Figure 7. Hourly animation of modeled SWE from 0 UTC April 4 through 23 UTC April 6,  illustrating rapid snow melt resulting from warm air temperatures and rain-on-snow, followed by snow fall and accumulation of the snow pack. Warm air temperatures and rainfall beginning on April 4 resulted in rapid, widespread ablation of the snowpack, but as the rain turned to snow, accumulation begins again, especially in the northwest part of the study area (central North Dakota primarily).  Conditions such as these are exceptionally complex from the standpoint of the physical processes involving snow accumulation and melt, but are not unusual in this part of the country.   Although quantitative validation of the model during this event would be exceedingly difficult, the model appears to simulate a snow pack response that is in accordance with conceptual ideas about rain-on-snow events and warm-air advection over snow.



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