Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
250 PM EDT Mon Jul 1 2024

Valid 12Z Thu Jul 04 2024 - 12Z Mon Jul 08 2024

***Major heatwave expected for the lower elevations of California
 and the Desert Southwest next week, and remaining hot and humid
 for the south-central to southeastern states***

...Overview...

The northern tier of the country will be in an active pattern as
multiple
shortwave pass through with accompanied scattered to numerous
showers and thunderstorms. The best potential will focus across
the Midwest and portions of the Central Plains/Middle Mississippi
Valley where the heaviest rainfall is likely. Heat and humidity
will continue to make weather headlines across much of the southern
tier states as a strong ridge of high pressure aloft governs the
overall weather pattern, and heat also expands across much of
California and the lower elevations of Arizona and southern Nevada
as the upper ridge builds across the West by the end of the
forecast period. There will likely be some abatement in the
thunderstorm coverage across the Southern Rockies after multiple
days of flash flooding concerns.

...Guidance/Predictability Assessment...

The latest run of models had a good grasp on the large scale
pattern with the West Coast ridging and multiple shortwaves passing
through the northern tier of the country. The forecast was based
on a blend of the deterministic models early in the period, with
inclusion and gradual increase of the GEFS and EC ensemble means to
about 40 percent by next Monday.

The National Hurricane Center has Hurricane Beryl crossing the
Caribbean Sea later this week and into the Bay of Campeche by this
weekend. The best model clustering shows Beryl being steered into
northeastern Mexico next weekend; however some guidance curves
the system farther north into southern Texas. Beryl's track will
continue to be monitored over the next several days, and see NHC's
website for official forecasts.


...Weather/Hazards Highlights...

By Day 4/Independence Day, the overall QPF signal in the guidance
is looking more diffuse with scattered higher QPF maxima, so a
broad Marginal Risk still seems to be the best way to go for now
from eastern Oklahoma/Kansas to western Pennsylvania. For the
Dakotas and Mississippi Valley, additional mesoscale convective
systems are likely to form and track through north-central parts of
the country. A Marginal Risk is in place for parts of the Upper
Midwest on Day 4, and then northern Wisconsin and the U.P. of
Michigan for Day 5. A Slight Risk was added with this forecast to
eastern portions of the Dakotas and much of central Minnesota where
there will be the best potential for several inches of rain to
focus over recently saturated soils. For the Day 5 period, a broad
Marginal Risk area is planned from eastern Oklahoma to the
Tennessee River Valley in the vicinity of a frontal boundary that
will intercept a hot and humid airmass with plenty of moisture
available. A cold front slowly pressing east will eventually spread
thunderstorms to the Eastern Seaboard into the weekend, while more
rounds of storms are possible in the central U.S. as well.

It will continue to remain hot and humid across the Southern U.S.
for the middle of the week and into next weekend, with the hottest
conditions centered across the Southern Plains on Wednesday-
Thursday where triple digit high temperatures are likely. The heat
will abate somewhat there into late week and the weekend (but still
feeling summer-like), while the Southeast to Mid-Atlantic should
see temperatures and heat indices rising. It will also be getting
very hot for the inland lower elevations of California and into the
Arizona Deserts with widespread 105-115 degree readings likely,
and locally higher for the normally warmer locations. Daily
temperatures records may be tied or broken. Above normal
temperatures by 10-20 degrees should stretch into Oregon and
Washington late week into next weekend as well.

Campbell/Hamrick


Additional 3-7 Day Hazard information can be found on the WPC
medium
range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw