Introduction

Welcome. This training website is intended to help the WFO forecaster better understand the process of how the HAS forecaster provides QPF/snow levels to the NWSRFS river model. The training has been organized into individual sections that describe key portions of the overall process and investigate some of the underlying concepts of the tools used by the HAS forecaster in forecasting precipitation.

HPC Guidance

The QPF process begins with HPC. They provide the HAS forecasters with the initial QPF guidance on a schedule of twice-daily final 3-day QPF products, as well as intermediate preliminary updates. The data are sent to the CNRFC as point data and is reviewed and/or adjusted by the HAS forecaster using Mountain Mapper software. In this section, we provide details on the important role that HPC plays in the QPF process.

HAS QPF Process

Probably the most important job of the HAS forecaster at the CNRFC is to provide QPF and freezing level input to the hydrologic model (NWSRFS). Accurate QPF is essential in the successful forecasting of the fast-responding rivers that characterize most of the rivers within the CNRFC area of responsibility. Because of NWSRFS model input requirements, QPF is provided in 6-hour timesteps for the next three hydrologic days (12UTC-12UTC) or a total of 72 hours. In this section, we describe the process and introduce you to the tools used in preparing the QPF.

Mountain Mapper

Mountain Mapper is actually a suite of software developed at the CBRFC in Salt Lake City, with the programming code developed by Senior HAS Forecaster Craig Peterson. Included in the Mountain Mapper suite are individual programs used to to generated gridded QPF from point QPF input, and also to quality control observed precipitation. Common to both of these programs is an underlying concept of using monthly PRISM data to account for the impact of terrain on the distribution of observed and/or forecast precipitation in developing a gridded dataset. This section will focus more on the QPF portion of the suite known as SPECIFY, which is ultimately used to generate Mean Areal Precipitaton (MAP) estimates that become input to the hydrologic models at the River Forecast Center.

PRISM

PRISM data is the foundation of the entire Mountain Mapper software process. This section will provide a brief description of PRISM data and how it was derived.

Orographic Aid

The orographic aid in its current state was developed by retired Sr. HAS Forecaster Owen Rhea in the mid to late 1990s. The aid is based on Owen's original orographic model concept developed in the 1970s. The aid has been used routinely at the CNRFC since about 1998 and has been automated to run using meteorological inputs from both the Eta and GFS models. The NWSRFS hydrologic forecast system actually uses 5 days of QPF, with the first 3 days provided by the HAS forecaster, and days 4 and 5 using output from the Rhea Orographic Aid based on the 00UTC run of the GFS model. This section will describe the inner workings of the Rhea orographic aid.

Page last modified: January 23, 2004