Help reading forecast

So when I look at the MSW "summary" forecast for Cape Kiwanda, for tomorrow, I see a 1.5 foot swell with a duration of 17 seconds at 6AM. Which looks fantastic, however when I click on the "full Swell Breakdown" I get a combined Swell of 4.6 feet with a duration of 20 seconds at 6 am. Here it lists the primary swell as 3.8 feet at 7 seconds and the secondary swell as 1.6 feet at 17 seconds. How can the summary be 1.5 and the combined be 4.6 for the same time? Can someone explain to me the differences between these three? I tried reading their help section but it didn't help.
Thanks in advance.

I'm gonna throw this at you:

http://forecast.weather.gov/MapClick.php?lat=45.20780329252139&lon=-123.98723602294922&site=sew&unit=0&lg=en&FcstType=text

MSW is kinda nice to look at, but the NOAA forecast is generally better.  I've also found that the NOAA forecast estimates on the high side.

NOAA drives me crazy also.
This is the one I have been looking at,
http://forecast.weather.gov/MapClick.php?lat=45.19945769007778&lon=-123.98998260498047&site=pqr&unit=0&lg=&FcstType=text

My NOAA Link,
Saturday: N wind 7 to 12 kt. Patchy fog before noon. SSW swell 4 to 5 ft at 17 seconds. Wind waves 1 to 2 ft.
Lee's NOAA Link,
Saturday: Variable winds less than 5 kt becoming NNW 8 to 13 kt in the afternoon. Patchy fog before 11am. WNW swell 3 ft at 17 seconds. Wind waves 1 to 2 ft.

The two spots can't be more than 1/2 away from each other the forecasts are pretty different.

At the bottom there is a disclaimer:

*Notices: (1) This forecast is for a single location. For safety concerns, mariners should be aware of the weather over a larger area. Forecast information for a larger area can be found within the zone forecast and the NDFD graphics.
(2) The forecast conditions at a particular point may not exceed the criteria of a Small Craft Advisory, Gale, Storm etc. These watches/warnings/advisories are issued for the entire zone in which the point resides and mariners should act accordingly.

I interpret that as "click around everything within 10 miles or so, and go with the average"

Because it's a model, and models get confused. I'd go with the averaging method, and use your interpretation. You can spend the entire weekend trying to figure out what a wave model is trying to say...or just go fishing.

Because it's a model, and models get confused. I'd go with the averaging method, and use your interpretation. You can spend the entire weekend trying to figure out what a wave model is trying to say...or just go fishing.

I will be fishing somewhere, the issue is determining whether a surf launch is doable/advisable.

That's why you consult multiple sources.  MSW is is giving you a "Surf" forecast.  This is what they expect to see hitting the beach at a given location.  This is influenced by bathymetry and headlands in the area.  Offshore, you'll see what's in the breakdown.

Check out Swellwatch3D and click on Charts to see each of the components of the swells over time.

BTW: I think that the influence of the south swell is being under-forecast for Saturday.  Expect to see dumpers on the far north end of the beach at Pacific City.  Remember, in general, the longer the period, the faster these swells are moving.

Or..... I could be full of $#!T 

-Spot-

The latest forecast updates for NOAA, NSW and SW3D show Cape K looking great for fishing on Saturday.

Looks like the South will blow right past Oregon.  I'll bet surf's gonna be great up on Vancouver Island Monday.

-Spot-