usually think about that. it can save a $150 repair job if they take precautions. >> you want to make sure they're either insulated or have a heat cable underneath the insulation on the exposed outside pipe. >> reporter: santa clara county has yet to declare a weather emergency. so there are not extra outreach steps being taken yet to get the homeless into shelters. that suits javier fine. he doesn't feel safe in those places. he's just going to tough out the cold weather. >> two blankets, one sleeping bag. >> is that enough? >> i think so. i can handle it with that. >> reporter: luckily most farmers have already completed their harvests, so most crops should not be affected. and the citrus farmers in the sierra foothills will only get concerned if the temperatures dip into the 20s. and i hope that doesn't happen. live in san jose, nannette miranda, nbc bay area news. it's going to be a with weekend at sierra ski resorts. people at donner ski ranch, last year it was open 42 days, barely enough to make ends meet. getting snow for the holidays is crucial to this mom and pop-owned business. >> we didn't have any snow on the ground here last year. this is a little bit of magic. >> beautiful snow. nice and cold powder. >> reporter: at north star, they're telling us today that recent snowfall is letting them open more trails and lifts for skiers and riders. drivers should carry chains if you're heading to the sierra this weekend. you can track the cold weather with our nbc bay area app. download it, touch the logo to bring the drop-down then ewe, find the latest forecast and temperatures for your neighborhood at your fingertips. the app is free for iphone and android devices. the protests over police shootings across the nation, the black lives matter protest took place at union square in san francisco, one of many held across the nation. kimberly terry live in berkeley where a singing protest is scheduled to begin in about an hour from now. kimberly, sounds like a different kind of protest. >> reporter: it is. one that is planned to be peaceful. and it's a call for justice, also a fund-raising effort which we'll talk about a little bit later. i want to bring your attention to be a earlier protest. organizers from the protest today across the bay in san francisco say that they are going to continue to call for an end to police brutality, until they see some justice. in san francisco there was a very heavy police presence during the demonstration which remained peaceful. >> black lives matter! >> reporter: a couple dozen demonstrators calling for an end to police brutality marched into a bustling union square after holding a moment of silence, the names of more than 30 black people killed by police were read. >> alan bloomford. black lives matter! oscar grant. black lives matter! >> reporter: to draw attention to their cause, protesters are hoping to get their message out to as many people as they can and they picked a good day to do it. the place was packed with shoppers and tourists. >> this is a time for us to celebrate and be with our families and remember our nation is at war right now. there's a genocide being committed against black people every day, including the day after christmas, including christmas. >> reporter: the use of the word genocide sparked a debate among bystanders. >> genocide, you know, is adolf hitler, rwanda. >> reporter: which ended in an argument over how to bring police and the community together. >> you're saying diversification works -- >> i'm not one person -- >> it's policy. >> reporter: many passing by told us they think in some cases police are being unfairly targeted. the one thing everyone could agree on is that change is necessary. >> it's an important conversation that's way overdue. and black lives matter. latino lives matter. gay lives matter. cops' lives matter. >> reporter: in about an hour in berkeley, musicians are expected to gather to sing songs that call for social justice. it's going to be a fund-raiser to raise money for the family of michael brown, who was killed by a police officer in ferguson, missouri. all the proceeds will go to his family. some bay area police officers left for the east coast to pay respects to the two nypd officers ambushed and killed in the line of duty. eight san francisco police officers flew to new york today. this as the wake for officer rafael ramos attracted a big crowd of mourners. he and officer liu were gunned down in brooklyn in their patrol car saturday. police say ismaiyl brinsley ambushed the officers before killing himself. some believe nationwide protests caused brinsley to attack. >> on social media, a lot of these things are self-despair but they're also anti-government. >> rafael ramos will be laid to rest on saturday. an nyc charity hopes to raise enough money to pay off the homes of the families of both of those officers. a mountain lion on the loose in a peninsula neighborhood. people are trying to get the word out about the danger. the wig cat attacked a deer on el cerrito avenue in hills borrow. a homeowner heard rustling in a tree, then heard the cat pounce on a deer in his yard. >> neighbors