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Posts posted by high risk
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48 minutes ago, Stormchaserchuck1 said:
This low pressure looks amped for severe wx chances tomorrow
Yes, but it's progged to split and then shear out a lot tomorrow as it comes east. Instability will be good, and there may be just enough shear for a few organized cells with some wind potential, but it sure doesn't look like a big day. Hell, I'm thrilled just to have a threat of convection again.
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classic playbook here: MCS dies on approach in the early morning hours but limits heating for the late afternoon show
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1 hour ago, yoda said:
There is a MRGL risk on Friday from SPC
That's for the afternoon cells. The morning MCS would be "regular" thunderstorms, but I hope it plays out. It's going to be an MCS party for the next 36 hours in the Mid-Atlantic - just a question of who gets invited.
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6 hours ago, Eskimo Joe said:
The flood watch is absolutely justified. PWATs are in the 95th percentile regionwide, with minimal steering flow aloft.
The flood watch was absolutely justified, but due to the PWATS and existing wet ground. The storm motions off of the 12Z IAD raob were faster than 30 mph.
The severe box was less justified. It verified well due to a bunch of reports at the far southern end, but most of the box was lacking in reports.
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9 minutes ago, mappy said:
Okay so some tweets I’m seeing about sneaky overnight tornado threat is real? I am northern MD…
I'm not sure that it's that sneaky if it's covered by an SPC 5% TOR risk. But yes, the shear is good and getting stronger, and forcing is arriving. The only question is whether the storms can root into the boundary layer. I'd say that's quite uncertain.
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1 hour ago, Stormchaserchuck1 said:
Still some instability here in Harford Co. I wouldn't be surprised if the severe risk extends back a little west for tomorrow.
The question is does the instability get swept off to the east by the approaching cold front before storms can initiate. The evening guidance now seems to be in fairly good agreement that storms will initiate along and maybe even slightly west of the 95 corridor by early afternoon. Even though the best chance of organized severe will be further east (and I'm talking DC, as northeast MD is in a good spot), the shear along the I-95 corridor might support splitting supercells.
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8 minutes ago, Kmlwx said:
The cell NE of Capon Bridge already seems to have some minor rotation with it potentially.
Agreed. And it should be rotating - the wind profiles definitely favor rotation, and the profiles are stronger to the east and northeast of those cells. I just wonder if it's rooted above the boundary layer. Would not be surprised if an MD came out for northern MD / southern PA at some point in the next couple of hours.
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1 hour ago, Kmlwx said:
The 23z HRRR gets northern Maryland with some activity overnight but seems it doesn't like the threat of an overnight batch as much (or at all) like some prior runs wanted to fire up.
The HRRR has been pretty consistent keeping the overnight activity north of the DC area, and storms are starting to fire now in northeastern WV. The shear tonight supports a tornado threat; it's just unclear whether the storms will be surface-based.
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2 hours ago, Kmlwx said:
I hope they have a fix for the HRRR over mixing in the works. It seems to do it EVERY time.
There will be no upgrades to the HRRR since it's slated for retirement.
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12 minutes ago, Kmlwx said:
Most of the guidance seems to be in agreement that there may be a late afternoon/evening round of showers/storms - but much of the guidance is pretty weak with that stuff. NAM and RAP seem to think best parameters may actually show up during the 3z-6z window...while it will suck for daylight, it's possible this can still perform. Wonder if the CAPE will remain surface based that late, though...may end up being elevated (admittedly I haven't looked closely at the soundings).
I'm not very intrigued for the early round...and I do wonder if that is going to stabilize some areas too much to have the nighttime round of storms.
Another storm day when I'm at work all day....
That's mostly how I see it too. I'll disagree on round 1 being "weak" - the HRRR simulated reflectivities are fine; isolated SVR seems likely, but I question the TOR threat with the weaker low-level winds. Shear cranks up after dark, but we'll be fighting decreasing instability. To me, the biggest potential overlap between increasing shear and still-sufficient sfc-based instability will be northwest of the DC area.
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Looking at the 00Z CAMs, I'd put the Monday TOR threat as an SPC 2% area instead of 5 for the local area due to weak low-level winds and limited storm coverage. The bigger TOR threat might be western MD and adjacent parts of WV/PA in the early evening.
There are also some timing differences for Tuesday. HRRR would require that the SLGT area be extended back west of DC, but it seems like an outlier for now.
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4 hours ago, Round Hill WX said:
Well aren't we special! Monday....
