I am a powder lover; I bet you are, too. But how do you know when the powder is coming? By using weather forecasting maps. Whether you are going on a backcountry trip looking for some sun or just looking for a powder dump, knowing how to read weather charts can help you find where the snow is going to fall.
Of the many concepts in the science of meteorology, most are not crucial for snow forecasting. We are mainly interested in air temperature and pressure, snow level, snow accumulation, and precipitation. First, let’s talk about temperature and pressure.
A key concept is the snow level, which is the minimum elevation at which snow falls. You may find maps for the freezing level, which is the elevation where positive temperatures meet negative ones. The snow level is below the freezing level because snow doesn't melt as soon as it goes into positive temperatures; it falls for a few hundred meters until it melts.
Let's look at this surface air temperature map (“2 meter” in this context means “surface”). The temperature scale on the right-hand side lists temperatures in Fahrenheit; they are shown as both numbers and colors. In this map, blue coloring inside the red lines means below freezing temperature (32°F). Therefore, all areas colored in blue can receive snow if there is enough moisture.
There are many other types of temperature charts, such as the 850hPa and 700hPa charts, which show the temperatures at approximately 5,000 and 10,000 ft, respectively.
You may be wondering what hPa is. It is the measurement of air pressure, which is another important part of weather forecasting. Millibars (mb) and hectopascals (hPa) are used interchangeably as the units for air pressure. The mean pressure on Earth's surface is 1013 hPa: any area of surface pressure above that is called a high, and any area of surface pressure below it is called a low. In North America, lows are the driving force behind most snow events.
Above is a 500hPa heights and MSLP map. 500hPa heights are on the scale on the right. The dam (or decameters, where 1 dam = 10 m) in this situation is the measurement between 500 and 1,000 mb. You don't really need to understand the full science behind it, but the lower the 500hPa height, the colder it will be. For example, a dam of 582 (orange) is going to be much warmer than a dam of 540 (light blue). A dam of 540 or below can lead to low-level snow (> 1,000 ft). Dams below 564 are generally needed to get snow below 12,000 ft or so.
The other concept in there is MSLP, or mean sea level pressure. The L’s and H’s signify lows and highs, respectively, with their MSLP numbers. The lower the pressure, the deeper the low becomes. A deep low is generally associated with cold air. The lines around the lows and highs signify the direction of the wind, with winds around lows being counterclockwise and winds around highs clockwise.
Thank you for reading this explanation into temperature and pressure weather charts. I hope you learned something. Next, I will explain precipitation and moisture maps. Until then, enjoy the remaining snow!
[All weather forecast charts are created by Levi Cowan, a PhD graduate student at Florida State University. Link here: http://www.tropicaltidbits.com/analysis/models/]
I also need to acknowledge the assistance of @SBrown for editing this article, and @Tricia and @Philpug for helping me to make this happen. Thanks all.
Of the many concepts in the science of meteorology, most are not crucial for snow forecasting. We are mainly interested in air temperature and pressure, snow level, snow accumulation, and precipitation. First, let’s talk about temperature and pressure.
A key concept is the snow level, which is the minimum elevation at which snow falls. You may find maps for the freezing level, which is the elevation where positive temperatures meet negative ones. The snow level is below the freezing level because snow doesn't melt as soon as it goes into positive temperatures; it falls for a few hundred meters until it melts.
Let's look at this surface air temperature map (“2 meter” in this context means “surface”). The temperature scale on the right-hand side lists temperatures in Fahrenheit; they are shown as both numbers and colors. In this map, blue coloring inside the red lines means below freezing temperature (32°F). Therefore, all areas colored in blue can receive snow if there is enough moisture.
There are many other types of temperature charts, such as the 850hPa and 700hPa charts, which show the temperatures at approximately 5,000 and 10,000 ft, respectively.
You may be wondering what hPa is. It is the measurement of air pressure, which is another important part of weather forecasting. Millibars (mb) and hectopascals (hPa) are used interchangeably as the units for air pressure. The mean pressure on Earth's surface is 1013 hPa: any area of surface pressure above that is called a high, and any area of surface pressure below it is called a low. In North America, lows are the driving force behind most snow events.
Above is a 500hPa heights and MSLP map. 500hPa heights are on the scale on the right. The dam (or decameters, where 1 dam = 10 m) in this situation is the measurement between 500 and 1,000 mb. You don't really need to understand the full science behind it, but the lower the 500hPa height, the colder it will be. For example, a dam of 582 (orange) is going to be much warmer than a dam of 540 (light blue). A dam of 540 or below can lead to low-level snow (> 1,000 ft). Dams below 564 are generally needed to get snow below 12,000 ft or so.
The other concept in there is MSLP, or mean sea level pressure. The L’s and H’s signify lows and highs, respectively, with their MSLP numbers. The lower the pressure, the deeper the low becomes. A deep low is generally associated with cold air. The lines around the lows and highs signify the direction of the wind, with winds around lows being counterclockwise and winds around highs clockwise.
Thank you for reading this explanation into temperature and pressure weather charts. I hope you learned something. Next, I will explain precipitation and moisture maps. Until then, enjoy the remaining snow!
[All weather forecast charts are created by Levi Cowan, a PhD graduate student at Florida State University. Link here: http://www.tropicaltidbits.com/analysis/models/]
I also need to acknowledge the assistance of @SBrown for editing this article, and @Tricia and @Philpug for helping me to make this happen. Thanks all.
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