Weather forecasters issued a winter weather travel alert Thursday morning and urged people to only venture out into snowy, slushy roads if it is essential. Car crashes have been a problem in the Denver metro area under the treacherous driving conditions. All lanes of northbound Interstate 25 were closed north of E-470 just before 8:30 a.m., said the Colorado Department of Transportation. RELATED: Denver weather: Cold and misty with up to 4 inches of snow Thursday If people have to drive they should plan for considerable delays due to the weather, the National Weather Service in Boulde reported. Between 2 to 4 inches of snow will accumulate Thursday in Denver, the NWS said. Delaying travel for a few hours will allow snow plows and the sun to improve road conditions, weather forecasters said. **WINTER WEATHER TRAVEL ALERT** Motorists doing essential travel this morning in the Denver metro area, foothills, I-70 mountain corridor and NW Colorado should plan for considerable travel impacts due to snow & winter driving conditions.