on our broadcast tonight, wild weather. tonight, has the american west on a crisis footing and there are fears it could get even worse. then there's what they're dealing with overseas. safer skies. last christmas, a bomber tried to bring down a plane to detroit. tonight, we go behind the scenes with the men and women who are flying undercover. does it work? a lot of people take it for the common cold. tonight, the experts are ready to weigh in. "making a difference." young people singing their hearts out for the cause. and why some experts say tomorrow will be the darkest day of our lives. turns out the reason isn't all that bad. "nightly news" begins now. captions paid for by nbc-universal television

good evening. california is getting pounded tonight by the most massive and relentless storm, coming in off the pacific and just pouring water on the west coast. it has caused a genuine emergency and for now it shows no signs of stopping. meaning a lot of people are now heading into another nervous night. hundreds of homes are threatened, thousands of people have been evacuated. it's been going on for days already. and a lot of records have already fallen. in some places, lives and property are in danger tonight, and we begin with nbc's miguel olmagare. he's in flintridge, california tonight. good evening. >> reporter: heavy rain has been pounding this area for five consecutive days and residents are trying to push flood waters from coming into their homes. in fact, right now they are still filling sandbags and more wet weather isn't over.

the foothill communities outside los angeles are beginning to look like a war zone. streets lined with sandbags, homes fortified with retaining walls. 12 inches of record rainfall has pounded these hills. the same area scorched by california's largest wildfire in 2009. now the drenched mountains threaten to slide into neighborhoods below. more rain is on the way. skeet mccolley has evacuated seven times in the last year. >> we live in fear, you know. you don't know when it's going to happen. >> reporter: in los angeles, the highway patrol responded to 355 car crashes in just four hours. 20 miles of the pacific coast highway is shut down by flooding. >> the pch says there's about three feet of mud and debris. >> reporter: the entire state affected, from the central valley to coastal cities. in kern county, flooding forced 2,000 to evacuate to higher ground.

in central california, homes are under water. in oceano, they got out any way they could. >> it's gotten to the point almost where we can't get in and out anymore. >> oh, my gosh. >> reporter: in the northwest, snow and ice led to a series of pileups in spokane, washington. in the colorado rockies, a white christmas in vail and aspen, if you can get there. a similar mess in california's sierra nevada. >> i'm chris warren with the weather channel in truckee, california. after a stormy weekend, more than a foot and a half of snow for some of the ski resorts and for residents, it's time to clean up. >> reporter: cleaning up, but according to forecasters, the worst is still to come. the forecast calls for 3 to 8 inches of rain in this area by wednesday. flash flood advisories are in effect across this region. a real washout all across california. brian? >> miguel starting us off from

flintridge, california. miguel, thanks. then there's the situation in europe where the holiday plans of thousands of people have been ruined. canceled because of a crippling situation there. canceled flights, canceled trains, lots of frustrated travelers. many of them families. our own stephanie gosk is at london's paralyzed heathrow airport tonight. and stephanie, a british friend of mine e-mailed today to say "this country is in shambles," at least it must seem that way where you are tonight. >> reporter: it certainly does, brian. a lot of people here are in shock. it's beginning to look a lot like christmas, but for those passengers stuck in heathrow the last couple of days, it's beginning to feel a lot like a nightmare. the snow fell saturday morning, just five inches in one of the world's largest and busiest airports ground to a halt. two days later with only one runway cleared, a majority of flights were canceled. two terminals were shut down in

the middle of the day. officials told passengers, no booking, don't bother. >> airports like chicago that have much more snow on an annual basis and they're able to have flights go out every day all winter. >> reporter: the earliest the airport will operate at full capacity is wednesday morning. but officials admit the backlog could last through christmas. until then, the stranded line hallways in makeshift camps, sleeping, eating, waiting. basically, if you can find a bed, you can spend the night. those thinking an escape to paris on the euro star train could be a good option were quickly disappointed. a line of frustrated passengers snaked outside london's station. six trains were canceled and those that did leave were two hours delayed. paris isn't much better. there are flight delays and

plenty of anger. >> i'm standing in the same shoes i've been wearing for three days. we can't get our luggage. they say too many bags, too many bags. >> reporter: northern europe is buckling under unusually arctic cold and snow. and many have been caught by surprise. at the brussels airport, they ran out of de-icing liquid. lack of snowplows has been blamed for heathrow's mess. but it's not an excuse many here accept, including london's outspoken mayor. >> aviation policy is not yet within the purview of the mayor of london. i do not run the airports, yet. >> reporter: it's flurrying here, brian, and there's snow forecast for later in the week. i'm about to join the thousands of other passengers crossing their fingers. i have a flight booked for thursday morning. >> stephanie gosk at london heathrow. what a mess and tragedy for all those families. stephanie, thanks. now we turn to capitol hill in washington.

