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Four Big Changes in the Nation's Weather This Week
Published: September 27, 2017
Four big changes in the nation's weather are expected this week thanks to a shift in the jet stream pattern over the U.S. this first full week of fall.
Mid- and late September have felt more like mid-summer for many in the Midwest and East, while it seems weather conditions skipped fall and went straight to winter in parts of the West.
By the end of the week, this pattern will essentially flip, at least for a few days.
(MAPS: Weekly Planner)
Here are the four big changes we'll see.
1. Summer-Like Heat Wave Is Slowing Coming To an End
After a relatively cool summer for areas from the Plains to the East Coast, the heat returned with a vengeance as fall officially arrived.
In fact, this heat wave has been historically late in some areas.
According to the National Weather Service in Romeoville, Illinois, in 146 years of records, a heat wave of this longevity and magnitude had never been observed this late in the season in Chicago.
Traverse City, Michigan, reached 95 degrees three consecutive days Friday, Saturday and Sunday, topping the previous record latest-in-season 95-degree-plus high in the northern Michigan city by one full week (Sept. 15, 1939).
On Friday, Milwaukee, Wisconsin, also recorded its record latest-in-season 95-degree-plus high, also previously set on Sept. 15, 1939.
Burlington, Vermont, had its record-latest highs in the 90s Sunday, Monday and Tuesday, topping the previous record by over a week (Sept. 16, 1939). Monday's high of 91 degrees broke the daily record high by 7 degrees, and Tuesday's high of 90 degrees broke the daily record high by 6 degrees.
Concord, New Hampshire also recorded highs in the 90s Sunday through Tuesday, making it the latest in the season, on record, that it reached 90 degrees for three consecutive days.
Daily records were set Sunday in Springfield, Illinois (94), Concord, New Hampshire (91), New York City (91), Pittsburgh (90), and Augusta, Maine (87). Several Midwest and Northeast locations Sunday were hotter than the Desert Southwest.
Daily record highs Monday included Cleveland (94), Springfield, Illinois (94), Traverse City, Michigan (93), Peoria, Illinois (92), Chicago (92), St. Louis (92), Allentown, Pennsylvania (92), Lansing, Michigan (92), Grand Rapids, Michigan (91), Buffalo, New York (91), Albany, New York (91), Madison, Wisconsin (90), Concord, New Hampshire (90), Sault Ste. Marie, Michigan (88), Augusta, Maine (88), Bangor, Maine (88), Caribou, Maine (88) and Worcester, Massachusetts (85).
The heat continued into Tuesday, setting daily record highs in Cleveland (92), Columbus, Ohio (92), Lansing, Michigan (92), Grand Rapids, Michigan (92), Traverse City, Michigan (91), Indianapolis (91), Syracuse, New York (91), Rochester, New York (91), Scranton, Pennsylvania (91), Milwaukee (91), Chicago (90), Albany, New York (90), Burlington, Vermont (90), Concord, New Hampshire (90), Alpena, Michigan (89), Buffalo, New York (88), Caribou, Maine (88), Binghamton, New York (85), and Sault Ste. Marie, Michigan (84).
Highs in the 80s and 90s, threatening more daily record highs, are possible from the Great Lakes to the Northeast through Wednesday.
The first signs of cooler conditions, however, have already started to move into the Plains as the pattern shift has begun.
This Week's Forecast
By late this week, it will finally begin to feel more like autumn in the eastern half of the U.S. as the jet stream kicks out the upper-level high-pressure dome.
Temperatures will generally be near average for the Midwest, Northeast and South, with cooler-than-average conditions in parts of the Plains. This translates into highs in the 60s and 70s for most areas east of the Rockies, except for 80s in portions of the South.
This change will lead to some big temperature drops. Minneapolis is one example, where highs tumbled from 90 degrees on Sunday into the lower 60s by Monday. New York City will also see a noticeable change, with highs in the lower 90s Sunday falling into the mid-60s by this weekend.
2. After Maria, Finally a Breather
Maria is now side-swiping the eastern coast of North Carolina with light to moderate rain and gusty winds.
Even while its center remains offshore, dangerous high surf, rip currents and coastal flooding will be concerns through much of this week along parts of the East Coast.
Projected Path of Maria
By the end of the week, though, Maria will be swept east into the north Atlantic away from the U.S.
For the first time in over a month, it doesn't appear any other tropical storms or hurricanes will threaten any land areas of the Atlantic Basin after Maria for at least a short period of time, giving a much-needed break in tropical activity.
3. Warmer Temperatures Return to the West, But Not Summer's Blazing Heat
Late last week, an area of low pressure brought another blast of colder-than-average temperatures and snow to parts of the northern Rockies and Sierra.
Over a foot of snow fell this past weekend in Utah's Wasatch mountains.
High temperatures also remained 5 to 15 degrees colder than average for much of the West through Tuesday, with highs topping out in the 40s and 50s for portions of the Rockies and in the 70s and lower 80s from the Northwest coast into portions of California.
An upper-level ridge will now start to build over the West Coast, and a gradual warming trend is expected into late week. As this ridge continues to build over the West, temperatures are expected to be slightly above average in the Northwest and closer to average for this time of year in the remainder of the region by late week.
This warm-up won't last long, up to three days in most spots, with the most anomalous temperatures occurring in the Pacific Northwest and northern Rockies.
Highs will climb into the 80s and 90s for much of California away from the coast, with 70s and 80s in the Northwest. Areas further east will see temperatures rise into the 60s and 70s, which will be more than a 20-degree temperature rise for some areas, compared to late last week.
This will also bring a return to a drier weather pattern, with the best chance of precipitation in the Four Corners region and the southern Rockies. However, a few showers will develop in the Pacific Northwest on Friday as the next cold front approaches the region.
4. A Plains Flood Threat
Deep tropical moisture intercepting a slowly sagging frontal boundary are teaming up to bring several rounds of heavy rain into parts of the Plains states.
The threat for additional heavy rain through much of this week will focus on parts of western Texas, where another 3 to 5 inches of rain may fall through Friday, with the highest rainfall totals expected to be around the Texas Big Bend.
(INTERACTIVE: Regional Radar Loop)
Locally higher amounts may fall in a short period of time where clusters of thunderstorms stall, triggering local flash flooding.
There were numerous reports of flash flooding on Tuesday, including in Midland and Odessa, Texas. Tuesday night, severe water rescues occurred in Laredo, Texas where more than 5 inches of rain fell on Tuesday. Near Laredo, from Monday into early Wednesday morning over 10 inches of rain was reported. For perspective, Laredo receives just over 20 inches of rain in an average year
Flash flood watches remain in effect for portions of the Texas Big Bend, west-central Texas and the Texas hill country, where rainfall totals of more than 6 inches are possible.
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