Key Facts

Weather Terminology | Technical Details

WEATHER TERMINOLOGY

Temperature — Outside air temperature displayed in degrees Fahrenheit (°F).

Wind Chill — Wind chill, displayed in degrees Fahrenheit (°F), takes into account how the speed of the wind effects our perception of the air temperature. The faster the wind blows, the faster heat is carried away from our bodies and the colder you feel. The wind chill is based on the ten-minute average wind speed.

Humidity — Humidity itself refers to the amount of water vapor in the air. Relative humidity takes into account the air temperature and pressure along with water vapor content. Displayed as a percentage indicating the ratio of the air's water vapor content to its capacity.

Dew Point — Dew point, displayed in degrees Fahrenheit (°F), is the temperature at which air must be cooled for saturation (100% relative humidity) to occur, providing there is no change in water content. The dew point is an important measurement used to predict the formation of dew, frost and fog.

Soil Temp — Temperature of the soil at approximately 4 inches deep displayed in degrees Fahrenheit (°F). NOTE: Soil temperature at any given location depends on several factors such as soil content, sunlight, etc. Therefore the actual temperature can vary accordingly.

Wind Speed — Wind speed displayed in miles per hour.

Wind Direction — Sector on the compass rose from which dominant wind is coming (e.g., north, southeast, etc.)

Heat Index — Heat index, displayed in degrees Fahrenheit (°F), uses the temperature and relative humidity to determine how hot the air actually "feels."

Solar Radiation — Solar radiation is a measure of the intensity of the sun's radiation reaching a horizontal surface, expressed in Watts / sq. m. See Solar-UV Radiation page for details.

UV Index — The UV Index is a forecast of the probable intensity of skin damaging ultraviolet radiation reaching the surface during the solar noon hour (11:30-12:30 local standard time or 12:30-13:30 local daylight time). The greater the UV Index is the greater the amount of skin damaging UV radiation. See Solar-UV Radiation page for details.

Barometric Pressure — The weight of the air that makes up our atmosphere exerts pressure on the surface of the earth. This is known as atmospheric pressure. The more air above an area, the higher atmospheric pressure. To compensate for changes in altitude, atmospheric pressure is adjusted to the equivalent sea-leve pressure. This adjusted pressure is known as barometric pressure.

Rainfall — Amount of rain measured in increments of 0.01 inch. Note: In the northwest, the "rainy" season begins October 1 and is measured through the following September 30.

Sunrise / Sunset — Refers to the times when the upper edge of the disk of the Sun is on the horizon, considered unobstructed relative to the location of interest. Atmospheric conditions are assumed to be average, and the location is in a level region on the Earth's surface. Sunrise and sunset times are calculated according to your latitude and longitude position on earth.

Mostly Sunny versus Partly Cloudy — Weather forecasters in the northwest including the National Weather Services (NWS) and local weather broadcasters use the following unofficial terms to describe sky conditions:

 

term	Percent (%) of sky obscured
Sunny	0 — 10
Mostly Sunny	20 — 30
Partly Cloudy	30 — 60
Mostly Cloudy	60 — 80
Cloudy	80 +

TECHNICAL

Weather Data Refreshed

• Every 15 minutes 5 AM to 9 PM Pacific Time.

Doppler Radar Image

• Refreshed at the AccuWeather.com site every 15 minutes.
• The doppler image is a display of echo intensity (reflectivity) measured in dBZ (decibels of Z, where Z represents the energy reflected back to the radar. "Reflectivity" is the amount of transmitted power returned to the radar receiver. Base Reflectivity images are obtained at several different elevation angles (tilts) of the radar antenna and are used to detect precipitation, evaluate storm structure, locate atmospheric boundaries and determine Hail potential. The base reflectivity image from AccuWeather is from the lowest tilt angle (0.5°). This means the antenna is tilted 0.5° above the horizon.

Weather Sensors Location

• Adjacent to fairway 8 at TPC Snoqualmie Ridge Golf Course
• Coordinates: Latitude 47.535605, Longitude -121.864095, Elevation 840 ft. (256 meters)

Weather Sensor Accuracy

Function	Resolution	Nominal Accuracy
Barometric Pressure	0.01 Hg, 0.1 hPa	0.03 Hg, 1.0 hPa
Outside Humidity	1%	3% RH; 4% above 90%
Dewpoint	1° F	3° F
Solar Radiation	1 W/m2	5% of full scale
Outside Temp	0.1° F	1° F
UV Index	0.1 index	5% of full scale
Wind Direction	1°	7°
Wind Speed	1 mph/1 kt	greater of 2 mph/kts or 5%
Wind Chill	1° F	2° F

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