A favorable large scale pattern set up across the Great Lake region to result in an impressive Lake Effect Snow Event for Upstate New York. NWS Forecasts of a considerable snow event were out days in advance, and would end of easily verifying. NOAA Satellite Imagery provided insight into this event, from the relevant large scale features down to the individual snow bands.
GOES Water Vapor Imagery, with an overlay of RAP 500 mb height contours, from late on the 16th through the first half of the 18th captured a series of shortwaves advancing through the region, helping to provide large scale forcing and additional moisture to the event (Fig 1). An initial shortwave exited the eastern Great Lakes early on the 17th. The second and more intense shortwave pushed across the eastern Great Lakes late on the 17th, and was easily diagnosed in satellite imagery with increasing moisture and cloudiness (light blue to white to green) apparent on the leading edge. In the wake of this wave, favorable westerly to southwesterly deep flow developed across the eastern Lakes, ahead of another shortwave entering the region early on the 18th.
GOES RGBs can be valuable tools to supplement radar data during Lake Effect Snow Events. Specifically, at night, Nighttime Microphysics RGB imagery helps to differentiate cloud types at night, including the mid-level and glaciated clouds associated with the LES bands (orange) from higher ice clouds (red) and lower liquid clouds (bright green). After sunrise and switching over to the Day Cloud Phase Distinction RGB, the mid-level glaciated clouds appear as yellow, while the lower-level stratus and liquid cloud (tops) are bright cyan and higher ice clouds are red. The animation in Fig 2 transitions from the nightMicro RGB to DCPD RGB, and helps to connect features and how they appear between the two. Also present in the animation is GLM Flash Extent Density, which revealed considerable lightning activity associated with the LES bands, helping to highlight the most intense convection and areas of snowfall. The organization of the LES bands is evident in the NightMicro imagery through the night on both eastern Lakes, and remain organized into the day on the 18th.
VIIRS Day Night Band Near Constant Contrast Imagery from the night of the 17th provides a visible like image of the LES bands, particularly the one that had matured over Lake Erie by this time and the early organization of the Lake Ontario band (Fig 3). The NCC imagery provides unique texture details of the cloud tops not available in IR imagery, helping the user to diagnose convective elements. With a lack of light at this point of the moon cycle, city lights begin to dominate. Being creative with color tables, one can try to isolate the city lights from the clouds, such as what is done in the figure. The city lights are in color, while the clouds are in grayscale.
In addition to the large scale support previously mentioned, the smaller scale setup favored the development of Lake Effect Snow bands during the night of the 17th into the 18th. DCPD RGB imagery with sfc, 850 mb, and 700 mb RAP winds, and 700 mb temperatures, show a favorable environment for LES had set up over Lake Erie by the morning of the 18th (Fig 4). The lower level winds showed little variation with height, and the 700 mb temperatures(~-20C) were considerable cooler than the Lake (~10C). Connecting the proper NWP variables with satellite observations can be a useful strategy for maintaining situational awareness, and connecting what the models are showing to what is being observed.
Leveraging the RGB + Derived Product Readout Menus in AWIPS (satellite > Local Menu Items), one can get even more information out of the satellite imagery. The DCPD RGB procedure, when sampled, reveals cloud top information such as cloud top height and phase (Fig 4a). Sampling the suspected LES band near Buffalo in this example confirms glaciated cloud tops, plus cloud top heights over 10,000 ft.
A 2-panel animation comparison the DCPD RGB with MRMS Composite Reflectively helps to show the relation between radar echoes and how those features appear in satellite imagery (Fig 5). This can be useful knowledge for when needing to diagnose snow bands below radar beams and in radar poor zones, but also to supplement available radar. Identifying trends such as increased cloud-top glaciation, cooling clouds, and increase in cloud texture could be useful in identifying intensifying snow bands. Re-positioning and re-orientation of show bands, as well as tightening of cloud edges, are also useful pieces of information that may be gleaned from the satellite imagery.
All of the aforementioned features are more easily diagnosed in 1-min imagery, such as the 1-min DCPD RGB imagery shown in Fig 6.
NUCAPS temperature and moisture profiles provide information about the thermodynamic environment between synoptic balloon launches. NUCAPS profiles sampled from both Lake Erie and Lake Ontario for this event in the middle of the night show decent lapse rates (even morose if you consider the warm lake temperatures and resulting lake-induced instability) and moist profiles (Fig 7).
Finally, the NESDIS Snowfall Rate product, derived from Microwave data on polar-orbiting satellites, captured intense instantaneous snowfall rates within the column, including rates of at least 0.14 in/hr liquid equivalent (Fig 8)!
Lake effect snow continued off of the two lakes, off and on, through Sunday evening, finally clearing by Monday morning. The animation in Fig 9, similar to in Fig 2, shows the evolution of the bands from Thursday night through Monday morning.
Bill Line, NESDIS