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Pattern Change Will Bring Record Heat to the Midwest, Northeast and Cooler Temperatures to Southwest
Published: June 16, 2018
A taste of the summer monsoon is about to cause a temperature flip-flop going into this weekend.
The remnants of Hurricane Bud and a southward dip in the jet stream will open a pipeline of moisture across the Southwest and Plains this weekend while a big dome of high pressure anchors itself over the Midwest.
(MORE: Extended Forecast)
The dome of high pressure will result in well above-average temperatures and a relatively dry period going into early next week across the heartland.
Temperatures will either drop to more comfortable levels or rocket toward record heat.
The Midwest and Northeast Heat Up This Weekend
As the jet stream digs southward into the Pacific Northwest, a ridge of high pressure will build over the central and eastern United States, likely bringing the first widespread outbreak of heat and humidity in the Midwest.
The above-average temperatures, which have been located over the Rockies and Plains, will be bunted eastward into the Midwest and Northeast this weekend into early next week by the digging jet stream in the West.
Midwest, Northeast Highs and Departures from Average
Several locations, including Cleveland, Chicago and Des Moines, Iowa, will be flirting with record temperatures this weekend. Much of the Midwest will likely be 15 to 25 degrees above average during this time period.
Highs will likely be in the mid-to-upper 90s from the central Plains to southern Michigan, but a few communities may see highs clinch the "century mark" on either day.
The Northeast will see temperatures and humidity increase this weekend, with highs 10 to 25 degrees above average Sunday and Monday. Monday will likely be the hottest day, with highs in the 90s expected from Boston to Washington D.C.
Record-high temperatures are also likely from Virginia to Massachusetts on Monday.
Dew points will also increase, making it feel humid. The combination of heat and humidity will result in high heat index values, meaning it will feel hotter than the air temperature indicates. For many locations, heat index values will approach and top 100 degrees.
This has prompted heat advisories to be issued in parts of the Plains, Midwest and mid-South. An excessive heat warning has also been posted for the Chicago, St. Louis and Minneapolis areas.
The National Weather Service office in Chicago noted that since the deadly 1995 heat wave, Chicago has specialized excessive heat warning criteria, and there appears to be "solidly greater than a 50 percent chance of Chicago reaching their three consecutive days of 100- to 105-degree criteria for an excessive heat warning."
In addition, low temperatures will also be well above average with lows generally in the 70s, although some locations may struggle to dip below 80 degrees. Numerous daily warm low-temperature records are anticipated from the Midwest into the Northeast into early next week.
The good news is that relief will be found early next week. A cold front will slide through the Midwest and Northeast, resulting in temperatures returning to closer to average for mid-June.
Bud Brings Some Cooling for the Southwest
Moisture from whatever is left of Bud will bring a wealth of tropical moisture from the Pacific and some cooler air, too.
The amount of moisture in the atmosphere may topple some moisture-content records in Arizona or New Mexico. This start to the monsoon may be one of the earliest on record with Bud's support.
High temperatures will drop 15 to 20 degrees from Thursday's readings by Saturday in parts of the Four Corners by added cloud cover and any showers or storms that develop.
This will drop most locations in Arizona and New Mexico from the 90s and 100s ahead of the cloud cover down into the 80s and low-90s as Bud's remnants arrive.
The coolest day will be Saturday when temperatures are likely to be 10 to 20 degrees below average from the immediate Four Corners region southward to the Mexican border.
Southwestern High Temperatures and Departures from Average
The cooler, relative to average, air will spread into much of the West as the dip in the jet stream brings its own slightly cooler air on this weekend before waning into the middle of next week.
Even without a tropical system in play, the beginning of the Southwest Monsoon (by the calendar, starting Friday, June 15) typically knocks temperatures down from June's dry heat to July's wetter pattern.
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