Long range forecasts: 3 to 10 days into the future

The trick to using long range forecasts is to know when there is or isn't skill ▾ in the forecast for your location.

The latest 10 day MSC GDPS model forecast is shown below in 6 hour steps. Cold air is blue/purple, warm air is yellow/orange. The blue sprinkles indicate precipitation. Storms grow where warm and cold air approach each other to form a stronger jet stream (where the coloured bands are tightly packed) and particularly in southwest flow.

Here are six forecasts for the same time today but made 7 to 10 days ago - chaos?
These were made in the last 3 days - order!

These forecasts for today were produced every 12 hours over the last 10 days. If the forecasts were perfect they would all be identical - All 20 forecasts

Here are the latest forecasts valid near midday for Canada on each of the next 9 or 10 days:
Fri04/Day1  Sat05/Day2  Sun06/Day3  Mon07/Day4  Tue08/Day5  Wed09/Day6  Thu10/Day7  
Fri11/Day8  Sat12/Day9  

Location is important. If you are located away from the jet stream then you will likely have a better forecast for further into the future.

The above illustrates the problem and for day-to-day use we also have map charts of precipitation averaged over many slightly different models (an "ensemble") on the EC/MSC website.


All frames are valid for the same time: 2025/04/05 18:00 UTC.
"ISSUED": the forecast issue time followed by the valid time (eg. "+120HR" indicates a 120 hour/5 day forecast).
Reset the animation to Current GDPS 10 day forecast.
first stop last slower faster   total-cloud
basemap for Canada GDPS 500 millibar geopotential height 102 hour forecast chart for Canada based on 2025/04/01 1200Z data GDPS total cloud 102 hour forecast chart for Canada based on 2025/04/01 1200Z data GDPS precipitation 102 hour forecast chart for Canada based on 2025/04/01 1200Z data GDPS 500 millibar geopotential height 090 hour forecast chart for Canada based on 2025/04/02 0000Z data GDPS total cloud 090 hour forecast chart for Canada based on 2025/04/02 0000Z data GDPS precipitation 090 hour forecast chart for Canada based on 2025/04/02 0000Z data GDPS 500 millibar geopotential height 078 hour forecast chart for Canada based on 2025/04/02 1200Z data GDPS total cloud 078 hour forecast chart for Canada based on 2025/04/02 1200Z data GDPS precipitation 078 hour forecast chart for Canada based on 2025/04/02 1200Z data GDPS 500 millibar geopotential height 066 hour forecast chart for Canada based on 2025/04/03 0000Z data GDPS total cloud 066 hour forecast chart for Canada based on 2025/04/03 0000Z data GDPS precipitation 066 hour forecast chart for Canada based on 2025/04/03 0000Z data GDPS 500 millibar geopotential height 054 hour forecast chart for Canada based on 2025/04/03 1200Z data GDPS total cloud 054 hour forecast chart for Canada based on 2025/04/03 1200Z data GDPS precipitation 054 hour forecast chart for Canada based on 2025/04/03 1200Z data GDPS 500 millibar geopotential height 042 hour forecast chart for Canada based on 2025/04/04 0000Z data GDPS total cloud 042 hour forecast chart for Canada based on 2025/04/04 0000Z data GDPS precipitation 042 hour forecast chart for Canada based on 2025/04/04 0000Z data
GDPS 500 millibar geopotential height 102 hour forecast chart for Canada based on 2025/04/01 1200Z data GDPS total cloud 102 hour forecast chart for Canada based on 2025/04/01 1200Z data GDPS precipitation 102 hour forecast chart for Canada based on 2025/04/01 1200Z data basemap for Canada
ISSUED: 20250401-1200 +102HR
VALID: 2025/04/05 18:00 UTC
GDPS 500 millibar geopotential height 090 hour forecast chart for Canada based on 2025/04/02 0000Z data GDPS total cloud 090 hour forecast chart for Canada based on 2025/04/02 0000Z data GDPS precipitation 090 hour forecast chart for Canada based on 2025/04/02 0000Z data basemap for Canada
ISSUED: 20250402-0000 +090HR
VALID: 2025/04/05 18:00 UTC
GDPS 500 millibar geopotential height 078 hour forecast chart for Canada based on 2025/04/02 1200Z data GDPS total cloud 078 hour forecast chart for Canada based on 2025/04/02 1200Z data GDPS precipitation 078 hour forecast chart for Canada based on 2025/04/02 1200Z data basemap for Canada
ISSUED: 20250402-1200 +078HR
VALID: 2025/04/05 18:00 UTC
GDPS 500 millibar geopotential height 066 hour forecast chart for Canada based on 2025/04/03 0000Z data GDPS total cloud 066 hour forecast chart for Canada based on 2025/04/03 0000Z data GDPS precipitation 066 hour forecast chart for Canada based on 2025/04/03 0000Z data basemap for Canada
ISSUED: 20250403-0000 +066HR
VALID: 2025/04/05 18:00 UTC
GDPS 500 millibar geopotential height 054 hour forecast chart for Canada based on 2025/04/03 1200Z data GDPS total cloud 054 hour forecast chart for Canada based on 2025/04/03 1200Z data GDPS precipitation 054 hour forecast chart for Canada based on 2025/04/03 1200Z data basemap for Canada
ISSUED: 20250403-1200 +054HR
VALID: 2025/04/05 18:00 UTC
GDPS 500 millibar geopotential height 042 hour forecast chart for Canada based on 2025/04/04 0000Z data GDPS total cloud 042 hour forecast chart for Canada based on 2025/04/04 0000Z data GDPS precipitation 042 hour forecast chart for Canada based on 2025/04/04 0000Z data basemap for Canada
ISSUED: 20250404-0000 +042HR
VALID: 2025/04/05 18:00 UTC
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