…Dangerous heat wave intensifies over the Midwest…
…Severe storms and isolated flash flooding possible for the Northern
Plains/Upper Midwest Sunday-Monday and Great Lakes Tuesday…
…Daily Monsoonal thunderstorms continue across the Four Corners region,
shifting eastward into the southern Rockies/High Plains…
An upper-level high building northward over the central/eastern U.S. will
help to expand/intensify a dangerous heat wave over the Midwest the next
couple of days. 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 Summer-time hot with highs generally
in the mid-90s.
Just to the northwest, a series of upper-level shortwaves traversing the
building high and an approaching cold front will continue to trigger
multiple rounds of showers and storms over portions of the Northern Plains
and Upper Midwest. The hot temperatures and plentiful moisture ahead of
the front will contribute to strong to extreme instability and the
potential for severe weather, with the first round of storms expected this
afternoon/evening (Sunday). The Storm Prediction Center has issued a
Slight Risk of severe weather (level 2/5) for the eastern Dakotas and
western Minnesota for the threat of some large hail and damaging winds.
The front will slowly push southeastward on Monday. Increasing winds aloft
with a stronger wave will bring greater shear, and the expectation for
more widespread/potentially organized lines of storms has resulted in an
Enhanced Risk (level 3/5) of severe weather from central Minnesota west
through eastern South Dakota. 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 stronger upper-level wave
will help to weaken the upper-high over the Great Lakes on Tuesday, with
increasing storm chances and a Slight Risk of severe weather, with more
instances of large hail and damaging winds expected. In addition to severe
weather, the plentiful moisture and high instability will lead to the
chance of some more intense downpours, and these higher rain rates along
with any organized/widespread storm coverage will also bring the risk of
some isolated flash flooding each day.
Daily Monsoonal thunderstorm chances will continue over the Four Corners
region today, shifting a bit eastward further into portions of the
southern Rockies and High Plains Monday-Tuesday. Some locally heavy
downpours remain possible, with the threat of isolated flash flooding,
especially for terrain sensitive areas along steeper hills/mountain ranges
and over burn scars. Some severe storms will also be possible through this
evening, with a Slight Risk over eastern Utah/western Colorado for the
threat of large hail and damaging winds. Some post frontal showers and
storms are expected into the northern Rockies through Monday 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.
Elsewhere, an upper-level wave over New England will bring some shower and
storm chances through Monday evening with some moderate to 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. The passing wave will also help to keep temperatures down
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 and a weakness in the upper-high passing overhead.
Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
