July 2, 2020 – The official Predictive Services outlook calls for drier and warmer than average conditions in the North Ops region through October. The above normal cured fine fuel crop will be vulnerable to rapid spread rates and extreme fire behavior during dry breezy weather patterns, which will become more common in Sept-Oct. Occasional lightning will lead to new ignitions, and the threat of these fires growing to significant sizes will increase in all areas in July. The most vulnerable areas for large costly wildfires in the North Ops Region are at elevations above 3000 ft.
Otherwise, a gradual increase in Initial Attack can be expected in all areas as fuels continue to dry. The SW Desert monsoon pattern is expected to impact the North Ops region with near to below normal lightning amounts in July-August. In general, any lightning above 3000 ft will pose a threat of large fires due to very dry fuels. Most areas at 3000 ft and above have Above Normal Significant Fire Potential in July-August. All areas are in the Above Normal category in September. In October the focus for Above Normal Significant Fire Potential is on areas from the western Cascade-Sierra slopes to the coast. All areas not mentioned above have “Normal” significant fire potential.
In July “Normal Significant Fire Activity” is defined as 1-3 large fires per PSA. In August the Bay Area averages near 1 large fire in each PSA, while the remainder of the PSAs average between 2 and 6 large fires. In September “Normal” is defined as 1-3 large fires per PSA. In October “Normal” is defined as 1.2 or fewer large fires per PSA.
July – October 2020 North Ops Highlights
• 2019-2020 rainy season produced 25-70% of normal precipitation. Light snow pack now melted off, weak runoff winding down
• Dead fuel moisture values below average as of early July
• Above normal fine fuel loading again in 2020. Fine fuel crop mostly cured below 4000 ft. Initial Attack increasing at all elevations in July
• Below average green up occurring/has occurred in most live fuels
• Warmer and drier than normal July through October
• Lightning poses a bigger threat of large fires July-Aug. N-NE/Offshore wind events become a bigger threat of large fires beginning mid Sept
• Above Normal Significant Fire Potential most areas above 3000 ft in July-August
• Above Normal all areas in September
• Above Normal Wrn Cascade-Sierra slopes to the Coast in October
Fuels and drought
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The U. S. Drought Monitor for California shows the impact of the warmer and drier than normal rainy season. Portions of NW CA are now considered to be in Extreme Drought, and the majority of the remainder of the region is in Moderate or Severe Drought. To the west of the Cascade-Sierra crest the spring fine fuel crop came in more robust than usual. It is mostly cured below 4000 ft elevation. Middle and upper elevations are seeing dead fuels continue to dry, and the region-wide 1000-hr fuel moisture index is slightly drier than seasonal normal values as July begins. The live fuel green-up phase is close to, or slightly weaker, than normal, with the drying phase commencing earlier than normal in many areas. The high elevation snow pack peaked at 67% of normal and has since melted off, a few weeks earlier than usual. The weak runoff from the snow melt is also winding down. The Evaporative Demand Drought Index (EDDI) shows the stress on vegetation from the below average rainy season. This chart is a good indicator of where fire danger is and will be the highest as the fire season progresses. Higher EDDI values can be seen in the south and southeastern portion of the region.
Low pressure systems moved through the North Ops region during the first half of June, but rainfall was very limited. Northwestern and eastern mountain areas received the most precipitation, but most of these areas still ended up with less than average June rainfall. Precipitation since the rainy season began on October 1, 2019 remains below average in all but a very small area in far NE CA. Much of the region has only received 25-70% of normal precipitation for the season as we enter the driest 3 months of the year. Temperatures were above average in most areas, with the warmest areas in the south and west. The equatorial Pacific is currently in the ENSO-neutral category, and now cooler than average. It is expected to continue to cool over the next several months. For the fall and winter there is now an equal chance of the status remaining neutral category or a weak La Niña pattern developing, but there is almost no chance of an El Niño event in the fall and winter