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National Weather Service
Missoula Montana
| FORECASTS |
The National Weather Service forecasts utilize a standard terminology to describe the expected
weather conditions. This page explains the terminology used. Missoula's forecast area encompasses central Idaho and western Montana. This area is broken down in segments (zones) based on either terrain or climatic regimes. The map to the right shows the zones in Missoula's forecast area and their associated names are listed below.
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Western Montana Zones
1 Kootenai / Cabinet Region
2 West Glacier Region
3 Flathead / Mission Valleys
4 Lower Clark Fork Region
5 Missoula / Bitterroot Valleys
6 Bitterroot / Sapphire Mountains
7 Butte / Blackfoot Region
43 Potomac / Seeley Lake Region
Central Idaho Zones
5 Northern Clearwater Mountains
6 Southern Clearwater Mountains
7 Orofino / Grangeville Region
8 Lower Hells Canyon / Salmon River Region
9 Western Lemhi County
10 Eastern Lemhi County
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| PRECIPITATION |
Uncertainty Terms
Indicate the percent chance of measureable (0.01 inches) precipitation occurring anywhere in the forecast zone or area. |
| Term |
Probability |
| Slight Chance |
10-20% |
| Chance |
30-50% |
| Likely |
60-70% |
| No term used |
80-100% |
Descriptive Terminology
Give further detail to the timing and type of precipitation forecasted.
Duration Terms include: Occasional, Periods, Frequent, Brief, etc.
Intensity Terms include: Very Light, Light, Heavy (Lack of an intensity term is moderate intensity)
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Areal Qualifiers
Indicate precipitation will occur in the forecast zone or area, but will only cover a certain percentage of the zone or area. |
| Term |
Coverage |
| Isolated |
10-20% |
| Scattered |
30-50% |
| Likely |
60-70% |
| No term used |
80-100% |
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Combining Terminology
Intensity terms can be combined with duration terms, uncertainty terms or areal qualifiers. Some common combinations - scattered light showers, periods of heavy rain, chance of heavy snow
Duration terms can NOT be combined with uncertainty terms or areal qualifiers. Uncertainty terms and areal qualifiers can NOT be combined with each other. A few INCORRECT combinations - chance of scattered showers, chance of occasional rain, periods of scattered showers.
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| SKY CONDITIONS |
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| Term |
Cloud Cover |
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Weather observations and aviation forecasts use areal terms, such as clear, few, scattered, broken or overcast.
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| Cloudy |
8/8 |
| Mostly Cloudy |
6/8 - 7/8 |
Partly Cloudy or
Partly Sunny |
3/8 - 5/8 |
Mostly Clear or
Mostly Sunny |
1/8 to 2/8 |
| Clear or Sunny |
less than 1/8 |
| TEMPERATURE |
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Specific
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Given for larger towns and listed below narrative forecast.
Specific forecasted highs and lows at NWS observation sites.
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Ranges
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Listed within the narrative forecast, either a number or descriptive range (see table below), expected high or low within a zone(s).
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Change
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Descriptive terms are used when the temperature change from one day to another is within certain limits (see table below).
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| Range |
Defined |
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Change |
Description |
| lower 50s |
50, 51, 52, 53, 54 |
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0 to 7 F |
no mention |
| mid 50s |
53, 54, 55, 56, 57 |
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7 to 20 F |
warmer, colder, cooler |
| upper 50s |
56, 57, 58, 59 |
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20 F or greater |
much warmer, colder |
| 60s |
60 through 69 |
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below zero |
very cold |
| WIND |
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Speed
Numeric (first two forecast periods) or descriptive (third forecast period and beyond).
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| Numeric |
Descriptive |
| 15 to 25 mph |
Breezy (mild), Brisk (cold) |
| 20 to 30 mph |
Windy |
| 30 to 40 mph |
Very Windy |
Direction
An eight point compass (N, NE, E, SE, S, SW, W, NW) is used.
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Utilization
Winds are only mentioned in the zone forecasts, when expected to be least 15 mph. Local mountain and valley breezes are not mentioned.
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