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 Post subject: Fire Weather Briefing - Red Flag Warning
Post Posted: Mar 20, 2017 7:53 am 
Whoa momma! A top Pinecam poster!
Whoa momma! A top Pinecam poster!
Joined: Dec 22, 2006 10:21 pm
Posts: 1942
Location: BFE
Synopsis: Well it’s Monday and it is another Red Flag day. Very warm and dry air remains over Colorado today. The winds will be a little lighter in general, but breezy conditions with low humidities are still expected in most foothill areas and in some locations on the plains near the mountains. Gusty winds are most likely to spread off the foothills in Boulder and northern Jefferson counties, and in locations just outside of those counties. Conditions will be worst this afternoon, and improve quickly this evening.

The long-term outlook through Friday: Fire Danger will decrease on Tuesday in most areas as a cold front affects northeast Colorado bringing cooler temperatures and higher humidity. The only exception would be over Park county and the southern Foothills.

Fire Danger will increase on Wednesday in the Foothills and along the Front Range as winds increase and humidity decreases. A storm system will affect the area Thursday afternoon into Friday. This system will bring cooler temperatures along with a good chance of widespread precipitation.

Fire Restrictions - Stage 2 Fire Ban are in effect for Clear Creek and JeffCo Details

Fire Danger for the Fire Districts is rated as EXTEREME.

Watches & Warnings

A Red Flag Warning
is in effect for the Front Range foothills and the lower elevations of Boulder and Jefferson counties...Fire Weather Zones 215...216 and 239.

* Timing...Conditions will be worst this afternoon, and improve
quickly this evening.

* Winds...West 10 to 20 mph with gusts up to 35 mph.

* Relative Humidity...as low as 11 percent.

* Impacts...Fires will start easily and may spread rapidly.

Hazardous Weather Outlook for today and tonight: Warm and dry conditions will continue today. Temperatures will likely be a couple of degrees cooler than yesterday, and winds will be lighter in most areas. There will still be wind gusts up to 35 mph in the mountains and foothills. These winds may also occasionally blow onto the nearby plains this afternoon, especially in Boulder and Jefferson counties.

There is a chance of light showers tonight, mainly in areas north of Interstate 70. Any showers will mainly be rain, with some light snow possible over the higher mountains.

For Tuesday through Sunday: On Tuesday there will be a chance of rain and snow showers in the mountains with the snow level around 10000 feet. Any snow accumulation will be minor. There will also be a slight chance of rain showers on the plains Tuesday afternoon and evening.

Warm, dry and breezy conditions will develop on Wednesday which will elevate the fire danger in the foothills and on the plains.

For Thursday into Friday, a storm system is projected to track slowly across Colorado bringing lower temperatures to the area. This system will bring snow to the mountains along with a good chance of rain to lower elevations especially Thursday night into Friday. Some snow may mix with the rain late Thursday night into early Friday at lower elevations.

Some mountain areas along with the higher foothills could see several inches of snow with moderate to heavy rainfall across the plains. Dry and warmer weather will then return the outlook area for Saturday.


Front Range Foothills Forecast
Today
Mostly cloudy, with a high near 68. Breezy, with a west wind 8 to 16 mph, with gusts as high as 25 mph.

Tonight
A slight chance of showers between 8pm and 2am. Mostly cloudy, with a low around 39. West southwest wind 5 to 10 mph becoming light west. Winds could gust as high as 16 mph. Chance of precipitation is 20%.

Tuesday
A 30 percent chance of showers after noon. Partly sunny, with a high near 59. Light and variable wind becoming east around 6 mph in the afternoon.

Tuesday Night
A 20 percent chance of showers before midnight. Mostly cloudy, with a low around 37. Light and variable wind becoming west southwest around 6 mph after midnight.

Wednesday
A 10 percent chance of showers after noon. Mostly sunny, with a high near 63. Southwest wind 5 to 8 mph.

West Denver Metro Forecast
Today
Mostly cloudy, with a high near 76. West southwest wind 5 to 14 mph, with gusts as high as 18 mph.

Tonight
Mostly cloudy, with a low around 46. West wind 5 to 9 mph becoming calm.

Tuesday
A 20 percent chance of showers after noon. Partly sunny, with a high near 66. Light and variable wind becoming northeast 5 to 7 mph in the afternoon.

Tuesday Night
A 20 percent chance of showers before midnight. Mostly cloudy, with a low around 41. East northeast wind around 6 mph becoming light and variable.

Wednesday
Mostly sunny, with a high near 71. Southwest wind 3 to 6 mph.

Fire Weather for the Western Metro Fire Districts below 6000 feet (Zone 239) –


Today...

Sky/weather.........Mostly cloudy.

Max Temperature.....74-78.
24 hr trend......Little change.

Min Humidity........10-14%.
24 hr trend......2-4% drier.

20-foot winds.......West winds 8-14 mph. Gusts up to 25 mph in the afternoon.

Haines Index........5 moderate.

LAL.................1.

CWR.................0 percent.

15K FT MSL winds....West 20-30 mph.

Mixing height.......3000-4000 ft AGL until 1100, then 13500-14500 ft AGL.

Transport winds.....Southwest 10-15 mph.

Smoke dispersal.....Poor until 1100. excellent after 1200.

Tonight...

Sky/weather.........Mostly cloudy until 0500, then partly cloudy (50-60%). Slight chance of rain showers after 2000 until 0100.

