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:
Wed22/Day1  Thu23/Day2  Fri24/Day3  Sat25/Day4  Sun26/Day5  Mon27/Day6  Tue28/Day7  
Wed29/Day8  Thu30/Day9  Fri31/Day10  

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.


Current GDPS 10 day forecast   legend ▾
500 millibar geopotential height:
cold/blue to warm/red

colour legend for 500 millibar chart

Instantaneous precipitation:
  0.5 - 1.0 mm/hr: light blue
  1.0 - 5.0 mm/hr: dark blue
5.0 - 10.0 mm/hr: green
      >10.0 mm/hr: yellow

Total cloud cover in percent of the sky:
(Click on 'tot-cloud' below)
  0 - 20%:   clear
 20 - 40%:  very light grey
 40 - 60%:  light grey
 60 - 80%:  grey
 80-100%:  dark grey

first stop last slower faster   total-cloud
basemap for Canada GDPS 500 millibar geopotential height 006 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 006 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 006 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 012 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 012 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 012 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 018 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 018 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 018 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 024 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 024 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 024 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 030 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 030 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 030 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 036 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 036 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 036 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 042 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 042 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 042 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 048 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 048 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 048 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 054 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 054 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 054 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 060 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 060 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 060 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 066 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 066 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 066 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 072 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 072 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 072 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 078 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 078 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 078 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 084 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 084 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 084 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS 500 millibar geopotential height 090 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 090 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 090 hour forecast chart for Canada based on 2026/07/22 1200Z data
GDPS 500 millibar geopotential height 006 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 006 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 006 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +006HR
VALID: 2026/07/22 18:00 UTC
GDPS 500 millibar geopotential height 012 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 012 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 012 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +012HR
VALID: 2026/07/23 00:00 UTC
GDPS 500 millibar geopotential height 018 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 018 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 018 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +018HR
VALID: 2026/07/23 06:00 UTC
GDPS 500 millibar geopotential height 024 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 024 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 024 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +024HR
VALID: 2026/07/23 12:00 UTC
GDPS 500 millibar geopotential height 030 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 030 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 030 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +030HR
VALID: 2026/07/23 18:00 UTC
GDPS 500 millibar geopotential height 036 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 036 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 036 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +036HR
VALID: 2026/07/24 00:00 UTC
GDPS 500 millibar geopotential height 042 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 042 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 042 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +042HR
VALID: 2026/07/24 06:00 UTC
GDPS 500 millibar geopotential height 048 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 048 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 048 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +048HR
VALID: 2026/07/24 12:00 UTC
GDPS 500 millibar geopotential height 054 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 054 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 054 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +054HR
VALID: 2026/07/24 18:00 UTC
GDPS 500 millibar geopotential height 060 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 060 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 060 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +060HR
VALID: 2026/07/25 00:00 UTC
GDPS 500 millibar geopotential height 066 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 066 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 066 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +066HR
VALID: 2026/07/25 06:00 UTC
GDPS 500 millibar geopotential height 072 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 072 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 072 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +072HR
VALID: 2026/07/25 12:00 UTC
GDPS 500 millibar geopotential height 078 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 078 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 078 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +078HR
VALID: 2026/07/25 18:00 UTC
GDPS 500 millibar geopotential height 084 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 084 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 084 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +084HR
VALID: 2026/07/26 00:00 UTC
GDPS 500 millibar geopotential height 090 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS total cloud 090 hour forecast chart for Canada based on 2026/07/22 1200Z data GDPS precipitation 090 hour forecast chart for Canada based on 2026/07/22 1200Z data basemap for Canada
ISSUED: 20260722-1200 +090HR
VALID: 2026/07/26 06:00 UTC
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