This storm will, once again, start out quite warm with high snow levels (above Sierra passes) initially. But colder air will filter in behind the initial cold front, bringing heavy snowfall to more reasonable elevations (and eventually down to 3-4k feet) by early next week. #CAwx

Although the risk looks low overall, a couple of strong to severe thunderstorms could occur in NorCal (mainly in Sac Valley/North Coast to SF Bay region), with weaker t-storms possible elsewhere.

Another winter storm will bring widespread rain and gusty winds to much of California this weekend. This one will be focused more on NorCal vs SoCal. Only minor rain/wind impacts are expected--but a notable coastal flood event may occur in SF Bay Area (see my other thread). #CAwx

This wknd's storm is not, by any metric, extreme! (It won't even be as strong as last week's.) And astronomical (sun & moon gravity-related) King Tide is typical, as well. But coincidental timing of KT + moderate storm, added atop SLR, will generate a notable coastal flood event.

As NWS Monterey has emphasized, predicted water levels in SF will be the highest ever observed except for the notable coastal flood events in 1982/3 and 1998. As a result, considerable inundation of low-lying roads, infrastructure, and communities along SF Bay is likely. #CAwx

A moderately strong winter storm this wknd will bring low pressure and onshore/southerly winds to the SF Bay region. When combined w/ very high astronomical (King) tides, plus aggregate effect of long-term sea level rise, a 2.5+ feet elevation of SF Bay water levels is expected.

Highest astronomical high tides of year (aka the "King Tides") will occur this weekend in NorCal. But this year, they will coincide w/additional storm surge from nearby low pressure--causing potential for SF Bay Area coastal flooding beyond what we've seen in recent years. #CAwx

Another winter storm will bring widespread rain and gusty winds to much of California this weekend. This one will be focused more on NorCal vs SoCal. Only minor rain/wind impacts are expected--but a notable coastal flood event may occur in SF Bay Area (see my other thread). #CAwx

Highest astronomical high tides of year (aka the "King Tides") will occur this weekend in NorCal. But this year, they will coincide w/additional storm surge from nearby low pressure--causing potential for SF Bay Area coastal flooding beyond what we've seen in recent years. #CAwx

TODAY at noon: Daniel Swain will give his final 2025 California weather livestream 🌦️

As we head into a new year, I wanted to share this conversation I had with @ittefaq.bsky.social on the big picture surrounding climate change: Where we are now; how much warming we're on track to see; & why it's so important to be honest about where we're headed.

I'll host a special New Year's Eve livestream (12/31 at noon PT!) to offer 1) a wrap up of 2025's exceptional hydroclimate whiplash in California, 2) details re: (yet another!) major rain event in SoCal this week, & 3) a brief update on the NCAR situation.

Due to very warm subtropical origins of this storm, snow levels will be exceptionally high in SoCal (~12k feet, so above even highest peaks) and very high (~8-10k feet) in NorCal, so almost no appreciable snow will fall (and some rain will fall on existing snow). #CAwx

The peak rain intensity will likely be mid-morning on New Year's Day. This will affect travel plans, and likely also the Rose Parade. In fact, current modeling suggests a band of quite heavy rainfall, possibility associated w/strong thunderstorms, from 8-11am right over LA. #CAwx

The developing storm is a pretty unusual one, with deep subtropical origins. The parent low pressure has formed quite far south--west of the southern tip of Baja CA! Accordingly, its associated air mass is warm & convectively unstable (w/lots of thunderstorms at present). #CAwx

Yet another major rain event will arrive in Southern CA on NYE & last into New Year's Day--and it could, once again, bring substantial impacts due to both timing on holiday and preceding exceptionally wet conditions. Peak impact will overlap exactly w/Rose Parade. [Thread] #CAwx

New Year's California weather update & a preview of tomorrow's livestream discussion: Warm subtropical system to bring heavy New Year’s rain to SoCal before a somewhat quieter pattern takes hold by mid January. #CAwx

Yet another major rain event will arrive in Southern CA on NYE & last into New Year's Day--and it could, once again, bring substantial impacts due to both timing on holiday and preceding exceptionally wet conditions. Peak impact will overlap exactly w/Rose Parade. [Thread] #CAwx

I'll host a special New Year's Eve livestream (12/31 at noon PT!) to offer 1) a wrap up of 2025's exceptional hydroclimate whiplash in California, 2) details re: (yet another!) major rain event in SoCal this week, & 3) a brief update on the NCAR situation.

As we head into a new year, I wanted to share this conversation I had with @ittefaq.bsky.social on the big picture surrounding climate change: Where we are now; how much warming we're on track to see; & why it's so important to be honest about where we're headed.

Un excellent article dans @letemps.ch sur la situation des scientifiques du climat aux USA: www.letemps.ch/sciences/le-... @weatherwest.bsky.social @effetsdeterre.bsky.social

geotripper.blogspot.com/2025/12/revi... There are flood stories all across the west right now, but Wrightwood is of special interest. It has a history. #CAfloods

Wow, xmas morning wind gusts up to 114 mph on Mount Hamilton, east of San Jose. Damaged the Lick Observatory. 🔭 🧪 bsky.app/profile/look...

