Make and check your own Lethbridge forecast
This is where it all comes together. Follow a forecaster’s routine, write tomorrow’s forecast for Lethbridge, then check it against a real weather station and keep score.
In this lesson
- A seven-step forecasting routine
- Local rules of thumb for southern Alberta
- Writing your forecast like a professional
- Scoring yourself, and learning from your misses
The seven-step routine
- What happened? Look at the last 24 hours at our station: highs, lows, wind, precipitation, and the pressure trend.
- The surface map now. Find the nearest highs, lows and fronts (Lesson F3). Use Environment Canada’s surface analysis.
- The upper air. Where are the ridges and troughs at 500 hPa, and which way is the flow over the Rockies (Lesson F4)?
- The models. What do they show for tomorrow? Do they agree? Are they doing well right now (Lesson F5)?
- Local effects. Run through the rules of thumb below.
- Write it down. High, low, wind, sky and chance of precipitation, before you look at anyone else’s forecast.
- Check it tomorrow. Score it honestly and write down why you missed.
Local rules of thumb
- Strong west or southwest winds forecast over the Rockies at the 700 and 500 hPa levels.
- A ridge over British Columbia.
- Pressure falling east of the mountains (a lee trough).
- A chinook arch and lenticular clouds to the west.
- Rising temperatures in Pincher Creek and the Crowsnest Pass before Lethbridge.
- Arctic air: when a cold front comes from the north, it often arrives faster and colder than the models show. Watch for north or northeast winds and rising pressure at stations to the north.
- Upslope snow: easterly or northeasterly winds with moist air and a high to the north can bring steady snow, even when there’s no big storm on the map.
- Clear, calm nights: with snow on the ground, light wind and clear sky, temperatures can drop far below the models’ forecast, especially in the river valley and coulees.
- Summer thunderstorms: they usually form over the foothills in the afternoon and drift east, reaching Lethbridge in the evening.
- Wind: tightly packed isobars and strong winds just above the ground mean gusty days. Lethbridge is one of Canada’s windiest cities.
Write it like a pro
Use Environment Canada’s style (Lesson F1). For example:
Tomorrow: Mainly cloudy. 40 per cent chance of flurries in the morning. Wind northeast 20 km/h. High minus 6.
Tomorrow night: Clearing. Wind becoming light. Low minus 18.
Your forecast card for each day:
| Element | My forecast | What happened | Points |
|---|---|---|---|
| High (°C) | |||
| Low (°C) | |||
| Strongest gust (km/h) | |||
| Precipitation? (yes/no) |
Print this page to use the card.
Score yourself
A simple, honest scoring system:
- High and low: 2 points each if you’re within 2°C (3.6°F), 1 point if within 4°C (7.2°F), 0 otherwise.
- Gust: 2 points within 10 km/h, 1 point within 20 km/h.
- Precipitation: 2 points if you got yes or no right (at least 0.2 mm counts as yes).
That’s 8 points a day. Score persistence (“same as today”) the same way, and see if you beat it. Then compare with the professionals: Environment Canada’s forecast and our own WXSIM forecast on the Forecast Scorecard.
Try it yourself: the one-week challenge
Every evening for a week, follow the seven steps and write tomorrow’s forecast card. The next evening, check it against the station:
Our West Lethbridge station now (6:28 pm): 9°C, wind calm, humidity 63%. Live station ›
At the end of the week, add up your points. Did you beat persistence? Which element was hardest? Most beginners find the overnight low hardest in winter.
🏫 For teachers and parents
- Time: one class to learn the routine, then 15 to 20 minutes a day for a week.
- Class forecasting contest: teams forecast each day; the class keeps a leaderboard on the wall, with persistence as an extra “team” to beat.
- Science skills: making predictions from evidence, recording data, comparing results, and explaining errors.
- Math link: averages, absolute error, and graphing forecast versus actual temperatures.
- Assessment: each student hands in their week of forecast cards with a short paragraph on their biggest miss and what they learned from it.
- More ideas in the Teachers’ Corner.
Key terms
- Verification
- Checking a forecast against what actually happened.
- Skill
- How much better a forecast is than a simple baseline like persistence.
- Radiational cooling
- Heat escaping to space on clear, calm nights, making it very cold near the ground.
Check your understanding
1. What should you do before looking at anyone else’s forecast?
Write yours first, or you’ll be tempted to copy, and you won’t learn as much.
2. Which is a sign a chinook may be coming?
Strong westerlies aloft crossing the mountains, with a ridge to the west, are the classic chinook setup.
3. A clear, calm winter night with fresh snow: what’s likely?
Heat radiates away to space, and cold air pools in valleys and coulees.
4. Why write down why you missed a forecast?
Learning from misses is how every forecaster improves.
Sources: Environment and Climate Change Canada forecast guide and surface analyses; local rules of thumb from southern Alberta forecasting practice and our station’s records. Scoring system adapted for learning; it is not an official verification method.
Weather School is for learning and enjoyment. It is not official guidance and may contain errors. For watches and warnings, always use Environment Canada (WeatherCAN app or weather.gc.ca).