AHPS

Advanced Hydrologic Prediction Services

Bias

An error (difference between forecast and actual) that favors a particular tendency

CFSv2

Climate Forecast System version 2

CHPS

Community Hydrologic Prediction System

Ensemble forecast

a set of single-valued forecast for the same location and times

Ensemble member

one of the single-valued forecasts in an ensemble

Ensemble spread

a measure of the average deviation between the individual ensemble members and the ensemble mean

EnsPost

Ensemble Post Processor (a function of the HEFS)

Exceedance probability

the probability of exceeding a given threshold; for example, a 0.25 exceedance probability implies that the threshold is (predicted to be) exceeded on 25% of occasions

EVS

Ensemble Verification System (a function of the HEFS)

GEFS

Global Ensemble Forecast System

HEFS

Hydrologic Ensemble Forecast Service

MEFP

Meteorological Ensemble Forecast Processor (a function of the HEFS)

NOAA

National Oceanic and Atmospheric Administration

NWS

National Weather Service (part of NOAA)

QPF

Quantitative Precipitation Forecast (part of NOAA

RFC

River Forecast Center

Single-valued forecast

A forecast with only one value for a given time and location

Uncertainty

In general terms, a lack of confidence about the "true" state of some environmental system (e.g. river stage at time X and location Y). This may be represented with a set of possible outcomes (possible "true" states) and their associated probabilities (as in the HEFS).

WPC

Weather Prediction Center (part of NOAA)