December 20, 2023 Wednesday Update
California storm with flash flooding
December 2023 was the warmest December in the 131-year national record (1895–2025), at 39.8°F against a 1991–2020 normal of 34.3°F (+5.4°F).
December 2023 was the 49th-wettest December in the 131-year national record (1895–2025), at 2.6in against a 1991–2020 normal of 2.5in (+0.1in).
NOAA/NCEI Climate at a Glance, contiguous United States. This is the observed record for the month, not a score of anything said in this piece — the forecast ledger begins 2026-08-17 and cannot reach earlier posts.
A slow moving upper-level low off the California coast is drifting southward bringing moisture onshore. The heaviest rain and potential for flooding is along the Transverse Range where 4-7” total may fall. Los Angeles will see 1-2” over the next 48-hours — welcome precipitation.
The low will move into the Southwest this weekend and then combine with another upper-level shortwave in the Rockies to yield our next storm system for Christmas Eve that could bring significant snowfall to Denver.
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