Mainly dry and warm weather is preferred for the key crop areas of the Canadian Prairies at this time. There are still crops remaining in the fields that need to be brought in and fieldwork in preparation for planting needs to be completed as well as early planting activities. The short- and medium-range outlooks, which take us through the May 13-14 weekend, are mostly favorable for these activities. In the longer range, attention will shift to rainfall chances and temperature forecasts for development of the crops; however, that discussion is for a later date.
The region has been generally dry during the first few days of May. Temperatures have mostly averaged above normal. Highs Wednesday were generally in the 16 to 22 C (62 to 71 F) range. This is above to much above normal. Normal high temperatures would be around 15 C (59 F) at this time of the year.
The region is expected to continue mostly dry through Friday. Saturday will be dry or with only a few light showers developing. Temperatures will again average above to well above normal during this period. High temperatures may reach 25 to 30 C (77-86 F) before moderating somewhat -- around 15 degrees Celsius (30 degrees Fahrenheit) above normal.
Scattered light showers with locally heavier and a few thundershowers are expected to develop Sunday and Monday. Rainfall forecasts at this time appear to be on the order of 2-9 mm (0.08-0.35 inch) and locally heavier. The heaviest of this activity is indicated over southern and eastern areas of the Prairies. Temperatures average above normal, dropping to near normal in Alberta, with above normal elsewhere in the region during this time frame.
The 6 to 10-day outlook for the region covering the period next Tuesday through Saturday, May 9 to 13, calls for temperatures to average mostly above normal in the west, and above to near normal in the east. Rainfall should average near to below normal during this period.
The upper-level pattern for the 8-10 day period features an upper level ridge with above normal heights (high pressure) over the Prairies. This is primarily the reason for the near to below-normal rainfall forecast for the 6-10 day period. This high tends to block systems from moving in off the Pacific Ocean and keeps them from moving northward from the U.S. also. There is a strong trough (low pressure) located just off the West Coast that needs to be watched. This trough could bring rains back into the area if the blocking ridge over the Prairies weakens with time. The Canadian Prairies ridge is held in place by a significant blocking pattern over eastern North America. This is indicated by a moderate-to-deep trough over southeast Canada and the northeastern U.S., and a moderate-to-strong ridge over northeast Canada. The U.S. model is somewhat weaker with this eastern blocking pattern, while the Canadian model shows a stronger block. The European model also features a stronger eastern blocking pattern.
The temperature forecast for the 6-10 day period is somewhat more uncertain. Normally, above-normal heights aloft lead to above-normal surface temperatures, but the strong eastern North America blocking pattern may change this somewhat. There are likely to be below normal temperatures in southeastern Canada and the northeastern U.S. under the upper-level trough. If this trough is stronger as depicted by the Canadian model, then the cooler weather will be more expansive and could back up into the eastern Prairies. I have only forecast down to near normal temperatures in Manitoba due to this factor, but it might come in colder under the right circumstances.
In either case, a period of more favorable weather for spring fieldwork in the Prairies is expected to last for at least the next 10 days, with the exception of the brief periods with light rainfall and the locally heavy showers possible for a time.
Joel Burgio can be reached at firstname.lastname@example.org
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