It has started snowing in the Philadelphia region and already the first major winter storm of the season has had a paralyzing effect.

All flights in and out of Philadelphia International Airport have been canceled for Saturday and SEPTA will suspend Regional Rail, bus and trolley operations at 4 a.m. NJ Transit is shutting down at 2 a.m.

States of emergencies are in effect in Pennsylvania and New Jersey and motor vehicles accidents are being reported around the region.

An already major-snow threat took a more menacing turn earlier Friday, and the latest projections say we could see from 15 to 20 inches of snow by the time the storm ends Sunday morning with dangerous blizzard conditions during the day Saturday.

Widespread power outages are possible.

Here's the latest information on the storm prep in the Philadelphia area.

Mass Transit

SEPTA: SEPTA will suspend service on all operations except on the Market-Frankford and Broad Street Lines starting at 4 a.m. Saturday with the aim of resuming operations Sunday. The subway/el lines will run continuously while the other services are suspended. www.septa.org

PATCO: PATCO has posted a special snow schedule for the weekend at its website, www.ridepatco.org.

NJ Transit: System will suspend operations at 2 a.m. Saturday.

Amtrak: Acela Express, Northeast Regional, and other services from Virginia to Boston, and Keystone service from Harrisburg to New York, will operate on modified schedules through the weekend with fewer trains. Most Northeast Corridor service between Washington and Boston will operate as scheduled Friday. www.amtrak.com

Weather

Snow began in the Washington area at midafternoon and hit Philadelphia after nightfall.

The National Weather Service has placed the entire region under a Blizzard Warning. The outlying areas are under Winter Storm Warning, a scaling back from Thursday. A Coastal Flood Warning also will be in effect at the Shore and along the Delaware Bay.

A Blizzard Warning means there is a potential for strong winds and heavy and blowing snow. Winds of 20 to 30 mph, with frequent gusts of up to 40 mph, will reduce visibility to a quarter-mile or less at times.

A Coastal Flood Warning means moderate coastal flooding is imminent and there may be localized areas of major coastal flooding. The coastal flooding could last for three consecutive high tides with water remaining trapped along the coast, and in the back bays and estuaries.

Government Actions

Philadelphia declared a snow emergency effective 9 p.m. banning parking on snow emergency routes. Parking Authority lots will offer 24-hour parking for $5 starting at 5 p.m. City Managing Director Mike Deberardinis urged residents to stay indoors and off the roads. Libraries and rec centers will be closed. Trash will not be collected Saturday. There will be no rear driveway collections next week. Those residents should put their trash out front.

Gov. Wolf's state of emergency, announced Thursday, enables state and local authorities to respond to any unmet needs as quickly as possible. For example, laws requiring bidding for services or supplies are suspended during the emergency.

New Jersey Gov. Christie returned suddenly from campaigning in New Hampshire and declared a state of emergency.

Municipalities surrounding Philadelphia also announced snow emergencies.

A Code Blue alert is in effect in most counties to provide shelter to the homeless or those without heat.

Highways

Crews have already started treating some roadways in advance of the storm. Officials in Pennsylvania and New Jersey have unleashed an an armada of plows and salt trucks, but accidents are being reported on highways in New Jersey and Pennsylvania.

Airlines

Philadelphia International Airport (www.phl.org) says all flights have been canceled for Saturday.

Bike Share

Indego, Philadelphia's bike-share system, said suspended service at 6 p.m. Friday. www.rideindego.com

Utilities

Utilities are monitoring forecasts and preparing for the storm. Crews backed by contractors will be on duty throughout the weekend. Local utility companies said they were prepared with extra staff, fueling trucks and spare equipment.

High winds and heavy, wet snow - the sort of conditions that are expected - can weigh down tree limbs and bring them into contact with power lines causing power outages. It also can bring down compromised trees. Outages can also occur due to drivers skidding into utility poles along icy and snow-covered roads.

Utility companies warned that snowy and icy conditions could make it difficult for crews to travel quickly, but said they would respond to emergencies 24/7.

Postal Service and Deliveries

Postal Service carriers will attempt to make deliveries wherever possible. The Postal Service is asking customers to help with the safe delivery of mail by keeping walkways and sidewalks clear of snow and ice. Letter carriers are instructed to use good judgment, if a potential hazard exists, and to hold mail to addresses where ice and snow are not cleared.

UPS said it would post zip codes online if there were areas where pickups and deliveries weren't being made because of weather conditions. The carrier said it was monitoring the storm and shipments would be made as conditions permitted.

Archdiocese of Philadelphia

The Archdiocese said priests will as much as possible maintain Sunday mass schedules. While there is no dispensation from attending mass, there are "legitimate circumstances" under which individuals can excuse themselves "without offending God and incurring any serious sin."

"In the face of the impending storm, Catholics of all ages - but especially the elderly - are advised to use extreme caution when making the decision about attending Mass," the archdiocese said in a statement.