George BM

Looks like we just got the watch! PDS Severe Thunderstorm Watch 379 in effect until 1AM EDT THIS IS A POTENTIALLY DEADLY SITUATION... Hazards: Numerous extreme and potentially deadly wind gusts up to 200mph Numerous giant and potentially deadly hail events of 12+ inches in diameter A few tornadoes likely with an intense tornado or two possible Discussion: With near 20,000 J/kg MLCAPE, 3,000+ J/kg DCAPE and high-end extreme effective bulk-shear (120-150+kts) storms will fire up over the higher terrain over the next few hours as the cap continues to erode. With the shear in place supercells will be the main storm-mode. These supercells will move eastward off of the higher terrain through the watch area through the evening. This is a potentially deadly situation. There may be wind gusts equivalent to that of a violent tornado and hail large enough to penetrate through roofs and multiple floors/ceilings of homes and structures in general. While there is definitely the possibility of a couple tornadoes given the extreme effective SRH (700-1200 m2/s2) the large difference between the temperature and dewpoint temperature (145/96 temperature and dewpoint respectively at KIAD) cloud bases will be very high so tornadoes will have a difficult time sustaining themselves, especially given the extreme downbursts that may undercut their inflow. Nevertheless, a few tornadoes may still become strong briefly given the intensity of the updrafts that are expected. Storms should move out into the ocean by 4z (Midnight EDT).

@WinterWxLuvr Do you have memory of the July 5th derecho that year (1980)? Currently 87/54 at IAD.

What would you guesstimate that the strength of the wind gusts were?

Correct. It was, however, only 5 degrees above the NNW horizon yesterday evening 80 minutes post-sunset (I did not see it). IIRC it will be 10 degrees above the horizon 80 minutes post-sunset by tomorrow evening (7/14) and up to 20 degrees above the NW horizon by 7/19 at the same time relative to sunset. All the while, however, it will probably ever so slowly be getting dimmer night by night as it moves away from the sun.

I was actually out for an early morning run (4am hour) this morning but never saw it despite clear skies. I was looking towards the northeastern horizon for it as I ran.

Yeap. Philippe Papin has a nice short thread about the feature from this morning.

@WxWatcher007 This is not going to develop into a tropical cyclone, obviously, but check out the convection associated with a vort-max feeding off of the 80F water temperatures of Lake Erie. Pretty neat.

IAD has also hit at least 90F for today.

The most exciting weather event of the year thus far locally.

Is her name one of these three? : Laura Paulette Sally

Nope. Nope. Nopity nope. Imagine trying to go for an early morning run with temps in the upper 80s with heat indices in the upper 90s. Currently a, by comparsion, comfortable 84/68 at IAD.

Is anyone else hearing some strange sounding thunder? Little quick pops/booms yet looking at the radar I see nothing of significance anywhere close by. Is anyone else hearing this?

Probably in the 1am hour. Radar image is from 5:33utc (1:33am edt). The downpours were moving SE.

And just where have YOU been? We are running 40-50+ degrees F above average with no sign of any snow coming at all. Why is there no panic room yet?! There are no survivors left on these boards expect for me... and probably Mappy. The screams from the tormented souls are absolutely deafening!

July weather is here. Starting out not too unusual.

Into the second half of the year we go.

Meanwhile at this moment 8 years ago........

I didn't mean until you're 'passed out drunk' away... I meant just drink 'for a good feeling' away.

@stormtracker and @mappy. Happy belated birthday to you both. Everyone else... drink away.

Indeed. Cells taking advantage of decent speed shear with otherwise modest instability would do that.

Why do you keep on living my nightmares?

75/56 at IAD right now. The drier air has moved in.

@BristowWx Claim away my friend!

PDS Tornado Watch 333 in effect until 9PM EDT June 23 2020 Hazards: Numerous long-track strong to violent tornadoes expected Numerous significant wind gusts to 115 mph likely Widespread large hail with scattered giant hail events to 5" in diameter likely Discussion: A well-developed and intense MCS/derecho continues to move through much of West Virginia AOA 65kts. The environment within the watch area is characterized by extreme instability (MLCAPE 7000-8000+ J/kg), impressive shear (EBWD 70-90 kts), high moisture content (Pwats of 2-2.25"+) and strong DCAPE (1200-1600+ J/kg). As the MCS moves into the mountains additional supercells are expected to rapidly develop by 19-20z along the foothills/Blue ridge ahead of the main line and move east through the DC and Baltimore metropolitan areas. With the extreme low-level shear also in place (effective SRH of 500-900 m2/s2) these cells will have a high risk of producing long-track and potenially violent tornadoes as well as giant, life-threatening hail. The greatest wind threat over this region will come with the main line of storms between 20-23z with high-end severe winds (possibly in excess of 115 mph). Storms will move out of the watch area by 00z. Forecaster: George BM Look at the 20z Mesoscale Analysis! Unreal. And just look at that sounding from the 20z special balloon launch!

Wow! I'm feeling extremely good about our storm prospects for later in the day! CAPE is already looking great as of 15z and shear will become extreme by the mid-late afternoon hours. All mesoscale guidance agrees on a very intense MCS screaming east through our region late this afternoon and into the early evening hours with supercells (likely tornadic) forming ahead of the main line by the mid afternoon hours. SPC already has us and a large portion of the Mid-Atlantic/Ohio Valley in a high risk for wind and tornadoes as of the 13z update!