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Winter Weather Watches
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Criteria / Definition
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Winter
Storm Watch
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Conditions
are favorable for hazardous winter weather conditions including heavy snow,
blizzard conditions, or significant accumulations of freezing rain or sleet
in the next 12 to 48 hours.
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Blizzard
Watch
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Conditions
are favorable for blizzard conditions in the next 12 to 48 hours.
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Wind
Chill Watch
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Conditions
are favorable for dangerous wind chills in the next 12 to 48 hours.
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Winter Weather Warnings
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Criteria / Definition
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Heavy
Snow Warning
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Below
6000 ft:
6 inches or more in 12 hours or 8 inches or more in 24 hours with no blowing
snow and sustained winds < 20 mph
Above 6000 ft: 8 inches or more in 12 hours, 12 inches or more in
24 hours with no blowing snow and sustained winds <20 mph
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Winter
Storm Warning
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Heavy
Snow Warning criteria for snow accumulation and sustained winds or frequent
gusts 25 to 34 mph with reduced visibility to ≤ ¼ mile for 3 hours or
more
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Blizzard
Warning
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Sustained
or frequent gusts of 35 mph or more, frequent visibilities of ≤ ¼ mile, falling and/or blowing snow
for 3 hours or more
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Wind
Chill Warning
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East of the Divide: Wind chills of
≤ -40 degrees with winds of ≥ 10 mph
West of the Divide: Wind chills of ≤ -20 degrees with
winds of ≥ 10 mph
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Winter Weather Advisories
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Criteria / Definition
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Snow
Advisory
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Below
6000 ft:
2 to 5 inches in 12 hours.
Above
6,000 ft:
Not issued.
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Blowing
Snow Advisory
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Wind
driven snow that occasionally reduces visibilities to ≤ ¼ mile.
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Snow
and Blowing
Snow
Advisory
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Snow
advisory and blowing snow advisory criteria together.
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Winter
Weather Advisory
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More
than one predominant hazard (i.e. Snow and Freezing Rain, Sleet and Freezing
Rain, etc) meeting or exceeding 12 and/or 24 hour advisory criteria for at least
one of the precipitation elements, but remaining below warning criteria.
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Wind
Chill Advisory
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East of the
Divide:
Wind chills of -20 degrees to -39 degrees with winds of ≥ 10 mph
West of the Divide: Wind chills of ≤ -10 degrees to -19
degrees with winds of ≥ 10 mph
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Freezing
Rain Advisory
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Glazing
of freezing drizzle or freezing rain with accumulations of less than ¼ inch.
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Wind and Fog Advisories
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Criteria / Definition
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Wind
Advisory
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Livingston Area / Beartooth Foothills - Sustained winds ≥ 40 mph for at
least 2 hours or any gust between 58 mph to 74 mph.
Western Montana - Sustained winds of 30 mph and or gusts of 40 to 57
mph.
Elsewhere in Montana - not issued.
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Dense
Fog Advisory
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Visibility
≤ ¼ mile for 3 hours more.
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Lake Wind Advisory
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Fort Peck
Lake – Winds sustained at
20 mph or higher for 3 hours or more, or any gusts to 30 to 57 mph.
Flathead Lake
- Winds sustained at 20 m ph and/or gusts to 30-57 mph.
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High Wind Watch / Warning
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Criteria / Definition
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High
Wind Watch
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Conditions
are favorable for high winds in and close to the watch area in the next 12 to
48 hours.
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High
Wind Warning
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Sustained
winds ≥ 40 mph for at least 2 hours or any gust ≥ 58 mph.
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