NOAA National Water Model Medium-Range Land Ensemble

GribStream Code: nwmmediumlandens

Current archive: GribStream indexes compatible source objects beginning January 1, 2025. NOAA describes the AWS source as a rolling four-week archive, so older retained objects should be treated as opportunistic rather than guaranteed permanent history.

Forecast timing: four cycles run each day. Member 1 reaches 240 hours, while members 2 through 6 reach 204 hours; all available land fields use 3-hour lead-time spacing.

Ensemble interpretation: these are six time-lagged, GFS-forced members. Their spread shows sensitivity to the forcing represented by those members; it is not by itself a calibrated probability.

Land fields only: this dataset contains the fixed 1 km land grid, not NWM's separate channel, reservoir, or terrain-routing outputs. Operational gaps and future NWM upgrades can affect availability or compatibility.

Description

The National Water Model is NOAA's operational continental-scale hydrologic forecasting system. Its land component uses Noah-MP to represent exchanges of water and energy among soil, vegetation, snowpack, and the atmosphere.

nwmmediumlandens extends that land view into the medium range with a six-member, time-lagged ensemble forced by GFS. Users can follow each member separately or combine members to examine central guidance and spread.

All members share the same 1 km CONUS+ grid and the same six land variables. Member 1 extends to ten days; the five lagged members end at 8.5 days. The collection is therefore most directly comparable across all six members through forecast hour 204.

This is a land-state dataset rather than a streamflow product. The inventory below lists the exact selectors, levels, units, lead times, and currently indexed availability.

Detail

• Archive begins: 2025-01-01
• Official NOAA National Water Model overview: https://water.noaa.gov/about/nwm
• Key features:
  • Six members selectable individually: member 1 through member 6.
  • Six source variables: ACCET, FSNO, SNEQV, SNOWH, SNOWT_AVG, and SOILSAT_TOP.
  • Snow-cover fraction, snow depth, snow water equivalent, and average snow temperature for medium-range snowpack guidance.
  • Accumulated evapotranspiration and soil saturation in the top two soil layers, representing approximately the upper 0.4 m.
• Resolution: Fixed 4,608 by 3,840 Lambert conformal grid with 1 km spacing over the CONUS+ land domain.
• Temporal coverage: Four cycles per day; 3-hourly lead times through 240 h for member 1 and through 204 h for members 2-6.
• Primary uses: Medium-range snowpack and melt scenarios, soil-wetness uncertainty, agricultural water planning, watershed situational awareness, winter operations, and comparison of land-state forecast spread.

Related datasets

• NWM short-range land forecasts for hourly guidance through 18 hours
• GEFS for broader atmospheric ensemble context
• HRRR for high-resolution short-range weather context

Parameters