U.S. Monsoon Flow To Improve North Plains, Canada Rain
By Drew Lerner
Kansas City, June 8 (World Weather Inc.) – As scary as the next few weeks may become in the central United States because of early season heat and dryness there is still hope for change later this summer as the southwestern U.S. monsoon season gets under way. The monsoon should pump 
moisture from Mexico into the western U.S., but instead of spreading it east across Nebraska and Kansas into the Corn Belt (as it does in many years) it will go further north first. That implies greater rain will fall in the far northern U.S. Plains and Canada’s Prairies during July and August while less rain impacts a part of the central Plains. Some of the rain from those higher latitudes may move over the top of a central U.S. high pressure ridge to bring a little rainfall and some infrequent bouts of cooling across the far northern and eastern Midwest. The monsoon flow will have considerable influence on the debate over whether the northern Plains and southern Canada’s Prairies will experience significant dryness or not and over how significant rainfall will or won’t be in key Midwestern locations.
World Weather, Inc. still believes the greatest heat and dryness problem will be in the west-central and southwestern Corn Belt and central and southern Great Plains for the summer growing season with the Delta and a few neighboring areas also included. Other areas in the eastern United States will experience periods of stressful weather and periods of timely rainfall. As a result of this pattern, some lost production is expected in the western Corn Belt, Delta and parts of the southeastern states while better weather in other crop areas will help to counter-balance “some of the production losses resulting from the hot and dry areas.
Some forecasters have suggested parts of Canada’s Prairies and the northern U.S. Plains will be included in the hot, dry, scenario. However, World Weather, Inc. believes the monsoon flow in the southwestern United States is likely to help prevent dryness from impacting those northern latitudes where spring wheat, canola, chickpeas, lentils barley, oats, sunseed, sugarbeets and other crops are produced.
The next few weeks may be most stressful for crops in the northern Plains because a ridge of high pressure that will evolve periodically will restrict northbound moisture from the Gulf of Mexico limiting atmospheric moisture. Low moisture in the air will restrict rainfall when storm systems move through the region and the presence of the high pressure ridge will further weaken weather events as they attempt to move through the northern Plains and Canada.
The ridge axis expected this summer will run from Texas to North Dakota. The feature will be most significant in the southern half of the Plains with the top of the ridge in the northern Plains and Canada somewhat weak. The weakness of the ridge in the north will help to induce some rain and thunderstorms periodically, but the limited moisture source in the next few weeks will result in locally intense thunderstorms not necessarily a general soaking of rain. The stronger thunderstorms will be intense enough to produce some hail, damaging wind and tornadoes, but greater moisture will have to flow into the region before rain can fall more generally.
The opportunity for more generalized will come when the monsoon flow evolves in the southwestern United States. The monsoon is already beginning to evolve in Mexico with rain expected to increase across that nation over the next couple of weeks. The precipitation will stay focused on central and southern Mexico into late month, but should reach the northern parts of Mexico in the final days of June.
July is the month in which monsoonal rain usually reaches into the southwestern United States. This year’s ridge of high pressure over the Plains will help to draw moisture northward out of Mexico and send it on a long journey into the northern Rocky Mountains. Normally, the monsoonal rain 
gets into the central Rocky Mountains and is then drawn out of the mountains and into the central Plains by frontal systems that move through the northern United States. This year’s frontal systems will be weaker and further north because of the central U.S. high pressure ridge. As a result rain will stay in the Rocky Mountain region and high Plains longer before moving east northeast.
Another feature to the summer pattern expected this year will be a quasi-permanent trough of low pressure over the Pacific Northwest and northern Rocky Mountain region. The trough will support cooler air in western Canada and the northwestern United States. The positioning of cool air in the northwestern U.S. and far western Canada while warm air dominates the middle of the United States is a natural set up for rainfall as the two air masses collide from time to time. All that is needed for significant rain to fall is a moisture source and that is expected to come from the monsoon flow.
Northward moving moisture from Mexico, cool air in the northwestern U.S. and far western Canada and very warm conditions in the middle of the United States will promote showers and thunderstorms from the heart of July through much of August. Any dryness that evolves in late June and early July in the northern Plains and Canada’s Prairies will likely abate by mid-July with a rainy finish to the summer expected in those areas.
One last feature resulting from the rainy weather in the northern U.S. Plains and southern Canada is the prospects for rain to move across the northern and easternmost parts of the Midwest. If the moisture influx from the monsoon flow is strong enough it will help to create large clusters of strong to severe thunderstorms near the peak of the high pressure ridge. The thunderstorms clusters, called Meso-Convective Complexes (MCC) will evolve at the peak of the high pressure ridge and then roll down the front side of the high pressure ridge. These MCC’s can bring significant rainfall to parts of the Midwest, depending on the ridge orientation.
World Weather, Inc. believes rainfall will be greatest in the Canadian Prairies and northern Plains, but there will be some periodic timely rainfall to impact areas from Minnesota and Wisconsin to Michigan and Ohio. If the ridge is sharp enough the storms could also impact parts of eastern Iowa, Illinois and Indiana, although that is not as likely as periodic rain further to the east.
World Weather, Inc. forecasts and comments pertaining to present, past and future weather conditions included in this report constitute the corporation’s judgment as of the date of this report and are subject to change without notice. Comments regarding damage or the impact of weather on agricultural and energy as well as comments made regarding the impact of weather on the commodity and financial markets are the explicit opinions of World Weather, Inc. World Weather, Inc. cannot be held responsible for decisions made by users of the Corporation’s information in any business, trade or investment decision.
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