That "pretty soon" part may come as early as Thursday in Philadelphia.
High pressure that's on the backside of the low that's funneling northerly chill into our region today will gradually swing around the low as it lifts north into Canada. The high positions itself off of the East Coast and will provide a southwesterly and westerly flow of air aloft at the surface. At the same time, the upper levels will warm as a ridge of high pressure and heat ridge begin to build over the Southeast.
|High pressure in the Atlantic will steer west and southwest winds overhead later this week, which will yield a return to summer.|
The result? We could be back around 80 on Tuesday, into the 80's on Wednesday, and pushing 90 by Thursday.
The length of the potential 90 degree run could be four or five days unless...and that's the asterisk in all of this...a backdoor front slips south on Friday afternoon. The Euro showed signs of this yesterday in the midday run but the GFS and both ensemble models disagreed then and disagreed last night. If the backdoor front pushes south, the heat would be muted a bit for the weekend (80's instead of 90+).
At this point, it doesn't look like a run deep into the 90's but a 90-93 type of heat with decent but not overly nasty humidity (dew points in the 60-63 range).
As usual, we'll keep you updated on the prospect for summer's eventual return.