A mid-upper level trough brought a variety of weather to the US during the first week of Feb 2020.
On 31 Jan, GOES-West WV imagery captured the early evolution of the trough over the central Pacific while a ridge was well established over the western US (Fig 1). Blending the satellite imagery with a model forecast not only allows one to guage model performance, but also provides a visualization of how features apparent in the imagery may evolve into the forecast period.
By 3 Feb, The ridge had eroded and the trough had advanced into the Great Basin, developing into a closed low (Fig 2). The periodic image degradation is due to the GOES-17 cooling system anomaly and and approaching vernal equinox.
The trough had sent a cold front south down the high plains during the overnight hours of the 2-3 Feb, with associated gravity wave perturbations evident in water vapor imagery (Fig 3). Combined with surface obs and RAP surface analyses, rapid pressure rises are apparent in the wake of the front, in addition to winds becoming northerly and then easterly and temperatures dropping considerable.
Nighttime Microphysics RGB imagery from GOES-West shows the rapid development of low clouds (dull yellow – green) across the high plains as temperatures dropped behind the front and the low levels became saturated. Surface obs also show winds becoming easterly upslope through the evening (Fig 4). Snowfall across the eastern plains to this point had been purely stratiform due to a saturated low layer and easterly upslope flow, per analysis of the RGB imagery.
After sunrise, cloud analysis is best done using the Day Cloud Phase Distinction RGB (Fig 5). The widespread low stratus deck (cyan) is obvious across the scene and contrasts with snow cover (green), high clouds (red), and clear ground (dark blue). By the end of this period, the upper low had advanced into northeast Utah, spreading stronger large scale forcing east across the Rockies, leading to increasing coverage of convective snow showers (textured reds).
Bill Line, NESDIS and CIRA