What window is being used?

[ciroque]

I have been unable to ascertain how the service determines the window of data being returned. I am using the /gridpoints/SEW endpoint. The first record seems to be some arbitrary time. How is the data window determined?

[JJKraw]

Not quite understanding the question. Can you show a specific query, the data returned, and which part of that data you are asking about?

[ciroque]

Hi, apologies for being vague. Given this query: https://api.weather.gov/gridpoints/SEW/119,76, as of the time of this writing the first record I get in the properties.temperature.values[0].validTime path has a value of "2021-10-25T04:00:00+00:00/PT2H".

I am wondering about the time component of that value. In previous queries the time component of the first value has been "T18:00:00+00:00".

If I could go back in time would I find that the previous entry had a duration that ended at this time?

[scadergit]

The gridpoint endpoint will collapse same forecast data into duration, in this case PT2H indicates that the same forecast data is valid for 2 hours versus the default one hour, or 04:00:00 and 05:00:00, and the next record would be for 06:00:00.

[scadergit]

I might have read that question too quickly, and over-simplied the answer.

[ciroque]

Appreciate the quick response!

My goal is to show a chart of the temperature over a period of 3 to 7 seven days (configurable by user). I was hoping to get the data from midnight for the current date on through the end of the data set (Side question: is it possible to limit the number of days returned?).

I can certainly extrapolate values backwards, or just fill them in with 0 if the data is not available. I cannot make an argument to cache data from previous queries, however as that over-complicates my app.

Back-padding shouldn't be too difficult, but if I am back-padding 18 hours worth of data it limits the usefulness of my app. So that's where my real question lies.

Is there a way to consistently determine how far off midnight the first record will be?

The RLE I get, and it's intriguing. That should not be too problematic to unroll.

[Rhut-virani]

is there a way to get data returned from midnight?

[dwhitemv25]

Please don't necro old threads. This one is from October 2021. Please post a new question next time.

No, there isn't a way to have the start time justify to midnight, not documented anyway. The NDFD elements that /gridpoints exposes don't all have hourly resolution, so in some cases their valid times will span "local midnight" instead of beginning or ending there. If it causes problems, write code that 'splits' the periods on day boundaries. Code libraries than can manage ISO8601 dates should be able to handle it.