A cut-off low pressure system is currently spinning west of California. It generated scattered mountain thunderstorms today, and will cause more widespread showers & thunderstorms (mainly in NorCal mountains, but locally elsewhere) Sun-Mon. A stronger cell or two are possible.

On Monday at 2pm PT, I'll discuss whether this weekend's showers might be the last of the season, where we currently stand water & snow-wise, and also the potential for a significant mid-May heatwave in California and across the broader West.

A period of warmer weather will return the rest of this week across most of California before yet another spring low pressure system brings unsettled conditions again this weekend. This will be a much more "typical" and lower-impact April showers scenario than recent storms.

U.S. President Donald Trump has fired all 24 members of the National Science Board, the body that oversees the National Science Foundation. https://scim.ag/4cxQWhl

Congratulations to #UCANR climate scientist Daniel Swain on this well-deserved recognition! The California River Award is a meaningful honor, & your reflection on rivers as “integrators of change” couldn’t be more timely. Thank you for your leadership and impact! @weatherwest.bsky.social

It's an honor to be receiving this year's California River Award from Friends of the River! I've taken a moment to reflect on the notion of rivers as "integrators of change"--from hydrological and human perspectives--during a period of rapid global change.

⚡️ Active 24 hours for NorCal! ⚡️ NWS tracked 11,705 total lightning strikes across the region yesterday, w/ over 1,400 striking the ground. 📍 Heavy activity: Central Valley into the Sierra Foothills. 🚨 Notable: Confirmed funnel cl... https://x.com/NWSBayArea/status/2046963638217384408

Strongest tornado in California since the Scotts Valley EF1 tornado in December 2024 www.ncei.noaa.gov/stormevents/...

Talking weather and climate with with Daniel Swain, @ucanr.edu climate scientist: A conversation regarding the record-smashing warm month of March for the western U.S. and what it means for the region going forward.

I'll have another "lunch hour" live virtual office hour at 12 noon PT on Tue, Apr 21, to discuss continuation of an unusually active spring weather pattern in California, broader context of strange 25-26 Water Year, and links to now record-warm NE Pacific.

Talking weather and climate with with Daniel Swain, @ucanr.edu climate scientist: A conversation regarding the record-smashing warm month of March for the western U.S. and what it means for the region going forward.

New Weather West post out this evening: "Unusually active April weather pattern to continue this week, and possibly beyond, as subtropical northeastern Pacific waters reach record warmth."

New Weather West post out this evening: "Unusually active April weather pattern to continue this week, and possibly beyond, as subtropical northeastern Pacific waters reach record warmth."

I'll have another "lunch hour" live virtual office hour at 12 noon PT on Tue, Apr 21, to discuss continuation of an unusually active spring weather pattern in California, broader context of strange 25-26 Water Year, and links to now record-warm NE Pacific.

News: a leading NSF supported University of Oklahoma atmospheric science summer undergraduate research program that has mentored hundreds of top atmospheric scientists over two decades has been canceled for 2026 due to funding loss. (repost w/correct link) More: tinyurl.com/3zjzf7vu

Monday, April 20, live at ~7:45am PT on CBS LA Daniel Swain @weatherwest.bsky.social, @ucanr.edu climate scientist, will talk about El Nino with @caliweatherguy.bsky.social www.cbsnews.com/losangeles/

In case you missed it live, the recording is available below (as always!). There were some great questions from the audience yesterday (which is usually true, but I always like to highlight the participatory nature of these sessions!).

Join #UCANR climate scientist Daniel Swain tomorrow, April 16, at 12 pm. ⬇️ @weatherwest.bsky.social

On Thursday, Apr 16 at noon PT, I'll have a "lunch hour" livestream to discuss the already prolonged & severe marine heatwave affecting Pacific ocean near California. Also: are upcoming April showers connected to a West Pacific supertyphoon?

Glad to see that the Sacramento Bee is advertising a cool new newsroom meteorologist position! Frankly, I think every major regional/national newspaper needs in-house expertise like this. Role requires degree in meteorology/atm science (as it should!)

How confident should we be in a prediction of El Niño? Seasonal forecasts show an emerging warm ENSO signal, but predictability remains low during the spring barrier. Read our blog diving deeper into how to interpret our ENSO-related seasonal forecasts ➡️ www.ecmwf.int/en/about/med...

I've excerpted a ~5 minute segment from my recent livestream discussing my deepening concerns regarding on the ongoing (and accelerating) threats not only to weather and climate science, but American science leadership and continuity at large.

Still expecting an unusually strong cold frontal passage (by NorCal April standards) later this PM. Expect a period of intense rainfall & embedded thunderstorms with gusty wind at lower elevs (locally severe near SF Bay), plus a burst of heavy & accumulating Sierra snowfall. #CAwx

I've have a short-notice pop-up livestream today at 2:30pm PT to discuss the outbreak of unusually widespread thunderstorms across Northern California this PM, including the potential for a few supercells/severe storms containing hail & isolated tornado.

