Winter Storm — Southern Coos, New Hampshire

2021-01-16 · Southern Coos, New Hampshire

Event narrative

Snow began on the morning of the 16th and continued into the mid afternoon hours. A mild mid-January air mass resulted in a strong elevation dependence to snowfall amounts. Snowfall amounts near 15 inches occurred in the higher elevations of the White Mountains with totals as low as 3 inches in the Connecticut River Valley.

Wider weather episode

On the 15th low pressure occluded over the Great Lakes and secondary cyclogenesis began near the triple point off the Mid Atlantic coast. Secondary low pressure rapidly deepened into the 16th. This strong low pressure developed an equally strong moisture transport which impinged upon the higher terrain with upslope enhancement. A very marginal air mass for mid January meant that snowfall totals were highly dependent on elevation in order for temperatures to be cold enough for all or mostly snow. Warmer temperatures and downsloping meant that valley locations had significantly less snow than higher elevations. Precipitation was heavy at times but generally fell over a 6 to 10 hour period and limited snowfall totals to around a foot at most.

Source: NOAA Storm Events Database, event_id 931621. Narrative written by the NWS forecast office that issued the report.