George BM

Forecast Discussion Thursday, August 11, 2022, 12:04PM EDT An arc of heavy rain and embedded tornadic supercells associated with the warm front continues to lift northwards across northern MD. Lots of areas picked up a quick 2 to 4, even locally 5 inches of rain as it this wave of rain pushed through the region. There’s also already been a number of confirmed tornadoes with this activity. However, this is only an appetizer to what will transpire during the afternoon. The surface low associated with the remnants of Earl is currently located near Roanoke, VA w/ a min SLP of 994mb. The arc of heavy rain and embedded tornadic supercells associated with the warm front continues to lift northwards across northern MD as the mid-level dry slot moves over the region. This dry slot is allowing for more breaks in the clouds and as a result temperatures will continue to rise into the mid to perhaps even upper 80s in spots through the afternoon. With the very high moisture content of the low-levels of the atmosphere (dewpts 77-80+F and PW near 2.25”) coupled w/ the drier and slightly cooler mid-level airmass moving in overhead this will result in MLCAPE of up to around 2500J/kg. As the surface low interacts with the strong SWT approaching from the west in will deepen through the afternoon as it moves NE through the region resulting in strong to extreme low-level shear in ahead of it across the region (effective SRH 450-650 m2/s2). The very high low-level moisture content combined with the added sunshine will result in high 0-3km CAPE of 175-225+J/kg. All of these conditions, along with 50-60kt effective bulk shear, will combine to make for an environment that is very conducive for supercells producing long-track and significant tornadoes, particularly between 1pm and 6pm. Significantly severe wind gusts are possible as well given the 70+kt 800-600mb flow. Despite the fairly warm mid-level temps (500mb temps of around -4C) ample shear aloft will allow for large hail to be a threat with these supercells. Even outside of any storms the synoptic winds will be quite impressive w/ 35-45mph gusts. While this is just below Wind Advisory criteria, given how wet it’s been in recent days a few weak trees may still come down. By late this evening the winds switch to westerly as the low-pressure center moves northeast allowing drier and cooler air to filter in… allowing for better conditions for cleanup to get underway. "Forecaster": George BM

Wet to start.

34F for the low at IAD.

Yeah. I've been keeping one eye on early next week myself. We're also getting into better CAPE season.

2022 Max Temps: DCA: 88F IAD: 89F BWI: 87F RIC: 90F

There appears to be a little bit of smoke and/or dust aloft now as the sun is looking a bit more colorful (orangy reddish) than usual.

It honestly amazes me how @wxdude64 has kept at it consistently since October 1979. True dedication.

This is just a hypothesis of mine and I have no evidence whatsoever to back this up but... this recent trend of a colder pattern for the northern US and Canada come springtime. There are studies showing that the stratosphere is becoming colder (and stronger?) on average during the winter as the troposphere warms. Ex: This past February saw the coldest 50mb temps on record in the stratosphere over the high latitudes. I wonder whether the colder SPV during the winter allows it to survive longer (on average) towards spring without a significant disruption until the sun angle increases forcing it to weaken anyway. When it finally does weaken it may affect the troposphere and lead to more high-latitude blocking depending on how dramatic the disruption and/or SPV split is. Of course, the SPV and TPV are not always connected as seen earlier this winter and many other times in the past. Also, one could argue that there isn't enough data yet to know for sure how climate change is affecting the SPV/TPV. Like I said... just a hypothesis of mine. I have no concrete evidence to back it up.

Herndon, VA 11/30/2021: T 1/03/2022: 6.0" 1/07/2022: 4.8" 1/16-17/2022: 2.8" 1/20/2022: T 1/28/2022: 0.8" 2/13/2022: 1.4" 3/12/2022: 2.5" 3/26/2022: T 3/27/2022: T 3/28/2022: T 3/30/2022: T 4/09/2022: T 4/18/2022: T 4/19/2022: T ... Total as of April 19, 2022: 18.3"

I saw a few mangled wet snowflakes and ice pellets mixed in w/ the rain att in Herndon.

Bump.

The sleet has gotten a bit heavier. 42/30 at IAD.

Sleet here in Herndon as well. The April traces continue!

I wonder if some of us see some hail/gusty winds later with any convection/storms that manage to develop in the region. MLLRs will be fairly steep w/ 500mb temps of -20 to -22C. LLLRs look to be very steep as well. Weak instability (MLCAPE generally less than 500J/kg) owing to fairly low dews (45-50F) while a limiting factor may be slightly offset by the very steep LLLRs. Not expecting anything too crazy. Maybe some gusty winds and some hail like I mentioned.

CAPE is very pleased about this.

This is a nice site for one-min obs at IAD. http://iadasos.org/IAD/index.html

Now IAD is at 85/58.

IAD has hit 83F so far today.

@SnowenOutThere Yeap. I know what you're about to post.

Oh wow. Both of you chasing. That's a nice duo between you and your wife.

Herndon, VA 11/30/2021: T 1/03/2022: 6.0" 1/07/2022: 4.8" 1/16-17/2022: 2.8" 1/20/2022: T 1/28/2022: 0.8" 2/13/2022: 1.4" 3/12/2022: 2.5" 3/26/2022: T 3/27/2022: T 3/28/2022: T 3/30/2022: T 4/09/2022: T ... Total as of April 10, 2022: 18.3"

Or some severe and upper 70s?...

Got my April trace! Just had a light shower w/ big raindrops mixed in with graupel at 52F.

The bolt was a powerful 194kA positive CG. Lots of jumps, yelps and/or more personal "events" were probably had by peeps in the strike region... especially with no previous bolt to signify lightning in the area.