…Rounds of thunderstorms with a heavy rainfall and flash flood threat
for the Upper Midwest through Monday…
…Scattered thunderstorms expected across portions of the
Northeast/Carolinas, Florida/Gulf Coast, and Southwest the next couple of
days will bring an isolated threat of flash flooding…
…Hazardous heat builds across parts of the Plains, Midwest, and
Mid/Lower Mississippi Valley through early next week…
An upper-level shortwave and accompanying slow moving surface frontal
system will trigger rounds of thunderstorms across much of the Upper
Midwest Sunday-Monday. Plentiful moisture/instability will promote heavy
downpours with organized clusters of thunderstorms contributing to
long-duration rainfall and heavy totals. There is a Slight Risk of
Excessive Rainfall (level 2/4) covering portions of the eastern Dakotas,
central/southern Minnesota, and western Wisconsin where scattered to
potentially numerous instances of flash flooding can be expected. As the
system progresses eastward Monday another Slight Risk is in effect
centered on portions of southern Wisconsin/far northern Illinois for
additional scattered instances of flash flooding. Scattered to widespread
thunderstorms are also expected across much of the eastern U.S. To the
north, storms along and ahead of a cold front pushing through the
Northeast/Ohio Valley on Sunday and into the Carolinas/southern
Appalachians Monday may lead to some isolated instances of flash flooding.
Additional storms are forecast across the Florida Peninsula and westward
along the central Gulf Coast the next couple of days, with a greater risk
for heavier rainfall/isolated flash flooding on Sunday. Further west, more
scattered to isolated thunderstorms are forecast over the Plains and into
the Southwest through Monday. However, plentiful moisture will bring the
threat for brief but potentially heavy downpours particularly over
portions of the southern High Plains into the Southwest, with isolated
flash flooding possible. Elsewhere, periodic upper-level waves and a
lingering frontal boundary will help to trigger scattered thunderstorms
across the northern Great Basin and into the northern Rockies on Sunday.
While heavy rainfall/winds are expected to remain well offshore the East
Coast as Hurricane Erin passes by to the east this upcoming week,
life-threatening surf and rip currents are expected and will begin
possibly as early as Monday.
Conditions will remain very hot and muggy over portions of the eastern
Plains, Midwest, and Middle/Lower Mississippi Valley to end the weekend
and through early next week. Heat Advisories cover much of the region as
afternoon heat indices willl climb into the 105-110 degree range. In
addition, lows in the mid- to upper 70s will bring little relief from the
heat overnight. While not quite as intense, another hot and humid day is
in store for much of the Northeast Sunday as highs climb into the low 90s.
However, a cold front will bring relief on Monday as highs fall into the
70s for most locations. Forecast highs will also remain Summer-time hot
and into the 90s across the Southeast, Gulf Coast, and northward through
the Plains Sunday-Monday. A growing upper-level ridge will bring hotter
temperatures to the Intermountain West as well with highs generally in the
80s on Sunday rising into the 90s Monday. Meanwhile, portions of the Upper
Midwest/Great Lakes north of a frontal boundary will remain unseasonably
cool, with highs in the 60s and 70s. The West Coast will also remain below
average Sunday-Monday, with 60s and 70s expected.
Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
