Winter Weather Smorgasbord Started on Thanksgiving Continues into the Weekend

On the Wednesday night before Thanksgiving, freezing rain first was reported  in Nebraska and has continued into Saturday. It was interesting to watching how that all came together and occurred.

 

How the different winter weather types occur. Notice the large area of warm weather with the small cold air wedge near the surface.
How the different winter weather types occur. Notice the large area of warm weather with the thin cold air wedge near the surface. Via NWS Northern Indiana.
Morning atmospheric sounding profile in Amarillo, Texas showing warm and cool pockets in the atmosphere. It's a perfect sounding for freezing rain.
Morning atmospheric sounding profile in Amarillo, Texas showing warm and cool pockets and the freezing line in the atmosphere . It’s a perfect sounding for freezing rain. Annotated blue and red boxes added later by author.

 

A block in the atmosphere over the Western United States helped to slow up the upper level flow across the United States and stall a cold front over the Midwest. The cold air over the Western US allowed for plenty of snow from portions of the West Coast east to Western North Dakota down to New Mexico. While the upper level flow slightly to the east of the cold front contained, as is usual, air that changed from below freezing temperatures to above freezing temperatures from high to mid-to-lower tropospheric level and remained unchanged as a result of the stalled flow, the lowest level flow continued to flow in from the north bringing cold air into the Midwest. This cooler and denser air created a wedge underneath the warmer air aloft and, coupled with moisture falling from above freezing temperatures to near or below freezing temperatures at the surface, allowed for rain that froze on the ground near the cold front.

 

Weather reports showing snow in the west, ice in the middle and rain totals and flooding east.
Weather reports showing snow in the west, ice in the middle and rain totals and flooding east.

An article by a local news station in Oklahoma, KOCO, reported over 50000 customers of OG+E electrical company were without power. OG+E had several crews on standby and could call other areas and other companies for help if needed. The fire department was also busy with over 70 calls reporting down power lines as the freezing rain coupled with wind created a hazardous situation.

 

5 day forecast of rain from the Wednesday morning before Thanksgiving to Monday morning the next week.
5 day forecast of rain from the Wednesday morning before Thanksgiving to Monday morning the next week. Via WPC.

 

Upper level wind pattern showing the air curving back toward the southwest in the Southwest indicating a block and the combined (phased) jets just south of the block enhancing precipitation in the Southern Plains
Upper level wind pattern showing the air curving back toward the southwest in the Southwest indicating a block and the combined (phased) jets just south of the block enhancing precipitation in the Southern Plains

 

At the same time, in front of the cold front, plenty of plain rain continued to flow through the Southern Plains including Northeast Texas. Here, a Flash Flood Watch is up until Sunday night and a Flood Warning is up until Monday morning indicating the amounts of rainfall. The WPC forecasted over 8 inches from Northeast Texas into Eastern Oklahoma. When combined with previous rainfall from the previous summer and fall seasons, Texas has reached an annual record for rainfall in the Fort Worth, Texas area and Waco, Texas has reached its fifth highest annual rainfall total according to the National Weather Service Office in Fort Worth. This will probably continue to increase as we head into December with El Nino continuing enforcing the subtropical jet, which helps enhance low pressure systems. This subtropical jet was further enhanced by the polar jet combining with it (called phasing) in the Southwestern United States.  The jet stream along the cold front in the area was also oriented from the southwest to northeast  (positively tilted), which allows more warm, moist air to flow in ahead of the cold front, further enhancing the moisture content along the front.

Record annual precipitation total acquired for the Dallas-Fort Worth area and 5th highest in Waco, Texas.

Record annual precipitation total acquired for the Dallas-Fort Worth area and 5th highest in Waco, Texas. Via NWS Fort Worth.

 

As a low pressure system forms in the Southwest, the moisture will be moved to the northeast and snow and rain will be the main precipitation types by Monday night.

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