A broad mid-upper level trough and associated shortwaves moving across the country resulted in numerous weather impacts, including but not limited to heavy snow, blowing dust, and severe storms. A detailed analysis of GOES water vapor imagery is provided by NWS/LUB, with associated imagery shown in Fig 1 and Fig 2.
“08Z analysis indicates a gradually amplifying, positively-tilted trough pivoting over the Great Basin with a shortwave trough embedded within the broader flow and rounding the base over southern Nevada, with the infant stages of a developing baroclinic leaf ahead of it as mid-level frontogenesis intensifies over the Intermountain West. A secondary, more-compact shortwave trough was analyzed over northern Sonora with a pair of vorticity lobes (induced via horizontal shearing instability due to the largely barotropic state of the atmosphere over the eastern two-thirds of the CONUS) rotating northeastward over the Texas Panhandle and the east-central Great Plains; all of which is seen on water vapor imagery.”
VIIRS Day Cloud Phase Distinction RGB imagery provided a high resolution (375 m) look at the snow cover (green) before (Dec 3) and after (Dec 11) the snowstorm over Colorado (Fig 3). The Colorado mountain snowpack had been well below normal prior to the storm.
Strong gusty winds (widespread over 35 knots, localized over 50 knots) developed across the southern Plains south of the surface low as the mid-upper level jet advanced over the region and deep vertical mixing set in during the afternoon. The relative position of the this jet core can be analyzed in water vapor imagery as strong cold to warm poleward temperature gradient extending southwest from the main shortwave. The 250 mb Jet as analyzed by the RAP NWP model aligns with that per the water vapor analysis (Fig 4).
The strong winds across dry antecedent lands resutled in widespread blowing dust across the southern plains. As has been discussed numerous times on this blog, the GOES 10.3 – 12.3 um Split Window Difference (SWD) captured lofted dust as near zero to slightly negative values compared to otherwise mostly positive values. The SWD in this case captures numerous large and long lasting dust plumes during the day, lasting into the early evening (Fig 5). Dust is not only diagnosed by the values, but also by the unique motion and streaky appearance of said values. Visibility was periodically reduced significantly within the blowing dust plumes.
Given the dry and windy conditions, rapid growth and spread of wildfires, should any develop, was also a concern. Several wildfires did indeed develop, including within the NWS/OUN forecast area. Forecasters at NWS/OUN were motioning GOES Imagery for wildfire hot spots, and blowing dust, writing:
“Several hot spots associated with wildfires have been observed on satellite so far this afternoon, as strong winds and low RH continue to lead to near-critical fire weather conditions. Clouds have been a bit more extensive than forecast across western portions of the area, with fires most prevalent so far within
clearing across central into southwest Oklahoma and western north Texas, on the western edge of the low-level thermal ridge. Expect fire risk to continue through the afternoon ahead of a cold front currently advancing into far northwestern Oklahoma….For this forecast, will mention MVFR restrictions in blowing dust at KLAW and KSPS ahead of the front closest to dust plume evident on satellite.”
Since wildfires and blowing dust often occur together, a Dust-Fire RGB was developed to highlight both in a single image, in addition to masking out clouds. The Dust-Fire RGB is shown over parts of OK and TX during the afternoon of the 10th (Fig 6). Blowing dust appears as relatively bright green, clouds generally as blue, and wildfire hot spots as red. The cold front is also diagnosed pushing south through the Panhandles and N OK by the end of the animation.
One-minute Imagery from GOES-East was available to forecasters to monitor the wildfire threat. Geocolor imagery also captured the blowing dust (and smoke plumes) well during the day, and can be combined with SWIR imagery to also highlight wildfire hot spots (Fig 7).
Natural Color Fire RGB imagery from VIIRS provides a detailed view of a wildfire, its smoke plume, and a large dust plume in North Texas near the S OK border (Fig 8).
Further east across the southeast, severe thunderstorms developed as the broader system brought anomalously moist low level air into the region along with favorable wind shear. GOES-East 1-min imagery was also available over this region to aid forecasters in tracking thunderstorm development and evolution. The thunderstorm associated with the Quad State tornado (moving from southwest to northeast across domain) exhibited a consistent and strong updraft per the cold OT, periodic AACP, and persistently high GLM flash rate (Fig 9).
Bill Line, NESDIS and CIRA