That icy glaze that has appeared on streets, sidewalks, and driveways this week is all but certain to reappear Wednesday and Thursday mornings as water continues to ooze from the snowpack by day and freeze at night.<\/p>\n
So-called black ice \u2014 ice that masquerades as harmless wetness \u2014 is especially dangerous, officials warn, and conditions are ripe for a harvest, given the generous snowpacks.<\/p>\n
\u201cRefreezing and black ice are definitely a concern,\u201d said PennDOT spokesperson Brad Rudolph. \u201cWe will continue to treat areas as needed.\u201d<\/p>\n
SEPTA<\/a> advised commuter to watch out for ice on platforms, walkways, and in parking lots.<\/p>\n Temperatures early Wednesday and Thursday are due to drop deep into the 20s. <\/p>\n But along with that winter landscape,<\/a> the atmosphere over the region is going to undergo radical changes by the end of the workweek, forecasters say, with a rapid but short-lived warmup, and something that\u2019s been missing around here lately \u2014 a soaking rain.<\/p>\n As for more snow, the atmospheric scientists are saying it\u2019s probably safe to put away the shovels for awhile, and not just in the Philly region.<\/p>\n \u201cIn my opinion, cold looks hard to come by for most of the United States through the remainder of December,\u201d said Amy Butler, research scientist at the NOAA Chemical Sciences Laboratory.<\/p>\n In short, prepare for a more typical Philadelphia December. <\/p>\n \u201cWith the pattern changing, we\u2019re kind of getting closer to where we should be this time of year,\u201d said Mike Lee, a lead meteorologist at the National Weather Service Office in Mount Holly. <\/p>\n The forecast for the rest of the week<\/p>\n Wednesday should be at least partially sunny with some substantial melting as temperatures are due to crack 40 degrees by early afternoon. <\/p>\n Then after one more overnight with readings dropping into the melt-freezing 20s, Thursday is forecast to become the first day with above-normal temperatures in Philadelphia since the Wednesday before Thanksgiving. <\/p>\n As temperatures rise through the 40s, several hours of soaking rain are forecast to begin in the early evening with the potential for up to an inch.<\/p>\n Throughout the region the snowpack contains about a half inch of water that will be heading to local storm sewers and local waterways, said the weather service\u2019s Lee. <\/p>\n In addition to the rain, the high moisture content of the air is one of nature\u2019s most-efficient snow-removal tools. When warm, moist air comes in contact with snow, it gives off a latent heating effect that accelerates melting.<\/p>\n \u201cWe\u2019ll have to watch for the possibility of some localized flooding,\u201d said Paul Dorian, a meteorologist with Arcfield Weather.<\/p>\n For now, Lee said, the weather service isn\u2019t contemplating flood advisories. Precipitation the last 90 days has been substantially below normal throughout the region, and a drought warning remains in effect for New Jersey<\/a>.<\/p>\n The outlook for the weekend and beyond<\/p>\n Friday\u2019s forecast high in the mid-50s is likely to occur in the early morning hours, and then temperatures are forecast to crash, with wind gusts to 40 mph possible.<\/p>\n Saturday is expected to be dry but chilly, with readings in the low 40s, warmer than it\u2019s been but still several degrees below normal, and in the mid-40s Sunday, closer to the long-term averages.<\/p>\n The polar vortex, the persistent low pressure system that spins around the Arctic and confines the cold air to the ice box of the planet, has been strengthening, said Butler. <\/p>\n It\u2019s possible that it would undergo \u201cstretching\u201d and allow cold air to sink into parts of the contiguous United States, but \u201cit\u2019s not a signal that is very robust,\u201d she said. <\/p>\n For now, she said no obvious dominant feature is emerging that would define the winter.<\/p>\n