…Life-threatening, catastrophic flash and urban flooding ongoing in the
Southern Appalachians due to rainfall from Helene…
…Risk of heavy rainfall leading to scattered instances of flash flooding
as well as high winds continues through tonight for portions of the
Southeast and Ohio/Tennessee Valleys…
…Heavy rainfall and isolated flash flooding due to Post Tropical Storm
Helene for portions of the Ohio/Tennessee Valleys Saturday…
…Well above average temperatures and summer-like heat expected from the
Southwest to the Northern Plains this weekend with numerous record
tying/breaking highs possible…
Now post-tropical storm Helene continues to move through the Southeast and
into the Tennessee/Ohio Valleys this afternoon with a broad swath of rain
stretching from the Mid-South east through the Ohio/Tennessee Valleys and
into the central Appalachians as well as the southern
Mid-Atlantic/Carolinas. While rainfall has trended down overall, or has
completely ended for some locations over portions of the southern
Appalachians, life-threatening, catastrophic flash and urban flooding
continues. There have been numerous high-water rescues, roads closed, and
at least one dam failure. The threat for flooding will also continue as
river levels remain at high to potentially record-breaking levels.
Additional locally heavy rainfall on top of already very wet antecedent
conditions elsewhere across the region will continue into the evening,
bringing the threat for additional scattered instances of flash flooding.
A broad Slight Risk (level 2/4) of Excessive Rainfall remains in place.
Strong, potentially damaging wind gusts will also continue into the
evening/early overnight hours as well. There is a possibility of
long-duration power outages in portions of the Southeast following the
storm. Remember, if you use a generator, be sure it is placed outside at
least 20 feet away from doors, windows, and garages to avoid deadly carbon
monoxide poisoning. The Storm Prediction Center has also outlined portions
of southeastern Virginia and North Carolina with Slight (level 2/5) to
Enhanced (level 3/5) risks of severe weather mainly for the threat of
tornadoes.
Post-tropical storm Helene and an upper-low that has been lingering over
the Mississippi Valley will begin to interact and bring additional locally
heavy rainfall to portions of the Ohio and Tennessee Valleys on Saturday,
with some isolated flash flooding remaining possible. The rainfall will
begin to reduce in coverage and shift eastward on Sunday as the upper-low
meanders eastward, with some isolated flash flooding possible in the
central Appalachians. A locally higher threat could materialize if storm
coverage/duration overlaps areas of wetter antecedent conditions from the
prior days rainfall due to the storm, with additional Slight Risks not out
of the question. Additional moderate rainfall is expected ahead of a
lingering quasi-stationary frontal boundary through the Mid-Atlantic this
weekend, though amounts here should remain lighter. Showers and
thunderstorms with locally heavy rainfall are also expected ahead of a
stalling cold front over the Florida Peninsula, with some isolated flash
flooding possible. The rest of the country will be mostly dry through the
weekend.
Much above average, summer-like heat continues under the influence of a
broad upper-level ridge over the western/central U.S., particularly for
the Desert Southwest, Great Basin, and northern Plains. Excessive Heat
Warnings are in place in the Desert Southwest as highs will soar into the
110s. Forecast highs are in the mid-80s to mid-90s over much of the
northern Plains and Great Basin, in some cases upwards of 20-30 degrees
above average. Numerous potentially record-tying/breaking highs are
possible. A Pacific system moving into the Northwest will bring
temperatures down to average for the northern Great Basin Sunday. While
not quite as warm, conditions will also be above average for the
Upper-Midwest as highs reach into the upper 70s to mid-80s. Elsewhere,
hot, humid conditions will continue ahead of a cold front in South
Florida.
Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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