We continue to see the elements in place for a lack of real threatening heat in the Corn Belt. As of Monday afternoon, the northern branch of the jet stream featured a trough over Alaska; blocking high pressure from western Canada through north-central Canada; and another trough over northeast Canada and Greenland. This is a warm to hot pattern for western Canada, while eastern Canada is mild and cool. The southern branch of the jet features a trough over the Gulf of Alaska; high pressure over the western U.S.; and a strong trough over south-central and southeast Canada extending southward into the central and eastern U.S. Subtropical high pressure is located over the southwest U.S. and southeast Florida.
The effect of this large-scale setup is comprehensive and widespread; and in fact, this pattern has been generally with us since back in February of 2013 (yes, it pre-dates the infamous Polar Vortex winter of 2013-14). We are experiencing the impact in the form of a very mild midseason.
And, things do not change much at all during the next ten days, which takes us to late July. During the six to ten-day period the northern branch of the jet stream will continue to feature a trough over Alaska, but will also feature more trough over western Canada as the blocking ridge gets displaced eastward into eastward Canada. This will be a mild and cool pattern for most of Canada as opposed to just the eastern portion to start out the week. The southern branch of the jet stream will feature a lower-amplitude flow with embedded disturbances across southern Canada and the northern U.S. To the south of this jet, a strong subtropical ridge (high pressure) will dominate the southwest U.S. with some weak trough to the east of this ridge over the southeast U.S. This will be an active rainfall pattern for the southern U.S during the next five days, less active over the Midwest and northern Plains due to the strength of the trough over the central and eastern U.S. forcing the main storm track well to the south. During the six to ten-day period, as the ridge strengthens in the southwest U.S., the main storm track will return to the Midwest and northern Plains.
This will be an unseasonably cool pattern for the central U.S. during the next 5 days due to the strength of the trough over the region. During the six to ten-day period, temperatures will become more variable as a boundary zone sets up between the cooler weather to the north and the warmer weather to the south with disturbances moving along this boundary zone causing temperatures to fluctuate.
But here is the kicker and the bottom line regarding crop weather--There is no indication at this time that building subtropical ridging in the southwest states will lead to a significant period of hot, dry weather in the Midwest.
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