A high-impact week, from a snowy Gulf Coast to shrieking California winds » Yale Climate Connections

Ironically, one thing that’s helping to make the Gulf Coast setup so unusually snow-favorable is dry air. About a mile above sea level, some of the driest air on record was flowing across the South toward the Gulf of Mexico. When the atmosphere is forced upward in a storm system, temperatures drop until the air is saturated (i.e., relative humidity hits 100 percent). Along the Gulf Coast, the ample moisture supply from the Gulf of Mexico often yields saturation at temps above freezing – enough to put the brakes on snow formation.

On Tuesday, the air aloft was saturating at temps just below freezing, allowing for a rare all-snow temperature profile (see Fig. 1 below), including at some places more accustomed to sleet, freezing rain, or snow mixed with rain when winter weather does occur. A NOAA website shows how the atmospheric structure can vary for each of these.

Below is a sampling of Gulf Coast cities that could end up with their heaviest snowfall in decades, along with the official National Weather Service forecasts as of Tuesday morning, January 21. As the numbers show, the event to beat is the jaw-dropping storm of February 1895 (see the recaps from Space City Weather and wunderground.com). Note that changes in the official observing sites (especially in the Houston area) can affect such records since the near-coastal region is prone to wide snow variations across small areas. Totals are also measured more often during modern snowstorms than the former once-a-day standard, and this can lead to higher totals than would have been recorded long ago.

Houston, TX
20.0”  Feb 14-15, 1895
3.0”  Feb 12, 1960
3.0”  Jan 22, 1940
2.6”  Jan 30, 1949
2.5”  Dec 21-22, 1929
2.0”  Jan 11, 1973
Forecast as of Tuesday morning, Jan 21: 3”-5”

Galveston, TX
15.4”  Feb 14-15, 1895
6.0”  Jan 12, 1886
4.0”  Dec 24-25, 2004
2.5”  Jan 11, 1973
2.2”  Feb 12-13, 1960
Forecast as of Tuesday morning, Jan 21: 3”-5”

New Orleans, LA
8.2”  Feb 14, 1895
4.0”  Jan 27, 1897
3.0”  Feb 12, 1899
2.7”  Dec 31, 1963
2.0”  Feb 12, 1958
Forecast as of Tuesday morning, Jan 21: 4”-8”

Baton Rouge, LA
12.5”  Feb 14-15, 1895
6.0”  Feb 25, 1914
3.5”  Dec 8, 2017
3.5”  Jan 23, 1940
3.2”  Feb 5, 1988
Forecast as of Tuesday morning, Jan 21:  3”-7”

Mobile, AL
6.0”  Feb 14-15, 1895
5.0”  Jan 24, 1881
3.6”  Feb 9, 197
3.5”  Jan 23, 1955
3.0”  Dec 31, 1963
Forecast as of Tuesday morning, Jan 21:  2-4”

Pensacola, FL
3.0”  Feb 14-15, 1895
2.3”  Mar 6, 1954
2.1”  Feb 12, 1899
1.9”  Feb 9-10, 1973
1.5”  Jan 31, 1977
Forecast as of Tuesday morning, Jan 21:  2”-4”

Tallahassee, FL
2.8”  Feb 12-13, 1958
1.0”  Dec 22-23, 1989
0.4”  Feb 10, 1973
0.4”  Mar 28, 1955
0.2”  Feb 2, 1951
Forecast as of Tuesday morning, Jan 21:  2” (including snow, freezing rain, and/or sleet)

On top of these impressive amounts, which could have major local impacts, enough cold will stick around for a day or two to help preserve the snowpack – and the snow itself may help temperatures to plummet to record lows once the skies clear.

Most of the rest of the United States won’t see much if any record cold, even with this week’s Arctic plunge. Although January has been colder than average for most parts of the contiguous U.S., the chill is noteworthy more for its persistence and expansiveness than its sheer bite. In fact, as of Monday, January 20, the nation had seen many more record daily highs than record daily lows for the month thus far (thanks in large part to relatively balmy temperatures in parts of Florida and Alaska). This is a far cry from truly historic cold outbreaks such as those in December 1983, February 1989, and December 1990, all of which pulverized many hundreds of daily records across the central and eastern United States.

