Strong northwesterly winds across North Dakota snowpack resulted in widespread blowing snow on 18 Jan 2022. The blowing snow reduced visibility considerably (less than 1 mile) in many areas, as was highlighted by NWS Bismarck, ND here (below) and here. NWS offices leveraged satellite imagery in their forecasts/analyses and communication of blowing snow during this event.
NWS Bismarck leveraged GOES satellite imagery to help shape their understanding of the blowing snow event and influence their forecast products. Specifically during the late morning, satellite imagery of blowing snow resulted in the addition of a county to the Winter Weather Advisory: “Quick update to add Divide County into the Winter Weather Advisory given satellite imagery suggesting significant blowing snow continuing from eastern parts of the county upstream into southern Canada.”
In the early afternoon, NWS/BIS provided a detailed update to the forecast/analysis of blowing snow, shaped by several observational data sources, including trends in satellite imagery: “Web camera trends suggest the lowest visibilities are more variable than ASOS/AWOS sensors alone would suggest, while satellite imagery suggests the most significant blowing snow is related to well-defined plumes that are occurring in Horizontal Convective Roles (HCRs). For the most part, those HCRs are relatively widely-spaced, leading to the variability in visibilities spatially, and temporally as the HCRs shift slightly with the background flow. Satellite imagery does suggest the most widespread blowing snow plumes are centered over Burke County and vicinity, where impacts are likely most significant. In the end, we continue to monitor trends for the need for any Blizzard Warning upgrades, but are holding off for now. Changes with this update cycle were mainly focused on observational trends through the afternoon hours, with no significant adjustments.”
GOES-East satellite imagery referenced in the discussion, specifically the default Day Snow-Fog RGB available in AWIPS, is shown in Fig 1. The plumes of blowing snow organizing into HCRs are easily diagnosed in the imagery streaming south across North Dakota. These are highlighted in the imagery as subtle difference in color (brighter red) compared with the background snow-covered surface, and the shadowing along the northern edges of the tall plumes.
As was introduced in this recent blog post, an attempt to further highlight areas of blowing snow, and associated HCRs, is made with an experimental Blowing Snow RGB (Fig 2). Regions of blowing snow, especially the HCRs, further stand out against non (or weaker)-blowing snow, snow-covered background.
Afternoon VIIRS passes provide a detailed view of the blowing snow plumes and HCRs via a similar experimental Blowing Snow RGB (Fig 3).
The afternoon NWS/BIS forecast discussion included further analysis blowing snow in satellite imagery. “Satellite shows well-defined blowing snow plumes embedded in Horizontal Convective Rolls (HCRs), which have been becoming somewhat more widespread in that corridor as temperatures fall to 0 F or below, increasing the ability for snow to be lofted, especially in areas where the heavy snow fell late last week and strong winds today eroded any crust….We will however continue to monitor the situation, especially since satellite trends do suggest some increase in HCRs and related blowing snow plumes recently, perhaps as the boundary layer depth shrinks a bit. Interestingly, those satellite images also suggest blowing snow is being transported as far south as Burleigh County, where the pre-existing snowpack on the ground is indeed sufficiently crusted to not be broken even with the winds today.”
NWS Grand Forks, ND also leveraged satellite imagery during this blowing snow event, discussing: “… along with horizontal convective rolls are producing snow showers and based on satellite trends, have increased in coverage, pushing into the central valley.” Downstream, NWS Aberdeen was monitoring satellite imagery for blowing snow: “Based off of satellite, we are seeing blowing snow in North Dakota continuing to push southeast. With the snow in our area crusted over, that should limit any lofting of snow from the strong winds…”
NWS/FGF further took advantage of satellite imagery by including it in their public messaging of the hazard (also below).
Compare the above RGBs with single-band VIS and IR imagery in Figs 4 and 5, respectively. While the presence of blowing snow/HCRs can be realized given the shadowing in the VIS and slight temperature difference in the IR, the exact location and extent of blowing snow, especially non-HCR areas, is much more difficult compared to in the multi-spectral, RGB images.
Bill Line, NESDIS and CIRA