GEOS Model Outputs for Early Season Snowfall in the Northeast US

Authors: William Putman

The mid-Atlantic and northeastern United States received an early season snowfall on December 11th 2023. The Goddard Earth Observing System (GEOS) atmospheric model estimates snowfall amounts using the amount of frozen precipitation that reaches the surface using either a simple 10:1 snow:liquid precipitation ratio (left, from GEOS-FP [forward processing system] at 12km horizontal resolution) or using by using the maximum temperature in the lower levels of the atmosphere to produce a varying snow:liquid ratio (right, from an experimental GEOS forecast at 4km resolution over the US). The improved resolution of ridges and valleys in the regional topography along with the more sophisticated snow:liquid ratio scheme produces a more realistic forecast for this early season snowfall.

slide graphic from snowfall
Figure 1: GEOS-FP 12km (left) and GEOS-Exp 4km (right) snowfall forecasts, Kuchera ratio, +30hr.

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