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Kmlwx

2019 Mid-Atlantic Severe Wx - General Discussion

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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. 

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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. 

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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.

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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.

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

 

image.thumb.png.6ea5757127156a7220b6cdbf41d9ef24.png

 

  

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Just now, Kmlwx said:

Clouds have thickened up here in Potomac, MD - need to get these out of here. My feelings on today are heading downward not upward at the moment. 

Getting some sun breaking through up here in Frederick currently. 

 

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2 minutes ago, Kmlwx said:

Clouds have thickened up here in Potomac, MD - need to get these out of here. My feelings on today are heading downward not upward at the moment. 

pretty typical. like high risk said, i think we still see some storms, but whether they are as severe as some of us would like to be, remains to be seen. 

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5 minutes ago, mappy said:

pretty typical. like high risk said, i think we still see some storms, but whether they are as severe as some of us would like to be, remains to be seen. 

Yeah - everything is far too conditional today for a shot at a moderate I think. In fact, if there was a gun to my head I'd actually learn more towards shrinkage of the ENH or elimination of it. 

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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1028 AM EDT Thu May 23 2019

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure will remain offshore today and a southerly flow
will continue to usher in warmer and more humid conditions. Max
temps will top off in the mid to upper 80s across most locations
with a few locations possibly approaching 90 degrees. The
increased heat and humidity will lead to an unstable atmosphere.
Latest modified KIAD sounding shows around 1-2KJ/KG of MLCAPE
developing this afternoon, with some locations possibility
reaching over 2KJ/KG. A convective system is also tracking
through the Ohio Valley into western Pennsylvania this morning.

This system will track through our area this afternoon into this
evening. Latest thinking is that this system will weaken as it
approaches late this morning, but re-development is possible
across our area this afternoon into early this evening due to
the increasing instability. Strong deep layer shear combined
with the instability suggests that severe thunderstorms are
possible this afternoon into this evening. Deep layer shear will
most likely be around 40-50 knots. Current thinking is that the
best chance for strong to severe storms will be near and east of
a pressure trough that should set up near the Blue Ridge and
Catcoctin Mountains this afternoon. However, given the strong
shear profiles and relatively favorable mid-level lapse rates,
there is a threat for severe storms across the entire area. Do
think that overall coverage of the severe storms will be
isolated to scattered since the lifting mechanism is relatively
weak. Locally damaging wind gusts and large hail are the primary
threats, but an isolated tornado cannot be ruled out due to the
strong shear profiles.

In preparation for today`s potential severe threat, ensure you
and your family have multiple ways to receive warnings and have
a plan and place to take shelter if needed.

Another round of showers and thunderstorms are possible later
this evening ahead of the cold front. Instability will be more
limited, but the shear profiles will be quite strong. Therefore,
an isolated severe storm cannot be ruled out with this activity,
especially across northern Maryland/northern VA/eastern WV.
Activity will diminish overnight as instability continues to
decrease and the cold front drops farther south.

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^^ said it yesterday. without the lift, we won't get anything discrete out ahead of the front. LWX agrees. 

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Tracking something like June 4, 2008 again would be a treat. I remember watching the event start to unfold at lunch and in my 6th period class where I had access to a computer. Sprinted home through the woods (I lived close) after school to fire up all of my radar programs (I had StormLab at the time). 

I was a total weenie back in 2008...

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1 minute ago, mappy said:

^^ said it yesterday. without the lift, we won't get anything discrete out ahead of the front. LWX agrees. 

        I'd argue that our best chances are ahead of the front, with redevelopment on the flanks of whatever is left of the ongoing OH/WV storms as they move east.    That front is going to arrive too far past peak heating for DC metro, but it could be ok for your area up north (as per the 12z NAM nest).   Our best chances further south are in the mid to late afternoon timeframe - I'm not as bullish as I was yesterday, but the CAMs overall are not doing well with ongoing upstream convection.     I'm prepared to bust badly with my optimism.

       

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2 minutes ago, high risk said:

        I'd argue that our best chances are ahead of the front, with redevelopment on the flanks of whatever is left of the ongoing OH/WV storms as they move east.    That front is going to arrive too far past peak heating for DC metro, but it could be ok for your area up north (as per the 12z NAM nest).   Our best chances further south are in the mid to late afternoon timeframe - I'm not as bullish as I was yesterday, but the CAMs overall are not doing well with ongoing upstream convection.     I'm prepared to bust badly with my optimism.

       

i hadn't checked 12z NAM yet. I see what you mean though. It has some nice cells pre-front around 18-19z, followed by the front later on 00-01z or so. 

i just know that we tend to need a lot of things to work out well here, and even one thing failing sends everything crashing downward. im sure somewhere there will be thunder and lightning. i'm just not sure how "enhanced risk" worthy it will be, ya know? 

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17 minutes ago, Kmlwx said:

Tracking something like June 4, 2008 again would be a treat. I remember watching the event start to unfold at lunch and in my 6th period class where I had access to a computer. Sprinted home through the woods (I lived close) after school to fire up all of my radar programs (I had StormLab at the time). 

I was a total weenie back in 2008...

What happened June 4, 2008? I don't remember that at all. Really the only true severe system I remember well was the derecho. Obviously there are certain thunderstorms that stick out in my mind.

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1 minute ago, osfan24 said:

What happened June 4, 2008? I don't remember that at all. Really the only true severe system I remember well was the derecho. Obviously there are certain thunderstorms that stick out in my mind.

https://www.weather.gov/lwx/events_20080604

https://www.weather.gov/lwx/events_20080604_lsr

http://voices.washingtonpost.com/capitalweathergang/2008/06/june_4_2008_severe_weather_out_1.html

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Been cloudier than I expected today, but that's the case with 95% of our severe weather days it seems.

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Maybe its just me but latest meso parameters aren't ugly the the DMV area.  CAPE is healthy just off to the west and plenty of shear around

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