9:20 AM | *What a difference a day makes…dramatically cooler today in much of the Mid-Atlantic region and the cool air sticks around into the weekend*
Temperatures on Wednesday afternoon were in record territory for the date in much of the Mid-Atlantic region and, in some cases, October monthly high temperature records were threatened or broken. In the overnight hours, however, a dramatic change in air mass has taken place in areas north of the PA/MD border as a back-door cool front dropped north-to-south across the region. Temperatures this morning across the northeast US were as much as 25 degrees colder compared to yesterday morning at the same time and they are likely to go nowhere over the next few hours in places like Philly and NYC. The cool air sticks around into the weekend and then it’ll turn a bit warmer early next week and that warm up could be associated with a significant rain event in the I-95 corridor.
What a difference a day makes! It has turned dramatically cooler in areas north of the Mason-Dixon Line as a cool front dropped through in the overnight hours from north-to-south. The cool front is working its way through the DC metro region at this hour and winds there have already shifted to a northeasterly direction. Low pressure will push along the frontal boundary zone over the next 24 hours and this will provide an extra push for the cool air mass to move even farther south of the Mason-Dixon Line. As a result, areas to the south of the PA/MD border like Washington, DC will experience even cooler conditions on Friday compared to today and Philly, NYC will stay quite cool as well. In fact, temperatures late tomorrow night and early Saturday are likely to be at the lowest levels so far this season in much of the Mid-Atlantic and NE US and there can even be some frost across interior sections of upstate, PA, NY and New England.
High pressure to the north that will anchor the cool air mass for the next few days will push off the coast later this weekend. As a result, southwesterly flow will develop along the I-95 corridor and this will allow for a bit of a warm up on Sunday and Monday. At the same time, another frontal system will be closing in from the west. This front will slow down as it approaches the eastern seaboard and the result could be a significant rain event in the late Sunday night/Monday time frame – something we haven’t seen much in recent weeks across the Mid-Atlantic. Once that next front passes off the east coast, it’ll usher in another cool air mass for Tuesday and Wednesday of next week. Looking even farther ahead, there are signs that a downright cold air mass will arrive in the Mid-Atlantic/NE US late next weekend (~10/13) which could result in the first serious threat for frost this season in many spots.
Meteorologist Paul Dorian