The 5% makes sense, given the southeasterly low-level winds progged by all guidance. What's keeping us from a higher threat is fairly weak surface wind speeds as well as lower speeds in the 900-700 mb level. If the low-level wind fields end up stronger, we would have more significant TOR potential.
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10 minutes ago, yoda said:
45 WIND ADDED ON 1730Z OTLK
I'm out of town tomorrow, so LOCK IT IN.
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13 minutes ago, dailylurker said:
Where is everyone? Hangovers? Tomorrow looks interesting. I'm going to head out towards Hagerstown tomorrow for work. I'm thinking about doing some storm chasing on my way back east alone 70. That area looks twisty.
The previous dozen posts discussing the higher end potential for tomorrow aren't enough for you?
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I'm still thinking SLGT for tomorrow for areas west and southwest of DC with the MRGL expanded into the DC-Baltimore corridor. Maybe we end up SLGT, but instability looks very limited. There might be more of a flash flood threat, although the dry week we just had might preclude that.
I'm fully expecting a Day 2 ENH for Monday. I think that there is enough in the CAMs to pull the trigger.
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2 hours ago, yoda said:
I've never seen such high numbers of STP that the 18z NAM NEST shows across our area
Granted it's just one model run and it'll probably be different at 00z, but 6 to 8? Wow
Good amount of PDS TOR tags too on the soundings across the region
It's partially driven by huge CAPE numbers which are being caused by the usual NAM bias of having dew points that are too high. That said, the shear will be good, and it will still be a very volatile environment on Monday.
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1 hour ago, Eskimo Joe said:
I'll put all my chips in on Sunday.
Sunday is challenged by very limited instability. But if we can get more unstable than currently progged, any storm that interacts with the boundary to the southwest could spin for a bit. I like the chances of evening convection moving southwest to northeast, but we have work to do to have it be severe.
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Looking at the morning CAMs, looks good for widespread Sunday evening convection. Low-level shear is interesting near the warm front, so the potential is there for a few spin-ups, but lack of instability and lack of discrete cells should temper the threat (maybe higher south and west of DC).
Monday has good potential to be an ENH day.
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1 hour ago, Kmlwx said:
"couple of tornadoes" or "isolated tornadoes" are such blanket terms.
It's those super rare times when you see "significant tornadoes" or "isolated strong tornado" that your ears perk up.
Yes, but they usually don't throw those terms around beyond day 2. Their usage of that wording reflects that the progged shear and especially the low-level shear Monday have been progged to be seasonably strong. I personally don't like them discussing tornado threats at this range, but I do understand what they're seeing.
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I haven't been a big fan of today's potential, because while there is some decent flow in the upper levels, the shear through the majority of the cloud layer sucks. That said, as others have pointed out, there is modest CAPE and decent downdraft CAPE, so there is *some* potential. IF the HRRR idea of an organized line with a coldpool is correct, the threat might be a bit higher than thought:
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Finally seem to be getting consensus now on a single line impacting much of the area, or at least from Alexandria or so northward. Looks like an early show, with the line initiating near the I-81 corridor by late morning and rolling into the DC metro area sometime between 1 and 3pm. The lack of lead convection increases the severe threat, and there is probably enough deep layer shear to justify the SLGT risk, although the lack of shear in the sfc-4 km depth might temper the threat a bit.
With only one round of convection, and it progged to be progressive, the flash flood threat is a bit lower than initially thought. That said, 2" PW values will create torrential downpours, and the areas that are soggy from the past few days will likely have problems.
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I completely understand the lack of trust in the guidance, given the past few days, but the HRRR wants to light up the DC-Baltimore corridor between 5PM and 10PM in the last two cycles.
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17 minutes ago, Kmlwx said:
That's the only activity that looks remotely interesting for the moment. Will see how this stuff looks as it heads into Loudoun - but pretty unimpressive thus far. That cell you mentioned might end up being what the 6z NAM showed with the UH track - but perhaps a little further south than forecast.
As you and I both noted earlier, the morning CAMs had the current cells coming off of the mountains and evolving into the show. But the new HRRR doesn't do much with them and instead initiates the show later. Certainly seems plausible with the current cells struggling.
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1 hour ago, George BM said:
Watching what that batch of convection in eastern WV will do over the next few hours.
Would expect an MD within the next hour as that convection approaches the better environment. The CAMs all turn that into either the show or part one of the show.
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2023 Mid-Atlantic Severe Wx Thread (General Discussion)
in Mid Atlantic
Posted
And of course SPC issues a SLGT right after I type that.....