Weather: Rain Freezing On Contact Causing Treacherous Conditions
By Kate Bilo
PHILADELPHIA (CBS) -- An extensive freezing rain threat has developed across the entire region this Sunday morning, as rain pushes in from the south and encounters arctic cold that failed to be displaced ahead of the system. As the rain falls, it freezes on contact and roads have been treacherous all morning across the region. Temperatures are warming rapidly along the coast and to the south, and will continue to warm into the afternoon, but for many areas, the damage has been done.
From a forecast perspective, I'd love to tell you we saw this coming, but it was a miss. All of our forecast guidance and modeling indicated that as this large, moisture-rich system moved up the coast, it would be preceded by a direct south wind which would rapidly warm the surface, thus lowering the risk of extensive ice. Thus, we forecasted a rainstorm. What actually happened was that a shallow freezing layer developed right above the surface, while a warm layer has developed just above this. Imagine a snowflake, falling through an area of warm air and melting - only to then encounter a layer of subfreezing air just at the end of it's journey to the ground and refreezing on contact. That's what's happening out there today.
And because the precip has been heavy from the onset, we're dealing with ice accumulating on roads and not just spotty icing like we saw last week.
The good news, if there is any, is that temperatures WILL continue to warm as we move into the afternoon, and by later today the ice threat should end. It will take longer in areas north and west than it will in the city. It's also good that today is not a work/school day for many, because then we'd be talking about even larger problems than we have now. However, for many the damage is already done.
We urge you to stay at home and avoid non-essential travel until the advisories have been lifted from your area. Later this afternoon, watch for pockets of heavy rain, wet roads and ponding as the storm travels up the coast.