So is climate change having any influence on the much-publicized polar vortex episodes of recent years? That’s been a topic of research and debate for more than a decade, especially with disastrous episodes like the 2021 Texas cold wave interspersed amid an overall warming of U.S. winters, and the research continues to evolve. We’ll take a fresh dive into the topic in a forthcoming post.

Fierce winds and unprecedented winter dryness keeps Southern California on edge

Yet another round of powerful Santa Ana winds was cascading through the coastal mountains of Southern California from late Monday into Tuesday. The winds warmed and dried as they flowed downslope toward the coast, sending relative humidity well below 10 percent and pushing fire weather into the top-end “extremely critical” category once again. The peak wind gust observed so far during the event was 88 mph at Magic Mountain Truck Trail (located about 20 miles north of Los Angeles) at 9:50 am PST Jan. 20. Sandberg, California (located about 65 mi NW of Los Angeles) had sustained winds of 48 mph, gusting to 74 mph, with a relative humidity of 11%, at 1:51 pm Jan. 20. The station stopped sending data thereafter, likely because the high winds damaged the station or its communications infrastructure.

The strong winds fanned multiple fires overnight, but quick action by firefighters served to squelch them before serious impacts occurred. The largest new fire, called the Lilac Fire, was located in San Diego County, and was 80 acres with 10% containment at 10 a.m. EST Jan. 21, according to Cal Fire. There were evacuation orders in place for the fire, but there were no reports of large numbers of buildings being torched.

Breaking… Bonsall, CA (North of San Diego). As of 6 a.m. PST, the #lilacfire had grown to 80 acres with a moderate rate of spread and is 10% contained. Most local TV stations in the #SanDiego area have live coverage. Evacuation map: pic.twitter.com/LdTzWLPcU5

— Warren Faidley – The Cyclone Cowboy (@Stormchaser) January 21, 2025

Strong Santa Ana winds are a normal part of the region’s winter climate. This month, the winds have been unusually frequent, and their power has been exacerbated at times by mountain-wave effects. These occur when strong winds blow nearly perpendicular to a mountain range and are joined by a temperature structure that allows energy to be trapped in a shallow layer and then forced to the ground well downstream. The winds on January 7-8 responsible for the catastrophic Eaton and Palisades fires near Los Angeles had strong mountain-wave components as well as a more north-to-south trajectory than usual, and that helped push the fires unusually far south into residential areas that hadn’t burned in modern times.

What’s been stoking the fire hazard isn’t just the sheer strength of the winds. It’s also that the winds are coinciding with parched conditions more typical of late summer and beyond anything on record for late January, a time when the winter wet season is typically nearing its peak. These intersections between the tail end of warm-season dryness and the front end of cold-season winds are becoming more of a threat as the rainy season contracts in our warming climate, a trend expected to continue.

As of Tuesday, January 21, downtown Los Angeles (data since 1878) and San Diego (data since 1851) had each received a mere 0.16 inches of rain since July 1. That’s unprecedented for San Diego, where the next-driest such period was 0.35 inches in 1962-63. In Los Angeles, the dryness is now in a tie with 1962-63, but another 0.40 inches of rain fell just before the end of January 1963. Every wet season on record in L.A. and San Diego has had at least 1.57 inches of rain by the end of February.

There’s finally a chance of rain in the Los Angeles and San Diego forecast this weekend, as the nation-straddling jet stream is projected to carve out a track off the Pacific coast before circling back eastward. The European ensemble model has been suggesting that as much as a half-inch could fall near San Diego, with an inch or more possible in the nearby mountains and lesser amounts toward Los Angeles. The GFS ensemble has been less enthusiastic, projecting amounts less than a half-inch almost everywhere. Only a slight change in the jet trajectory could make the pattern windy and dry instead of wet.

In any event, it’ll take far more rain than predicted to bring the region anywhere close to normal values for the wet season, which typically starts winding down by late March.