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FXUS02 KWBC 040654
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
254 AM EDT Thu Jul 4 2024

Valid 12Z Sun Jul 07 2024 - 12Z Thu Jul 11 2024

***Major heatwave continues for the lower elevations of California
 and the Desert Southwest into next week, and Beryl approaches
 southern Texas Sunday into Monday***

...Overview...

An intense and prolonged heatwave is forecast to impact much of
California and extending into the lower elevations of the Desert
Southwest through the middle of next week, and also extending into
the Intermountain West. Meanwhile, the track and intensity of
tropical cyclone Beryl will bear close watching as it will likely
track close to or over southern Texas by late Sunday into Monday.
Meanwhile, a quasi-stationary front across the eastern U.S. will
serve as a focusing mechanism for showers and storms south of the
boundary across the Deep South and Southeast/Mid-Atlantic region,
and this will be ahead of an upper level trough that is expected to
build across the Northern Plains and Upper Midwest. Hot and humid
conditions will also continue for much of the southern states and
extending to the East Coast.

...Guidance/Predictability Assessment...

The 00Z model guidance suite indicates very 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. The guidance suggests this ridge should slowly move
east over the southern Intermountain West by next Tuesday and
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
Wednesday/Thursday.

The latest forecast from the National Hurricane Center has tropical
cyclone Beryl tracking across the western Gulf of Mexico, and
making landfall just south of Brownsville, Texas Sunday night. The
GFS guidance remains on the northern side of the track, and the
UKMET/ECMWF/CMC near or just south of the track. It is interesting
to note recent runs of the ICON and JMA models take the storm
farther east and affect the central and eastern coast of Texas, but
these solutions are not currently favored. The QPF for Beryl
during the Sunday-early Tuesday time period was primarily derived
from 40% ECMWF/20% ECENS/20% CMC/20% previous WPC. 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...

Going into the Day 4 period Sunday, the official NHC track of
Beryl has it making landfall just to the south of Brownsville,
Texas, and a slower forward motion. Given this forecast track,
rain and embedded thunderstorms would be increasing in coverage
across Deep South Texas through the day Sunday into Sunday night,
with the potential for some 3+ inch totals by 12Z Monday south of
Corpus Christi. Therefore, a Slight Risk area is maintained for the
Day 4 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 Slight Risk area is also
maintained for central Oklahoma into southern Kansas, with
increasing model support for development of some MCS activity
northeast of a surface low and and upper trough.

Heavy rainfall concerns continue going into Monday across the Lower
Rio Grande area of Texas as Beryl moves farther inland and weakens.
There is still some notable model differences regarding the
placement of the higher QPF, but given forecast heavy rain the day
prior and the NHC track, a Slight Risk is planned for the new Day
5 ERO for portions of Deep South Texas and extending farther
inland. This is subject to change as the forecast track becomes
more certain and the models get a better handle on the situation. A
separate Marginal Risk is also planned for Day 5 near the Red
River Valley of TX/OK and into Arkansas and Missouri for additional
MCS activity. Scattered showers and storms are likely to persist
across much of the Gulf Coast, Deep South, and the East Coast
states going into the middle of next week with a moist and unstable
airmass remaining in place.

Major heat will continue to make weather headlines for the West
Coast states, with 100+ degree high temperatures extending to
northern Washington for the entire forecast period. Highs will
likely reach the 110s for the lower elevations of inland
California, southern Nevada, and southern Arizona, with some 120s
possible for the normally hotter locations. Some of this extreme
heat will likely expand eastward to include much of the
Intermountain West, including Utah and Idaho where some triple
digits readings are expected. Numerous daily records are likely to
be established during this prolonged and dangerous heat event, with
major to extreme heat stress conditions. Even Wyoming and Montana
get above average temperatures by next Wednesday/Thursday as the
upper ridge slowly moves inland across the Rockies. Elsewhere,
seasonal levels of heat and humidity can be expected most days for
the southern and eastern parts of the country, although there will
likely be some days that reach heat advisory criteria in some
areas.

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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