Red Flag Warnings and lightning in the West

Red Flag Warnings issued Thursday for areas in Oregon, Utah, Wyoming, and Colorado

lightning
Lightning between 6 a.m. Aug. 28 and 6 a.m. Aug. 29, 2019 MDT.

Moderate amounts of lightning occurred Wednesday in Southern Oregon, Northern California and Central Nevada, while larger numbers of strikes were detected in New Mexico and Arizona. Most areas where the lightning occurred in Oregon, California, and Nevada received light rain but many locations in Arizona and New Mexico saw heavier precipitation along with the lightning.

Here is a summary from the Northwest Geographic Area Coordination Center issued Thursday at 6:57 a.m. PDT:

Thunderstorms moved north across the Pacific Northwest spreading moderate lightning from the California border to the Puget Sound. Pockets of lightning occurred in South Central Oregon, the Oregon and southern Washington Cascades, and Western Oregon and southwest Washington, with scattered light precipitation. Isolated lightning strikes in Eastern Washington and Northeast Oregon. Light initial attack occurred with the largest fire reported in Central Washington for approximately 100 acres.

 

Observed precipitation
Observed precipitation between 9 a.m. CDT Aug. 28 and 9 a.m. Aug. 29, 2019.

Dry lightning is in the forecast for most of Utah Thursday, resulting in Red Flag Warnings.

Red Flag Warnings
Red Flag Warnings for August 29, 2019.

(Red Flag Warnings can be modified throughout the day as NWS offices around the country update and revise their weather forecasts.)

More than 7,000 lightning strikes in Washington and Oregon Saturday

lightning strikes recorded Washington Oregon
There were 7,436 lightning strikes recorded in Washington and Oregon during the 24-hour period ending at 8 a.m. PDT August 11, 2019.

The Northwest United States experienced another day of lightning Saturday.

Lightning strikes map
Lightning strikes and precipitation observed during the 24-hour period ending at 6 a.m. MDT August 11, 2019.

Lightning and rain in the Northwest, Red Flag Warning in five states

lightning precipitation August 9
Lightning and precipitation for the 24-hour period ending at 6 a.m. MDT August 10, 2019. Scroll down to see a map showing precipitation for the 48-hour period ending at 5:15 a.m. PDT August 10, 2019.

Thunderstorms were prevalent in the Northwest United States on Friday with many areas receiving rain ranging from a trace to about half an inch in some locations in Northwest California and Southwest Oregon.

Thunderstorms apparently affected the route of Air Tanker 911, a DC-10, as it ferried from Moses Lake, Washington to Sacramento McClellan Friday night, lengthening the planned 600-mile flight to 749 miles.

Tanker 911 MWH to MCC
During a ferry flight from Moses Lake, Washington to Sacramento McClellan, Air Tanker 911, a DC-10, apparently had to divert around thunderstorms in Oregon, increasing the planned 600-mile flight to 749 miles, arriving at MCC at 9:27 p.m. PDT August 9, 2019. Flightaware map.
precipitation 48 hours August 10, 2019
Precipitation during the 48-hour period ending at 5:15 a.m. PDT August 10, 2019.

Some rain will continue on Saturday across Washington, Montana, and Northern Idaho.

Precipitation forecast Northwest US
Precipitation forecast for the Northwest US at 11 a.m. PDT August 10, 2019.

The threat of thunderstorms, lightning, gusty winds, or dry fuels have triggered Red Flag Warnings across six states

Red Flag Warnings
Red Flag Warnings in effect at 5 a.m. PDT August 10, 2019. Red Flag Warnings can be modified throughout the day as NWS offices around the country update and their forecasts.

Red Flag Warnings and Lightning strikes, August 2, 2019

Lightning strikes map
Lightning strikes during the 24-hour period ending at 4:29 a.m. MDT August 2, 2019.

Lightning strikes, above, and accumulated precipitation, below.

Accumulated precipitation
Accumulated precipitation during the 72-hour period ending at 4 a.m. MDT August 2, 2019.
Dry lightning strikes
Dry lightning strikes shown with the degree of dryness, August 1, 2019.

 

On Friday the Red Flag Warning areas in Washington, Idaho, and southwestern Montana could experience additional lightning with little or no rain.

Red Flag Warnings August 2, 2019
Red Flag Warnings August 2, 2019

Lightning blankets Montana and the Northwest

lightning map montana washington idaho oregon
Lightning detected between 6 a.m. June 27 and 6 a.m. June 28 (MT).

Thousands of lighting strikes hit Montana, Idaho, Washington, and Oregon Thursday and Thursday night. Much of the area also received at least a little precipitation over the last 48 hours, which could reduce, but not eliminate, the threat of new wildfires.

lightning precipitation rain
Precipitation that occurred during the 48 hours ending at 8 a.m. MDT June 28, 2019.

About a quarter of lightning-caused fires that grow large are not reported within first 7 days

holdover lightning-caused wildfires
(From the research) Locations of lightning-initiated holdover wildfires in the contiguous United States which grew to sizes ≥4 km2 between 2012 and 2015. Map was created using ArcGIS® software by Esri. Basemap is a source of the National Geographic Society and Esri (2019).

Researchers have found that about a quarter of the fires caused by lightning that grow to more than 4 km² (988 acres) are reported more than a week after they are ignited.

A paper published in the Fire Open Access Journal describes how the National Lightning Detection Network (NLDN) and U.S. Forest Service fire data were used to determine the correlation between lightning strikes and the reported location of lightning-caused wildfires.

The NLDN, which has been used operationally for several decades, consists of 113 sensors across the continental United States and has a reported flash detection efficiency of cloud to ground flashes between 90–95%, with spatial errors that are typically less than 500 meters for the flash data used in the study.

The researchers found, of lightning-caused fires that grew to more than 4 km² (988 acres):

50% reported the same day
71% reported within 3 days
73% reported within 5 days
77% reported within 7 days

Holdover fires that are not reported for days or weeks after the lightning occurs can be problematic for land managers. Shortly after a thunderstorm has left the area, fire detection efforts are often ramped up and may continue in that mode for a few days. Fires that smolder in duff or under snow and suddenly grow can be unexpected. Firefighting resources that may have been staged in anticipation of emerging fires could be released or assigned to active incidents, complicating efforts at quick initial attack with overwhelming force.

Authors of the paper: Christopher J. Schultz, Nicholas J. Nauslar, J. Brent Wachter, Christopher R. Hain, and Jordan R. Bell.