An intense upper trough digging into the southwest US resulted in widespread strong winds and regions of blowing dust during the day on 15 Feb 2022. Per NWS Las Vegas, NV: “This mornings water vapor imagery (Fig 1) depicts a compact closed low dropping southward through central California with a swift southwesterly flow extending out ahead of it. Winds have been picking up through the night but will continue to increase through the remainder of the morning hours aided by a strengthening pressure gradient and daytime mixing.”

In association with the south-moving cold front and possibly convectively enhanced, a wall of dense blowing dust, or haboob, surged south through Death Valley in CA near the NV border. See photo here. Again from NWS VEF: “Visible satellite imagery also depicted a well developed wall of dust progressing southward across Death Valley, possibly enhanced by some shower activity enhancing post frontal surface winds. Given the satellite presentation and susceptibility to dust storms in Death Valley, issued a Dust Storm Warning through 245 pm for the Furnace Creek and Death Valley junction region.”

NWS VEF leverages GOES visible, Geocolor, and Dust RGB imagery in their decision making during such blowing dust events. In events such as this one, satellite imagery is the primary method for deciding to issue a Dust Storm Warning. Corresponding GOES-West Geocolor imagery and referenced Dust Storm Warning polygon is shown in Fig 2. The wall of dust is obvious in the imagery surging south along the CA/NV border. Also notable in the imagery is the lack of data between 1900 and 2010 UTC. This was a planned GOES-17 outage. Note, GOES Geocolor imagery will be available to all NWS offices in the coming months.

GOES-16 also provides useful imagery over the region, and captured the haboob well (Fig 3). The SWD (Fig 4a) signal was quite strong, resulting in the obvious signature in Dust RGB imagery as well (Fig 4b).

VIIRS Day Land Cloud RGB imagery provided a 375 m resolution view of the haboob as well, including 3 images during a ~100 minute period (Fig 5).

Considerable blowing dust developed elsewhere across the southwest US within the increasing southwesterly winds, resulting in multiple Dust Storm Warnings and Blowing Dust Advisories. An SWD-IR-L2 product combo, newly available with the recent AWIPS TOWR-S update, captures the many areas of lofted dust (dark gray) well, while also providing cloud brightness temperature information (Fig 6). Note, it is recommended to adjust the SWD colortable range to ~ -2 to 8 when using the SWD with B-W colortable to detect blowing dust.

One can access hidden L2 product information from this new menu item by sampling the scene, in this case revealing a confirmation of dust (Aerosol Dust product), as well as the considerably dry airmass (TPW) in NW NM (Fig 7). The Dust RGB + L2 Readout option includes similar information.

NWS El Paso, TX notes their use of satellite imagery in tracking the lofted dust during this event (Fig 8): “Winds are increasing, especially across the Bootheel where a wind advisory remains in effect this afternoon and evening. Satellite imagery also shows several dust plumes moving NE out of Mexico with the thickest dust noted in Luna County. Deming is reporting 2 to 4 mile vis, while the Border Patrol station at Columbus reported 100 feet. A blowing dust advisory is in effect to account for this plume as well as some other plumes over Hidalgo County.”

NWS Phoenix, AZ was also busy tracking areas of blowing dust in satellite imagery throughout the day (Fig 9): “So far today, wind gusts upwards of 45-55 mph have been recorded across portions of southeast California with slightly stronger gusts recorded in southwest Imperial County. As a result, areas of blowing dust have been generated. The most notable dust plumes showing up on visible satellite imagery this afternoon have been originating near Anza Borrego and spreading eastward across Imperial County. Additional dust plumes have been noted across eastern Riverside County near Blythe. Visibility in these areas have dropped down to around a mile or even lower at times. Thus, A Blowing Dust Advisory is in effect for much of southeast California through this evening.

Bill Line, NESDIS and CIRA, Stanley Czyzyk, NWS/VEF

Previously warm temperatures across the region had caused an aging the snowpack to crust over, limiting its “blowability”. However during the day/evening of the 10th, another quick-moving shortwave brought an additional round of fresh snowfall to Red River Valley region in E ND and W MN. As discussed in a great NWS/FGF forecast discussion on the 10th:

“This is a classic arctic front blizzard set up. The main issue is that the warm temperatures ahead of the cold front will make the current snowpack nearly unblowable. With that said, water vapor imagery indicates an upper level wave (currently way upstream) that should lead to an area of very light falling snow behind the cold front, and combined with the strong winds would lead to a 3-5 hour period of blizzard conditions. Most guidance does indicate very light QPF. Typically, in these CAA regimes we tend to develop additional convective snow showers, which would prolong the blizzard type impacts. However, the development and intensity of these convective snow showers is uncertain. If the snow showers persist, blizzard conditions would last into Friday afternoon.”

As discussed in the above forecast, plummeting temperatures and strong winds behind the front indeed resulted in widespread blowing snow by the early morning hours of the 11th, lasting into the afternoon and aided by the development of HCRs, especially across the Red River Valley. GOES-East imagery was utilized by NWS/FGF forecasters during this event to narrow down the spatial extent of the Blizzard Warning, as discussed here and below. Corresponding GOES-East Imagery is shown over the region in Fig 1, along with the warning decision on the NWS WWA map (Fig 2).

“Along the glacial lake valley floor horizontal convective rolls can be seen on satellite and from KMVX radar indicating blizzard conditions with widespread white outs causing many east to west road closures in MN and portions of I29. With the help of the satellite imagery did narrow the blizzard warning and removed the tier of counties from Roseau to Mahnomen along with western Walsh and Cavalier in ND.”

Afternoon VIIRS passes provide an alternative, high resolution view of the blowing snow and related HCRs (Fig 3+4).

A full day (2/11) GOES-East animation captures the longer term evolution of the blowing snow and HCRs across the Red River Valley (Fig 5).

Bill Line, NESDIS and CIRA

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)