NWS Forecast update:
https://www.weather.gov/sto/
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Red Flag Warning for gusty onshore winds on top of low humidity on the lee of the Sierra 11 am Monday until 5 am Tuesday.
Winds turn out of the NNW Tuesday-Wednesday but most of the energy focuses into a cut off low over Arizona and the rest of the trough is just progressive across the midwest. So some isolated gusty winds but not a serious event as of right now.
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There seems to be an anomaly this Fall compared to the last few years. We shall see if this holds up:
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Waiting patiently for some of the pros to chime in on this…
Here is my take: early troughing now into mid October means the end of the month into November should be drier than average, because our weather in CA is very cyclical. So if we do not get a lot of wetting rain that ends fire season then offshore flow should return as the 12-15 day cycle of ridging amplification comes back around, with still the threat of fire danger… followed by another troughing cycle into mid-late November.
If we do not get a lot of atmospheric rivers this year to make up for the precipitation deficits we will be in a world of hurt come March and while early season storms look very promising a lot is hinging on where the hurricane in the Atlantic, and the typhoon in the Western Pacific go in relation to other features. These strong features always complicate model runs as a whole as they move north they destabilize cold arctic air.
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Good morning, everyone.
I am working on a video for The Lookout about the spread of the Dixie Fire on the 4th-6th of August and wondering if anyone if interested in collaborating on some imagery of the frontal passage on the afternoon of the 5th. I have this screen capture video (Twitter link), but am looking for imagery that starts earlier in the day and goes thru dark.
I’d like to animate a sequence that shows how the frontal passage helped drive the strong southerly winds that caused the massive run west of Chester that took out 100,000 acres in 2 days. The GOES RAM Slider website doesn’t have archived data going back past about a week anymore, so looking for a source for a good high-res animation.
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Interesting article. I’ve definitely noticed this:
[Nighttime air in the western U.S. has turned drier, drying out fire fuels - The Washington Post](https://Nighttime air in the western U.S. has turned drier, drying out fire fuels - The Washington Post)
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Continued moderated fire weather is still on track. Granted forecasting in the long range can require a crystal ball. This outlook for October is still refreshing to see.
NWS SF Forecast Discussion This Morning: By late weekend and early next week the closed low will have strengthened somewhat with falling 500 mb heights and advanced toward and across SoCal and eventually the Desert Southwest with some wet weather. If the GFS verifies the northernmost extent of light wet weather from this low would reach Santa Barbara County later Monday, too far south for our cwa. The door then opens up for one of the long wave troughs across the northern hemisphere to advance to the west coast mid to late next week, with increasing agreement and confidence in this solution in the deterministic and ensemble forecasts. Seeing this much activity so early in the jet stream is a sign of strength and a sign that shortwave troughs are prevailing feeding back to the long wave troughs (active wave pattern), overlapping our typical offshore flow season. Statistically and historically we can get wet weather this early in the season, what remains to be seen is will wet/wetter weather hold as we continue deeper into fall then winter before stabilizing to west coast ridging, which typically occurs temporarily mid-winter. Early next week cooler temps commence with a steady transition to troughing along the west coast with possibly wet weather later next week as multiple shortwaves dig into the long wave trough. This is a promising stretch of news especially because the trough and cooler temperatures could linger into the second week of October; this is typically our warm/hot offshore flow season.
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It’s early but there is increasing confidence that a potential Diablo wind event of moderate to strong strength could occur around the 12th-14th. Tonight’s model runs of the ECMWF and CMC bring a sharp trough through the Great Basin and into AZ. It is extremely cold in nature for this time of year and would bring snow to eastern mountain slopes like the Sierra. The trough axis as of current model runs is directly over the Sierra Nevada and this would bring a lot of upper level support but humidity levels could be non critical, at least the first part of the offshore wind event.
Will continue to monitor for model track adjustments but this does appear to be a strong offshore wind event signal with the typical mid range forecast track adjustments pending on the upper level features. Tonight’s GFS model run is further west but it’s ensemble mean is in line with the ECMWF so it’s wise to discount the wetter further west solution at this time.
From NWS Bay Area AFD
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Looking out through November from ONCC Predictive Services, in spite of the mild fire weather in September there is above normal significant fire potential due to combination of dry fuels and lack of significant season ending rain.
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221 PM PDT Thu Oct 7 2021
…Fire Weather Watch for Monday afternoon into Tuesday
evening for gusty north winds along the eastern interior areas of
the North Bay mountains, East Bay hills, and East Bay valleys.…
The next weather system will impact the area early next week.
Moderate to high confidence in stronger north winds and drier air
early next week behind a passing cold front. The eastern interior
areas of the North Bay mountains, East Bay hills, and East Bay
valleys have the highest confidence in seeing gusty north winds.
The window for strongest winds will be from Monday morning through
Tuesday evening. These winds, in conjunction with little to no
recent precipitation and near to record dry fuels across the
interior, may lead to an increased risk of critical fire weather
concerns for the specified locations.
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NWS SF - 2:30pm The northerly pressure gradient will rapidly increase Sunday night, with 925 mb winds increasing to 35 to 50 kts across the North and East Bay Mountains and Hills. By Monday morning, these stronger 925 mb winds start to spread south into Santa Cruz, San Benito, and Monterey Counties. While this looks like a traditional offshore wind event, there are some differences. The first of which is this is truly a more northerly type event, with the winds staying either northerly or north northeasterly. This can be seen with the strongest gradient being between KACV and KSFO, rather than KWMC and KSFO. The other somewhat interesting thing about this event is that the gradient peaks twice, once around early Monday morning, with a secondary peak at Monday afternoon. All the models are consistent with these peak times, but vary on the strength. As a result, have already issued a wind advisory for the North Bay mountains, East Bay hills and interior valleys, starting late Sunday evening through Monday. As these winds spread south through the early morning hours on Monday as we start to get some mixing, believe that these strong winds will also develop across the North Bay valleys and coastal areas as well as the San Francisco Peninsula, the South Bay, and all of the Monterey Bay region. The ensembles are even hinting at gusts in the 40 to 50 mph range by Monday afternoon for many of our guidance locations. Some of the strongest sites include Napa, Concord, Livermore, San Francisco, and Monterey, so believe the wind advisory is warranted for these areas as well. Expect these gusty north to north northeast winds to quickly decouple after sunset Monday evening for the valley and coastal areas, but believe that the mountain regions will continue to gusty conditions through Monday night and evening into Tuesday. As for fire weather concerns, have expanded the Fire Weather Watch to include the Santa Cruz Mountains, the mountains of interior San Benito and Monterey Counties, and the Santa Lucia Mountains and Los Padres National Forest. Humidity values will rapidly drop during the day on Monday as the cooler and extremely dry air filters into the region. At this point in time, have left the remaining valley and coastal location out of the watch, as they should have a good recovery Monday morning before the strongest winds kick in. It is really a questions of timing, but think they will be okay, with less than 8 hours of the low humidity and wind criteria. Although some gusty north winds may continue into Tuesday across the mountain areas as well as the East Bay interior valley, do expect them to be weaker than what we experience on Monday. Another weaker inside slider will move through the region late Tuesday into Wednesday, but given the current trajectory and strength, do not expect to see the same kinds of winds with this weaker slider. However, very dry conditions will remain in place. High pressure will then finally build back over the region for the latter part of the work week and next weekend, with dry and warmer conditions developing once again.
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Red Flag Warnings now for North Bay Mountains and Santa Cruz mountains
https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=sto&wwa=red%20flag%20warning
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North Ops weather video for Sunday: https://gacc.nifc.gov/oncc/predictive/weather/brief_files/brief.mp4
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