The Nation’s Weather

…There is a Slight Risk of excessive rainfall over parts of the
Mid-Atlantic, Central Appalachians, and Ohio Valley on Friday…

…There is a Slight Risk of severe thunderstorms over parts of the
Southern Plains and the Southeast on Thursday and the Southeast to the
Mid-Atlantic on Friday…

A wave of low-pressure south of Long Island will move eastward out over
the Atlantic by Friday. A second wave of low pressure over Georgian Bay,
Ontario, Canada, will dissipate by Friday morning. The areas of low
pressure will draw moisture off the Atlantic over the Northeast into the
Great Lakes, producing rain over parts of the Great Lakes and Northeast on
Thursday.

A third wave of low pressure develops over the Southern Plains on
Thursday, moves northeastward to the northern Mid-Atlantic by Friday
evening, then moves over New England by Saturday. Moisture will surge
northward over the Southern Plains as upper-level energy moves across
Texas, producing showers and severe thunderstorms. Therefore, the SPC has
issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the
Southern Plains through Friday morning. The hazards associated with these
thunderstorms are frequent lightning, severe thunderstorm wind gusts,
hail, and a few tornadoes. However, there is an increased risk of hail,
two inches or greater, over the region.

Similarly, moisture will move northeastward out of the Gulf of America as
another area of upper-level energy moves across the Southeast, creating
showers and severe thunderstorms. Therefore, the SPC has issued a Slight
Risk (level 2/5) of severe thunderstorms over parts of the Southeast
through Friday morning. The hazards associated with these thunderstorms
are frequent lightning, severe thunderstorm wind gusts, hail, and a few
tornadoes.

Moreover, an upper-level low over the Central Plains/Middle Mississippi
Valley will trigger showers and thunderstorms over parts of the Central
Plains/Middle Mississippi Valley and Ohio/Tennessee Valleys. On Thursday,
showers and thunderstorms will develop over the Central Rockies.

On Friday, as the third wave of low pressure over the Ohio Valley moves
into the Mid-Atlantic, showers and thunderstorms will develop with heavy
rain over parts of the Ohio Valley, Central Appalachians, and
Mid-Atlantic. Therefore, the WPC has issued a Slight Risk (level 2/4) of
excessive rainfall over parts of the Ohio Valley, Central Appalachians,
and Mid-Atlantic from Friday through Saturday morning. The associated
heavy rain will create mainly localized areas of flash flooding, with
urban areas, roads, small streams, and low-lying areas the most vulnerable.

The cold front, associated with the third wave of low pressure, will cause
showers and severe thunderstorms over parts of the Southeast and the
Mid-Atlantic region. Therefore, the SPC has issued a Slight Risk (level
2/5) of severe thunderstorms over parts of the Southeast to the
Mid-Atlantic from Friday into Saturday morning. The hazards associated
with these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a few tornadoes.

Furthermore, showers and thunderstorms will develop over parts of the
Great Lakes and Ohio Valley on Friday, and rain will also fall over parts
of the Northeast.

Meanwhile, a front over the Pacific Northwest on Thursday moves eastward
to the Northern High Plains into the Great Basin by Friday morning,
dissipating by Friday evening. The system will produce scattered rain over
parts of the Northwest, expanding into the Northern Intermountain Region
by Thursday evening. Overnight Thursday, showers and thunderstorms will
develop over the Northern/Central Rockies. In addition, showers and
thunderstorms will develop over the Southern Plains on Friday through
Saturday morning. Moreover, showers and thunderstorms will develop
overnight Friday over the Central/Southern Rockies.

Elsewhere, an upper-level low over Southern California will slowly move
southwestward over Northwestern Mexico by Friday evening, and a ridge of
high pressure will develop over California and into the Great Basin on
Friday morning. The upper-level ridging will allow temperatures to rise
into the low hundreds, prompting Heat Advisories and Extreme Heat Warnings
over parts of California on Friday.

Ziegenfelder

Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php