Usually at Starpath we concentrate on marine weather, being the weather on ocean, coastal, and inland waters, but this is a note about weather on land, anywhere in the US.
The National Weather Service (NWS) is the primary source, and there are indeed free mobile apps to access NWS products. But there are ways for us to get more specific and more timely information than available in standard NWS products, and some of this information we cannot get from the NWS, although the NWS themselves use this same data when making their forecasts.
I refer to the numerical forecasts of the National Blend of Models program, and especially their continental US version, called NBM CONUS. This model gives a forecast every 1.35 nmi (2.5 km) across the US and large parts of Canada and Mexico.
The forecasts are for every hour, out to 18 hr, then every three hours for 2 days. It extends farther out in time, but that is not pertinent, because the main value of these forecasts are their immediacy. The model forecasts are updated every hour, so the primary value here is for shorter term forecasts of say a day or so, then we just update this same forecast as often as we like.
The reason I title this "best app" and not just "best model" is the app I refer to (LuckGrib for iOS) is the only app I know that can access and display what I believe is the best data set for land based weather. It is also well suited to be set up for your area of interest, after which you can just turn it on and refresh for latest forecast, with all parameters laid out in a nice meteogram format.
The meteogram display is a very convenient way to look at the forecast. This can be for just 18 hours, or ask for 3 or more days. The screen can also be captured in your phone or tablet to refer back to once you learn what really occurred with the wind, rain, temperature, and so on.
The LuckGrib app (LG) includes many sources of data, meaning many different numerical models. It is my belief that this source (NBM CONUS) is the best for inland weather, but I will leave that argument for another article; everyone can establish their own conclusions with experience. Screen capture the forecast then compare with what subsequently happens.
Besides the fact that the NBM encompasses all data and numerical models that are available (it is a blend, not a single model), and that it is updated every hour, a key attraction is it also presents the statistical dependability of the forecasts in the form of a standard deviation (SD) parameter. This was not shown in Figure 2 (to simplify that first look at a meteogram), but we can select it in the list of parameters when setting up the forecast. For daily use of this app and forecast it would seem logical to include this important information.
Figure 3. Landscape view of the temperature forecast (solid line) along with the SD (dashed line) at two different times.
From this we can say that the forecasted temperature at 2 hr into the forecast is 37º ± 1.1º and at 17 hr into the forecast the temp is 48º ± 1.7º. In other words, we can think of the SD as an error bar or uncertainty in that simple manner, but the information in the SD is actually much more specific. The diagram below shows how the SD is used to characterize a statistical distribution of results.