…Record heat on tap for the Ohio Valley, Tennessee Valley, southern
Appalachians and Mid-Atlantic, but relief on the way…
…Active thunderstorms, heavy rains, flash flooding and severe weather
possible over large portions of the north central to east central U.S…
…Fire weather threat for portions of the Northwest/Northern Rockies,
along with early season high elevation snow…
Much above average temperatures will continue over the next few days
across a large portion of the nation from the Central to Southern Plains,
east into the Mississippi Valley, Ohio Valley, Southeast and Mid-Atlantic.
Across much of these areas, high temperatures are forecast to be from 10
to 15 degrees above average. This will result in the potential for record
high temperatures across much of the Ohio and Tennessee Valleys into the
Southern Appalachians and Mid-Atlantic on Wednesday and across the Ohio
and Tennessee Valleys and Southern Appalachians on Thursday. The
combination of the much above average temperatures and continued high
levels of humidity will produce maximum heat indices on Wednesday and
Thursday in the 105 to 110+ degrees F range across these areas, producing
major to extreme heat risks through the Ohio/Tennessee Valleys into the
Mid-Atlantic. Excessive Heat Warning and Heat Advisories are currently in
effect across much of these areas, affecting over 77 million people. Some
relief is in store for portions of the U.S. on Wednesday that have had
very hot temperatures the past few days. A cold front will be pressing
south out of the Upper Great Lakes into the Mid-West tonight, bringing
relief to the very hot recent temperatures for southern Michigan into
central to southern Wisconsin, northern to central Illinois, eastern Iowa
into northeast Missouri. This front will continue to press southeastward
Wednesday night bringing relief by Thursday to the heatwave for the
Mid-Atlantic region into the Upper Ohio Valley. The trend of shrinking
areal extent of major to extreme heat risks will accelerate by the
beginning of the holiday weekend across large portions of the nation.
The frontal boundary sinking southeastward from the Upper Mississippi
Valley/Upper Great Lakes region and a second strong front moving from the
Northern Rockies/North High Plains tonight into the Northern to Central
Plains/Upper Mississippi Valley region Wednesday into Thursday will be the
focus for areas of active thunderstorms. With moisture values expected to
be much above average along and ahead of each of these fronts, locally
heavy rain and isolated flash flooding is possible from the Great Lakes
into the Ohio Valley late this afternoon into early Wednesday, and across
the Ohio Valley into the Mid-Atlantic, and portions of the Northern Plains
into the Upper Mississippi Valley late Wednesday into Thursday. In
addition to the heavy rain/flash flood threats, these thunderstorms may
also produce severe weather across these areas, with large hail and high
winds the greatest threat, with a lesser threat for tornadoes.
The strong front pushing east form the northwest late this afternoon will
produce strong gusty winds in its wake over the Northern Great Basin into
the Northern Rockies. These windy conditions, combined with low relative
humidities will produce fire weather threats into Wednesday , with Red
Flag warnings in effect across these areas. The cold temperatures in the
wake of this strong front will also support snowfall potential above 5000
feet in the northern Rockies of Montana where snowfall amounts of 3 to 6
inches are possible on Wednesday.
Oravec
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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