. . . a) Southeasterly low-level flow developed over Lake Huron early on 08 Dec 1995. The low-level instability was high, with a 16 deg C difference between the water temperature at mid-lake, and the 850mb temperature at Y62. Visible satellite imagery showed that an extremely long and persistent mid-lake band developed over the lake early in the day with an open water trajectory > 100 nm. This band remained to the south of Sault Ste. Marie most of day, but moved slowly northward as evening approached. Heavy snowfall began at dusk, and by noon (LST) the next day, 24.7" of snow had accumulated. During more than 50% of this period, overriding cirrus hid the LES band from view.
. . . b) When the surface low moved northeastward, low-level flow veered gradually to become southwesterly. This change of flow direction brought low-level air from Wisconsin and the upper Michigan peninsula, temporarily ending the lake effect snow. A total of 1" of snow fell during the transition period which lasted from about 1600 UTC on 09 December, until about 1030 UTC on the 10th.
. . . c) Following a 19 hour respite, west-northwesterly low-level flow developed across Lake Superior, and northern Michigan. The low-level instability was again quite high with a 23 deg C difference between mid-lake and the 850mb temperatures at 0000 UTC on 10 December, and 19 deg C at 1200 UTC. Infrared satellite imagery showed the development of a long, persistent mid-lake band over Lake Superior with the deepest convection in a position to deposit the majority of the heavy snow over Sault Ste. Marie. A secondary enhancement seems to have occurred through convergence with a lake-parallel band from the Superior shore of the upper Michigan peninsula. As the snowband moved into the Y62 area, snow to liquid ratios decreased from about 28:1 to about 18:1. Total snowfall during this period was 32".
. . . d) Analysis of sounding data from Sault Ste. Marie shows that the air within the LES band was substantially different from the surrounding environment. The height of the -15 deg C level above cloud base seems to be important in determining the periods of heavy snow, at least in this event. Since cold air advection was occurring throughout this period, and presumably mixing between the LES band and its environment was cooling the cloud, it is not surprising that the height of the -15 deg C level lowered. Forecasting when this cooling will occur within a given LES band may be important, but with current capabilities there is no easy way to do it.
. . . e) Combined information from satellite imagery, soundings, and cloud physics principals helped in understanding the nature of the convection within these lake bands, and furnished an explanation for the water signature observed in the combined 3.9/10.7 um product.
. . . f) Satellite imagery was found to be helpful in a variety of ways, including; 1) determining cloud top temperature to compare with the lake surface temperature as a measure of buoyancy, 2) positioning the lake effect band in the absence of radar, 3) locating the active convection in the line to specify places with the heaviest snowfall, and 4) Using the 3.9 um imagery to identify active LES bands with detectable liquid water at cloud top. The 3.9 um imagery also provides a potential tool for learning more about the kinematics and microphysics occurring with the Lake Effect Snow bands.