Fire weather outlook, September 3 through 8

Yet another upper level trough providing some active fire weather conditions today across northern CA/southern OR and most of WY/western SD. With this trough, a lack of mid-level moisture is preventing any thunderstorm activity across the northwestern US. However, very dry conditions (aggravated by drought in CA/OR) combined with windy conditions are developing critical fire weather conditions in both these regions. A surface cold front associated with the trough will slide southeast across the northern Rockies Wed evening and into Thurs. This front will increase humidity across WY/SD lessening fire danger and shifting winds to the north for Thurs.

The same cold front will push south/west across OR/CA overnight Wed. This front will continue mixing overnight with breezy winds and poor RH recovery-continuing elevated fire danger through Wed night. Through late week and into the early weekend, easterly winds will provide additional downsloping off the Rockies and continue increased fire risk with poor overnight RH recovery through Sun. With an off-shore trough developing late-week and weak ridging over the Rockies, temperatures will increase to 90F+ across much of CA/OR/WA. Very dry conditions and RHs at/below 20% will expand eastward/northward across the region and into the central Rockies through the weekend. Breezy easterly winds will continue through Fri for much of OR/northern CA/NV and gradually diminish overnight Fri. As the off-shore upper level trough approaches the West Coast Sun/Mon, westerly winds will increase for much of the northern CA/OR/WA/ID, which may develop widespread critical fire weather conditions. No precipitation is expected for northern CA/NV and WA/OR/ID through the period.

The other major weather highlight will be soon-to-be Hurricane Norbert near the California Peninsula. Current forecast model trends depict moisture streaming northward into the southwestern US by late weekend. Developing monsoonal conditions across AZ/NM/UT/CO late week will provide chances of scattered thunderstorms. However, much more widespread rains/storms could develop for portions of southern CA/NV and much of AZ/UT/CO with the influence of Norbert. Great uncertainty still exists on the exact track of this system, though confidence is increasing on widespread heavy rains late weekend/early next week.

WPC 5-day OPF
Quantity of precipitation forecast for September 3 through 8, 2014. Rains continue to avoid much of the Pacific Northwest and western US, with some much needed relief for southwest US. Image from the Weather Prediction Center.

Weather Highlights:

WY/western SD/northern CO/NE Panhandle: Critical fire weather Wed with breezy westerly winds, RH’s <20%, and warm conditions. Cold front crossing region tonight increasing RH and winds increasing and turning northerly post-front. Becoming very dry/warm Sun/Mon with increasing fire weather threat.

OR/northern CA/northern NV: Critical fire weather Wed through Thurs with breezy northerly wind, turning easterly Thurs AM. Very warm/dry with poor overnight RH recoveries expected through Sat with continued enhanced fire weather conditions. Additional critical fire weather conditions possible Mon/Tues with breezy westerly winds.

WA/ID/MT: Increasing fire weather threat as temperatures warm into the weekend with breezy westerly winds possible late weekend. Continued dry conditions with no precipitation expected (with exception of northern ID/MT Wed/Thurs).

AZ/UT/NM/southern CO: Monsoonal flow returning Thurs/Fri/Sat with scattered thunderstorms, rain becoming more numerous over the weekend, especially across AZ/UT with flooding possible.

Southern CA/southern NV: Very dry and warm through late week. Increasing showers/storms Sun/Mon with flooding possible.

Chip

Wildfire potential, September through December

The Predictive Services section at the National Interagency Fire Center has issued their Wildland Fire Potential Outlook for September through December, 2014.

The data represents the cumulative forecasts of the eleven Geographic Area Predictive Services Units and the National Predictive Services Unit.

If their predictions are accurate, firefighters could be busy in Washington and Oregon through October, and busy in southern California into December. The fall fire season in the southeast looks like it will be normal or slower than normal.

September

September wildfire outlook

  • Above normal fire potential will remain across southwestern Oregon through September for lingering dryness and potential dry, east winds.
  • Fire potential will remain elevated across portions of California. Continued dry fuels will couple with potential offshore winds.
  • Below normal fire potential is expected to continue for some portions of the eastern U.S. and the Hawaiian Islands.

