I just want to confirm, or not, in EPA SWMM, that entering a non-zero value for Ponded Area is supposed to have the effect of raising the HGL at the flooded node?

Yes, if you also check Allow Ponding in the Options / General section.

Unrelated... If you've spent any time searching for NOAA's 1981-2010 US precipitation normals, you may be interested in the webpage I created that displays the data in a simple table. See http://www.dynsystem.com/NetSTORM/USPrecipNormals.htm for the list of 1,000 or so monthly and annual normals.

If you enter a non zero value for ponding at a node and have the ponding allowed option flag turned on as Mitch mentions then the node depth increases above the rim elevation of the node IF there is node flooding and the downstream link should have increased flow due to the higher HGL. You can also see the amount of flooding stored in the ponded area if you graph the node.

If you enter a zero value for ponding at a node have the ponding allowed option flag turned on then the node depth does NOT increase but there is flooding that you can graph. The downstream link does not increase its flow.

The precipitation normal page is great, Mitch. I could use some help interpreting some of the flags, though

Flag  Explanation 
C     Complete 
P     Provisional 
Q     Quasi-normal 
R     Representative 
S     Standard