Precipitation hits some areas in Western U.S.

(Originally published at 2:40 p.m. MDT October 3, 2018)

Precipitation last 72 hours
Precipitation 3 p.m. Sept. 30 to 3 p.m. Oct. 3. NWS. Click to enlarge.

(Originally published at 2:40 p.m. MDT October 3, 2018)

Quite a number of areas in the Western United States have received significant precipitation over the last 72 hours. The green, yellow, and red areas in the map above represent locations with more than one-third of an inch, which should impede the ignition or growth of wildfires.

The data in southern Arizona that shows two to four inches explains why rescues like the ones below were occurring in Phoenix.

Wildfire potential October through January

(Originally published at 4:48 p.m. MDT October 1, 2018)

On October 1 the Predictive Services section at the National Interagency Fire Center issued their Wildland Fire Potential Outlook for October through January. The data represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.

If their analysis is correct, the only areas with above normal wildfire activity in October will be California, Southern Idaho, and Northern Nevada. Those areas will shrink in November to just Central and Southern California, and in December to just Southern California and the Central Coast. In January only Hawaii will have above normal potential.

Below:

  • An excerpt from the NIFC narrative report for the next several months;
  • More of NIFC’s monthly graphical outlooks;
  • NOAA’s three-month temperature and precipitation forecasts; and,
  • Drought Monitor.

“October and November mark another transition in the western fire season as the focus typically shifts to California as occasional Foehn wind events develop. The Southeast also typically experiences a fall peak during this period. The fall season this year might not follow the traditional script, however. Expected long-range weather patterns for at least October do not support the development of a significant number of wind events. While they may occur, the total number of events should be less than average. Considering that expected precipitation will be below average during this period, this could be a big factor in keeping some of the impacts from having an elevated potential at bay. Across the Southeast, conditions have been very wet over the past several months. With the potential development of an El Niño, the wet pattern is not likely to change. This should result in overall Normal to Below Normal significant wildland fire potential throughout the remainder of the fall.

“Transitioning from November into December and January, all regions are expected to experience reduced fire activity with the arrival of winter. Brief periods of critical fire weather conditions could elevate fire potential during occasional wind events over areas that are not snow covered. Events such as this are generally short in duration. Areas to monitor are along the Rocky Mountain Front, the Great Basin, the Southwest, and the southern Great Plains (during January.) All of these areas were experiencing some measure of drought at the end of September though some improvement is expected along the Rocky Mountain Front in southern Colorado and New Mexico.”

wildfire potential september through January

Continue reading “Wildfire potential October through January”

Most of U.S. predicted to have above normal temperatures the rest of the year

temperature precipitation outlook

Today the National Weather service issued their long range temperature and precipitation outlooks for October through December. If their forecast is correct almost all of the United States is likely to have higher than normal temperatures the rest of this year. The precipitation outlook is more varied, with the Northwest expecting below normal amounts, while the Southwest, Southern Plains, the Gulf Coast and East Coast should receive above normal precip.

 

Wildfire potential September through December

Originally published at 10 p.m. MDT September 1, 2018)

wildfire potential September OctoberOn September 1 the Predictive Services section at the National Interagency Fire Center issued their Wildland Fire Potential Outlook for September through December. The data represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.

If their analysis is correct, in September the wildfire potential will decrease in the Northern Rockies, which is not unusual for this time of the year, but remain elevated in Central Texas, California, Nevada, and the Cascades. For October through December the potential should remain high in Southern California, with no sign of a busier than usual fall fire season in the Southern Great Plains or the Southeast.

Below:

  • An excerpt from the NIFC narrative report for the next several months;
  • NIFC’s monthly graphical outlooks;
  • NOAA’s three-month temperature and precipitation forecasts; and,
  • Drought Monitor.

“The significant wildland fire potential forecasts included in this outlook represent the cumulative forecasts of the ten Geographic Area Predictive Services units and the National Predictive Services unit.

“The western fire season peaked in August as very hot and dry conditions continued under the presence of a very strong, persistent high pressure ridge during the first three weeks of the month. Many approached or broke all-time record highs during the second week of the month. Not surprisingly, many fires became quite large including the Mendocino Complex which burned more than 420,000 acres making it the largest fire on record in California. Most fires observed were in areas of preexisting or developing drought.

“Along the West Coast, drought intensification and expansion was observed across Oregon and Washington. Further inland, abnormally dry conditions developed across Nevada, Idaho, and western Montana. Drought intensification and expansion was also observed across the Great Lakes region. While pockets of extreme to exceptional drought continued across the Four Corner states, the active monsoon was allowing for some improvement to occur. Nearly the entire West Coast received less than 25% of average precipitation. Significant deficits extended inland into the Great Basin and the Northern Rockies where large areas received less than 50% of average precipitation.

