Fire Weather Cloud Chart Fire Weather and Fire Behavior Impacts from Clouds High Clouds: Cloud bases typically 16,000 - 50,000 ft (5 - 15 km) Usually seen as indirect indicators of potential behavior Cirrus Streaks Cirrus Cirrus Cirrus Cirrostratus Cirrostratus Cirrostratus Cirrocumulus - Single or multiple bands - Dense, in patches, not - Anvil-shaped remains - In hooks or filaments, - Cirrus bands, transparent, - Cirrus bands, covering - Sun mostly visibile -- Alone or with some cirrus across sky indicating jet increasing, or with tufts of a thunderstorm increasing in density relatively near the horizon majority of the sky with - No significant impact on or cirrostratus stream aloft - No significant fire weather - Watch for gusty winds - Often indicates cold air aloft, - Typically indicates weather sun obscured fire weather or fire - Very high instability, usually - Possible instability or surface or fire behavior expected from nearby decaying watch for possible instability fronts are 2 to 3 days away - Typically indicates weather behavior little impact on surface winds increasing fire behavior thunderstorms leading to more active fire fronts are one day or less away conditions Middle Clouds: Cloud bases typically 6,500 - 23,000 ft (2 - 7 km) Can be direct and/or indirect indicators of potential behavior Altostratus / Nimbostratus Altocumulus Wave Clouds (ACSL) Altocumulus Altocumulus Altocumulus Altocumulus Castellanus (Top) Altocumulus - Usually dense enough to - Semi-transparent, one level - Formed by strong winds - One or more bands or layers, - From the spreading of - Generally opaque layers, Altocumulus Floccus (Bottom) - Chaotic sky, cloud bases hide the sun or moon - Indicates weak mid-level over uneven terrain, often expanding, thickening cumulus or cumulonimbus possibly containing virga - Flat base with turrets or at several levels - Often contains steady rain, instability and increasing repeating downwind - Indicates instability present, - Could indicate presence of - Weak instability, virga may cumulus-like tufts - Lower cloud base may block watch for slippery footing, moisture, possible monsoon - These strong winds may monitor for additional nearby thunderstorms, caution result in gusty winds, - When observed in morning view of higher based storms, expect minimal fire activity thunderstorm development surface and result in development for gusty winds generally from cloud density usually hours, often indicates afternoon/ hides potential for lightning within 24 hours running fire the direction of the clouds inhibits further convection evening thunderstorms and gusty winds Low Clouds: Cloud bases up to 6,500 ft (0 - 2 km) Usually have direct impact on potential fire weather and fire behavior Fair Weather Cumulus Cumulus Cumulonimbus (aka Cb) Stratocumulus Stratus Stratus Fractus / Stratocumulus & Cumulus Mature Thunderstorm - Flattened appearance - Moderate/strong vertical - Tops not fibrous, no anvil - Moderate instability - Smooth appearance, Cumulus Fractus - Usually associated with - Strong downdraft winds, - Weak instability present, development, or towering - Significant vertical motion - Showers and downdrafts continuous low layer - Occurs with rain or snow cool weather lightning, heavy rain, and hail but rarely results in further cumulus present, gusty downdrafts likely, thunderstorms - Often inhibits aircraft - Usually associated with cold - Fire activity may possible underneath development, active fire -- Atmosphere is unstable, likely, thunderstorms are possibly hidden, variable use, minimal fire activity front, winds may push fire increase with afternoon - Distant terrain channelled behavior still possible, monitor for futher possible, erratic fire activity fire behavior heating and instability winds and lightning possible especially under low humidity development and increased fire activity *Note: Clouds with a red box indicate clouds of critical concern PMS 438 Special Cases: for firefighters as outlined in S-290 and S-490. NFES 001976 These phenomena Sept. 2016 occur under significantly unstable conditions. Exercise extreme caution when they are observed, Pyrocumulus Tornado Fire Whirl Shelf Cloud Virga particularly when - Unstable conditions where - Rapidly rotating column - Localized, intense wind swirl - Represents the leading edge - Rain or snow that evaporates fire is between you smoke moisture condenses that touches the ground under unstable conditions with of strong winds in advance before reaching the ground to form cumulus under a thunderstorm possible speeds exceeding 50 mph of a thunderstorm - Sudden, gusty outflow winds This poster was produced by NOAA’s National Weather Service in conjunction and it. - Downdrafts, rain, lightning - Seek immediate shelter in - Can scatter fire, spot across - Can extend ahead and past may dramatically increase with Predictive Services (https://www.nifc.gov/, https://www.weather.gov/fire/). possible a sturdy building lines, and enter safe zones the main thunderstorm column fire behavior .