We now have 13 different models with 637 different ensemble members with El Niño forecasts out through at least September 2026. They suggest a best estimate of 2.2C for September; interestingly ECMWF (which was seen as particularly hot when it came out) is right around the middle of the pack:

Today was already quite active in NorCal, w/several severe thunderstorms & at least one photogenic supercell. Fri & Sat will be even more unusual, w/widespread t-storms & likely at least a few severe ones. I may have a pop-up livestream, time TBD, on Fri or Sat for a radar tour!

Bonkers photo from that Central Valley supercell. @phaneritic.bsky.social or anyone else that way catch a glimpse?

I've excerpted a ~5 minute segment from my recent livestream discussing my deepening concerns regarding on the ongoing (and accelerating) threats not only to weather and climate science, but American science leadership and continuity at large.

In case you missed the livestream yesterday, the recording is available via the link below! The next few days look very active by CA April standards. I also discussed my growing concerns regarding the immediate near-term risk to American science continuity.

I couldn't agree more with Kate that it's okay--even necessary--to get mad, stay mad, and channel that anger along any number of constructive avenues in this disconcerting moment.

I'll host a live office hour on Wed, Apr 8 at 2pm PT to discuss imminent shift to a more unsettled weather pattern across CA & the West, including potential for widespread thunderstorm activity & beneficial precip. Also: I'll offer another federal update.

Since there's, uh, absolutely nothing else going on in the world right now, you might consider reading this late evening blog update on a potential NorCal thunderstorm outbreak over the next few days and a chaotic Pacific-wide weather pattern this April.👀

Since there's, uh, absolutely nothing else going on in the world right now, you might consider reading this late evening blog update on a potential NorCal thunderstorm outbreak over the next few days and a chaotic Pacific-wide weather pattern this April.👀

Another significant weather pattern shift is imminent in California and perhaps also across broader portions of the American West. Despite return of strong ridging & record warmth over the weekend, this setup is more transient and will soon be replaced by unsettled conditions.

I'll host a live office hour on Wed, Apr 8 at 2pm PT to discuss imminent shift to a more unsettled weather pattern across CA & the West, including potential for widespread thunderstorm activity & beneficial precip. Also: I'll offer another federal update.

Finally: This also applies to use of non-nuclear weapons against nuclear & petrochemical facilities in densely populated regions. While consequences for global climate in such a scenario are lower, the risk of large scale radiological or other toxic contamination is very real.

I can't believe we have reached this point, but this bears crystal clear emphasis: Our global climate system ensures that even "limited" use of lower-yield "tactical" nuclear weapons against civilian or industrial targets would have major regional-to-global scale consequences.

The Trump budget once again proposes to eliminate NOAA OAR, which brings you the CO₂ Keeling Curve. In this piece, I argued that the Keeling Curve is a treasure that belongs to humanity as the most poignant indication of our impact on the environment and as a testament to our ability to document it.

Amidst everything else, the Trump regime has quietly killed off the U.S. Forest Service 🌲 “One hundred and ninety-three million acres of your national forests… just handed, on a silver platter, to the people who’ve spent their entire careers trying to destroy it.” www.hatchmag.com/articles/tru...

News: WH released proposed FY27 budget, continuing to push plan to eliminate NOAA Research and massively cut Earth sciences - while NOAA grant data for FY2026 shows only 7 new grants so far compared to 379 in FY2025, further evidence of curtailed science budget execution. tinyurl.com/5e3ptub2

Yet another "shocked, but based on the way things have been going, not surprised" moment.

A couple of notable early season wind-driven grass and brush fires in SoCal today, most notably the 1,500+ acre #SpringsFire just north of Lake Perris. Evacuation orders have been expanding and structures are immediately threatened; it's quite warm, dry and windy out there.

After this cooler & wetter interlude, there are once again strong signals than anomalous April warmth will dominate the West for much of rest of April. It won't be as extreme as March, relatively speaking, but return of warmth & dryness will likely allow rapid snowmelt to resume.

But from broader snowpack perspective, it's simply too little, too late. This week's cooler temperatures & mountain precipitation will allow snow water equivalent to flatline or even tick upward a few percentage points. But SWE will generally remain near or below record lows.

Well, I do have some good news to report: yesterday's weather system "overperformed" somewhat in NorCal! Convective activity and even some stronger thunderstorms developed in the unusually warm/moist/unstable airmass, bringing some more widespread downpours than expected.

📋Upon further investigation, March 2026 also had the highest anomaly (avg. temp compared to normal) for ANY month at 12/13 of our climate sites. 🤯🤯🤯 https://x.com/NWSBayArea/status/2039416664018559450

Well, I do have some good news to report: yesterday's weather system "overperformed" somewhat in NorCal! Convective activity and even some stronger thunderstorms developed in the unusually warm/moist/unstable airmass, bringing some more widespread downpours than expected.

In case you missed this yesterday, the recording is available below!

Number of 80°+ days in March in Denver: 1972-2025: 7 days 2026: 8 days #COwx

🌡️Every single weather station we have recorded the warmest March on record. Most would have been the warmest April too. More sites below🧵 https://x.com/NWSBayArea/status/2039348328870129861