2019 Mid-Atlantic Severe Wx - General Discussion

[ErinInTheSky]

Looks like I am JUST in the enhanced risk in Germantown. Give me a nice severe storm.

[mappy]

16 minutes ago, jewell2188 said:

Tired of slight risk!! When was the last enhanced or mod risk we had ??

drive an hour or so north and you'll find it. 

[mappy]

SPC overnight outlook seems uncertain for today. lots of the factors in play, which seems par for the course for us around here. 

Quote

...Upper Ohio Valley eastward toward New York, Pennsylvania, and Maryland... The forecast in this region will be somewhat complicated by mid-morning to mid-day convection expected to traverse the region from west to east - particularly across Pennsylvania. Nevertheless, models indicate the development of weak to moderate instability ahead of a cold front that will migrate southward across the region. This destabilization will occur amidst a strongly sheared airmass, with 30-40 kt westerly 850 hPa flow veering and strengthening to northwesterly aloft. Convection is expected to evolve into a series of mixed modes (both linear and cellular) with tornadoes, hail, and damaging wind gusts all possible. Convection will migrate southeastward toward Maryland, Delaware, and New Jersey during the evening before waning with near-surface stabilization late in the period.

If we can get out of the clouds and warm quickly today, it will bode well for us later. 

[mappy]

updraft swaths, from 3K NAM

La Plata? 

[frd]

Seems the HRRR idea of the mid afternoon storms having more impact than the Midwest complex slated for evening has gained a "bit" more support. But, as Mount Holly NWS states the Midwest complex needs to be watched 

Great job by Mount Holly in the discussion this AM. covers everything in detail ! 

This is just a snippet 

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

630 update:

Showers and thunderstorms will continue to move across northern
portions of the forecast area (generally along and north of
I-78) for the next couple hours. Occasional bursts of moderate
rain will be the main concern with these AM storms. Regarding
the stronger storm potential later in the day 06Z guidance has
trended a bit more towards the HRRR solution in the morning
discussion e.g. an initial line of stronger storms passing
through the area mid-afternoon and then less activity in the
evening (generally missing the area to the north). Consequently
the line of storms currently extending through the Midwest will
bear watching.

 

 

[Kmlwx]

Sun is out here with thin clouds around. On my way to work (currently between Silver Spring and Rockville) 

[high risk]

The CAM solutions are a bit mixed, mostly based on how they evolve the ongoing OH storms.    The "good" CAM solutions have storms forming on the outflow of that system (or least some sort of remnant boundary) and rolling through here during the 3-5pm timeframe or so.   Mappy correctly notes that getting some good heating would help a ton, and most guidance makes that happen.      The shear definitely supports some supercells in addition to line segments, although I think it's more of a hail/wind day than a tornado day.

[mappy]

2 minutes ago, high risk said:

The CAM solutions are a bit mixed, mostly based on how they evolve the ongoing OH storms.    The "good" CAM solutions have storms forming on the outflow of that system (or least some sort of remnant boundary) and rolling through here during the 3-5pm timeframe or so.   Mappy correctly notes that getting some good heating would help a ton, and most guidance makes that happen.      The shear definitely supports some supercells in addition to line segments, although I think it's more of a hail/wind day than a tornado day.

Agreed. I think the 5% tornado threat per SPC is generous for us. 

If any one wants to see a good storm, they have to hope things go discrete before the main line comes through. otherwise, you'll get embedded cells in the line that won't be nearly as exciting. 

... if you're a weenie like me who wants a really good storm  

[Eskimo Joe]

55 minutes ago, jewell2188 said:

Tired of slight risk!! When was the last enhanced or mod risk we had ??

The LWX forecast area averages 3 Enhanced Risks per year and 1 Moderate Risk per 3 years.

[frd]

13 minutes ago, Eskimo Joe said:

he LWX forecast area averages 3 Enhanced Risks per year and 1 Moderate Risk per 3 years.

Wow,  never knew that Moderate Risk only averages once every three years.  That explains a lot about the frequency of severe weather in our parts. 

[George BM]

3 minutes ago, frd said:

Wow,  never knew that Moderate Risk only averages once every three years.  That explains a lot about the frequency of severe weather in our parts. 

Yeap. Our last moderate risk was actually a while ago June 13, 2013. (6 years ago)

[Kmlwx]

Yeah the most recent HRRR runs pretty much suck - just isolated activity. 

[George BM]

Just now, Kmlwx said:

Yeah the most recent HRRR runs pretty much suck - just isolated activity. 

It's also killing off the MCS way too fast.

