Areas of Excessive Rainfall from Southwest U.S. Monsoons; Monitoring Tropical Cyclone Formation Which Could Impact the Southeast U.S.

In Arizona and New Mexico, heavy to excessive rainfall from monsoon thunderstorms may bring isolated flash and urban flooding today into Sunday. Tropical wave (AL94) is likely to become a depression by late Friday or over this weekend in the vicinity of the Bahamas. Significant uncertainty remains in the track and intensity, but chances for impacts to the southeast U.S. coast are increasing. Read More >

Summary infographic of the warm stretch

What is Noteworthy About This? While 50s and even 60s certainly do happen in December, this prolonged duration was particularly noteworthy because it was accompanied with a great deal of sunshine and occurred late in the month (more rare) and overlapped the Christmas holiday.

Why So Warm? The weather pattern for several weeks had generally been a mild one. In fact December 2019 has only had five days with below normal temperatures in Chicago. The pattern has also been notably drier than much of the autumn was. The drier pattern has resulted in well below normal snowfall for December, and without snow on the ground locking in colder air, any cold surge has been temporary. Finally, southerly winds were dominant for days, resulting in inching up temperatures, and the sunny pattern (helped by lack of snow cover in the region), further resulted in warming.

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Areas of Excessive Rainfall from Southwest U.S. Monsoons; Monitoring Tropical Cyclone Formation Which Could Impact the Southeast U.S.

Late December 2019 Warmth