Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
356 AM EDT Thu Aug 18 2022

Valid 12Z Thu Aug 18 2022 - 12Z Sat Aug 20 2022

...There is a Moderate Risk of excessive rainfall over parts of the
Southwest from Friday into Saturday morning...

...There is a Slight Risk of excessive rainfall over parts of the
Southwest/Great Basin, Central Gulf Coast, and the Southeast from Thursday
into Friday morning...

...There is an Excessive Heat Watch and Heat Advisory over parts of the
West Coast through Friday night...

Monsoonal moisture and upper-level energy over parts of North-Central
Mexico will aid in producing showers and thunderstorms with heavy rain
over parts of Utah, Arizona, and far eastern Nevada. Therefore, the WPC
has issued a Slight Risk of excessive rainfall over parts of the Southwest
and Great Basin through Friday morning. The associated heavy rain will
create mainly localized areas of flash flooding, with urban areas, roads,
and small streams the most vulnerable.

On Friday, upper-level energy over parts of North-Central Mexico will
merge with upper-level energy over California to produce an upper-level
low over the Southwest that will start to move eastward on Saturday. The
upper-level low and tropical moisture will aid in producing showers and
thunderstorms with heavy rain over southern Arizona and southern New
Mexico. Therefore, the WPC has issued a Moderate Risk of excessive
rainfall over the Southwest near the U. S./Mexican border from Friday into
Saturday morning. The associated heavy rain will create numerous areas of
flash flooding. Furthermore, many streams may flood, potentially affecting
larger rivers.

Meanwhile, a weak front extending from the Southeast roughly westward to
the Southern Plains, tropical moisture, and upper-level impulses will
produce showers and thunderstorms, with heavy rain over Mississippi and
Louisiana and a second region over parts of Florida, America s Georgia,
and South Carolina. Therefore, the WPC has issued a Slight Risk of
excessive rainfall over parts of the Central Gulf Coast and the Southeast
through Friday morning. The associated heavy rain will create mainly
localized areas of flash flooding, with urban areas, roads, and small
streams the most vulnerable. On Friday into Saturday, the threat of
excessive rainfall decreases slightly; however, the threat of excessive
rainfall moves into the southern Mid-Atlantic. Therefore, the WPC has
issued a Marginal Risk of excessive rainfall over parts of the southern
Mid-Atlantic, Southeast, Gulf Coast, and Southern Plains from Friday into
Saturday morning. The associated heavy rain will create localized areas of
flash flooding, affecting areas that experience rapid runoff with heavy
rain.

Furthermore, a front over the Upper Midwest moves to the Upper Great Lakes
to the Central Plains by Saturday. The boundary will produce showers and
thunderstorms with the possibility of heavy rain over the area. Therefore,
the WPC has issued a Marginal Risk of excessive rainfall over parts of the
Upper Mississippi Valley and Northern Plains through Friday morning. The
associated heavy rain will create localized areas of flash flooding,
affecting areas that experience rapid runoff with heavy rain. On Friday,
the threat of excessive rainfall moves into the Middle Mississippi Valley,
where the WPC has a Marginal Risk of excessive rainfall from Friday into
Saturday morning.

Elsewhere, upper-level ridging will build over the Rockies, allowing
temperatures to rise into the low-to-upper hundreds over parts of
California, prompting a Heat Advisories over the Sacramento and San
Joaquin Valleys through Friday evening. As the upper-level ridging builds
over the Northwest, temperatures climb into the upper nineties to low
hundreds over the interior Northwest, prompting Excessive Heat Watch and
Heat Advisories over the region into Friday night. Additionally,
record-breaking relatively high low temperatures will contribute to areas
not cooling off overnight, which will also contribute to the effects of
heat.


Ziegenfelder


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