a different kind of backlog there. the clock is ticking down to the holiday break. president obama has delayed his own trip to hawaii with his family. there are still two big dramas playing out in the so-called lame duck congress. one on arms control, the s.t.a.r.t. treaty. the other on the emotional fight over new help for 9/11 first responders. our own kelly o'donnell on the hill all day, tracking it all. kelly, good evening. >> reporter: good evening, brian. after eight republicans helped democrats repeal don't ask, don't tell over the weekend, now republican leaders are battling democrats and the white house over a new nuclear arms reduction treaty with russia. and the president's been working the phones, the pentagon weighed in trying to get senators to ratify this before the christmas break. republicans opposed say it's flawed, giving up too much to the russians on nonnuclear missile defense. and it appears there is new momentum on a different issue. democrats want to get health care coverage for those 9/11 responders whose serious illnesses are tied to their work at ground zero.

under the senate rules there might not be enough time to get that done. brian? >> kelly o'donnell with an update from the hill tonight. kelly, thanks. in other news tonight, overseas, despite its threats, north korea has not retaliated and says it will not for the latest live fire military exercises by south korea. they took place overnight. the drills were conducted on the same island that north korea attacked nearly a month ago, killing four people. this time, as a precaution, south korea evacuated hundreds of people, sent others into underground bunkers. in england, 12 young men were arrested this morning in a sweep targeting suspected terrorists. uk authorities say the suspects had been under surveillance for weeks and were planning a large-scale attack on targets inside great britain. counterterrorism experts here in the u.s. say there's no evidence of any connection to this country. it was just last christmas day, you'll recall, that a man who came to be known as the underwear bomber tried to bring

down a commercial airliner on final approach into detroit. because of the explosive he tried to use and how he tried to do it, we've seen the controversial rollout of those full body scanners and patdowns that a lot of passengers don't like. but there's another layer of security on board the aircraft, the air marshals who in the early days were not that plentiful and fairly easy to spot, but not anymore. they've been training hard to become more effective. and a large undercover force in the air each day. our own tom costello has been given exclusive behind the scenes access to the places where these men and women are trained to keep the skies safe. >> be alert! >> reporter: they may be the most secretive, least understood component of aviation security. the exact number of air marshals is classified. the government will only say there are thousands, their identities secret. nine years after 9/11, the air marshals insist the service has matured and evolved to match the constantly changing terrorist

threat. >> good morning. >> good morning. >> reporter: while half the new recruits have some law enforcement background, the rest are former lawyers, students, stockbrokers, even teachers. 27-year-old britney is just finishing the academy and undercover. this could mean you come face-to-face with a terrorist. >> it could. >> reporter: are you ready for that? >> i'm ready, absolutely. >> this is ridiculous. i can't believe this. >> reporter: today, being ready means an intense focus on behavioral recognition. >> sir, how are you? >> none of your business how i am. >> reporter: watching for the signs of stress, fear and deception that could give away a criminal or terrorist and then striking up a conversation. >> going to orlando too, huh? >> yeah, i am. >> this is about behaviors. they are involuntary, physiological responses to different stimuli. >> reporter: much of this is about deterrence. they concede they've never knowingly stopped a terrorist but they train for the ultimate confrontation nearly every day.

at 35,000 feet, marksmanship has to be deadly accurate. >> you don't have a lot of tactical options. it's not like you can take the high ground or the wide flank. >> reporter: the hope is this never becomes necessary, that before a suspect ever boards a plane or makes it through a checkpoint, he or she is identified and pulled aside. at the rarely seen air marshal command center in virginia, a constant juggling act, assessing the latest intelligence, then assigning marshals in tus and overseas to the right seats on the highest risk flights. >> we can't be all places at all times to all people. so we have to use the latest intelligence to inform our judgments and decisions. >> reporter: the typical air marshal will fly 1,000 flights over 200 days each year. no napping, no frequent flyer miles. on the front lines of a very real and lethal threat. tom costello, nbc news, atlantic city. we got a rare glimpse today of the reverend billy graham,

who at age 92, does not make too many public appearances. today, he did, however, at the billy graham library in charlotte where former president george bush and first lady laura bush signed copies of their books. before the signing, the bushes had lunch with reverend graham, whose son franklin escorted his faith tore the signing. still ahead as our broadcast continues on a monday night, does it work? once and for all, the experts say they're going to weigh in on a supplement millions of people swear by when treating the common cold, echinacea. later, how sweet the sound, talented young people making a joyful noise. making a difference in a place that could use it.

millions of people take it because they're convinced it works to combat the common cold for which there are, of course, is no cure. there have been various studies over the years, but tonight the results are in from the largest ever study of echinacea,

including the big question here, does it work? our report from our chief science correspondent robert bazell. ♪ >> reporter: in this season of travel and shopping, the common cold is a frequent, unwelcome visitor. everyone has a favorite remedy. >> plenty of orange juice. >> chicken noodle soup. >> green tea. >> those zinc things. >> reporter: another is the herb echinacea. the fifth most popular herbal supplement, with sales of $16 million a year. native americans used echinacea, and it became a popular homeopathic remedy. smaller studies of its effectiveness have produced conflicting results. but the biggest and best study, financed by the federal government, finds it offers virtually no relief. >> there are no proven treatments for common cold in terms of reducing the length of the cold or the overall severity. >> reporter: in the latest study, more than 700 people, aged 12 to 80, got the herb or a placebo at the first sign of a cold.

