Update: The tornado watch issued Friday for Philadelphia county was canceled shortly before 3 p.m., about two hours before it was initially set to expire, according to the National Weather Service.
A National Weather Service meterologist said it was likely the flood watch issued for Philadelphia would also be cancelled before 5 p.m., as the storm moved out of the region.
The rain was forecast to stop Friday evening, though the National Weather Service said some lingering showers were possible.
Original story: Forecasters are warning of potential tornadoes and flooding in the Philadelphia area today.
The National Weather Service has issued a tornado watch for the region, in effect through 5 p.m.
Additionally, a flood watch is in effect through 10 p.m., and severe thunderstorm warnings have also covered various parts of the area.
Hail and strong winds are possible as storms move through the area this afternoon, forecasters say.
The combination of the rain and melting snow may lead to flooding, particularly in areas where storm drains remain covered by snow or ice.
Mild temperatures -- the high is expected to reach 52 degrees -- combined with "a brief period of moderate to heavy rainfall" in the afternoon, will speed up the snow-melting process, the weather service says.
In some parts of the region, more than four inches of "rain" are stored within the snow that's on the ground, according to the weather service.
Officials say flooding is possible in poor drainage areas and along rivers or streams.
Most places should see a quarter- to half-inch of rain, with the heaviest rain likely between 1 and 4 p.m. Thunderstorms and strong wind gusts are also possible during that timeframe.
Forecasters were expecting just minor flooding, but warned that even a small uptick in rainfall amounts or high temperatures could lead to more widespread floods.
A significant amount of snow is also expected to melt over the weekend, with high temperatures of 57 and 50 degrees forecasted for Saturday and Sunday, respectively.
Authorities were also warning Philadelphia-area residents to be on alert for dense fog this morning, with a fog advisory in place until noon.
Visibility may be less than a quarter-mile at times, the weather service said, and motorists should use caution during the morning commute.
Many flights at Philadelphia International Airport have been delayed or canceled this morning due to the fog. The airport says planes to Philadelphia are being held at their places of origin until noon, and customers should check with their airlines for updates on their flight status.
The fog conditions are expected to improve as a warm front moves through the region throughout the day.
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Contact the Breaking News Desk at 215-854-2443 or BreakingNewsDesk@philly.com. Follow @phillynews on Twitter.