Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
421 PM EDT Sun Jul 16 2023

Valid 00Z Mon Jul 17 2023 - 00Z Wed Jul 19 2023

...There is a Moderate Risk of excessive rainfall over parts of New
England on Sunday...

...There is a Slight Risk of severe thunderstorms over parts of New
England and Central Plains/Middle Mississippi Valley...

...Excessive Heat Warnings and Advisories from the Pacific Northwest,
California,  and the Great Basin to parts of the Southern Plains, Central
Gulf Coast, and southern tip of Florida...

...Air Quality alerts over parts of the Northern High Plains, Upper
Midwest, and Ohio Valley...

A weak front extending from the Northeast to the Southeast and then
westward to the Southern Plains slowly weakens by Tuesday. The boundary
and a plume of tropical moisture extending from the Central/Eastern Gulf
Coast over the Mid-Atlantic coast into New England work together, creating
showers and thunderstorms with heavy rain. Therefore, the WPC has issued a
Moderate Risk of excessive rainfall over parts of New England through
Monday morning. The associated heavy rain will create numerous areas of
flash flooding. Furthermore, many streams may flood, potentially affecting
larger rivers.

In addition, the front will produce showers and severe thunderstorms over
parts of New England. Therefore, the SPC has issued a Slight Risk of
severe thunderstorms over parts of New England through Monday morning. The
hazards associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, few tornadoes, and a minimal threat of hail.

Moreover, the front mentioned earlier, showers and thunderstorms will
develop heavy rain over parts of eastern Texas and Louisiana along the
western portion of the front. Therefore, the WPC has issued a Slight Risk
of excessive rainfall over parts of the Southern High Plains/Lower
Mississippi Valley through Monday morning. The associated heavy rain will
create mainly localized areas of flash flooding, with urban areas, roads,
and small streams the most vulnerable.

Further, a wave of low pressure along a second front extending from the
Great Lakes southwestward to the Central Plains/Middle Mississippi Valley
will create showers and severe thunderstorms over parts of Kansas and
northwestern Missouri. Therefore, the SPC has issued a Slight Risk of
severe thunderstorms over parts of the Central Plains and Middle
Mississippi Valley from Sunday into Monday morning. The hazards associated
with these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a minimal threat of tornadoes. Additionally, there is a
threat of hail two inches or greater over central Kansas.

On Monday, farther northwestward along the western portion of the front,
as mentioned earlier, showers and severe thunderstorms will develop over
parts of Wyoming, South Dakota, and northeastern Nebraska. Therefore, the
SPC has issued a Slight Risk of severe thunderstorms over parts of the
Northern/Central Plains from Monday through Tuesday morning. The hazards
associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a few tornadoes. In addition, there is
a threat of hail two inches or greater over the area.

Also, on Monday, the threat of excessive rainfall decreases over the lower
forty-eight, with a marginal risk of excessive rainfall over parts of the
Northeast to the Ohio Valley. The second area of excessive rainfall will
develop over parts of eastern Florida, with a third over the Central Gulf
Coast. A fourth area of excessive rainfall develops over parts of the
Southwest and a fifth over parts of the Northern/Central Plains. The
associated heavy rain will create localized areas of flash flooding,
affecting areas that experience rapid runoff with heavy rain over those
regions.

On Tuesday, a front extending from the Lower Great Lakes westward to the
Central/Northern Plains produced showers and thunderstorms with heavy rain
over two regions, Northeast and Ohio/Middle Mississippi Valley. Therefore,
the WPC has issued a Slight Risk of excessive rainfall over parts of the
Northeast and a second area over Ohio/Middle Mississippi Valley on
Tuesday. The associated heavy rain will create mainly localized areas of
flash flooding, with urban areas, roads, and small streams the most
vulnerable.

Moreover, showers and strong to severe thunderstorms will develop along
the boundary from the Western Ohio Valley northwestward to the
Northern/Central Plains and a second area over the Northern Plains.
Therefore, the SPC has issued a Marginal Risk of severe thunderstorms over
parts of the Western Ohio Valley, Middle Mississippi Valley, and
Northern/Central Plains. On Tuesday, the second area will be over the
Northern Plains and Upper Mississippi Valley. The hazards associated with
these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a minimal threat of tornadoes.

Meanwhile, upper-level high over California/Great Basin eastward to
western Texas will extend upper-level ridging into parts of the Pacific
Northwest, bringing hot high temperatures and low temperatures not cooling
off much overnight, which have contributed to Excessive Heat Warnings and
Heat Advisories over California, Nevada, Arizona, New Mexico, and
Louisiana and parts of Texas, Arkansas, Mississippi, Alabama, Oklahoma,
and the southern tip of Florida.

In addition, the ridge will bring an extremely dangerous heat wave over
the Southwest into the following weekend. Dangerous heat may continue into
next week for parts of the region. All-time heat records could be
approached or reached at some locations in the Southwest. The all-time
heat records would likely be on Sunday, particularly in the San Joaquin
Valley, Mojave Desert, and Great Basin regions. Phoenix is also likely to
register its hottest week on record by 7-day average temperature. Take the
heat seriously and avoid time outdoors. Temperatures will reach levels
that pose a health risk and are potentially deadly to anyone without
effective cooling and/or adequate hydration. Heat is the leading
weather-related killer in the U.S..

Lastly, wildfire smoke from Western Canada will reduce air quality over
parts of the Northern High Plains, Upper Mississippi Valley, Great Lakes,
and Western Ohio Valley, prompting Air Quality Warnings over the area.


Ziegenfelder


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