How to get the latest forecast for a given valid time?

[williamhobbs]

This is somewhat related to #464.

In the examples, HerbieLatest can be used to get the latest forecast with a given lead time (including the default of fxx=0), https://herbie.readthedocs.io/en/stable/user_guide/tutorial/latest.html. Is there a way to get the latest forecast for a given valid time?

That seems like it would be useful, for example, if I want to know what the HRRR forecast is for tomorrow at noon local time. That's a little tricky, because I need to know how long it takes HRRR outputs to be available and I may need to remember which HRRR runs go out more than 18 hours.

I tried this:

today = pd.Timestamp.now(tz='US/Central').floor('1d')
noon_tomorrow = today + pd.Timedelta('36h')
print(noon_tomorrow)
H = HerbieLatest(model="hrrr", valid_date=noon_tomorrow)
H

but it gives me

2025-08-06 12:00:00-05:00
💔 Did not find ┊ model=hrrr ┊ product=sfc ┊ 2025-Aug-05 15:00 UTC F00
✅ Found ┊ model=hrrr ┊ product=sfc ┊ 2025-Aug-05 14:00 UTC F00 ┊ GRIB2 @ aws ┊ IDX @ aws

which is not what I was hoping for.

[blaylockbk]

I see what you mean. It's been awhile since I wrote HerbieLatest, but it should work for this case, but I guess what your looking for is not something I ever tested.

Given HerbieLatest(model="hrrr", valid_date=noon_tomorrow), I would expect it to look for a file with fxx=0, then increment to fxx=1, until Herbie finds a file (or until it hits some predefined max fxx so it doesn't infinant loop)