It has been an active Winter across the northern US plains as it relates to ground blizzards. NWS Grand Forks, ND (FGF) has been particularly impacted, including a couple of significant blowing snow events captured on this blog here and here. Recently, NWS/FGF investigated the use of the VIIRS Snowmelt RGB as a tool for helping to determine blowing snow potential, in addition to traditional techniques that involve environmental temperature, wind speed, and age of snowpack. The Snowmelt RGB, unique to VIIRS, is discussed in this blog post.
By end of January, a nearly uniform appearing snowpack was present across E ND/W MN, per the consistent and relatively light shade of blue across the scene in the VIIRS Snowmelt RGB (Fig 1).
Liquid wintry precipitation (freezing drizzle/rain) fell across portions of the snowpack 30-31 Jan. The result on the snowpack was a “crusting” of the outer layer, and enlargement of the average grain size. This region of crusted snowpack is visualized in VIIRS Snowpack RGB imagery on 01 Feb as a swath of relatively dark blue over eastern North Dakota (Fig 2). A crusted snowpack will be less susceptible to blowing snow, even with gusty winds and cold temperatures.
Also on 01 Feb, strong northwesterly winds (>35 knots widespread) developed across the area in the presence of cold temperatures (single digits). An experimental ABI blowing snow RGB is shown in Fig 3 to characterize the extent of blowing snow with this event. An outline of the crusted snow, based on the Snowmelt RGB, is included on the imagery. Cloud cover is present much of the day over far northeast ND. While plumes of blowing snow (relatively light pink to mustard) are present across the scene over the snowpack (red), including over the crusted region, they appear to originate west (and east) of the crust. Plumes of blowing snow behave similar to plumes of blowing dust, capable of traveling far from their source regions.
A higher resolution VIIRS version of the experimental blowing snow RGB also supports the claim from ABI of a lack of blowing snow originating from the crusted region (Fig 4).
Environmental conditions did not support blowing snow on 02 Feb, but appeared possible (but quite marginal) on the 3rd. Therefore, a NWS/FGF forecaster mentioned the following in their Forecast discussion when considering the potential for blowing snow: “Uncertainty lies in snowpack susceptibility in being blown around. Latest VIIRS Snowmelt RGB reveals a ripened or crusted over snowpack in much of central ND extending into the Devils Lake basin and northeast North Dakota west of the Red River Valley. This may be evidence of limited “blowability” by the snowpack in these locations, and could limit the amount of blowing snow impacts and/or coverage.”
Blowing snow was not observed across the region on the 3rd (Fig 5). While temperatures were still quite cold (around zero degrees Fahrenheit), winds generally remained less than 30 knots, likely influencing a lack of blowing snow, in addition to the crusted snowpack.
The following day (Feb 4), the Snowmelt RGB depicted a similar pattern of crusted snowpack (Fig 6). Gusty northwesterly winds and very cold temperatures within the Red River Valley resulted in blowing snow originating just east of the crusted snowpack, as was shown in both ABI (Fig 7) and VIIRS (Fig 8).
Zooming into the northern US Red River Valley, the region of apparent blowing snow originates just outside of the eastern edge of apparent crusted snowpack (Fig 9).
Thereafter, a series of light snow events crossed the area, followed by a period of warming above freezing. By the 10th, the snowpack across the region appeared to have a uniform and comparatively crusty (darker blue) appearance (Fig 10). Another quick-moving shortwave brought snow, wind, and cold temps to the region on 11 Feb, resulting in another round of intense blowing snow (see post here).
Important to note is that the VIIRS Snowmelt RGB is not available to forecasters in AWIPS. Forecasters view the imagery on CIRA SLIDER, which does not have an ideal projection of VIIRS imagery for CONUS users, and does not include an option for political boundary overlays outside of State Boundaries, making geolocation of features difficult. Ideally, forecasters would have this information in AWIPS to allow for more efficient and accurate analysis, and for viewing in concert with other datasets. In the meantime, an online “CONUS-friendly” projection and display of VIIRS products such as this one, with political boundary overlays, would be appreciated by users.
Bill Line (NESDIS and CIRA) and Carl Jones (NWS/FGF)