Premium: Inland freeze tonight, incoming storm Thursday
High pressure from Canada will allow cold air to surge into the area over the next few days, an airmass will be characterized as unusually cold even for late October. After mostly sunny skies this morning, some atmospheric instability with daytime heating and moisture aloft will lead to more clouds mixing in with sunshine this afternoon. High temperatures throughout the NYC Metro Area and the Northern Mid Atlantic will reach into the middle 50’s, with continually breezy conditions thanks to a tight pressure gradient with a low pressure over the Canadian Maritimes.
Skies will clear during the evening hours tonight, and winds will become lighter overnight as instability diminishes with the loss of daytime heating, all as very cold air seeps into the area from the northwest. This will support very cold temperatures overnight and by daybreak on Wednesday, temperatures will have dropped into the middle and upper 30s over NYC and other urban and coastal areas. Many of the suburbs will drop into the lower to middle 30s, with some middle to upper 20s possible over parts of over the interior and higher elevations. This could lead to a freeze with some patchy frost in those areas that have not experienced frost or freeze yet this cold season. Therefore, the National Weather Service has issued Freeze Warnings for many of the inland suburbs tonight and even Frost Advisories for urban areas around Philadelphia.