Philadelphia has yet to see its first 70 degree day of the year -- we've only been in the upper half of the 60's twice this year (yesterday and January 30th). That may very well change next week in advance of a storm system that's poised to develop in the Midwest. Modeling shows a storm system developing across the Midwest, with high pressure building in across the Southeast. This setup typically produces the potential for a warm surge across the Mid Atlantic to the south of any frontal boundaries (warm or cold, depending on their tendency) as west and southwest surface winds pump in warmth down the Appalachians and into our region.
This warmup won't last tremendously long -- perhaps two to three days at the most and it may not even happen depending on how aggressive any back door chill ends up getting. Given it's April and given the level of cold that's permeated around the Northeast over the past month, the potential for some stale bootleg cold to sneak in does exist...but looking at guidance this far out we may a good shot of getting at least one 70 or warmer day in.
Of course, if you look at the Euro graphic back at the top and see that cold front pushing in from the north across New England, a faster moving cold front could put the clamps on any major warmth and set the stage for some chill coming from Canada. As of right now, we should be able to avoid this for at least one day.
This setup is also conducive to some severe weather in the Plains, Midwest, and Ohio Valley during the middle portions of next week as well. That will likely be a rather big weather story nationally as we could see the spring's first big time severe weather outbreak.