First major Santa Ana event of the season underway as snowstorm exits the Rockies
As another early-season snowstorm exits, Santa Ana winds will develop over California.
By
Brian Thompson, AccuWeather meteorologist
Published Oct 9, 2019 2:49 PM EST
This feels like déjà vu! My last blog post before I left on vacation two weeks ago was about the late-September snowstorm in Montana. Now, I have returned… and there is another snowstorm in the northern Rockies.
This storm will end up being a larger, more widespread storm than the September one, as this one will bring heavy snow to parts of the Dakotas as well.
Great Falls, Montana, has already picked up 26.5 inches of snow so far this season as of midnight Wednesday morning, and it was still snowing. That’s already 42% of the city’s normal annual snowfall of 62.9 inches - pretty incredible considering it’s the ninth day of October.
Even farther west, Spokane picked up 3.3 inches of snow and has already received 6.6 inches of snow so far this season - a very strong start to the season.
As is typically the case with early-season snow like this, the snow was enough to pull down trees and power lines.
As this snowstorm pulls away, a strong high pressure area will slide down through the Rockies from Thursday into Friday.
A forecast surface map valid late Wednesday night, Pacific time. Take note of the 1039 mb high pressure area building across Montana. The tight pressure gradient that results from this high building in will be the mechanism for the Santa Ana winds.
This will set the stage for a strong Santa Ana event across California, probably the first really strong setup we’ve seen so far this season. There have been some offshore wind events, but there hasn't been really anything like this so far.
The higher terrain and especially the canyons and passes of Southern California will be most at risk to record wind gusts as high as 50 or 60 mph.
I won’t go into all the details of the event, as they’re laid out very well in the news story we have up now.
Let’s dig a little deeper into the fire danger with this event. Compared to last year, it has been a far quieter fire season across California. There were even a couple of fires that burned over 100,000 acres last June and July. Two of those fires, the Carr Fire (229,000 acres) and Mendocino Complex (459,123 acres), each burned more acreage than has burned all year so far in California.
With that in mind, this year has certainly been different than last. Only about 5% of the state is in a drought condition as of last week's Drought Monitor, mainly in the deserts bordering Arizona.
Rewind to last year at this time - 88% of California was in drought, with 23% in severe drought.
The Drought Monitor from early October of last year, showing how widespread drought conditions were. The color scale is the same as the the above image from 2019.
While the lack of drought is definitely a very good thing for the water tables, wildfires are still a significant danger. Given the climate of California produces very little rain during the summer and early fall, the brush is naturally dry this time of year.
With last year being such a wet winter, that provides more brush to burn when these Santa Ana conditions set up, so we have to be vigilant that things could ramp up quickly even though it’s been a quiet season so far.
As is pointed out in our story about the event, one positive this time around will be that it will not be hot as it can get. These types of events can push temperatures into the 90s and even into the triple digits in October along the coast.
This particular Santa Ana event will actually usher in cooler air across the deserts, with temperatures dropping 10-15 degrees in some areas. There will be some warming along the coast, but highs are not expected to get much above 80 in San Diego through the event and should stay in the 80s in Los Angeles.
As the high weakens and slides southeastward, the fire threat will decrease into the weekend.
Looking into next week, we’ll be watching a pair of troughs swinging through - one coming Sunday into Monday and another coming later next week.
The first trough will reinforce the chilly air in the Northwest and produce very little rain. Even with the reinforcing shot of cooler air, the near-record cold at night with lows in the 30s in places like Seattle and Portland will ease into next week.
The second trough is still a week or so away, so there will be plenty of time to fine-tune the details on this. Even so, it looks deeper than the early-week system. This means that in addition for a heightened risk for rain and mountain snow, the precipitation could reach farther south down into California.
We’ll take a look at that again later this weekend.
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Weather Blogs / Western US weather
First major Santa Ana event of the season underway as snowstorm exits the Rockies
As another early-season snowstorm exits, Santa Ana winds will develop over California.
By Brian Thompson, AccuWeather meteorologist
Published Oct 9, 2019 2:49 PM EST
This feels like déjà vu! My last blog post before I left on vacation two weeks ago was about the late-September snowstorm in Montana. Now, I have returned… and there is another snowstorm in the northern Rockies.
This storm will end up being a larger, more widespread storm than the September one, as this one will bring heavy snow to parts of the Dakotas as well.
Great Falls, Montana, has already picked up 26.5 inches of snow so far this season as of midnight Wednesday morning, and it was still snowing. That’s already 42% of the city’s normal annual snowfall of 62.9 inches - pretty incredible considering it’s the ninth day of October.
Even farther west, Spokane picked up 3.3 inches of snow and has already received 6.6 inches of snow so far this season - a very strong start to the season.
As is typically the case with early-season snow like this, the snow was enough to pull down trees and power lines.
As this snowstorm pulls away, a strong high pressure area will slide down through the Rockies from Thursday into Friday.
A forecast surface map valid late Wednesday night, Pacific time. Take note of the 1039 mb high pressure area building across Montana. The tight pressure gradient that results from this high building in will be the mechanism for the Santa Ana winds.
This will set the stage for a strong Santa Ana event across California, probably the first really strong setup we’ve seen so far this season. There have been some offshore wind events, but there hasn't been really anything like this so far.
The higher terrain and especially the canyons and passes of Southern California will be most at risk to record wind gusts as high as 50 or 60 mph.
I won’t go into all the details of the event, as they’re laid out very well in the news story we have up now.
Let’s dig a little deeper into the fire danger with this event. Compared to last year, it has been a far quieter fire season across California. There were even a couple of fires that burned over 100,000 acres last June and July. Two of those fires, the Carr Fire (229,000 acres) and Mendocino Complex (459,123 acres), each burned more acreage than has burned all year so far in California.
With that in mind, this year has certainly been different than last. Only about 5% of the state is in a drought condition as of last week's Drought Monitor, mainly in the deserts bordering Arizona.
Rewind to last year at this time - 88% of California was in drought, with 23% in severe drought.
The Drought Monitor from early October of last year, showing how widespread drought conditions were. The color scale is the same as the the above image from 2019.
While the lack of drought is definitely a very good thing for the water tables, wildfires are still a significant danger. Given the climate of California produces very little rain during the summer and early fall, the brush is naturally dry this time of year.
With last year being such a wet winter, that provides more brush to burn when these Santa Ana conditions set up, so we have to be vigilant that things could ramp up quickly even though it’s been a quiet season so far.
As is pointed out in our story about the event, one positive this time around will be that it will not be hot as it can get. These types of events can push temperatures into the 90s and even into the triple digits in October along the coast.
This particular Santa Ana event will actually usher in cooler air across the deserts, with temperatures dropping 10-15 degrees in some areas. There will be some warming along the coast, but highs are not expected to get much above 80 in San Diego through the event and should stay in the 80s in Los Angeles.
As the high weakens and slides southeastward, the fire threat will decrease into the weekend.
Looking into next week, we’ll be watching a pair of troughs swinging through - one coming Sunday into Monday and another coming later next week.
The first trough will reinforce the chilly air in the Northwest and produce very little rain. Even with the reinforcing shot of cooler air, the near-record cold at night with lows in the 30s in places like Seattle and Portland will ease into next week.
The second trough is still a week or so away, so there will be plenty of time to fine-tune the details on this. Even so, it looks deeper than the early-week system. This means that in addition for a heightened risk for rain and mountain snow, the precipitation could reach farther south down into California.
We’ll take a look at that again later this weekend.
Report a Typo