A winter storm produced 6-8 inches of snowfall from the eastern Texas Panhandle to central Oklahoma on 03 January 2019 (NWS Amarillo |  NWS Norman). On the following day, GOES-16 “Red” Visible (0.64 µm) images (above) revealed the areal extent of the snow cover, with significant melting occurring by the late afternoon hours. The snow cover seen in the far northwestern portion of the images is from a winter storm that occurred 8 days earlier on 27 December 2018.

In a comparison between Terra and Aqua MODIS Visible (0.65 µm) images and the corresponding Land Surface Temperature product at 1757 and 1936 UTC (below), LST values in the 30s F (darker shades of blue) were 20ºF colder over the snow cover than over adjacent bare ground in Oklahoma, and 35-40ºF colder than the more sparsely-vegetated bare ground in Texas. By increasing the surface albedo, the snow cover acted to suppress daily maximum temperatures by several degrees.

===== 05 January Update =====

A sequence of GOES-16 “Red” Visible (0.64 µm) images on 04 and 05 January (above) showed the continued melting of residual snow cover.

A toggle between NOAA-20 VIIRS True Color Red-Green-Blue (RGB) images on 04 and 05 January as viewed using RealEarth (below) provided a higher-resolution view of the snow cover just after 1 PM local time on those two days.

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Portions of West Texas received a light accumulation of ice from freezing rain/drizzle/fog during the daytime and evening hours on 02 January 2019. On the following morning prior to melting, in a comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above) the semi-transparent glaze of ice that covered the surface was not apparent in the Visible imagery but exhibited a darker appearance in the Snow/Ice imagery (since snow and ice efficiently absorb energy at the 1.61 µm  wavelength). Some localized white patches of light snow cover could also be seen, primarily in the Big Spring (KBPG) and Snyder (KSNK) areas.

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* GOES-17 images shown here are preliminary and non-operational *

GOES-17 Mid-level Water Vapor (6.9 µm) images with an overlay of 250 hPa wind isotachs from the GFS90 model (above) showed a string of disturbances (surface analysis) along the axis of a 180-knot “Japan Jet” across the North Pacific Ocean on 02 January 2019.

GOES-17 Split Ozone (9.6 µm – 10.3 µm) Brightness Temperature Difference images (below) include an overlay of PV1.5 pressure (an indicator of the height of the “dynamic tropopause”) — they showed the difference between cold polar air having a low tropopause (shades of cyan to blue) north of the jet stream and warm tropical air having a much higher tropopause (shades of yellow). The Split Ozone BTD is the Green component of the Air Mass Red-Green-Blue (RGB) product.

Rawinsonde data also showed the significant difference in tropopause height between St. Paul Island, Alaska (pressure=314 hPa, height=8.1 km) in the polar air of the Bering Sea and Lihue, Hawai’i (pressure=82 hPa, height=17.9 km) in the tropical air of the central Pacific (below).

GOES-17 Air Mass RGB images from the UW-AOS site (below) further illustrated the sharp contrast between the cold/dry polar air to the north and warm/moist tropical air to the south of the strong jet stream. The purple hues along the northwestern edge of the scan are a result of the “limb cooling” effect, as the satellite’s infrared detectors sense radiation from colder upper levels of the atmosphere at large viewing angles.

In addition to the series of larger disturbances along the jet stream axis, there were also some smaller-scale storms apparent in the Bering Sea (surface analyses). Better detail of these high-latitude features could be seen using Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images separated by 10 hours (below).

Regarding the strong Japan Jet, GOES-15 (GOES-West) Derived Motion Winds (source) tracked targets having velocities as high as 200 knots at 03 UTC (below).

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GOES-16 (GOES-East) Near-Infrared “Snow/Ice” (1.61 µm) images (above) revealed a darker swath — oriented southwest to northeast, from central South Dakota to central Minnesota — highlighting areas which received an accrual of ice (from freezing rain/drizzle) during a 30 December – 31 December 2018 mixed precipitation event (surface analyses). Light to moderate Freezing Rain was reported at Watertown SD (KATY) for 3.5 consecutive hours (plot | text).

As seen in a plot of ABI Spectral Response Functions (below), snow and ice are efficient absorbers of radiation (and therefore exhibit a low relectance) at the 1.61 µm wavelength, making them appear darker on the Snow/Ice imagery — and since ice absorbs more strongly than snow, it appears as the darkest shades of gray/black. Strong northerly winds in the wake of the precipitation event then swept the residual ice-crusted snow cover clear of any new snowfall.

A higher spatial resolution view using VIIRS Near-Infrared “Snow/Ice” (1.61 µm) images from NOAA-20 (at 1839 UTC) and Suomi NPP (at 1931 UTC) is shown below. The darkest areas on the Snow/Ice images appeared to be over the southern/western portion of Deuel County in South Dakota and much of Chippewa County in Minnesota.

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