Cold front over Great Lakes will not reach the East Coast until Saturday. As it creeps east...wetness will slowly increase coming to a head Friday/Saturday for East Coast with 1-3" of rainfall. Below..satellite picture shows moisture moving from south to north with cold front over mid section of the Nation.
Below...map showing amounts of rain from Friday into Saturday...with an average of 1-2"...locally more than that over the Appalachians.
Above...map shows how temperatures will average by day thru May 22nd. Orange = warm .....blue = colder. Below - map shows how daytime temperatures will average from May 22 to May 26....which includes Memorial Day Weekend. Good luck !