…Unsettled weather across the East through Sunday…
…Multiple days of heavy rain may cause flash flooding for portions of
central Texas and the western Gulf Coast…
…Well above average, hot late-summer temperatures forecast in the
northwestern U.S. this holiday weekend…
An upper-level trough and associated surface cold front will progress
eastward this weekend, extending from the Northeast southwest through the
Ohio/Tennessee Valleys, Middle Mississippi Valley/Mid-South, and into the
Southern Plains. A round of showers and thunderstorms is expected along
and ahead of the length of the front through tonight, with moist air and
instability likely leading to some more intense thunderstorms, heavy
downpours, and the potential for isolated flash flooding. A locally higher
threat is expected across portions of the northern/central Appalachians
given the potential for some training/repeated rounds of storms across
more sensitive mountain terrain. The region is under a Slight Risk of
Excessive Rainfall (level 2/4) for the threat of a few more scattered
instances of flash flooding. In addition, stronger winds aloft with the
passing upper trough will bring increased shear for some more organized
storms. The Storm Prediction Center has also included a Slight Risk of
severe weather (level 2/5), mainly for the threat of some damaging winds.
The fronts forward progression will slow through into early Sunday,
especially with southwestward extent, leading to additional rounds of
storms on Sunday with moderate to locally heavy rainfall from the southern
Mid-Atlantic/Carolinas west through the Tennessee Valley, Mid-South, and
into the Southern Plains. Some isolated flash flooding will remain
possible, especially for the southern Appalachians/Mid-Atlantic and
Carolinas. A secondary cold front sweeping in from the north will bring an
end to precipitation chances for most areas outside of the
Southeast/Southern Plains later Sunday night.
Further south, another area of storms is expected to continue today in
vicinity of a coastal low near the western Louisiana and upper Texas Gulf
Coasts. Another Slight Risk of Excessive Rainfall is in place as slow
moving and very heavy rainfall-producing storms given abundant Gulf
moisture may lead to some additional scattered instances of flash
flooding, especially given wetter antecedent conditions from rainfall the
past few days. At least an isolated threat for flash flooding will exist
into Sunday, though rainfall amounts may trend downward. Shower and
thunderstorm chances should increase to end the weekend and into Labor Day
throughout central Texas as a lingering stalled frontal boundary and
upper-level energy ejecting out of northern Mexico combine to produce
areas of heavy rain and scattered flash floods. Daily thunderstorms are
also forecast for the Florida Peninsula, with some isolated instances of
urban flooding possible for South Florida today. Temperature-wise, relief
from the more intense heat this past week will finally come to the Middle
Mississippi, Ohio, and Tennessee Valleys as increasing storm chances and
the approaching front keep temperatures down a bit, with highs generally
in the 80s and low 90s. Low 90s will also be common across the Southeast
with mid-80s to low 90s for the Appalachians and southern Mid-Atlantic.
Highs will remain cooler and mainly in the 70s to the north of a warm
front for the northern Mid-Atlantic and New England Saturday, with a
rebound into the low 80s expected for many locations Sunday as the warm
front lifts north. The Northern/Central Plains and Midwest will see highs
in the 80s today before a cold front brings cooler temperatures in the 70s
Sunday. Conditions will remain much below average for late Summer over the
Lower Mississippi Valley and Southern Plains, with highs generally in the
mid-80s outside of south Texas. Some 70s will be possible for west Texas.
Well above average, hot late-summer temperatures will continue into the
weekend for the northwestern U.S. as a broad upper-level ridge remains in
place over the West. Highs are forecast into the 90s to near 100 across
the interior Pacific Northwest, northern Great Basin, and northern
Rockies, which have prompted some Heat Advisories for the northern Great
Basin/Rockies given the heightened risk of heat-related illness. This heat
is then forecast to shift eastward into the northern High Plains and
northern Rockies on Labor Day, with highs also reaching into the
mid-to-upper 90s. Those with outdoor plans for the holiday weekend should
remember to take more frequent breaks from the heat in the shade and stay
hydrated. Highs elsewhere across the West will not be quite as above
average, but still hot, with 90s for the Great Basin and interior
California and 100s in the Desert Southwest. Portions of the
Southwest/Four Corners Region will be a bit cooler with shower and
thunderstorm chances expected in vicinity of a lingering frontal boundary,
with highs in the upper 70s and 80s.
Snell/Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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