[Kmlwx]

Dews need to come up in a hurry. We are still in the low to mid 50s for dews at best. That'll help a lot with instability. Hopefully we can advect some juicy dews in. 

[high risk]

1 minute ago, George BM said:

It's also killing off the MCS way too fast.

    THIS.     If you look at what it has at 13z compared to radar, it's failing on the OH storms.      The earlier runs had a much better handle on that activity and look much better for us.

[Eskimo Joe]

Just now, Kmlwx said:

Dews need to come up in a hurry. We are still in the low to mid 50s for dews at best. That'll help a lot with instability. Hopefully we can advect some juicy dews in. 

It's not happening here today.

[Kmlwx]

Just now, Eskimo Joe said:

It's not happening here today.

I think I might slowly be turning into you...should I be worried? 

[frd]

Just now, Eskimo Joe said:

It's not happening here today.

I know your insight is much valued. But, maybe we can at least get some rainfall. In this case for the plants.

 

[H2O]

1 hour ago, mappy said:

updraft swaths, from 3K NAM

La Plata? 

That starts near my house.  I'm down.  Wall cloud, funnel and then let her rip, potato chip across the Potomac

[Kmlwx]

Just a little humor - the CIPS analogs from the 0z run for the 24hr mark have 5/31/2008 as an analog. I mention this because a few days later that year on June 4th we had one of our more impressive severe weather outbreaks in the last 15 years. That was a lot of fun IMBY. 

SET THE TABLE

[Eskimo Joe]

16 minutes ago, frd said:

I know your insight is much valued. But, maybe we can at least get some rainfall. In this case for the plants.

 

Yes, we need rain...too muc pollen in the air!

[Kmlwx]

SPC seems to hint at a chance of an outlook upgrade later pending trends. 

[high risk]

I'm still not sure about coverage, but I do think there will be SVR in the DC-Baltimore corridor later today.

[mappy]

SPCs 13z outlook wording for those who don't know where to read it, or are too lazy  

Quote

...Ohio Valley to Mid-Atlantic... Scattered thunderstorms are expected through afternoon, moving eastward across the outlook area, with damaging gusts, sporadic hail and the potential for a few tornadoes.

Low-level warm/moist advection from the southwest is expected to combine with diabatic surface heating to destabilize the boundary layer across the region, ahead of the vertical-motion plume related to the MCV and its attendant trough. In the presence of weak MLCINH and areas of surface confluence/convergence, this should be sufficient to support convective development, perhaps including an eastward shift/re-intensification of the ongoing arc of convection over portions of OH. Surface dew points will increase into the 60s, beneath ribbons of residual Mexican EML air advected from the southern Plains. This should support the development of MLCAPE generally in the 800-1500 J/kg range, potentially reaching 2000 J/kg on a brief/local basis. A well-mixed sub cloud layer will support strong-severe thunderstorm winds, as well as maintenance to the surface of severe hail. Despite slightly veering to unidirectional winds with height, sufficient low-level and deep shear is forecast, with a component orthogonal to the main belt of convective forcing, to support a blend of multicell and supercell modes. Slightly greater moisture/CAPE but weaker deep shear will occur with southward extent through central/southern VA and the corresponding latitudes of Chesapeake Bay and the Delmarva Peninsula.

Isolated to widely scattered thunderstorms, also offering some severe threat, may form behind the initial arc this afternoon as well, but sufficient destabilization and air-mass recovery to support an organized severe threat with this regime remains quite uncertain/conditional at this time. Should confidence increase in this scenario, as mesoscale diagnostic/prognostic trends warrant, additional or reshaped probabilities could be required in one of today's outlook updates.

i remain neutral for now. all the ingredients are there for discrete cells to develop. 

[Eskimo Joe]

11 minutes ago, Kmlwx said:

SPC seems to hint at a chance of an outlook upgrade later pending trends. 

I mean, the setup is there but it's super conditional today on all the dominoes falling in symphony.  I'm all but out on this, but there might he one or two rogue cells down this way where someone jackpots. 

[H2O]

DP up over 60 now.  

[Eskimo Joe]

39 minutes ago, Kmlwx said:

I think I might slowly be turning into you...should I be worried? 

No you're just learning to be cautious.

[87storms]

i like that there's already sun (first checkbox) and i like that the airmass is a little stagnant (light breeze).  i don't hate our chances for pop ups later...hopefully it won't be too hit/miss.

[frd]

From Severe briefing NWS Mount Holly released this AM. For the NE part of the sub forum 

 

 

  

[Mrs.J]

Current conditions over in Frederick are overcast skies 64.9 74/56 with light winds out of the SE