heard the screech as well, scream. what worries me is there's a lot of people that walk in the dark. right underneath the tree that hangs out over the street. >> he called police. when officers arrived they found a dead deer in the yard. they believe the deer was mauled by a mountain lion. now he's telling neighbors and passersby to keep a lookout for the mountain line onsince that spot is near two schools. the fire that burned down two homes in san francisco's potrero hill neighborhood on christmas day, authorities say the fire caused more than $1.3 million in damages and killed two cats. the fire was reported at about 6:30 in the morning, 200 block of mississippi street, three alarms before it was put out. the cause of the fire is under investigation. christmas may be in the rear-view mirror but the shopping season is still on. huge day for sales and returns brought shoppers back to the mall in droves. our business and tech reporter scott budman was among them, he's live tonight outside valley fair mall in san jose. >> reporter: between the cars outside and the people inside, it is almost as busy on is day after christmas as it is on the days leading up to christmas. almost as much of a tradition too. we found lots of deals inside the mall along with lots of shoppers. the mall was the place to find the hottest post-christmas gifts and deals on this december 26th. >> clothes, shoes. >> phone. >> day after christmas sales. >> reporter: big discounts. in the case of the apple store, big lines. it was a day to shop for sales and get money back by returning gifts. >> a little bit of both, yeah. we just like going to the mall, hanging out, me and the kids. we drove to see if we could find anything, any sales, something like that. >> reporter: she wants an elsa dress. shouldn'ts the guy on the abercrombie and fitch bag. >> why are you carrying a naked man? shocking. >> reporter: there are all sorts of reasons to shop today. >> i just used $800 worth of gift cards. >> reporter: each one getting all of these shoppers a little closer to what they really wanted. it probably won't surprise you not all the action was in the malls. online shopping did very well. amazon.com said 10 million people signed up for its amazon prime delivery service this holiday season alone. coming up, a surprise box office hit. "the interview" sells out in nearly every theater it's shown in. how much money the controversial movie made in its limited release. a big upgrade for tesla's first car. why drivers will be able to drive farther an ever before. >> i found out all this stuff about rail. then i found out how much they cost. they cost a lot. >> 12-year-old goes from playing with legos to using them to help the blind read. a story that will make the bay area proud. emeryville into san francisco, 50s for now. later tonight temperatures close to freezing. especially in north bay valleys. more on that cold snap now arriving in the bay area when we come back. take him out. >> you want us to kill the leader of north korea? >> yes. >> whaaat! >> "the interview" earned more than $1 million this weekend. i know that doesn't sound like much but it only played at 300 theaters, less than 10% of the screens originally planned for. the movie studio was targeted in a cyber attack allegedly by north korea and the hackers threatened attacks on theet there's showed the comedy about the assassination of north korea's dictator. many people ended up watching that movie online. sony released it to youtube and other streaming services a day before its theatrical release. right now it is youtube's most popular video. today hackers are explaining why they played grinch on christmas day and kept gamers from going online. lizard squad shut down both x-box live and playstation networks by overwhelming the servers with fake user traffic. the website reports say the group hacked the systems "for laughs" but also to get microsoft and sony to upgrade their security. the report says the group did it on christmas day to anger the largest amount of people and prompt angry calls to the companies. games are still reporting spotty service today. south bay officers are searching for whoever may be responsible for three car fires set in a couple hours. firefighters found an suv in san jose's evergreen neighborhood early tuesday morning. two hours earlier they responded to two more car fires near delmar high school. according to arson investigators there's evidence that the fires are not related. police say arson is suspected in all three fires. silicon valley is full of stories of tech titans who started in the garage and went on to make billions. today's "bay area proud" is different. this one starts at a kitchen table. as nbc bay area's garvin thomas shows us, this future tech giant is out to help others not cash in. >> 12-year-old bannerjee is described by parents and teachers as a sweet, sensitive kid. smart too. just how he's put those three qualities to good use is our next "bay area proud." the route to success can often be discovered in odd places. bannerjee's happened to be hiding under his bed. it's where you see him store old