October

October wildfire outlook

  • Above normal fire potential will persist across California as fuels will remain dry and off shore flow season arrives in earnest. Northern and central California will return to normal potential by the end of the month.
  • Below normal fire potential is expected to continue for some portions of the southern Plains, Florida, and Hawaii.

November and December

(Note: there was a technical problem in getting a good copy of the image below.)

November December wildfire outlook

  • Above normal fire potential will persist across southern California as offshore flow potential continues. Expect a return to normal potential from north to south beginning in late November through December.
  • Below normal fire potential is expected to continue for the Gulf and Southeast Coasts, and Hawaii.

Fire weather outlook, August 29 through September 2

An upper level trough will cross the northwest Pacific states Fri/Sat and eject into the central Plains on Sun. This will bring periodic windy conditions across the western US and cooler weather for the northwest. No critical widespread critical fire weather is expected, although some areas will have enhanced conditions that will aid in fire spread, especially with drought conditions across the west. Continued heat is expected for the southwest with dry conditions prevailing.

The primary fire threat across the US will focus on warm temperatures and low RHs in the western Great Basin Fri and Sat. Breezy westerly winds are expected Fri/Sat especially across much of NV due to the approaching upper level trough. As the trough shifts eastward, wind conditions will move across northern UT and southern WY/northern CO into Sun/Mon. Dry conditions over much of WY/CO will provide an increased fire risk with these strong westerly winds.

The southwestern US will remain dry and hot through the period. Portions of central/eastern CA/NV/AZ will have poor RH recovery overnight. Though no windy conditions are expected across this region, above average temps and below average precipitation will lead to conditions conducive to human caused fire starts and challenges for suppression

A cold front crossing WA/OR will bring breezy conditions Fri, however, temperatures are expected to remain cool and RH is expected to remain above critical levels. A lack of upper level moisture will prevent any thunderstorm development, however some light rains are possible along western slopes. A stable post-frontal air mass will provide quiet conditions for the Pacific Northwest and eastward with the front’s advancement through the weekend. Cooler weather is expected to continue through the period for WA/northern OR/MT/northern ID with warming conditions likely Tues in advance of the next system.

Long term into mid-week, a summer type pattern looks to return for the central US with another trough pushing into the west. This may develop enhanced fire weather conditions across the western US mid-week and central Rockies mid-to-late week and should be monitored.

Five-day precipitation outlook
Five-day precipitation outlook, issued August 29, 2014.

Weather Highlights:

Eastern CA/NV: Breezy westerly winds Fri/Sat with low RH and warm temperatures. Locally critical fire weather is possible, otherwise generally enhanced fire weather is expected across the region. Winds will be decreasing Sun.

WA/OR: Breezy conditions are likely today across central portions of OR/WA on the eastern sides of the Cascades. Moderate temperatures and RH should prevent any increased fire risks. Warming with decreasing RH across southern OR late weekend and moving northward into next week.

Southern WY/northern CO/northern UT/southern ID: Developing strong westerly winds Sun/Mon. Combined with warm and dry conditions, this will lead to an enhanced fire threat continuing into mid-week.

Southern/central CA/AZ: Continued warm and dry with poor RH recovery. Some breezy winds Fri in eastern CA, otherwise no significant winds/thunderstorms.

A rainy week

7-day precip 8-25-2014

The last seven days have been very wet in some parts of the United States, especially in north-central Montana where, according to the NOAA map above, some areas had five to eight inches of precipitation. (Click on the map to see a larger version.)

Fire weather outlook, August 23 through 28

A large, slow-progressing upper level trough has brought copious moisture to much of the northern Rockies and Eastern Great Basin. Even some winter weather advisories with very a cool air mass over MT. Widespread fire weather threats have been minimal across much of the western US and will likely remain quiet through the weekend. Despite the lack of optimal large fire conditions, several areas will need to be monitored for developing potential into mid-week.

