Cool, dry air to follow frontal showers

Published 7:00 am Saturday, November 30, 2019

By Skip Rigney

Thanksgiving Day was as beautiful as was forecast a week earlier. A ridge of surface high pressure extended down the Mississippi River Valley from Minnesota to the northern Gulf Coast.  High pressure in the upper atmosphere was centered over the Gulf of Mexico and extended northward. The effect of high pressure from the surface upward seven miles high into the atmosphere was to keep our skies sunny and temperatures mild on both Thursday and Friday.

However, some big changes are expected on the weather map on Saturday across the central United States, and they will translate into a major swing in our weather over the next few days.

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As is often the case, the major player in these changes is headed our way from the West Coast. On Thursday a large and intense low pressure system gave southern Californians a memorable Thanksgiving. The enormous cyclonic circulation brought cold air, rain, and snow to areas that don’t often see much of those weather phenomena.

Radio disc jockeys with a sarcastic bent in Los Angeles and San Diego must have been tempted to reach into the archives and play the 1970s hit “It Never Rains in Southern California” as precipitation drenched the region. Anaheim, home of Disneyland, picked up over an inch of rain on Wednesday and Thursday.

Adding to the misery of visitors to the “Happiest Place on Earth” it was a cold rain. Anaheim set a new record for lowest November 28th high temperature ever, reaching only 54 degrees.

Meanwhile on Thursday, less than 100 miles inland from Disneyland, the cold low pressure system was dumping copious amounts of snow in the high desert and mountains. I don’t usually think of southern California as a snow skiing mecca, but there are several large ski resorts in the mountains east of Los Angeles. With the storm providing one to three feet of the white stuff there, the ski resorts have what they need for a big post-Thanksgiving weekend of business.

By midday Friday, the center of the low pressure system had moved eastward into Utah, and snow was falling from the mountains of Arizona in the south all the way to Montana’s border with Canada in the north. Today the low pressure system will continue to move northeastward into the northern Great Plains, bringing a blizzard to parts of Wyoming, Nebraska, and South Dakota.

Stretching southward from the low is a cold front that will move into Louisiana and Mississippi causing showers tonight and early Sunday morning. There will likely be a few thunderstorms mixed in with the showers, and while there is a risk that a few of the storms could become strong, forecasters expect that risk to be low. Rainfall totals are expected to be light, probably less than one-quarter inch.

Behind the front on Sunday afternoon it should be sunny with low humidity, but it will also be about 10 degrees cooler than Saturday with highs in the 60s.

Northerly winds will continue to bring even cooler air in with Monday’s highs remaining in the 50s. A light freeze is possible Tuesday morning.

Keep your sunglasses handy Sunday through Wednesday as high pressure keeps our skies clear before clouds return on Thursday and showers on Friday.