007
FXUS02 KWNH 010658
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EDT Mon Jul 1 2024

Valid 12Z Thu Jul 4 2024 - 12Z Mon Jul 8 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...

Multiple shortwave passages across the northern tier of the nation
will fuel scattered to numerous showers and storms for the middle
to end of the week, particularly 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 00Z guidance has a good overall depiction of the synoptic scale
pattern for the end of the week, with improvement in the models
with respect to the Western U.S. and the evolution of the upper
ridge near the West Coast. The CMC is displaced some to the east
with the ridge axis and farther inland compared to the model
consensus. The updated 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 half by
Day 7/Monday.

Hurricane Beryl is forecast to reach the Bay of Campeche by Friday
evening based on the latest NHC track. The best model clustering,
along with the ML guidance, shows Beryl being steered into
northeastern Mexico next weekend. But there is some guidance that
curves the system farther north into southern Texas, including the
00Z CMC that seemed to be a faster and northern outlier, and the
12Z JMA from yesterday, but those solutions are not currently
favored. 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,
with potential Slight Risk areas in future updates as the details
become more evident. Farther north, 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. Good support for lift should be present there
with an incoming shortwave, but with less anomalous moisture
compared to areas farther south. 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. Above normal
temperatures by 10-20 degrees should stretch into Oregon and
Washington late week into next weekend as well.

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






$$