A major change in the weather pattern is coming as a massive heat dome develops over the Heartland of the United States later this week, and it may persist through much of the second half of August, AccuWeather meteorologists warn.
Along with triggering a string of days where temperatures push the upper 90s to 100 F in many areas of the nation’s midsection, some relief from heat and dryness is anticipated in parts of the South and West as the setup shifts, forecasters say.
Texas has been the focal point of unrelenting heat this summer with the temperature in Dallas, Austin, San Antonio and Houston running 3 to 5 degrees above the historical average since meteorological summer began on June 1.
Houston has experienced 100-degree temperatures every day this month, except for Aug. 3, when the high was 99. The historical average high is 94 for the Texas city situated near the northwest Gulf Coast. Additionally, the mercury has only dipped below 80 on two nights during the month, compared to a historical average low temperature in the mid-70s.
Extreme heat has not only been commonplace in Texas, but it has also reached as far to the east as Florida and as far to the west as interior Southern California this summer.
“The same type of weather system that has been responsible for relentless heat in Texas and the South-Central states as well as the interior Southwest much of this summer will regroup and set up shop farther north starting late this week,” AccuWeather Senior Meteorologist Adam Douty said.
The heat dome represents a zone of high pressure from near the surface of the Earth to the level where jets fly at. Once established, it can create a cycle of building heat and dryness that is difficult to break.
“The heat dome and associated heat wave may have the staying power to last for five to seven days in some areas,” AccuWeather Long-Range Meteorologist Brandon Buckingham said.
Cities in the central and northern Plains to parts of the Midwest could experience the highest temperature readings so far in 2023 as heat surges in this weekend into next week.
For example, the highest temperature Des Moines, Iowa, recorded all summer was 98 degrees on July 28. AccuWeather meteorologists are projecting that temperatures may reach or exceed the 100-degree mark there a couple of days early next week.
Other major cities on the list that are most likely to experience season-high marks with temperatures reaching well into the 90s early next week include Minneapolis and Chicago. Temperatures in some locations will fall short of the hottest weather of summer so far, but these same places will experience extreme heat nonetheless. Highs near or just above the 100-degree mark are likely in Omaha, Nebraska; Kansas City, Missouri; St. Louis and Topeka, Kansas.
A factor contributing to the quick buildup of heat has been a stubborn drought over the middle of the nation. Portions of Kansas, Nebraska, Missouri, Iowa, Minnesota and Wisconsin are experiencing severe to exceptional drought, according to the United States Drought Monitor.
Dry ground tends to heat up more quickly than moist ground as less of the sun’s energy is used up in the process of evaporating moisture.
Not every location will bake and broil across the U.S. Some areas will even trend cooler and wetter compared to much of the summer.
“On the rim of the massive heat dome, moisture and cooler air will be found,” Douty said. “These fringe areas will include the Gulf Coast, the western third of the nation and the Northeast.”
The clockwise circulation around the massive high pressure area will allow tropical disturbances to track westward across the Gulf of Mexico.
“The influx of moisture should bring some relief from heat along the Gulf Coast and from heat and drought in parts of Texas by early next week,” AccuWeather Senior Meteorologist Heather Zehr said.
“Not only may these grab moisture from the Gulf, but one or more could also develop tropically,” Douty added. “It would not be out of the question for a tropical depression or storm to brew over the western and northern part of the Gulf and move into Texas with heavy rain next week.”
Another zone where moisture will come into play and help to ease heat, drought and the wildfire risk will be along the Pacific coast and perhaps as far inland as Arizona, New Mexico, Utah, Idaho, and Alberta, Canada.
A dip in the jet stream will help to direct moisture in from the North Pacific and perhaps the tropical Pacific as well starting late this week.
“The influx of moisture will help bring opportunities for cloud cover and much-needed rain, as well as lower temperatures in the western parts of the U.S. and Canada from late this week to next week,” Buckingham said.
On Sunday, temperatures topped 80 in Vancouver, and 100 in Portland, Oregon. Temperatures approached 90 in Seattle. Record-challenging heat is in store into midweek in the Northwest. However, as the new pattern evolves, temperatures will be slashed by 20-30 degrees Fahrenheit. Highs in the low to mid-70s are in store for Seattle by the end of the week, forecasters say.
A budding tropical system, which is likely to be named Hilary, in the eastern Pacific, may help to direct some moisture into northwestern Mexico, part of California and the southwestern U.S. by this weekend. Over the past week or so, a limited amount of Pacific moisture streamed into parts of the Southwest and has ignited only spotty shower and thunderstorm activity.
Should tropical moisture blast the region, then spotty thunderstorms with the risk of lightning-induced wildfires could escalate into locally heavy rain with the potential for flash flooding in parts of the Southwest starting this weekend.
“Meanwhile, on the northeastern periphery of the massive high pressure area, fast-moving complexes of severe thunderstorms may dive from central Canada to across parts of New England, the central Appalachians and the mid-Atlantic zone this weekend to next week,” Douty said.
Similar patterns in the past have triggered powerful thunderstorm wind gusts over a broad area. This type of damaging thunderstorm complex is known as a derecho to meteorologists. The upcoming pattern could yield some of the strongest storms of the summer with the most extensive scope of damaging winds as thunderstorms erupt along the clash of hot air to the south and cooler air to the north.
It is possible that complexes of thunderstorms will begin to break down the heat dome and cause it to shrink southward later next week, but not before many locations in the middle of the nation have several days to perhaps a week of extreme heat, Buckingham said.
Source : Aol