Weather Alert in Alaska
Winter Storm Watch issued March 20 at 4:03AM AKDT until March 21 at 7:00PM AKDT by NWS Juneau AK
AREAS AFFECTED: Glacier Bay; Eastern Chichagof Island; City and Borough of Sitka
DESCRIPTION: ...SNOW SHOWERS ON FRIDAY REPLACED BY ADVANCING SYSTEM SATURDAY... .Confidence is increasing on seeing a more significant round of snow this weekend as cold temperatures aloft remain in place and another round of moisture move in. There remains some uncertainty for snow accumulations at the surface as we are starting to see warmer day time temperatures into the mid to high 30s to around 40 due to increasing daylight and sun angle, however, temperatures aloft are still very favorable for accumulating snow amounts. If the heavier precipitation rates are significant enough to overcome the warmer surface temperatures, snow accumulations will be greater. But if the temperatures are able to overcome the precipitation rates, snowfall will be limited as it melts by the time it reaches the surface. This will need to be monitored for any changes in potential snow accumulation. The orientation of the low and where the showers move into the panhandle will also impact the snow amounts, with how northward and inland the heavier moisture will push and how organized the bands of snow are expected to be when moving through this weekend. * WHAT...For the Winter Weather Advisory, snow. Additional snow accumulations of 2 to 5 inches through Friday. For the Winter Storm Watch, heavy snow possible. Total snow accumulations of 4 to 9 inches possible. Winds could gust as high as 50 mph. Visibilities reduced to one mile or less. * WHERE...Gustavus, Sitka, Hoonah, and Tenakee Springs. * WHEN...For the Winter Weather Advisory, until 7 PM AKDT this evening. For the Winter Storm Watch, from late tonight through Saturday evening. * IMPACTS...Travel could be very difficult and is discouraged. The hazardous conditions could impact the evening commute. Gusty winds could bring down tree branches. * ADDITIONAL DETAILS...Snowfall accumulation will be variable, and rates may diminish during the daytime hours as warming surface level temperatures slow snow accumulation.
INSTRUCTION: Slow down and use caution while traveling. Monitor the latest forecasts for updates on this situation. People are urged to prepare their property before the onset of winter weather. For the latest road conditions, where available, call 5 1 1 or visit 511.alaska.gov.
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Weather Topic: What is Precipitation?
Home - Education - Precipitation - Precipitation
Next Topic: Rain
Precipitation can refer to many different forms of water that
may fall from clouds. Precipitation occurs after a cloud has become saturated to
the point where its water particles are more dense than the air below the cloud.
In most cases, precipitation will reach the ground, but it is not uncommon for
precipitation to evaporate before it reaches the earth's surface.
When precipitation evaporates before it contacts the ground it is called Virga.
Graupel, hail, sleet, rain, drizzle, and snow are forms of precipitation, but fog
and mist are not considered precipitation because the water vapor which
constitutes them isn't dense enough to fall to the ground.
Next Topic: Rain
Weather Topic: What are Shelf Clouds?
Home - Education - Cloud Types - Shelf Clouds
Next Topic: Sleet
A shelf cloud is similar to a wall cloud, but forms at the front
of a storm cloud, instead of at the rear, where wall clouds form.
A shelf cloud is caused by a series of events set into motion by the advancing
storm; first, cool air settles along the ground where precipitation has just fallen.
As the cool air is brought in, the warmer air is displaced, and rises above it,
because it is less dense. When the warmer air reaches the bottom of the storm cloud,
it begins to cool again, and the resulting condensation is a visible shelf cloud.
Next Topic: Sleet
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