258
FXUS21 KWNC 031806
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 03 2025

SYNOPSIS: An increased risk for extreme heat is forecast across the West at the
beginning of week-2, but chances decrease later in the outlook period as the
mid-level ridge of high pressure weakens. Only a slight risk of heavy
precipitation is posted for southeastern Arizona and southwestern New Mexico
due to diverging model solutions. On July 11 and 12, a slow-moving front is
forecast to be the focus for thunderstorms with locally heavy rainfall from the
Mid-Atlantic west to the Tennessee Valley.

HAZARDS

Moderate risk of extreme heat for the San Joaquin Valley of California, Fri,
Jul 11.

Slight risk of extreme heat for parts of the West, Fri-Sat, Jul 11-12.

Slight risk of heavy precipitation for southeastern Arizona and southwestern
New Mexico, Fri-Thu, Jul 11-17.

Slight risk of heavy precipitation for parts of the eastern U.S., Fri-Sat, Jul
11-12.

DETAILED SUMMARY

FOR SUNDAY JULY 06 - THURSDAY JULY 10:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY JULY 11 - THURSDAY JULY 17: The GEFS and ECENS depict a 500-hPa
ridge strengthening over the West during the early to middle part of next week.
These ensemble mean solutions remain consistent that this ridge peaks in
strength on day 7 (July 10) when 500-hPa heights reach 597-dam across southern
California and the Southwest. Thereafter, a shortwave trough is expected to
move inland from the northeastern Pacific and suppress the longwave ridge over
the West. A moderate risk of extreme heat, valid July 11, is only posted for
the San Joaquin Valley where the GEFS and ECMWF Probabilistic Extremes Tools
(PETs) have near a 40 percent chance of maximum temperatures exceeding the 85th
percentile and 100 degrees F. The moderate risk was discontinued for the Desert
Southwest due to slightly lower 500-hPa heights among the ensemble means by
July 11 and less than a 40 percent chance that maximum temperatures reach 110
degrees F according to the PETs. Although above-normal temperatures are likely
to persist throughout much of the West through the end of week-2, a slight risk
of extreme heat is valid only through July 12 as chances that maximum
temperatures reach extreme heat thresholds decrease to below 20 percent. The
anomalous warmth during mid-July would lead to the additional drying of fuels
and elevate the wildfire danger across the interior Pacific Northwest and
northern Intermountain West.



Following Hurricane Flossie in the East Pacific, the National Hurricane Center
states that there is a 80 percent chance of another tropical cyclone (TC)
forming in the East Pacific during the next week. Many of the GEFS ensemble
members have this potential TC taking a northwest track which could eventually
lead to a surge of enhanced low to mid-level moisture northward from the Gulf
of California into the Desert Southwest. However, the ECENS ensemble members
are generally weaker with any TC that develops and favor a more westward track
with enhanced moisture less likely to reach the Desert Southwest. Based on the
wetter GEFS PET and also its more favorable 500-hPa ridge axis closer to the
Four Corners, a slight risk of heavy precipitation is posted for parts of
Arizona and New Mexico for all of week-2.



A slow-moving front is forecast to be the focus for thunderstorms with locally
heavy rainfall across the parts of the Mid-Atlantic, Southeast, and Tennessee
Valley. The spatial extent of the slight risk of heavy precipitation, valid on
July 11 and 12, is generally based on where there are enhanced 24-hour rainfall
amounts from the GEFS and ECENS. Beyond the early part of week-2, any diurnal
convection is expected to become more scattered across the eastern U.S. which
precludes the continuation of the slight risk past July 12.



An amplified 500-hPa trough is forecast to become established over Alaska by
the beginning of week-2. This anomalous trough favors much cooler temperatures
and above-normal precipitation across much of Alaska. Unseasonably cold
temperatures and even snow may affect the Brooks Range and North Slope later
next week.

FORECASTER: Brad Pugh

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