Philadelphia Weather: Blizzard warning expanded as philadelphia weather turns to heavy snow overnight

philadelphia weather is headed into a dangerous late-winter storm as a Blizzard Warning goes into effect Sunday for most of the viewing area and now includes Philadelphia. The heaviest snow is expected Sunday night and will continue into Monday, a timing that could make travel very difficult and drive significant accumulation.

Blizzard Warning expanded to Philadelphia, suburban Pa. counties, New Jersey and Delaware

A Blizzard Warning has been issued for Philadelphia, several suburban Pa. counties, along with the entirety of New Jersey and Delaware. The warning goes into effect Sunday for most of the viewing area and is tied to sustained wind and snowfall conditions that meet the formal blizzard definition: three or more hours of winds gusting to 35 miles an hour or greater, falling or blowing snow, and visibility less than a 1/4 of a mile.

There are no requirements for the amount of snow when it comes to a blizzard, so the warning is focused on wind, blowing snow and visibility rather than a specific accumulation threshold.

Timing of precipitation: light showers Sunday morning, changeover to snow by evening

Light precipitation is expected to begin Sunday morning, with areas northwest of the city likely starting with light snow showers. Ground temperatures are expected to be above freezing and air temperatures in the mid 30s early in the day, so snow will likely initially melt as it hits the ground.

Cloudy, cooler conditions Sunday will bring rain and snow showers developing through the day, with a high near 39 degrees. As temperatures fall later in the day and into the evening, any rain or mixed precipitation will change to snow for all areas.

Heaviest snow overnight into Monday, creating ideal conditions for accumulation

The heaviest snow is set to fall Sunday night and will last into Monday; that overnight timing creates ideal conditions for accumulation because temperatures drop as the storm intensifies. Snowfall rates are expected to pick up Sunday evening through Monday morning, and drivers are urged to use caution and consider staying off the roads during that window.

By Monday morning, snow will begin tapering off from west to east as the coastal storm continues to strengthen and move away from the coast.

Wind, visibility and coastal threats: AccuWeather Alert covers Sunday into Monday

An AccuWeather Alert is posted for Sunday into Monday for heavy snow, blizzard conditions for most of the area, high winds, coastal flooding and beach erosion. Gusty winds could bring down tree branches and result in isolated power outages, and areas of blowing snow could significantly reduce visibility to less than a 1/4 of a mile.

Those combined hazards—high winds, blowing snow and low visibility—are the reason the Blizzard Warning covers such a wide area and includes both inland and coastal communities.

Local variations in precipitation and expected coastal totals

A mix of rain and snow is expected around Philadelphia, with rain showers forecast for areas south and east while areas northwest of the city are more likely to see earlier snow showers. Temperatures in the mid 30s early on will allow some early melting, but the evening changeover will bring accumulating snow across the region.

The storm is expected to bring between 12 and 18 inches of snow to coastal areas of South Jersey and Delaware, while accumulation inland will depend on timing of the changeover and local temperature trends.

Motorists and residents should prepare for disruptive travel and the potential for isolated power outages as gusts and heavy snow affect the region from Sunday into Monday.