Update.--The weather app Intellicast will be discontinued in the near future. The company is merging their app into the weather app Storm. This app has a lot of the same features and tools, just different in presentation, so it's a good one to replace Intellicast.
Original Post.--There are a lot of weather applications for iPhones and iPads (which I own one of each) and I often buy them to see what they offer and have with the applications, especially the number of sites around where I live and the state of Washington and around the world.
While I have probably about half a dozen or so, I only keep 3-4 on my iPhone and iPad in addition to the Yahoo one that comes with the iPhone/iPad which is really a waste and ignore. The other three are the Yahoo expanded app, the Weather Live app and the Intellicast HD app. The extra one for my iPad is MyRadar.
So what my thoughts on them? For one the Yahoo expanded app is ok and worth keeping for the immediate weather where you live or want to travel. It's easy to use and has a wide range of local, national and global sites.
The MyRadar app is good for what it offers, which is the high resolution last 90 minute radar image for the home or where you're at. As a note about weather apps, I turn off the location access for this and the other weather apps so it always defaults to my home and I add other sites I commonly travel.
Weather Live is a good app for the simplicity and presentation, although the data isn't as extensive as other apps. What I used to like about is that it had some of the lesser known weather sites, such as Ashford, Washington, which is a few mile west of the Nisqually (Longmire) to Mt. Rainier NP.
The National Weather Service (NWS) has an official weather station at Ashford, which would be good for travellers see the actual weather up to the hour for this area, but this site is often not working or data not available.
With that in mind, Weather Live gets their data from the Weather Underground and their Ashford weather site is not the NWS but one north of Ashford, meaning it doesn't offer actual data through the app but just forecasts. Historical and current data is available from their Website.
What interested me about this app is that it offered the Paradise Inn Weather site, which I thought was the NPS-NWS weather site, but it's not that site but Crystal Mountain Resort, which is the commercial ski resort just northeast of the northeast (White River) entrance.
You can get the actual data for Paradise Inn if you're going there, along with Longmire inside the southwest enterance which is kept open everyday except for unusual weather conditions, eg. snow, floods, etc. Otherwise, remember the Weather Live Paradise Inn isn't what they advertise.
The best weather app I've found and use is Intellicast HD, especially on the iPad. It has tons of information and forecasts. While some of the details, like timing of rain, is often off at times, it's been a good app to plan walking trips around the area.
This apps has excellent maps with all sorts of overlays, with past recent data or forecast data, along with hourly and 10-day forecasts. This app also uses Weather Underground for data, which is one of the three major sources of weather data.
Anyway, that's what I've found so far. And while I like the Weather Live for it's simplicity and thought it was very useful for visitors to Mt. Rainier NP, I have second thoughts the weather sites they use, the Ashford site isn't an official one and the Paradise Inn is actually Crystal Mountain Resort.
And for that I wouldn't recommend it for visitors, and maybe skiers to the resort. I would use the NWS Website and bookmark the individual weather sites in and around Mt.Rainier NP.