lego kits. the ones he's been playing with since about the age of 2. >> you can be creative. you can do anything. >> reporter: as he's grown, he's now a seventh grader at san jose's champion school, so have his legos, his ambition, and clearly his heart. >> i think i'm actually doing something that can actually help people. >> reporter: which brings us to this. $350 lego mindstorms kit. and what he spent an entire month creating out of it at the kitchen table. >> i thought i could do it. i mean, i didn't know if it was possible but i really wanted to do it. >> reporter: it started with a flyer on the doorstep. one asking for donations for the blind. he'd never before thought about how blind people read. so he asked his dad. >> so then he said, google it. so i googled it. and i found out all this stuff about braille printers and braille. and then i found out how much they cost. and they cost a lot. $2,000. >> reporter: he decided he could do it cheaper out of lego. and after seven different failed prototypes, late one night he struck on the right configuration, and his printer struck out the very first letter. >> it was like a eureka moment. i said, mom, dad, it works. my mom is like, yeah! whoa! then, yeah, it was all crazy. >> reporter: he debuted his lego braille printer, braigo, at his school's science fair. and while his teachers say there were more complex entries there, there were none more compassionate. it's why his story has continued to grow. his videos on youtube have been seen by hundreds of thousands. people both sighted and blind have sent their admiration and congratulations from around the world. even lego corporation tweeted. just about everyone, it seems, is impressed by this 12-year-old technological whiz kid. one able to see solutions in the the unlikeliest of ways. a lot has happened since we first aired that story in february. he was invited to the white house to participate in their first-ever maker fair. and in november, he became the youngest person ever to receive venture capital funding to help develop his next generation nonlego braille printer. >> if you know of someone doing something nice for others, garvin would like to hear from you. go to nbcbayarea.com/bayareaproud. i might tell marvin about rob mayeda. the cold snap is just about here. >> we saw a bit of it this morning for places that saw winds overnight. you notice, no doubt, the clear skies over my shoulder. san francisco still 56 degrees. the flag there moving a bit. but as the winds back off tonight that's when temperatures are really going to drop. low 50s this evening. but by 11:00 tonight it's possible upper 30s in some of the valleys before midnight. the winds out of the north, instead of a sea breeze, these dry north winds really help to clear our skies out. you saw in san francisco. the low clouds and fog acting like a blanket overnight the heat we gamed during the day that put temperatures in the 50s and 60s is going to escape out to space. sort of like sleeping inside a blanket overnight. here's what's interesting. the dew point temperatures, normally 40s and 50s, then the fog forms, not the case with dry air in place. 20s and 30s for dew points. so that is almost a kind of sneak preview of how cold the temperatures could get toward tomorrow morning without any clouds in place, winds back off, temperatures dropping more than we're used to. could see upper 20s to mid 30s in parts of the coldest valleys around the north bay. mainly cloud-free now. a large storm north of hawaii, typically you'd think that should bring us rain, except when you have a ridge of high pressure acting like a wall. underneath it the dry air in place. so patchy frost possible, especially for tomorrow morning, maybe less so heading into sunday where some of the coldest temperatures we should see around the bay area will be as cold as near 30 degrees in santa rosa. two to three hours of at freezing or slightly below. nasa and walnut creek in that range, livermore, toward the tri-valley, downtown san jose will be warmer at 35 degrees. low 30s further south of downtown. like we saw today, once the skies clear during the day, we got mostly sunny skies. no clouds around. we'll warm up nicely despite that chilly start. should still reach the upper 50s around san jose. san francisco in the mid 50s for tomorrow. the north bay close to 60 again around santa rosa, pleasanton, livermore in the upper 50s. this is the first half of the story. the second half of your seven-day forecast could get very interesting come tuesday, wednesday. an even colder system dropping down that could drop our highs as well into the 40s and 50s. limited moisture but we'll have to watch it. depending when it arrives, with that cold air in place, snow levels as low as 2,000 to 3,000 feet. the time to watch, tuesday afternoon, you've got showers. that wouldn't be low slow. watch what happens tuesday night into midnight on wednesday into early wednesday morning, there's that brief chance we could see a few stray showers. you can see here the moisture that does come in tuesday into wednesday, not a lot. again, hyperprecipitation, possibly snowflakes