12-13 January Historic Snowstorm

 

This was a historical storm that was well predicted. Significant amounts of snow were predicted well in advance of impact, but as usual, the details of determining where the maximum snowfall would fall was a challenge. In the end, the axis of maximum snowfall fell over western and southwestern New England. An unofficial 24 hour snowfall of around 40 was reported in Savoy, MA, which would be a new 24 hour record for the state of Massachusetts if it is verified. Additionally, over 22 inches of snow in 24 hours was reported in the Hartford, CT area, which could break a 24 hour record if verified. Extreme 850-700 hPa frontogenesis and strong vertical motion through the dendritic growth zone contributed to more snowfall than model or ensemble guidance suggested. The 850 hPa easterly jet was nearly parallel to the 850-700 hPa thermal gradient, which can also enhance vertical motion within the axis of maximum frontogenesis. This was another case of needing to use a higher snow to liquid ratio with model/ensemble QPF. Below is just some of the guidance and data that forecasters used to predict this historical storm that was preliminarily ranked as a NESIS category 3.

 

ECMWF 500 hPa Long-Range Guidance from 7-8 January 2011.

 

 

 

 

 

 

ECMWF MSLP Long-Range Guidance from 7-8 January 2011.

 

 

 

GFS Ensemble 500 hPa, MSLP, 850 hPa winds and Prob24 hour 1 inch Long-Range Guidance from 7 January 2011.

 

 

GFS and NAM MSLP from 9 January 2011.

 

 

Short Range Ensemble Forecast (SREF) 500 hPa, MSLP, 850 hPa winds and Prob24 hour 1 inch Long-Range Guidance from 7 January 2011.

 

 

GFS Ensemble plume guidance from 10 January 2011 for Albany, NY, Keene, NH and Islip, NY.

 

 

Short Range Ensemble Forecast plume guidance from 10 January 2011 for Albany, NY, Bradley, CT, Boston, MA and Islip, NY.

 

 

 

NAM 850-700 hPa temperatures and 700 hPa 2-D frontogenesis from 12 January 2011.

 

 

NAM cross section through southwestern New England and time section in northwestern CT from 12 January 2011.

 

 

Surface maps

 

 

Upper air data from 925 hPa, 850 hPa, 700 hPa, 500 hPa and 300 hPa

 

 

 

Radar Loops

 

 

Satellite imagery

 

 

Pictures from Savoy, MA 1-2 days after the snow ended.

 

 

Preliminary NESIS Scale