Prescriptions

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Prescriptions
Gary Jarvis Fire Planner National Forests in
Mississippi
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Key Points

• Demonstrate how to develop prescribed burn
  parameters
• 2.Demonstrate how to use the
• BEHAVE program when developing a
  prescription.

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5142.3 Pre-Ignition Briefing and Forecast
Requirements   1. Utilize the most current fire
weather forecasts and spot weather forecasts in
making pre-ignition decisions. Use the National
Weather Service (NWS) or other reputable source
(Forestry Commission or SRI meteorologists for
example) for fire weather and spot
forecasting.   2. Place 10-hour fuel moisture
sticks on or near prescribed burn units (or
cluster of prescribed burn units) to determine
fuel moisture. Each Forest should develop
fuel-stick moisture values that provide for the
accomplishment of specific resource objectives.
Refer to 5140 Exhibit 02, Standards for
Prescribed Fire Parameters for the regional
standards for fuel moisture.   3. A fire weather
forecast from the NWS or other reputable source
with 20-foot wind speeds predicted between 15-20
MPH is accepted as compliant with the Regional
maximum standard of 18 MPH. Gusts are to be
considered as part of the forecast. Predicted
20-foot wind gusts over 20 MPH are out of
prescription with regard to wind.   4. Fire
weather forecast items should include maximum
temperature, minimum relative humidity, maximum
20 foot wind speed-direction (a.m./p.m.),
transport wind speed-direction, mixing height,
smoke dispersion index, ventilation rate or
category day, sky condition, probability of
precipitation-duration-amount, frontal passages,
and severe weather outlook. Provide feedback to
the fire weather forecaster for their fire
weather forecasts. Attach forecasts to RxBP.

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NF in MississippiSupplement 5140-93-27

• Parameters - Dormant Season Understory
• Temperature
• RH 30-60
• 20ft wind speed 5-15mph
• 10 hr fuel moisture 7-15
• KDBI
• Ignition probability
• NFDRS Class day A-C

Caution SO Approval 72 25-29 16-18mph 301-350
D
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Behave Runs Flame Lengths 7 ft ROS 8 Heat Per
Unit Area 2694 Fireline Intensity 386
90
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S
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S
2000
50
60
69
300
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It is the day of your prescribed burn, what
weather information will you need?
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The End
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Mixing Height
Wind
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Transport Winds

• Average horizontal wind speed and direction
  between the surface and the mixing height

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Mixing Height

• The height below which relatively vigorous mixing
  in the atmosphere is taking place

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