Seasonal Outlook for September through December 2021

WEATHER/FUELS/FIRE POTENTIAL:

Over the last 30 days precipitation has been well below normal across Western, Central and Southern Nevada and well above normal across the rest of the Great Basin due to several surges of monsoon moisture. Temperatures have been near to below normal across the Great Basin. (Fig 1) The water year precipitation, dating back to October 1, 2020 remains well below normal in nearly all areas. Only portions of Western and Eastern Idaho, Wyoming, Northwest Nevada and parts of Utah fared slightly better with precipitation near or above 70-80% of normal. The wetting rains from the surges of monsoon moisture were not nearly enough to alleviate the precipitation deficit across the eastern half of the region. ERCs dropped to well below normal over northern and eastern areas of the Basin in August, but due to drier weather returning have increased again to near to even above normal for early September. The exceptions are over drier areas of Western Nevada and the Sierra Front where ERCs are still at records for the time of year. (Fig 2)

Extreme to exceptional drought continues across most of Utah, the southern and western two thirds of Nevada and parts of Idaho, with moderate to severe drought in all other areas of the Great Basin. The drought is likely to persist through the next few months despite the recent wet weather across Idaho, Wyoming, Utah and the Arizona Strip. (Fig 3) Soil moisture remains in the lowest percentile along the Sierra Front and over parts of Southwest and Central Idaho and Eastern Utah. (Fig 4) WEATHER/FUELS (cont.) Fine fuel loading is lower this year as compared to recent years across much of Nevada and Utah due to low elevation snowfall. Most areas saw a poor green-up this year with minimal new fine fuel growth due to the drought, although parts of northern Nevada saw some growth due to late spring precipitation. The lack of fine fuels will minimize the threat for fall cold frontal wind driven fires in the lowest elevations. Pinyon and Juniper fuel moisture and 1000-hr fuels are particularly low this year, with reports of significant PJ die off due to drought across Utah and into Eastern Nevada. This will keep fire potential higher in the mid to higher elevations. A Fuels and Fire Behavior Advisory is expected along the Sierra Front in the mid to higher elevations much of September.

Warm and dry conditions are expected as we head into September, especially over the Western Great Basin, which will keep fire potential high along the Sierra Front in the higher elevations and over parts of Southern and Central Idaho where fuel moisture has remained lower than other areas of the Great Basin. Smoke will also continue affect the Great Basin downwind of California wildfires. Any showers and thunderstorms through September will mostly affect the eastern half of the Great Basin. By October through December, wetter weather may return to Idaho and Wyoming with drier weather for the southern half of the Great Basin. (Fig 5 and 6)

FIRE POTENTIAL

Above normal fire potential is expected in September for the mid to higher elevations of the Sierra Front and over parts of Southern and Central Idaho. Otherwise, initial attack will likely continue throughout September, but most fires will likely remain small. Areas of the Sierra Front may see above normal fire potential going into the fall/winter if conditions remain dry. Normal (low) fire potential should return to most other areas.

Fig 1. (30-day Temperature / Precipitation) Fig 2. (Current ERC)

Fig 3. (Drought) Fig 4. (Soil Moisture)

Fig 5Fig 5 (CPC Sep 2021 Outlook) Fig 6. (CPC Oct - Dec 2021 Outlook)

Gina McGuire Palma

Meteorologist - Predictive Services

Great Basin Coordination Center, Salt Lake City UT