, northwestern VA, and up into PA. Maybe an isolated cell can pop across the DC metro area, and it would have severe potential if it did, but the threat appears low there at this time.

Looking at the 00Z guidance, the timing for Wednesday now appears slower which probably reduces the severe threat for those of us in central MD. Some thoughts: 1) Several CAMs show an intense, forced line of convection sweeping through during the midday hours. Wind fields are intense, but there just isn't any instability until you get south of Richmond, and it's pretty meager down there too. If there is a severe threat with this feature, it's likely well south and southeast of the DC area. 2) As the dry slot approaches and much colder air aloft overspreads the area, convection is likely to form later in the day over western VA and move eastward. Wind fields are weaker but still sufficient for a severe threat, and there may be just enough sfc-based instability for a low-end wind threat and perhaps some hail too. What's not as good is that the timing of the system reduces the instability, especially for areas on the east side of the Potomac. There is still some severe threat, but it's highest over northern VA.

The models all ingest the same weather balloon data.

Uh, because guidance shows actual sfc-based instability this far north…..