Jump to content
  • Member Statistics

    16,972
    Total Members
    7,904
    Most Online
    UHF120HzWave
    Newest Member
    UHF120HzWave
    Joined

2020 Mid-Atlantic Severe Weather - General Thread


Kmlwx
 Share

Recommended Posts

mcd1669.gif

   SUMMARY...Thunderstorms are expected to develop from northern
   Virginia into northern Maryland and southeast Pennsylvania by
   21-22Z. A few supercells capable of damaging wind gusts and isolated
   tornadoes will be the main threats. A tornado watch will likely be
   needed prior to 21Z.

   DISCUSSION...As of mid afternoon a progressive vorticity maximum was
   situated over southwestern PA and will continue east into the Middle
   Atlantic region during the late afternoon and evening. A band of
   low-topped convection has already developed in association with this
   feature extending into northern WV where instability is limited.
   Farther downstream, a lee trough resides just east of the central
   and southern Appalachian mountains. East of this feature
   temperatures have warmed to the upper 80s F with dewpoints in the
   low to mid 70s contributing to 1500-2000 J/kg MLCAPE despite very
   weak mid-level lapse rates resulting from warm temperatures aloft.
   As the corridor of deeper ascent attending the shortwave trough
   continues east and begins to overtake the western edge of the moist
   warm sector, additional storms will likely develop from northern VA
   into southeast PA. Winds in the 850-500 mb layer will undergo a
   modest increase with approach of the impulse, resulting in 35-40 kt
   effective bulk shear and 100-200 m2/s2 storm relative helicity. This
   environment should be sufficient for some organized storm structures
   including a few supercells capable of locally strong to damaging
   gusts and a couple of tornadoes through early evening.
  • Like 2
Link to comment
Share on other sites

Mount Holly updated AFD for severe threat this evening and tomorrow-

Quote

As we head through the late afternoon and particularly into this evening, expect showers back over western MD into west Virginia associated with a disturbance aloft to intensify into storms as they move east and conditions become more unstable with time. This should result in storms entering our western zones (SE PA into Delmarva) early this evening. Storm mode will likely be mixed but tends toward a broken line or clusters. Think there is the potential for at least some of these storms to be severe as ML CAPES will be in the neighborhood of 1000 j/kg with deep layer shear around 35 knots or so. 0-3 km shear will also be around 30 knots due to fairly strong belt of mid level winds. Best chance for severe weather looks to be in our western zones (especially MD eastern shore) with damaging winds being the main threat. However, due to good low level turning of the winds as well as shear still can not rule out the possibility of a tornado or two. LCL heights are also low. Limiting factor though will be deep layer shear being a bit less than optimal for tornadic supercells.

 

Quote

***Severe weather possible late day Thursday***

A weak, diffuse frontal boundary will sit across the area to start the day Thursday as the area will also continue to lie just south of the jet core aloft. Through the day Thursday there will continue to be disturbances moving through aloft roughly aligned with this boundary and the strongest of these will help develop a wave along the front by late day with another round of strong to severe storms expected. The day will start dry though with even some sunshine in the morning. However mid and high clouds increase during the afternoon ahead of this developing wave. Expect that storms will develop by mid afternoon to our west over central PA and move into the area by the late afternoon / early evening time frame. Conditions look to be even more favorable for severe weather compared to today and the SPC has upgraded our Delmarva zones as well as extreme southern NJ to an enhanced risk for severe storms. ML CAPEs look to reach the 1000-2000 j/kg range with deep layer shear around 40 knots. There will also be veering low level winds with the low level warm advection profile. The upshot is the environment looks to be favorable for supercells and all severe weather threats will be on the table...damaging winds, large hail, and even the threat for tornadoes. Again, highest threat looks to be over Delmarva but the threat exists farther north as well. Storm coverage also looks to be fairly widespread. Mode looks like it will tend towards multi-cell clusters with again, embedded supercells possible.

 

Link to comment
Share on other sites

3 minutes ago, Kmlwx said:

Today is looking super lame at least at the current moment. More eggs into the tomorrow basket perhaps. 

     Yeah, I'm a bit surprised, and I think that SPC is too.    Latest HRRR still suggests that the convection firing near the I-81 corridor will still become a bigger deal further east in a few hours.

Link to comment
Share on other sites

3 minutes ago, high risk said:

     Yeah, I'm a bit surprised, and I think that SPC is too.    Latest HRRR still suggests that the convection firing near the I-81 corridor will still become a bigger deal further east in a few hours.

There's probably enough moisture to support a threat for storms (some strong maybe) past sunset. For the superstitious/non-scientific side of us - this could bode well for our odds to see stronger storms tomorrow. We just can't seem to string multiple days together - the area of focus always shifts a little bit day to day - even when it seems like we'll be bullseyed for days on days. 

I personally thought that earlier mesoscale discussion was VERY high probs for something that had not even developed yet - and didn't look insanely good on modeling. 

  • Thanks 1
Link to comment
Share on other sites

10 minutes ago, Kmlwx said:

There's probably enough moisture to support a threat for storms (some strong maybe) past sunset. For the superstitious/non-scientific side of us - this could bode well for our odds to see stronger storms tomorrow. We just can't seem to string multiple days together - the area of focus always shifts a little bit day to day - even when it seems like we'll be bullseyed for days on days. 

I personally thought that earlier mesoscale discussion was VERY high probs for something that had not even developed yet - and didn't look insanely good on modeling. 

      SPC Mesoanalysis shows the supercell composite here increasing to 8 here over the next couple of hours.     Given that and most of the CAMs showing convection developing by now, I'm assuming that's why they went with such high watch probs.      I'd think that the convection to the west should do better as it moves east into the better environment, but we'll see.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...