high risk

getting drowned with this batch right now in southern Howard County with a lot of this batch still to move through. Watching the line along the I-81 corridor as well. Thinking that the recent dryness will prevent widespread flash flood potential but would not be surprised to see a FFW or two overnight.

This was always going to be a later event here, and that hasn't changed. Interesting now that the cell north of Harrisburg has a TOR warning, and the one near Gettysburg may have one soon.

for everyone talking this down, there is no doubt that if you require supercells or a big ugly bow echo (like in PA) yesterday to be validate a threat, it's not a day for that. but there will be convection moving through the area later (maybe most likely from DC and points north), and our forecast soundings have that inverted-V structure which favors a downburst threat (it's shown in the high downdraft cape values). Shear and instability are modest for sure, but the watch is totally justified, IMHO.

alarming, to say the least. But the HRRR and HiResWindow ARW2 still like DC and areas north.

time to invoke this forum's scale for level of interest by user. It won't be any sort of high end day for sure, but I'm still feeling good about some organized line segments with severe potential tomorrow.

yep. about 70.

Had a glorious view of that York cell from southern Howard County. Could see a fair amount of lightning within it too.

yes, but there is still some organization and a clear sfc cold pool. Deep layer shear isn't quite as good as in some other CAMs, but the inverted-V sounding structure will definitely promote robust cold pool formation. I think we'll wake up tomorrow in a SLGT.

The next few hours are when a drop in dew points would occur if it does. The HRRR was most aggressive with that southwest of DC - will be worth watching. Still 65 here. Also, the day 2 kept MRGL here, but the discussion specifically mentioned a potential upgrade for our area in later outlooks. I personally think there was enough in the morning guidance to give us a day 2 SLGT, but I'll defer to the experts

Yes. The new MD mentions potential back building into north-central MD. Very little guidance has a good handle on the ongoing convection.

It's not going to be a huge day, but most of the various CAMs show about 40 kt of deep layer shear and inverted-V soundings, so some organization of cold pools is quite possible. The explicit reflectivity solutions across the hi-res windows, NAM nest, HRRR do show some organization.

Agreed. The 12z CAMs continue the idea of fairly good coverage of storms tomorrow. Deep layer shear isn't awesome, but it's probably enough for at least scattered SVR. The updated day 2 will maintain the MRGL for sure, and I wouldn't rule out a SLGT.

agreed. if something can race south earlier than progged, and the instability isn't killed by lowering dew points, northern and central MD could still be in the game.

We didn't have too many CAMs back then. The NAM nest was running, and it whiffed badly on that event. The HRRR did ok, but it was experimental, and not many people saw it. A key for today will be dew points. The HRRR is most aggressive in mixing them out (downsloping factor?). Most guidance mixes them out to some extent but try to have them recover closer to 00z, especially across northern MD. I certainly can't disagree with everyone ready to punt today, but I'm not ready to close the book quite yet, at least for those of us north of DC.

There will be some drying, due to what looks like modest downscoping, but the HRRR tends to overmix. I think that's why its dew points are a fair amount lower than most of the other guidance here tomorrow.

yes, but several other hi-res models look pretty good, especially for areas north of DC

I actually thought that the overnight guidance took a nice step forward for tomorrow, with several CAMs bringing activity through the area either late Wednesday or Wednesday evening. It's reflected in the HREFv3 (updated version coming later this year with extension to 48h) that shows decent changes of 40 dbz at both 21 and 00z tomorrow: (to be clear, these aren't huge probs, but it's a step forward for sure)

went back through the thread, and I'm officially issuing my mea culpa.

Soundings for Wednesday definitely look great. Shoutout to Kmlwx for noting this threat way in advance. While the dynamics as currently progged aren't great, a nearby front and small height falls could be enough. If we can trigger storms, the setup for SVR will be pretty robust.

definitely weakening. The evening period was always our best shot (if you back in the SVR thread, the guidance was pretty clear about this) at storms, but it's arriving just too late, as nocturnal cooling has really kicked in.

nice work, everyone! I remember that event quite well. I was warning people at work not to be on the roads at rush hour. That alert didn't work out too well......

The EML is definitely essential here if we want a wind system to survive its trip over the mountains. In 2000, a bow echo was racing east towards us, and SPC put out the rare PDS severe thunderstorm watch, and it completely crapped out trying to cross the mountains of West Virginia and Virginia. We ended up with showers that gusted to 30 kt.

Blue box issued. Montgomery and Howard are in the far southeastern corner, consistent with the idea that this first show will mainly be a fair distance northwest of the I-95 corridor.

I'd say overall that southern PA has a slightly higher threat for SVR than the DC area, with a clear CAM consensus for a batch of storms to develop by mid afternoon over far eastern WV and northwest MD and track northeast towards the York and Harrisburg area.

https://www.spc.ncep.noaa.gov/exper/href/ (under forecast tools) and if you want information on the upcoming HREFv3 upgrade: https://www.emc.ncep.noaa.gov/users/meg/hrefv3/