as low as 2,000 to 3,000 feet. maybe not around the bay area but we'll see highs if you want to call them highs in the low 50s by tuesday and wednesday ringing in the new year on a chilly note. some parts of the north bay tuesday, wednesday looking at highs in the upper 40s. you'll notice the morning temperatures again dropping down to possibly seeing more patchy frost or ice in a few spots maybe too in the north bay. so the taste of what we're getting right now tonight, it's going to continue if not get slightly cooler by the middle part of next week as we ring in the new year. coming up next, u.s. troops preparing to leave afghanistan. where they will be heading to next. throngs of new members. scott budman was talking about this, how amazon prime added new users at a record-setting pace. . >> got a tip for nebraska bay area's investigative unit? 888-996-tips or e-mail theunit@nbcbayarea.com. america's longest war is pretty much down to its final week. after more than 13 years, the afghanistan war will come to an end on january 1st. but not all the troops are coming home. more than 5,000 troops expected to stay behind in afghanistan through much of next year to help rebuild the country and assist iraqi forces in their fight against isis. america's mission is ending but the fighting is not. >> the war is heating up. it's turning into an all-out ethnic civil struggle. >> the president says there are new priorities for our u.s. servicemembers around the world and at the top of the list, fighting ebola in west africa. it was one of the deadliest natural disasters in modern history. today people across southeast asia marked the tenth anniversary of a devastating tsunami. people in a thy fishing village honored victims by releasing hundreds of lanterns into the sky. in india, families left behind flowers and prayers at a cemetery. the tsunami hit a dozen countries around the indian ocean, killing 230,000 people. millions were left homeless. tells la with a big announcement about a vehicle it doesn't make anymore. upgrades are now available for the roadster that can make it run better than new. the company says a new battery and improved aerodynamics means that roadsters will have a range of 400 miles on one charge. way better than the current 250 miles. that would manner a trip from l.a. to san francisco without a pit stop. roadsters are not back on the market but current owners can upgrade to reap the rewards. the company says it is working on upgrades for the popular model "s." busy week for robots at amazon.com. the online shopping site says more than 10 million people tried the amazon prime service for the first time during the holiday season. this is the company subscription service, an annual $99 fee. one of the most popular items, the so-called sophie the giraffe toys. shoppers purchased enough to equal the height of nearly 800 real giraffes. sophie's only about six to eight inches tall. that's a lot. kwanzaa celebrations next. tonight at 6:00, in troubled waters. >> extinction vortex. >> salmon on the verge of extinction. what experts say needs to happen to keep the species from vanishing completely. christmas is over but another holiday is just beginning. ♪ a kwanzaa celebration got under way in los angeles. the holiday highlights the rich heritage of average arms. it's also meant to bring families together to reflect on the past year's blessings and the promise thes of the year to come. the celebration is observed today through january 1st and ends with a feast and a gift giving. one more check of the weather on this first day of kwanzaa. >> yes, and chilly right now. temperatures starting to cool off, right now in the 50s. but overnight tonight down the central valley, 20-degree temperatures off to our east into solano county, fairfield, vacaville, numbers closer to 30. patchy frost bay area. north bay, east 8 bay, tri-valley between 3:00 and 8:00 a.m. have a chance of getting close to freezing with patchy frost. morning temperatures around the bay area will be dropping into the low 30s in north bay. frost for the morning. more of this coming up as we go through the next few daze. you may see overnight temperatures creeping up sunday into monday. then another area of low pressure dropping down. daytime highs 40s and 50s through the middle part of next week. >> thank you for watching. "nightly news" is next. you can find us online at nbcbayarea.com. on the broadcast tonight, paying tribute to the two police officers gunned down in the line of duty. a tense time for communities and police across the country. the day after draws millions back to the stores in search of one more big deal. plus a retailer with a bold new idea on how to use those gift cards. ten years later, remembering the day when the sea took an awful toll. we're in the tsunami zone with some of those who survived. follow that bag. just what happens when you check your luggage. tonight, an inside look at how millions of bags get screened. and "unbroken," the new blockbuster about a hero of the greatest generation. tom brokaw goes behind the scenes with director angelina jolie. "nightly news" begins now.