Min Temperature.....42-46.
24 hr trend......4-7 degrees cooler.

Max Humidity........55-65%.
24 hr trend......35-50% wetter.

20-foot winds.......Northwest winds 5-11 mph.

Haines Index........3 very low .

LAL.................1.

CWR.................0 percent.

15K FT MSL winds....West 20-30 mph.

Mixing height.......10500-11500 ft AGL until 2000, then 2000-3000 ft AGL.

Transport winds.....Southwest 10-15 mph until 2100, then light.

Smoke dispersal.....Excellent until 1900. poor after 2100.

Tuesday...

Sky/weather.........Partly cloudy (40-50%) until 1200, then mostly cloudy. Slight chance of rain showers after 1200.

Max Temperature.....63-67.
24 hr trend......10-15 degrees cooler.

Min Humidity........27-35%.
24 hr trend......20-25% wetter.

20-foot winds.......North winds 4-7 mph shifting to the east 4-8 mph in the afternoon.

Haines Index........3 very low .

LAL.................1.

CWR.................0 percent.

15K FT MSL winds....West 25-35 mph.

Mixing height.......4500-5500 ft AGL.

Transport winds.....Light winds.

Smoke dispersal.....Poor.


Fire weather for the foothills fire districts above 6000 feet (zone 216) -


Today...


Sky/weather.........Partly cloudy (50-60%) until 0900, then mostly cloudy.

Max Temperature.....63-73.
24 hr trend......Little change.

Min Humidity........10-16%.
24 hr trend......2-4% wetter.

20-foot winds.......
Valleys / lower slopes...West winds 11-17 mph. Gusts up to 20 mph increasing to 30 mph in the afternoon.
Ridges / upper slopes....West winds 11-21 mph with gusts to 30 mph.

Haines Index........4 low .

LAL.................1.

CWR.................0 percent.

15K FT MSL winds....West 15-25 mph.

Mixing height.......3500-4500 ft AGL until 1100, then 14000-15000 ft AGL.

Transport winds.....Southwest 15-20 mph.

Smoke dispersal.....Fair until 1100, then very good.

Tonight...

Sky/weather.........Mostly cloudy until 0500, then partly cloudy (40-50%). Slight chance of rain showers after 1900 until 0200.

Min Temperature.....35-43.
24 hr trend......2-4 degrees cooler.

Max Humidity........51-61%.
24 hr trend......25-35% wetter.

20-foot winds.......
Valleys / lower slopes...West winds 5-11 mph. Gusts up to 20 mph in the evening.
Ridges / upper slopes....West winds 6-12 mph. Gusts up to 20 mph in the evening.

Haines Index........3 very low .

LAL.................1.

CWR.................0 percent.

15K FT MSL winds....West 20-30 mph.

Mixing height.......10000-11000 ft AGL until 2100, then 2000-3000
ft AGL.

Transport winds.....Southwest 10-15 mph until 2300, then light
until 0300, then west around 10 mph.

Smoke dispersal.....Very good until 2000, then poor.

Tuesday...

Sky/weather.........Partly cloudy (40-50%) until 1200, then mostly cloudy. Chance of rain showers after 1200.

Max Temperature.....56-66.
24 hr trend......4-7 degrees cooler.

Min Humidity........19-29%.
24 hr trend......4-7% wetter.

20-foot winds.......
Valleys / lower slopes...Southwest winds 4-7 mph shifting to the south 4-8 mph in the afternoon.
Ridges / upper slopes....Southwest winds 6-12 mph.

Haines Index........3 very low .

LAL.................1.

CWR.................0 percent.

15K FT MSL winds....West 25-35 mph.

Mixing height.......3000-4000 ft AGL until 1100, then 11000-12000 ft AGL.

Transport winds.....West around 10 mph until 0700, then light until 1000, then southwest 10-15 mph.

Smoke dispersal.....Poor until 1100. very good after 1400.

Fire weather terms and abbreviations

LAL – Lightning Activity Level:
LAL 1 - No thunderstorms
LAL 2 - Isolated thunderstorms. Light rain will occasionally reach the ground. Lightning is very infrequent, 1 to 5 cloud to ground strikes in a five minute period.
LAL 3 - Widely scattered thunderstorms. Light to moderate rain will reach the ground. Lightning is infrequent, 6 to 10 cloud to ground strikes in a 5 minute period.
LAL 4 - Scattered thunderstorms. Moderate rain is commonly produced Lightning is frequent, 11 to 15 cloud to ground strikes in a 5 minute period.
LAL 5 - Numerous thunderstorms. Rainfall is moderate to heavy. Lightning is frequent and intense, greater than 15 cloud to ground strikes in a 5 minute period.
LAL 6 - Dry lightning (same as LAL 3 but without rain). This type of lightning has the potential for extreme fire activity and is normally highlighted in fire weather forecasts with a Red Flag Warning.

Haines Index (HI) - Is a numerical value that indicates the potential for large wildfires to experience extreme fire behavior. The HI combines both the instability and dryness of the air by examining the lapse rate between two pressure levels in the atmosphere and the dryness of one of the pressure levels.
HI 2 or 3…..Very low
HI 4………..Low
HI 5………..Moderate
HI 6………..High

CWR – Chance of Wetting Rain. Measurable rain above 0.10 inches.

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