Yet another round of heavy showers and thunderstorms, some strong to even severe, immediately inbound into the SF Bay Area this evening. Yet more strong/damaging winds likely, plus torrential downpours & urban flooding in some areas. A brief tornado remains possible. #CAwx

And now there's officially a Tornado Warning out for Santa Cruz County for this offshore mini-supercell thunderstorm, which is likely producing a waterspout over water that could move inland as a tornado near Santa Cruz. #CAwx

Pretty impressive mini-supercell thunderstorms over Monterey Bay right now with a tight rotational couplet and even a bit of a hook echo. This cell is likely producing a waterspout, and is headed for Santa Cruz area. A brief tornado is possible when it makes landfall. #CAwx

Although atmospheric river portion of CA storm has ended, a much colder & unstable/sheared airmass will continue to bring Intermittent waves of strong to severe t-storms--w/widespread strong wind gusts, scattered flash flood/isolated tornado potential, plus heavy mtn snow. #CAwx

Well, it has turned into a sleepless night for many in the SF Bay Area due to severe weather. Squall lines containing severe thunderstorms have brought torrential rain (leading to flash flooding) and damaging wind gusts of 60-80 mph. Lots of NWS warnings out. Quite a storm! #CAwx

In addition to widespread urban/freeway flooding in LA metro today, there has been less reported but much more serious flooding in mountain/desert regions. Several entire smaller communities are under evacuation orders, roads are impassable, & numerous rescues are ongoing. #CAwx

A large region of showers & thunderstorms, which may be strong to severe, is swirling toward SF Bay Area from the S/SW. There are multiple areas of strong low-level storm rotation offshore (blue outline), suggestive of waterspouts that could move inland as brief tornadoes. #CAwx

Tornado Warning inside a Severe Thunderstorm Warning inside a Flash Flood Warning in LA County at the moment, if you're wondering how things are going... #CAwx #LArain

Heavy to locally torrential rainband slowing down and intensifying as approaches central Los Angeles County. Widespread roadway flooding and debris flows are already being reported; this could escalate considerably over next 2-3 hours especially if this band stalls out. #CAwx #LArain

A squall line/narrow cold frontal rainband (NCFR) has developed over Ventura County, generating torrential rainfall, wind gusts to 60 mph, and iso. t-storms. This line will likely produce flash flooding as it moves eastward into LA County. Note very mild airmass in mid 60s! #CAwx

Flash Flood Warnings now in effect for most of SoCal Transverse Ranges as powerful storm slowly into the region. Rainfall has been torrential already in Santa Barbara/Ventura counties, but mostly light in LA. That will change soon, and flood risk will sharply rise. #CAwx

One thing that really stands out about this week's California storms is the highly unusual risk of severe thunderstorms, both overnight Tue Wed and then again late Wed into Thu. Multiple low-topped supercells may generate very strong wind gusts and even a few tornadoes. #CAwx

Recorded live and now available at the link below. #CAwx

One thing that really stands out about this week's California storms is the highly unusual risk of severe thunderstorms, both overnight Tue Wed and then again late Wed into Thu. Multiple low-topped supercells may generate very strong wind gusts and even a few tornadoes. #CAwx

Recorded live and now available at the link below. #CAwx

At 1pm PT today, I'll offer a brief (30 min) pop-up live update regarding the pair of very strong/high-impact storms which will bring major flash flood risk to SoCal/LA area tomorrow, plus the possibility of severe thunderstorms nearly statewide. #CAwx

CA storm update: #1 risk is serious flash flood threat in SoCal mountains & adjacent valleys on Wed (inc. LA metro). #2 concern is possibility of severe t-storm outbreak along CA coast Tue-Thu. #3 concern is uncertainty re: NorCal winds. Will discuss in livestream @ 1pm PT. #CAwx

A bipartisan group in Congress formally pushed back against administration plans to dismantle NCAR, while the country experiences a record warm Christmas week with monthly records - and CA braces for more serious flooding and wind (and eventually snow). More: tinyurl.com/3b2tsp7m

At 1pm PT today, I'll offer a brief (30 min) pop-up live update regarding the pair of very strong/high-impact storms which will bring major flash flood risk to SoCal/LA area tomorrow, plus the possibility of severe thunderstorms nearly statewide. #CAwx

NWS WPC has issued a top-of-scale "high risk" flood outlook in/near Transverse Ranges of SoCal; most of the SoCal urban corridor is in "moderate"(second highest) tier. This is a strong signal that significant flash flooding/urban flooding/debris flows are possible on Wed. #CAwx

An even more ridiculously warm day across most of the central and western United States, with numerous locations seeing not only calendar date record highs but in many cases all-time December monthly records. Wow. 🫠 #AZwx #NMwx #TWwx #COwx #OKwx #WYwx #KSwx #NEwx #UTwx

#ICYMI During office hours today, @weatherwest.bsky.social discussed #CA’s active weather week—warm atmospheric rivers, record-low Sierra snowpack (rain even above 10,000 ft), and a stronger storm bringing heavy rain, winds, and SoCal flood risk. #CAwx ➡️ www.youtube.com/watch?v=m5iM...

National Center for Atmospheric Research closure. “Most academics in the weather and climate world have in some way passed through or connected with the National Center for Atmospheric Research.” - UCANR climate scientist, Daniel Swain @weatherwest.bsky.social www.theatlantic.com/science/2025...

Reminder: I'll be going live @ noon Pacific time today to discuss incoming series of (very?) strong winter storms slated to affect all of CA. Wind risk & flood risk have notched upward vs my blog post yesterday in some spots; I'll discuss in detail. #CAwx

Reminder: I'll be going live @ noon Pacific time today to discuss incoming series of (very?) strong winter storms slated to affect all of CA. Wind risk & flood risk have notched upward vs my blog post yesterday in some spots; I'll discuss in detail. #CAwx

New Weather West post out now: A wet and stormy week ahead in California, with substantial SoCal flood risk and initially warm Sierra rain transitioning to very heavy snow. Plus, join me tomorrow (Mon Dec 22) for a live discussion (link therein!). #CAwx

I'll host a "lunch hour" livestream on Mon, Dec 22 (noon PT) discuss the inbound series of strong winter storms in California, including the exceptionally warm initial airmass, SoCal flood risk, and eventual return of Sierra snow (yes, finally!). #CAwx