BP's reluctance to declare the capping operation a success is understandable, especially when you look at the string of failed fixes and low-ball oil flow estimates from the early weeks of this disaster. Anybody remember "top kill?” After 3 months of this environmental horror show we're all anxious to hear the words, "we have killed the well." But we're not there yet. The experts keep telling us much can still go wrong. Even if the capping turns out to be an unqualified success, they've got to complete the relief wells in order to close it off for good – and that too is not a sure thing.

On tonight's broadcast we will look at the factors behind the "cautious optimism" being expressed by the folks in charge of the operation and the unknowns that are still keeping them awake at night.

In the meantime the rest of us -- especially those who live and make their livings along the Gulf -- can only look at the underwater video and take comfort in the fact that at least for now there is no oil escaping into the sea. Tonight we'll also hear from some of those residents, and look at the cleanup challenge ahead.

I hope you're having a good Sunday. We'll look for you later on NBC Nightly News.

If you're suffering in the heat today here's an interesting fact you can use when someone asks "is it hot enough for you?" According to the National Climatic Data Center, the period from January to June was the warmest six months on the planet since records were first kept. This current heat wave blankets a big part of the country this weekend. Here in the east it's that wicked combo of heat and humidity, while the west is baking in a virtual dry oven with temperatures in some spots reaching into the triple digits. I found myself fantasizing about winter today, which is a sure sign the heat is getting to me (in January I'll be blogging about the joys of July). We'll have more on the heat on tonight's broadcast.

We're of course also keeping tabs on the undersea drama in the Gulf of Mexico. A lot of eyes are keeping watch on that new containment cap over the ruptured well, and so far all the readings look good -- meaning no signs of leaks. We'll update the operation and look ahead at the next major challenges in this disaster.

Remember all those pets that needed homes after Hurricane Katrina? The oil crisis threatens to create a similar predicament for those suffering economic hardships in the Gulf and our Michelle Kosinski will share some of those heart breaking stories on tonight's program.

Thanks for checking in. We'll look for you tonight on NBC Nightly News.

I can't recall exactly when I read "To Kill a Mockingbird." I do recall that as for many of you, it was required reading at some point in my education. I also remember its raw and layered portrait of the Jim Crow era South – told through the voice of a child – resonated with me for a long time. Harper Lee's Pulitzer Prize-winning work turns 50 this weekend. Unfortunately I have forgotten some of the key plot twists, and thought this might be a good time to re-read this American classic. But I have to admit I was a little surprised to find Amazon.com customers gave it only 4 out of 5 stars. Certainly a good rating, but I guess not what I expected for a cherished literary piece. I'll read it again and judge for myself. In the meantime, we'll take a few minutes on tonight's broadcast to look back on "To Kill a Mockingbird," and examine why it endures – 4 stars not withstanding – as a must-read for so many Americans.

Also, NBC News science and environmental expert Jeff Corwin is going to join us live from the Gulf to show us how scientists are desperately trying to save already endangered sea turtles from the ravages of the oil slicks now covering their habitat. We'll also have more encouraging reports coming from BP on progress being made on two fronts to both contain the leak and plug the well.

I hope you'll join us tonight for NBC Nightly News.

The video feed from below the Gulf of Mexico is even more sickening to watch today. The oil is now flowing unchecked into the water after robots removed the containment cap that was helping to capture some of the escaping oil. It could flow like that for a couple more days. Okay, that's the glass half empty assessment. Now for the glass half full. By removing the cap, BP engineers will now position a new, better fitting cap that -- if all goes perfect -- could effectively contain the leak by early in the week. There are plenty of ifs and wiggle room built into the timetable of this operation, but it's hard not to get the feeling that the end game, as far as stopping the flow, could be in sight. Our Anne Thompson, who has been on this story from the beginning, will tell us what the game plan is, and update us on where it stands.

We'll see you later for NBC Nightly News.

I hope you're having a good Independence Day weekend. No rest for the weary in the Gulf of Mexico of course, but just might be something to celebrate. BP's new executive in charge of the oil response says the relief well, meant to cap the oil leak, could be finished sometime this month, ahead of schedule. That declaration included a lot of "ifs" about the weather cooperating and other variables. Given their track record, it's understandable that up until now BP has been trying to under-promise progress, predicting they'd finish the relief well in August. NBC's correspondent Thanh Truong has been out with the Coast Guard today and will have a better read for us on where things stand on our broadcast tonight. Kerry Sanders is also going to give us some insight into how those undersea robots tending to the well are actually operated. It's delicate work, especially given they're operating 5,000 feet under the surface and their operators are in Houston.

As many of us find time to celebrate and enjoy some time off this holiday let's remember all the hard working folks on beaches, ships, and seaborne platforms who will be pushing straight through the weekend trying to stop and contain the damage from this horrible scourge.

In the meantime we'll look for you tonight for NBC Nightly News.

Greetings from a hot and steamy New York City. It seemed like such a good idea to walk to work today. Sitting in front of a fan for 15 minutes once I got here turned out to be an even better idea. Memo to self: New York City cabs are air-conditioned.

We're juggling a lot for tonight's broadcast including more on what tropical depression – but soon to become a tropical storm again – Alex is going to do once it gets back out over the Gulf of Mexico. We'll have more from Anne Thompson's extraordinary tour of the rig where crews are drilling one of the relief wells that are expected to stop the oil leak once and for all. We're previewing this week's Senate confirmation hearing for Elena Kagan's nomination to the Supreme Court. Also, Richard Engel has the story of one of the deadliest attacks on U.S. forces in the war in Afghanistan, and the parents of the dead who refused to stop pressing the Pentagon for answers about how and why they died.

I hope you will join us tonight for NBC Nightly News.

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