"Four years of river forecast verification statistics at the ABRFC show an overall improvement of nearly 4% in forecast accuracy with river forecasts based on QPF. River forecasts with QPF are more accurate than non-QPF river forecasts during the cooler months, mainly due to the more synoptic-scale precipitation systems. On the other hand, non-QPF river forecasts outperform QPF river forecasts during the warmer months due to small-scale convective precipitation systems. This has resulted in the ABRFC re-thinking the amount of QPF used during the warm season. QPF is a powerful tool, but due to the probability of error the farther away from the current time, deterministic forecasts using QPF may be implying more confidence than we have. Therefore, the ABRFC is considering using six-hour QPF during the warm convective season and 12-hr QPF during the cool synoptic season. Longer duration QPF's should be used operationally through the issuance of River Flood Watches and Outlooks"--Conclusions.

National Weather Service (NWS)

Arkansas