307
FXUS02 KWBC 030658
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Wed Jul 3 2024

Valid 12Z Sat Jul 06 2024 - 12Z Wed Jul 10 2024

***Major heatwave expected for the lower elevations of California
 and the Desert Southwest next week, and Beryl eventually headed
 for the Western Gulf***

...Overview...

The main thing making weather headlines during this forecast period
will the intense and prolonged heatwave encompassing much of
California and extending into the lower elevations of the Desert
Southwest. Hot and humid conditions will also continue for much of
the southern states and extending to the East Coast. A low pressure
system is forecast to cross the northern Great Lakes with a
trailing front across the Eastern U.S., with showers and storms
firing near boundary across portions of the Southern Plains and
extending east to the Ohio Valley and the Mid- Atlantic region. The
track of Beryl is expected to enter the Bay of Campeche and the
Western Gulf by Saturday with rainfall chances increasing for
portions of southern Texas by the weekend.

...Guidance/Predictability Assessment...

The 00Z model guidance suite indicates good overall synoptic scale
agreement across the Continental U.S. going into the weekend, and
better agreement on the massive upper ridge building over the West
Coast, likely reaching 600dm. The guidance suggests this ridge
should slowly move east over the southern Intermountain West by
next Tuesday/Wednesday. Meanwhile, a general trough axis situated
over the north-central U.S. should be anchored in place by another
ridge axis over the western Atlantic Ocean, with a somewhat blocky
pattern developing. A general deterministic model blend sufficed
as a good starting point in the forecast process for
the weekend, and then increased the ensemble means to about 40% by
next Tuesday/Wednesday.

The latest forecast from the National Hurricane Center has
Hurricane Beryl reaching the Yucatan Peninsula around Friday
morning, and then emerging over the Bay of Campeche by Saturday,
followed by more of a northwestward turn. There remains a split in
the guidance as the storm approaches the Mexico/Texas coast, with
the GFS/GEFS mean to the north, and the ECMWF/UKMET farther south,
and the CMC a middle ground solution. The trough over the Central
U.S. will be a big factor in determining the eventual track.
Beryl`s track will continue to be closely monitored over the next
several days, and the NHC has additional information pertaining to
this.


...Weather/Hazards Highlights...

On Saturday, there is enough of a model signal to maintain the
Marginal Risk area for portions of the Mid-Atlantic, where some
strong thunderstorms with heavy rain rates could develop quickly in
the vicinity of the cold front with its forward motion slowing
down. This is also extended to the north to include parts of New
England where some heavy downpours will also be possible. Some of
the outer rain bands of Beryl could be approaching southern Texas
by late Saturday and into early Sunday, but the intensity and
location of Beryl will likely keep the heaviest rainfall just off
the coast.

Going into the Day 5 period Sunday, the official NHC track of Beryl
has it getting close to Brownsville, Texas, although there is still
considerable uncertainty in where it could ultimately go. Given the
forecast track, rain and embedded thunderstorms would be increasing
in coverage across Deep South Texas through the day Sunday, with
the potential for 3-6 inch totals by 12Z Monday south of Corpus
Christi. Therefore, a Slight Risk area is planned for the Day 5 ERO
for this area, and a broader Marginal Risk area extending farther
northward along the Texas coast to account for periods of heavy
rainfall with the outer rain bands. Farther to the north across the
Central Plains, a Marginal Risk area is also planned where some MCS
activity may develop in the general vicinity of a surface low and
upper trough.

A major heatwave will be ongoing for the inland lower elevations
of California with widespread 105-115 degree readings likely.
Readings could reach 120 degrees at the hottest locations in the
Desert Southwest. Daily temperatures records may be tied or broken
in many cases. The heat is forecast to expand across inland
portions of Washington, Oregon, and much of the Intermountain West
for the first half of next week, with 100+ degree highs likely for
the lower valley locations. Elsewhere, widespread 90s for highs can
be expected for much of the Southern U.S. and extending eastward to
the East Coast, along with high humidity making it feel 5-10
degrees hotter in many cases.

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
















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