UPDATE @ 10:50 p.m., Sept. 7

The Boulder Office of Emergency Management, after surveying 5-10% of the burned area, has identified 53 houses that have been destroyed by the Fourmile fire. Due to the fire activity, they were not able to collect data in other areas.

ABC7 has information about the early stages of the fire, including transcripts from radio conversations and a report that a vehicle colliding with a propane tank may have started the fire.

At 8 p.m. the Rocky Mountain Area Coordination Center reported:

Type 1 Incident Management Team, Thomas in briefing at 1000 on 09/08. 6,128 acres. IR [fixed-wing Infrared] flight tonight to determine size. Counting of structures lost will begin tomorrow. 20 Subdivisions west of Boulder have been evacuated and 3 major county roads are closed. Fire is growing around the entire perimeter. Crowning, running, and spotting fire behavior has been observed.

In fact, one of the US Forest Service infrared aircraft, a Super King Air 200 twin-turboprop, N149Z, has already flown over the Fourmile fire, and it looks like the Cow fire in Rocky Mountain National Park as well. The map below shows the aircraft’s flight path as it arrived into the area from Boise, flew over the two fires, possibly dodged some rain or thunderstorms, and landed at Rocky Mountain Metro Airport at 8:08 p.m. It has the capability to downlink the digital imagery wirelessly via Aircell while airborne. Then an Infrared Interpreter retrieves the files from a server, analyzes the data, produces a map showing the heat sources, draws an accurate fire perimeter, and calculates the acreage of the fire.

So, within a matter of hours we should have an accurate fire perimeter and acreage.

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UPDATE @ 6:15 p.m., Sept. 7

At a 4 p.m. press briefing today fire officials said that 7,100 acres had burned (later changed to 6,168 acres at the InciWeb site) and the fire had forced the evacuation of 3,000 residents. An inversion in the morning prevented air tankers from taking off, but later in the day eight air tankers had dropped 90,000 gallons of fire retardant by the time of the briefing. Three helicopters are also working on the fire. About 2,000 residences are without electricity in the fire area. With about half of the burned area being surveyed, they have identified 63 structures that have burned.

Here is a map produced today by Boulder County showing the perimeter and the evacuation area for the Fourmile fire. (We added the notes in red at the top.) The original higher resolution version of the map is HERE.

Click the map to enlarge it.

Another map of the fire perimeter can be found at the InciWeb site.

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UPDATE @ 5:00 p.m., Sept. 7

Here are some updated maps of the Fourmile fire near Boulder, Colorado.

HERE is a link to a topographic map showing the fire perimeter as of noon today, but it is difficult to make out much detail.

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UPDATE @ 12:20 p.m., Sept. 7

Five heavy air tankers were available at the Rocky Mountain Metro Airport as of this morning at 10:30.

Here is the “spot weather forecast” issued by the National Weather Service at 11:00 a.m. this morning  specifically for the area of the Fourmile fire near Boulder:

REST OF TODAY

SKY/WEATHER………MOSTLY SUNNY.

MAX TEMPERATURE…..72-76.

MIN HUMIDITY……..9-13%.

20-FOOT WINDS…….UPSLOPE/UPVALLEY 6-12 MPH UNTIL 1500…THEN

SOUTHEAST 10-15 MPH.

TRANSPORT WINDS…..SOUTHWEST 12-20 MPH.

MIXING HEIGHT…….4000 FT AGL UNTIL 1400…THEN 7000 FT AGL.

AGL.

SMOKE DISPERSAL…..POOR UNTIL 1100…THEN GOOD UNTIL 1200…THEN

VERY GOOD UNTIL 1700…THEN GOOD.

HAINES INDEX……..4 LOW.

TONIGHT

SKY/WEATHER………PARTLY CLOUDY(40-50%).

MIN TEMPERATURE…..50.

MAX HUMIDITY……..45-55%.

20-FOOT WINDS…….SOUTHEAST WINDS AROUND 10 MPH UNTIL 2000…THEN

WEST 8-16 MPH WITH GUSTS TO 25 MPH ON THE RIDGES.

TRANSPORT WINDS…..SOUTHWEST 12-20 MPH.

MIXING HEIGHT…….6000 FT AGL UNTIL 1900…BELOW 1000 FT AGL

AFTER 2100.

SMOKE DISPERSAL…..FAIR UNTIL 1900. POOR AFTER 2100.

HAINES INDEX……..3 VERY LOW.

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UPDATE @ 9:42 a.m., Sept. 7

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The Fourmile fire has burned at least 3,500 acres and destroyed dozens of homes northwest of Boulder, including the homes of four firefighters who were working on the fire. Some of the communities impacted by the fire include Four Mile Canyon, Sunshine Canyon, Gold Hill, Sugarloaf, Pinebrook Hills, and Boulder Heights. Approximately 3,500 residents are under mandatory evacuation orders.

The map of the Fourmile fire near Boulder shows that the fire has spread quite a bit towards the northeast compared to the map we published yesterday.  On Monday the strong winds prevented aircraft from working on the fire until after 5:00 p.m. when the winds decreased and three were assigned, but on Tuesday morning four heavy air tankers, one lead plane, one large Type one helicopter, and two air attack ships will assist the ground-based firefighters, according to the Rocky Mountain Area Coordination Center.

A few hours after the fire started a Type 2 incident management team was ordered, but due to the size and complexity a higher-qualified Type 1 team was ordered last night. On Tuesday the one of the Rocky Mountain Area Type 2 teams will work with the Boulder County Type 3 team.

Cooler temperatures and winds speeds of 8-12 mph on Tuesday should produce less extreme fire behavior than we saw on Monday.

For official information about evacuations, visit the Boulder Office of Emergency Management web site.

Here is a 3-D map of the Fourmile fire showing heat detected by satellites. Click on the map to see a larger version.

We will update this article throughout the day. Check back for more information.