MU has been tweeting a lot about the upcoming pattern - this is all from the past hour:
(1/3) Now that's a change! The Madden-Julian Oscillation (MJO) wave has migrated into phase 1. In an ENSO-neutral April, there is a strong correlation between phase 1 & the large-scale pattern across North America. Unfortunately, phase 1 promotes below-normal temps in the East.
(2/3) The ECMWF computer model 500 mb height anomaly forecast for the upcoming weekend looks a lot like the MJO phase 1 pattern. A ridge over the West (+PNA) will combine with high-latitude, Greenland blocking (-NAO) to suppress the Jet Stream over the eastern U.S..
(3/3) What does this mean for us? To make a long story short, the summerlike warmth of recent weeks is gone. Highs will be stuck in the 50s/60s each afternoon through at least May 5th. And yes, we'll deal with a few "cold rains" and perhaps another frost or two. I'm not a fan..