Ashfall may originate directly from a volcanic eruption or from the re-suspension (by wind) of a significant amount of relic ash.Ī Winter Storm Watch is issued when there is the potential for significant and hazardous winter weather within 12 to 48 hours. Widespread or localized blowing dust reducing visibilities to 1/4 mile or less.Īirborne ash plume resulting in ongoing deposition at the surface. Long duration event of widespread or localized blowing dust reducing visibilities to one mile or less, but greater than 1/4 mile.Ī sudden drop in visibility to 1/4 mile or less resulting in widespread or localized blowing dust.Ī long duration event of widespread or localized blowing dust reducing visibilities to 1/4 mile or less. It is only meant to convey the official information from the state and local air quality agencies.ġ) Air quality conditions reach or are expected to reach "unhealthy" or worse (AQI 151 to 200 or above)Ī sudden drop in visibility to one mile or less, but greater than 1/4 mile, resulting in widespread or localized blowing dust. Used to relay non-routine air quality alert messages issued by state and local agencies. Issued for atmospheric conditions stable enough to cause air pollutants to accumulate in a given area.ġ) Morning and afternoon mixing height of 1,500 ft AGL or lessĢ) Morning and afternoon transport winds of 10 kts or lessģ) Conditions to continue for at least 72 hoursĤ) Conditions are underway or are expected to start within 24 hours For example, this product may be used to inform users of radar equipment outages or special information clarifying interpretation of radar data originating from an unusual source which may be mistaken for precipitation (such as chaff drops, smoke plumes, etc., that produces echoes on the radar display.Ī product issued by local NWS offices to inform users of reports of severe and/or significant weather-related eventsĪ product used to convey information regarding weather or hydrologic events in the next few hours. Snowfall/rain totals, observed wind speeds, etc)Ģ) A current or expected nonhazardous event of general interest to the public that can usually be covered with a single message (e.g., unusual atmospheric phenomena such as sun dogs, halos, aurora borealis, lenticular clouds, and stories about a long-term dry/cold/wet/warm spell).ģ) Public educational information and activities, such as storm safety rules, awareness activities, storm drills, etc.Ĥ) Information regarding service changes, service limitations, interruptions due to reduced or lost power or equipment outages, or special information clarifying interpretation of NWS data. Each segment of the HWO will contain 3 sections: short term through Day 1, long term for Days 2-7, and spotter information.Ī narrative statement issued by a NWS Spokane that can be used for:ġ) Disseminating observations and accumulation reports during and after a weather event. The outlook contains two segments: One segment for the marine zones and adjacent land-based (i.e., coastal) zones and the other segment for the rest of the land-based zones. The Hazardous Weather Outlook will describe potential hazardous weather and hydrologic information of concern in Days 1 through 7. Definitions of Weather Watches, Warnings and Advisories
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