careful examination showed no change in the inflammatory reaction that causes the crummy feeling of a cold. the common cold is not just unpleasant, adults get two or three a year, children many more. it's responsible for an estimated 20 million to 30 million lost days of work and school every year, with an economic impact of $40 billion. decongestants and cough medicines relieve some symptoms, but not the underlying infection that can be caused by more than 200 viruses. although there's been almost no progress toward a cure, the doctor in charge of the echinacea study believes there will be. >> i certainly hope so. i just turned 50 and i plan to retire in maybe 20, 30 years and between now and thenally do my best. >> reporter: his best will be needed. echinacea is just the latest remedy shown to be no match for the common cold. robert bazell, nbc news, new york. and still ahead here, what's

going to keep a lot of folks up late tonight and why you might want to be one of them.

something's going to happen tonight up in the sky that hasn't happened since 1638. and as a result, as one website put it, tomorrow will be the darkest day in 372 years. that's because after midnight tonight, the winter solstice arrives, the shortest day and

longest night of the year, at the same time as the total lunar eclipse, visible all over north america. it works like this, the moon will go into a partial eclipse around 1:30 a.m. eastern time and then it should take on a red color until about 3:30 a.m. before finally returning to normal at around 5:00 a.m. dr. tyson at the planetarium here in new york says experts like him will be watching for something specific, the shade of red the moon takes on at the height of that eclipse. >> and so i will look forward to learning what is going on in our atmosphere from that signature of the reflected light on the moon, how much volcanic ash is still up there, what kind of pollutants are there, what kind of -- what are dust storms that kicked up just before the eclipse unfolded. there's some information that you can learn by earth's atmosphere by monitoring the color of the eclipsed moon.

>> dr. tyson estimates 1.5 billion people around the world will watch at least part of tonight's show in the sky. tonight's nfl game is going to be cold, and because of that, it's already controversial. windchill at game time in minneapolis, right around zero with about 3 to 5 inches of fresh snow. the game is being play outdoors. the university of minnesota's home stadium because snow, of course, did in the roof at the metrodome. while outdoor winter games still happen in the nfl, modern football fields have heating elements beneath the turf. tonight's field does not. they've removed 3,400 tons of snow from the stadium this past week. it snowed there most of the day today. one vikings player said the field is going to be like concrete. the game is going to be a train wreck. some players are concerned about injuries on that hard surface. the league has been attempting to warm the turf under a tarp. but tonight we'll see the game as it was once played.

"snl" veteran and "30 rock" co-star tracy morgan has undergone a successful kidney transplant. he was diagnosed with diabetes 15 years ago. because of the surgery, which took place on december 10th, he hopes to miss a minimal number of "30 rock" episodes and he'll be back at work after the holidays. up next here tonight, voices, all together making a difference. ♪

finally here tonight, our "making a difference" report comes from a part of l.a. that has become known across the country for all the wrong reasons. but tonight, you're about to see a positive side of this community because something good is getting a lot of attention and inspiring hope during this holiday season. nbc's kristen welker has our story. ♪ >> reporter: at compton's greater zion church family, pastor michael fisher uses the power of music to help transform a city plagued by poverty and crime. >> the message is hope, integrity, character, that there's an alternative to what is presented to us in the city

of compton, which is gang violence or throwing away your life. >> reporter: with a lot of tough love, fisher leads 40 young men and women from the neighborhood. he calls them voices of destiny. tell me what it means to you to be a part of voices of destiny, what impact has it had on your life? >> if i weren't part of voices of destiny, i would literally be in the streets somewhere. i wouldn't be the same person that i am. >> it keeps me out of trouble, because the type of neighborhood i live in, there's so much going on. there's crime and violence and gangs. >> reporter: but being a part of this gospel choir requires dedication and discipline. >> we have strenuous choir rehearsals and the hours are long. but we're a family. >> reporter: that work paid off when the choir performed at verizon's premiere gospel competitions. they wore red and blue, colors

of conflicting gangs, symbolizing instead a unified compton. and they won. >> congratulations! >> they always say nothing good comes out of compton, but you can't say that anymore. >> reporter: the prize money, $40,000, will help build a youth center at the church, the first in this neighborhood. >> compton is filled with so many young people who plan to achieve their dreams. you'll be shocked and surprised by all that comes from this city. >> reporter: a city lifted up by one man and a musical group, hitting all the right notes. kristen welker, nbc news, compton, california. >> by the way, you can read more about voices of destiny, you can hear more of that good gospel music on our new "making a difference" website. you'll see a link that takes you right there on the website of this broadcast, nightly.msnbc.com. for us, for now, that's our broadcast for a monday.

thank you very much for being with us as we start off a new week. i'm brian williams. we hope to see you right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com . six months after the shocking killing of a community leader, police say they have their man. good evening. i'm tom sinkovitz. >> i'm jessica aguirre. an arrest in the murder that stunned the community. david lewis was gunned down at the hills dale shopping center in san mateo in june. tonight they say they know who pulled the trigger. jean elle is at headquar