“Most of Texas and the central Great Plains received above average precipitation in August. Amounts across Oklahoma, Kansas, and Arkansas received 200% to 400% of average precipitation. The East Coast received similar amounts. Temperatures nationwide were generally near to slightly above average except across the central Great Plains where they were a few degrees below average. Alaska fully exited the season mid-month as a wet and cool patter took hold across the Interior. Hawaii experienced large fire activity as well; however, the heavy rains from Hurricane Lane quickly reduced fire potential across the state.

“September is a transitional month for the West. Critical fire weather periods become increasingly driven by occasional wind events resulting from passing cold fronts or by a strong westerly flow. The transition this year began a few weeks early. A shift to a fall-like pattern began the last week of August. Overall normal significant large fire potential is expected in most areas across the West except along the Canadian border with northeastern Washington, extreme northern Idaho, and northwestern Montana where above normal potential is expected. Debris from Hurricane Lane may produce heavy dead fuel loadings across Hawaii which could become receptive should abnormally dry conditions develop. Portions of northwestern Nevada and northeastern California could remain elevated as well given continued fuel dryness and a propensity for wind events.

“In October, the continued seasonal transition into fall will allow for colder air to become entrenched across the Great Basin thus creating a high pressure ridge that should periodically induce Foehn Wind events across both Northern and Southern California. Other regions across the Westshould fully exit fire season. In the East, preexisting drought conditions across the Great Lakes Region cloud promote wind-driven events should the fuels remain dry after leaf drop. The remainder of the East is largely free of drought entering late fall.

“November and December are traditionally months where fire activity is reduced. The focus during this period generally shifts from California to the Southeast where during dry years, significant fire activity can be observed. Latest data suggests that the late fall period will experience at least average conditions if not wetter than average conditions in some locations. So, Normal Significant Large Fire Potential is expected across most of country during the remainder of the outlook period.”

wildfire potential November December

Continue reading “Wildfire potential September through December”

Fall-like weather could slow wildfires in Northern Rockies

The trend could last into next week

weather forecast northern rockies
Graphic produced by the National Weather Service office in Missoula, Montana August 21, 2018 at 8:30 p.m. MDT.

(Originally published at 9:12 a.m. MDT August 22, 2018)

When I saw the prediction from the Missoula National Weather Service office above, it got me thinking about how this cooler, possibly wetter weather is going to affect the dozens of large wildfires currently burning in the northwest United States. Two of the fires we have written about over the last couple of days, Watson Creek in Oregon and Howe Ridge in Montana, recently had small amounts of precipitation, certainly not enough to put them out, but it will absolutely slow their spread for a day or two.

No doubt other fires were also were affected, as you can see in the map below showing precipitation over the last 48 hours. But it looks like Washington, western Oregon, and most of northern California remained dry.

weather 48-hour precipitation map
Estimated precipitation for the 48-hour period ending at 8 a.m. CDT August 22, 2018.

More rain is expected in the Northern Rockies into next week. Below is the forecast for precipitation on Monday afternoon, August 27. The “haze” shown in California and Oregon is presumably smoke from the Mendocino Complex of Fires.

precipitation August 27 2018
Predicted precipitation for August 27, 2018.

Next are the predictions for precipitation and temperature August 27 through 31.

Continue reading “Fall-like weather could slow wildfires in Northern Rockies”

Record-setting heat helped keep California wildfires active at night

July in the state had the highest minimum temperature on record

Above: Credit Los Angeles Times

There are many ways that a warmer climate can influence wildfires, causing them to burn more intensely. Higher temperatures can lower the relative humidity, lower the amount of moisture in the vegetation (fuel), raise the temperature of the fuel itself, and cause more powerful thunderstorms with  lightning. But one factor that we don’t think about very often is that the heat can persist through the night, influencing fire behavior.

When today’s senior firefighters began their careers, they could usually count on fires “laying down” at night. The intensity and rate of spread would decline to the point where night shift personnel could more easily and safely “go direct”, constructing fireline very close to the edge of the fire.

During the month of July in California, many of the large fires continued to grow rapidly at night, which often required firefighters to drop back to a safety zone and simply watch, since there is little that they could do without putting themselves in harms way.

Of course it is too early to say that this will be a permanent change, but in the last month a new record was set for California’s average minimum temperature; it was the highest since records have been kept. And this was not just a one-month event. The trend has been increasing since the 1980s.

Many of those senior firefighters have been known to to lament the trend in the last couple of decades of incident management teams declining to have a night shift. The justification of the teams was that it was not safe to have firefighters working at night because of snags falling, steep terrain, and other issues. After observing the nighttime fire behavior in recent years, the senior firefighters might now be less inclined to argue strongly in favor of night shifts, at least in certain geographical areas and weather conditions.