Snow Module s00

Weather forecast maps

We have described how to read, interpret, and forecast temperatures from weather maps. Admittedly, this is only one of the important weather variables. We've also taught you how to read wind barbs, but haven't yet explained how to interpret them to real-world winds in the mountains. We'll cover moisture/clouds/precipitation in subsequent sections of the course. For this case, we'll tell you what the forecasted winds and moisture/clouds/precipitation will be.

It is currently early Sunday morning, and the weather model forecast provided below starts on Saturday evening. This is the model data that would realistically be available to you at the time of making your decision. The model forecast goes out seven days into the future, to the following Saturday evening (i.e. the forecast horizon is seven days).

70.0-kPa weather maps

Clicking the links or button below will take you to an animated loop of 70.0-kPa pressure-level maps at regular 3-hourly intervals within the forecast horizon. Temperature at 70.0 kPa is contoured with black lines, where dashed black lines represent below-freezing values. Winds are displayed with wind barbs (which we'll help you with in this case). In these maps, the top row contains:

[Weather model name] | [Date/Time in Pacific Time] | [Date/Time in Universal Coordinated Time]

The latter time zone is used frequently in meteorology — it is a standard, universal time zone so that scientists around the world can reference times without having to convert. The row beneath the map tells you what weather fields are plotted.

Tip: If you click in the slider bar at the top of the controls, you can step back and forth with the keyboard arrow buttons.

70.0 kPa weather maps

The Link above, and button below, point to the same URL, in case one or the other doesn't work for you. 

If neither of these options work for you (to view the 70.0kPa weather maps) try the link below. This will bring up a PDF file showing all the weather forecast maps in sequential order. 

70.0 kPa weather maps

Interpretation Tips

• There is a cold front (you'll learn more about these in the next module) moving onto the BC Coast around midday on Sunday. This front weakens quite a bit as it moves inland across BC Sunday and Monday.
• The wind barbs indicate light to moderate winds from the northwest on Monday. After that, winds look generally light throughout the week. Look at the wind barbs yourself, and using what you've learned, see if you can follow this interpretation.
• It will help you to make a temperature forecast for the week, considering the elevation(s) of the traverse, using your new skills from the learning goals.
  

Sea Level Pressure / Clouds / Precipitation maps

You've learned about pressure and sea level pressure. Sea level pressure is plotted in contours in the animated maps accessed below ("Sea Level Pressure/Clouds/Precipitation weather forecast maps"). The trickiest part of interpretation might be that not all of the contours are labeled. However, you should still be able to figure out if there is high or low pressure over BC during this forecast period.

Clouds are in grey shading, with darker greys representing thicker, darker clouds. Note: the plot does not tell you what elevation the clouds are at. They indicate that there will be some cloud over the Wapta area for Monday with the front. After that, there are occasional clouds, but other data (not shown) indicates that the clouds will be few. Assume that after scattered clouds on Monday, clouds for the remainder of the week will be above the elevation of the traverse.

Precipitation is shaded in blue and green colours. We haven't covered precipitation type (i.e., rain vs. snow) yet, so for this case assume all precipitation is falling as snow in the mountains. As a brief overview of precipitation, the lightest shade of blue (0.25-0.5 mm in 3 hours) would be very light precipitation (snow flurries), the next shade of blue (0.5-1.0 mm in 3 hours) is light snow, dark blue and green shading (1-4 mm in 3 hours) is moderate-heavy snowfall, and above that is very heavy snowfall.

Lastly, this is liquid equivalent precipitation — this is how much liquid would result if you melted the snow that fell. To convert this to snowfall amounts, the simplest rule is to multiply by 10, e.g., 1 mm of liquid equivalent precipitation would be 1 cm of snow. Note: this rule does not always apply, but it's good enough for this exercise.

The header and footer on the plots indicate the same as in the 70.0-kPa plots, explained above.

Sea Level Pressure/Clouds/Precipitation weather forecast maps.

The Link above, and button below, point to the same URL, in case one or the other doesn't work for you.

If neither of these options work for you (to view the Sea Level Pressure weather maps) try the link below. This will bring up a PDF file showing all the weather forecast maps in sequential order. 

Sfc weather maps

Interpretation tips

• Think about what type of weather you might expect with this pressure pattern.
• Remember to consider the elevation(s) you'll be skiing at.
• If you find it hard to identify the pressure pattern from the isobar contours, then the other variables should actually help you to do this!