…A couple of days of intense heat and humidity expected to impact the
Midwest…
…Severe storms and isolated flash flooding possible across the Northern
Plains/Upper Midwest today and the Great Lakes on Tuesday…
…Daily monsoonal thunderstorms shifting eastward into the southern
Rockies/High Plains…
A couple of days of intense heat and humidity are expected to impact the
Midwest as deep southerly flow behind an intensifying upper-level high
unleashes the heat from the southern Plains. Forecast highs in the
mid-90s to near 100 combined with high humidity will send heat indices
into the 105-115 degree range, with widespread heat-related advisories and
warnings in place. Morning lows will also remain very warm, in the mid-
to upper 70s, providing little relief from the heat overnight. Numerous
record-tying/breaking highs will be possible both over the Midwest as well
as into portions of the Southeast on Tuesday. Those without efficient
air-conditioning or who must spend time or effort outdoors will be at a
heightened risk of heat-related illness. Remember to drink plenty of
water and seek out relief from the heat. An approaching cold front and
increased storm coverage will help to bring relief to portions of the
upper Midwest on Tuesday. While the southern Plains will see some relief
from the record heat that has plagued the region, conditions will still be
hot with highs generally in the mid to upper 90s.
Meanwhile, as upper-level shortwaves eject out of the northern Rockies and
interact with a low pressure wave tracking along a couple of fronts across
the northern Plains, multiple rounds of showers and thunderstorms are
expected to impact portions of the northern Plains into the upper Midwest.
The hot temperatures and plentiful moisture ahead of the front will
contribute to strong to extreme instability leading to the potential for
rapid development of severe thunderstorms. The Storm Prediction Center is
forecasting an enhanced risk of severe weather from eastern South Dakota
through southern Minnesota into central Wisconsin today into tonight as
the center of the low pressure wave tracks just to the south. Very large
hail, widespread and potentially significant damaging winds with any
organized lines of storms, and a few tornadoes will all be possible. A
broader Slight Risk covers portions of the Upper Midwest and
northern/central Plains for some more isolated instances of large hail and
damaging winds. The upper-level shortwaves will help to erode the
upper-high over the Great Lakes on Tuesday mainly across the Great Lakes.
In addition to severe weather, the plentiful moisture and high instability
will support areas of intense downpours which could organize into more
widespread heavy rain coverage at times, leading to the risk of some
isolated flash flooding each day.
Monsoonal thunderstorm chances today are shifting a bit eastward into the
southern Rockies and High Plains, with similar activities returning later
on Tuesday. Some locally heavy downpours remain possible along with the
threat of isolated flash flooding especially across terrain-sensitive
areas along steeper hills/mountain ranges and over burn scars. Some
post-frontal showers and storms are expected into the northern Rockies
through this evening as well. Temperatures over portions of the West will
remain well below average following a frontal passage and under the
influence of an unseasonably strong upper-trough. Forecast highs in the
70s will be common over the northern/central Rockies and eastern Great
Basin. More seasonably warm temperatures will return by Tuesday with highs
back up into the 80s. However, a cold front moving into the Pacific
Northwest will drop highs into the 60s and 70s along with the arrival of
showers and embedded thunderstorms on Tuesday mainly over western
Washington.
Elsewhere, instability associated with an upper-level trough dipping into
New England will bring shower and storm chances through this evening with
some moderate to possibly locally heavy rainfall. Some severe storms will
also be possible, with a Slight Risk over southern New England for the
potential of some large hail and damaging winds. Plenty of clouds will
help to keep temperatures cool here compared to elsewhere in the eastern
U.S., with highs in the 70s and low 80s. Daily showers and storms are also
expected over Florida and along the Gulf Coast into south Texas with a
lingering frontal boundary in the region as an upper-level low tracks
westward into southern Texas.
Kong/Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php