401
FXUS02 KWBC 050700
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Fri Jul 5 2024

Valid 12Z Mon Jul 08 2024 - 12Z Fri Jul 12 2024


...Beryl likely to affect Texas early next week...

...Dangerous heat wave in the West persists into next week...


...Overview...

What is currently Hurricane Beryl is forecast to move into far
northern Mexico or southern Texas around the time the medium range
period begins on Monday, with windy conditions and heavy rainfall.
Moisture from Beryl may linger in Texas into midweek as it could
interact with a frontal system ahead of an upper-level trough. This
trough will gradually move eastward through the period, with
scattered storms across the eastern half of the U.S. at times.
Meanwhile, a persistent upper ridge over the western U.S. will
continue to cause a dangerous and likely record-setting heat wave
in much of the West into next week. Hot and humid conditions will
also continue for much of the southern states and extending to the
East Coast.


...Guidance/Predictability Assessment...

Early in the medium range period, model guidance is fairly
agreeable with the synoptic pattern, so the main concern is Beryl`s
track. 12/18Z operational models generally showed Beryl`s center
moving inland just south of Texas into far northern Mexico early
Monday. However, AI/machine learning (ML) models have been denoting
a landfall point a bit north into South Texas. Now the later-
arriving 00Z ECMWF and especially the 00Z GFS show a northward
trend compared to the previous model cycle. Then uncertainty builds
with the possible interaction with a digging frontal boundary into
the Plains, helping to recurve the system further into Texas or
alternatively, the system stays south along the Mexico/U.S. border
before dissipating. Now that the 00Z ECMWF has come in with more
recurvature, the latter is looking less likely. The variety in
Beryl`s track creates plenty of variability in the QPF footprint as
well. See NHC for the official track forecasts for Beryl.

Farther north, models are agreeable with the pattern of an upper
high atop California shifting gradually east into the Central Great
Basin/Four Corners with time, while the troughing across the
central U.S. early week lifts north while moving eastward as the
week progresses. The most uncertain aspect of the northern stream
is when/how shortwaves move into British Columbia mid- to late
week, affecting the pattern in the northwestern U.S. and northern
tier. Details for those systems will have to be refined in future
cycles.

The WPC forecast used a multi-model blend favoring the 18Z GFS and
12Z ECMWF and CMC early in the period. Included the GEFS and EC
means in the blend from Day 5 onward, ramping up the ensemble
means` percentage to half by Day 6 and more Day 7 as model spread
increased.


...Weather/Hazards Highlights...

Beryl is likely to produce several inches of rainfall in South
Texas during the first half of next week. As such, Slight Risks are
in place in the Day 4-5 EROs for Monday and Tuesday. Monday`s
Slight Risk is considered a higher-end Slight where Beryl tracks.
On Tuesday, there is more model spread and thus lower confidence in
how Beryl may interact with an approaching frontal boundary
farther north into central/east-central Texas, but potential exists
for organized convection capable of producing heavy rainfall. The
broad Slight Risk delineated for now on Day 5 may be able to be
refined with time. There is certainly potential for upgrades to
Moderate Risks in future updates if placement of higher totals
comes into better agreement. This front and moisture could linger
into midweek.

Scattered thunderstorms are likely across the Gulf Coast states
through much of next week given a moist and unstable airmass in
place. Farther north, the upper trough pushing one or more cold
fronts through the north-central to northeastern U.S. also will
lead to some storms, with the bulk of the activity moving east with
time from the Midwest/Great Lakes Monday toward the eastern U.S.
Tuesday-Thursday. Some focus of the convective rain and sufficient
instability for heavy rain rates in much of New York and
Pennsylvania have prompted a Marginal Risk in the ERO for Day
5/Tuesday. Meanwhile, by Tuesday and beyond, some moisture may feed
into the Four Corners states in a monsoonal pattern, and have a
Marginal Risk in place for Day 5/Tuesday mainly for New Mexico,
especially considering sensitivities due to burn scars and areas
that have seen ample rainfall recently.

The West will continue to see a major to extreme and long-lived
heat wave into next week. Highs exceeding 110F should be widespread
in the Desert Southwest, with typically hotter locations exceeding
120F. Farther north, highs into the 100s are forecast into Oregon
and Washington and east into the Intermountain West, as
temperatures soar 10-20F above normal with locally higher
anomalies. Numerous daily records are likely to be broken during
this heat wave, with monthly records not out of the question. The
prolonged nature of the heat wave and record warm overnight
temperatures will increase heat stress. Meanwhile, warmer than
average temperatures in the Northeast early in the week should
moderate by midweek. The Southeast should see near normal heat for
this time of year--which is still hot and humid. The south-central
U.S. should see some minor heat relief with below average
temperatures given the clouds and rain chances.


Tate


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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