346
FXUS02 KWBC 060634
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
234 AM EDT Sun Jul 6 2025

Valid 12Z Wed Jul 09 2025 - 12Z Sun Jul 13 2025

...Hazardous heat and humidity continues for parts of the East
while the heat builds over the West...


...Pattern Overview...

The large scale pattern will transition from being quasi-zonal to
having an upper ridge over of the West/Southwest with troughing
into the Northeast. This change will limit monsoonal flow to the
Southwest while bolstering widespread heat. A low pressure system
will advance through the northern/central states toward the
Northeast and will be the focus for scattered showers and
thunderstorms.


...Guidance/Predictability Assessment

The latest guidance has above average confidence for hazardous
heat with the upper ridge building over the west and for multiple
impulses to track through the flow as troughing setups up over the
Northeast. The main feature tracking from the eastern Pacific to
the Northeast remains faster with the GFS/GEFS mean whereas the CMC
is deeper with the closed low/trough exiting the Dakotas. The
spread was still acceptable however weighting of those solutions
were reduced later in the extended period. WPC utilized a
combination of the OOZ ECMWF/GFS/Canadian/UKMET/ECMWF ensemble
mean/GEFS mean, continuity and the NBM.

...Weather/Hazards Highlights...

Showers and thunderstorms are expected to be focused in proximity
to progressive cold fronts, stalled boundaries and round the upper
high in the Southern Rockies. The wavy front into the eastern U.S.
may be a focus for heavier rain and thunderstorms. This includes
areas from the Corn Belt into the Midwest and Ohio Valley,
Appalachians, Mid-Atlantic, and Northeast. There are Marginal Risks
in place (level 1 of 4) for the Central Plains/Midwest for Day 4,
for the parts of the Dakota/Upper Mississippi Valley on Day 5 and
for portions of the Mid-Atlantic/coastal Carolinas for Day 4/5 for
an axis of heavier rainfall possible south of a frontal boundary.

Many locations will have daily maximums climbing well into the
100s at lower elevations across the Southwest, which will greatly
limit rain except for perhaps far southeastern Arizona into New
Mexico early in the week. Experimental HeatRisk values may rise to
Major or Extreme levels (3 out of 4 or 4 out of 4) from the
California deserts into southern Nevada, Utah, and Arizona. Extreme
Heat Watches have been raised for parts of Arizona through at least
Thursday.


Campbell

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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