January 2025 Review

January was much drier than normal for most areas west of the Continental Divide. The pattern was active during the first week of the month, and then a blocking ridge of high pressure became the dominant pattern over the West Coast, which acted as a barrier to storms.

On the eastern periphery of the high-pressure ridge, more storms slid down the eastern side of the Continental Divide, producing above-normal precipitation and snowfall for eastern parts of Montana, Wyoming, and Colorado.

Heading into early February, snowpack is below normal across most of the West, with a few pockets of above-normal snowpack in Oregon, Southwest Idaho, and North Central Montana.

This map is valid as of February 3rd, and an atmospheric river event has brought substantial moisture to the Sierra, Southern Cascades, and parts of the Northern Rockies during the first few days of the month, so some of these regions now have higher snowpack percent of average numbers than they did a few days ago. 

Temperatures in January were colder than normal across the Rockies and warmer than normal across the West Coast. The middle to latter part of the month in particular was very cold, including an arctic blast during the second half of the month that led to well below-normal temperatures.

The coldest temperature anomalies were over Southern Wyoming, Central Colorado, and Eastern New Mexico, while the warmest temperature anomalies were over Northern California. 

February 2025 Outlook:

The first few days of February have started out much more active across a large portion of the West compared to what we saw during most of January. 

A strong atmospheric river event has resulted in substantial precipitation across California and the Northern Rockies with heavy snow and rain, though warm temperatures have resulted in rain for some mountain areas that don't often see rain at this time of year.

The Northwest and far Northern Rockies have seen substantial snowfall, colder temperatures, and lower snow levels in this pattern.

The remainder of the first week of February continues to look active across the West Coast and Northern/Central Rockies, but considerable uncertainty exists heading into mid-month and beyond with some models projecting a relatively active pattern to continue while others are hinting at a high-pressure ridge building back in over the West Coast.

NOAA's Monthly Outlook has a high likelihood of above-average precipitation from Northern California (including Tahoe) to Western Washington, and also over Southern Idaho, but the recent atmospheric river event likely has a lot to do with this.

Areas further south including most of Utah and Colorado have "equal chances" of above or below-normal precipitation.

We have seen a sharp temperature gradient early in the month with very cold temperatures over northern portions of the West and unseasonably mild temperatures over southern and central portions of the West.

We may continue to see sharp divides between colder and warmer air moving forward, though it looks like we could see a cold snap across much of the West heading into mid-month based on medium-range model projections. 

For the month as a whole, below-normal temperatures are favored over the Northwest, and above-normal temperatures are favored over the Southern Rockies with no clear signal in between. 

Thanks so much for reading! I will post the next monthly update in early March.

Alan Smith