As the trough begins to lift northeast into the northern Plains and Canada early week, another final shortwave will rotate around the apex on Monday. This will bring a slight chance of showers and thunderstorms across portions of NV/UT. With lack of low level moisture and drying taking place over the weekend, a few isolated dry thunderstorms are possible. No strong winds are anticipated outside of thunderstorm outflows. The threat will diminish Tuesday evening.

A big story will be developing, with upper level ridging along the West Coast and subsequent drying conditions and warming temperatures early week. These conditions will aggravate already drought stricken regions and provide ripe conditions for fire growth for CA and northward into OR/WA. No widespread thunderstorms or wind events are anticipated. However, temperatures above 90F and widespread RHs <20% with some <10% for central OR and northern CA by Wednesday will promote extreme fire behavior.

Weather Highlights:

NV/UT/southern ID: Isolated dry thunderstorms Mon/Tues. Becoming hot and mid-week.

OR/WA: A few scattered showers on Sun, lingering into Mon. Becoming very hot and dry Tues and continuing into late week.

CA: Warm and dry Sat/Sun. Becoming very hot and critically dry by mid-week.

Chip

Fire weather outlook, August 18 through 22

Lack of widespread critical fire weather has kept fire starts down across much of the western US. Expect fire weather to become more critical today in OR/CA and spread eastward into ID/WY through late-week.

A cut-off upper level low off the coast of north CA will provide enough moisture and instability for scattered dry thunderstorms over high elevations. Very dry surface conditions combined with hot temperatures will make fuels very receptive to dry lightning. Tues, the low will drift southward along the coast, but lose ample moisture to provide widespread storms, however a few isolated storms are possible in central/north CA through Tues evening.

A more potent upper level trough will enter dig into the Pacific Northwest Tues, and begin to eject over the Northern Rockies on Wed. In advance of this trough, surface pressure falls are expected across central OR/WY creating breezy westerly winds Tues and Wed. Combined with warm temperatures and dry conditions, fire suppression will become difficult. Higher moisture across extreme northern WA/ID/MT will develop scattered rain and wet thunderstorms over higher elevations bringing some relief mid-week, with a higher heavy rain threat for eastern MT late week.

Surface low pressure will begin to develop across the central Plains in response to the eastward movement of these upper level features. With high pressure over the Rockies and the western US, a strong pressure gradient will set up over WY and southern ID, and northern CO late week. This gradient will develop breezy conditions across these areas leading to critical fire weather. In addition, increased upper level moisture will provide ample conditions for scattered dry thunderstorms across the same areas, especially over higher terrain. Cooler conditions will develop across the northern Rockies late weekend. Meanwhile, warm and dry conditions will continue for CA and western/central OR/WA with isolated locations of gusty winds through the weekend.

Weather Highlights:

CA: Critical fire weather Monday due to dry lightning, warm temperatures and dry conditions. Threat will lessen and drift southward on Tues/Wed. Continued hot and dry through the period.

OR/WA: Scattered dry thunderstorms across higher elevations of southern OR Monday. Increasing winds Tues/Wed with critical fire weather conditions expected Wed. A few wet thunderstorms over higher terrain of extreme nrthern WA.

Southern ID/WY/northern CO: Very breezy conditions developing with warm temperatures and dry conditions continuing into the weekend. Scattered dry thunderstorms possible through the period over higher terrain. Critical fire weather expected Wed through Fri.
MT: Isolated dry thunderstorms possible Wed through Fri for southern MT, with wet thunderstorm chances across northern MT. Otherwise warm and dry through Thurs with heavy rain possible Fri across eastern MT.

Chip

July brought extreme temperatures

July extreme temperatures

The graphic shows how July 2014’s average temperature ranked across the lower 48 states when compared to the last ~120 years. Click on the image to see a larger version.

Some areas in the central states had the coolest or the near-coolest July on record while it was just the opposite in the northwest.