The Predictive Services 4-month weather outlook for the North Ops region calls for mixed temperature anomalies with near to below normal precipitation. Drought conditions are expected to intensify but not strengthen as significantly the next 2 to 3 months compared to what it did last year due to less extended heat wave events. Critically dry dead and live fuel alignments will increase across the low and most mid elevations during June with an above normal significant fire potential forecast for elevations below 5500 feet and excluding the N. Coast. Elevations above 3000-3500 feet will take longer to come into flammable fuel alignment during June compared to the lower elevations. Fuels will become more flammable, without an elevation restraint, during July and August with above normal significant fire potential. Exceptions to the above normal areas for July and August do exist including the near Coastal influenced areas due to expected deeper, cooler, more moist onshore flow at times. Critical fuel dryness should occur across all of the area during September with a return of some dry-northerly wind flows, thus prompting above normal across the entire region. Lightning ignitions should be most problematic during June and July.
It should be mentioned that acute and flammable fuel anomalies exist across the Tahoe, Eldorado and 6 Rivers N.F due to widespread blow-down from winter storms during December. Beetle or drought caused tree mortality is also a concern across the forests due to the multi-year significant drought.
During June and July normal Significant Fire Potential is 1 to 3 large fires per PSA. During August, 2 to 5 large fires occur per PSA with the exception of less than 1 large fire in the Bay Area PSAs. During September most PSAs average 1 to 3 large fires excluding the Bay Area and Far Eastside PSAs which is less than 1.
Weather Discussion
Weather pattern during May was mixed with cool-moist periods as well as warm-dry periods. Despite some unsettled weather most the region experienced below to well below normal precipitation although the N. Coast observed near to above normal returns. Average temperatures were split with generally cooler than normal across the northern half, especially near the OR border, while near to a little above normal occurred across southern areas, especially Sacramento Valley.
The outlook for the North Ops region is for mixed temperature anomalies with near to a little below normal June-July and then near to slightly above normal August-September while precipitation should be near to below normal during the 4-month period.
The weather pattern for June appears to be dry overall with just some minor moisture intrusions favoring the north as the Jet Stream dips south at times. Some Trough passages during June will bring lightning to the region. There is higher confidence for the Southwest Monsoon to be extra active this year west of the Continental Divide and make frequent intrusions into southern CA/NV as well as the Four-Corner states during July, then shift a little further away from northern CA during August. Onshore flow is expected to trend a little deeper during July and August. La Niña and a negative Pacific Decadal Oscillation (PDO) are likely to continue to influence the weather patterns during the next several months.
Fuels Discussion
A mosaic of fuel conditions and flammability exists across northern California due to green-up and curing in the live fuels and fluctuating dead fuel moistures due to recent changeable weather patterns. Fuels overall have become more flammable across the lowest elevations as evident from fire business trends during the latter half of May.
Dead fuel moisture is generally near to below normal thanks to overall drying during May with peak dryness occurring on the 25th. The 1000-hour dead fuel moisture chart illustrates the overall drying trend. The current values, represented by the blue line, are found below the average grey line and above the record minimum red line and more like late June readings. Live woody shrubs and tree canopies are in a mixed flammability state due to various advancements in green-up across the mid elevations and generally curing across the low elevations and is species dependent. Chamise is curing and becoming more flammable while Sage has likely peaked in moisture content. Herbaceous fuels are in a mixed state of curing & growing with mostly cured annual and perennial grasses found below 2500 feet, excluding the N. Coast, while some sort of green-up state is found between 2500 to approximately 6500- 7000 feet. Herbaceous fuel loading appears to be near to a little above normal this year with the above normal anomalies more prevalent across the Sacramento Valley, Modoc County and portions of the Far Eastside and Bay Area PSAs. Significant grass growth along the shoulder of Hwy 299 east of McArthur in Lassen County. Snow water content lowered from 30-40% of normal at the beginning of May to 5-15% at the end of the month.
June – September 2022 North Ops Highlights
- Weather outlook for June to September calls for mixed temperature anomalies with near to slightly below normal June and July then near to slightly above normal during August and September with near to below normal precipitation.
- Increasing flammable alignments between live and dead fuels during June and July.
- Significant Fire Potential starts with Above Normal during June for elevations below 5500 feet and excluding N. Coast then expands to all elevations July-August although excluding Coastal influenced areas such as the N. Coast and Bay Marine PSAs then above normal areawide during September.