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Tuesday, December 23, 2025, 10:00 UTC





500 hPa geopotential and 500 hPa geopotential
anomaly over the US,
24.12 12 UTC
Source: wxcharts 		5-day precipitation totals over
California,
until 28.12 12 UTC
Source: CNRFC 		2 m temperature anomaly over the US,
25.12 21 UTC
Source: wxcharts 		Flash flooding risks over the US,
25.12
Source: WPC NOAA


Heavy precipitation, record warmth
USA

Issued: Tuesday, December 23, 2025, 10:00 UTC

A potent atmospheric river will bring abundant precipitation to the Western US over the Christmas period. 5-day precipitation totals of more than 250 mm are likely in the mountain ranges of California. Over the Midwest, a strong subtropical ridge will lead to well-above average temperatures. In the Great Plains, the warmest Christmas Day on record may be observed.

23.12.2025

An active Pacific jet stream pattern is currently affecting North America. A large trough is located off the west coast of the US. Ahead of said trough, a potent atmospheric river has developed, bringing moist air masses to the Western US. In the past few days, heavy rains have already impacted California. In parts of the Sierra Nevada, precipitation totals of more than 500 mm have already been observed in the past 72 h. Throughout the Christmas season, another powerful storm is expected to impact California. Along westward-facing flanks of the Coastal Mountain ranges and the Sierra Nevada, 5-day precipitation totals well above 250 mm are likely.

Sinking snow levels will lead to a considerably larger fraction of snowy precipitation during the Christmas Days across the Sierra Nevada. For most of the Sierra Nevada, the Christmas Day storm will mark the first significant snowstorm of the season. Widespread fresh snow accumulations of more than 1 m above 2000 m are likely. Locally, multiple meters of fresh snow accumulation must be expected, accompanied by hurricane-force winds. Heavy precipitation is expected to raise serious flooding concerns across California. Especially in the LA metropolitan area, the flash flood risk is high due to the devastating wildfires in January.

East of the trough, a subtropical ridge will expand across much of the Central and Eastern US, leading to well-above-average temperatures across the Midwest. In the Great Plains, temperatures are expected to soar to record-breaking levels for Christmas Day. In Texas, temperatures of more than 25 °C are predicted. As far north as Illinois, temperatures may reach 20 °C.

Tuesday, December 23, 2025, 10:00 UTC
KG

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