027
FXUS21 KWNC 301836
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 30 2025

SYNOPSIS: Mid-level high pressure is forecast to strengthen and slowly
retrograde into the western contiguous U.S. (CONUS) during week-2. This
supports an increased risk of extreme heat across portions of the Northwest,
extending southward through the California Central Valley. Extreme heat also
remains a concern across the Southern Plains and Lower Mississippi Valley due
to elevated humidity levels combined with above-normal temperatures. Monsoon
activity remains forecast across the Southwest, further enhanced by continued
tropical cyclone activity across the East Pacific. A slow moving frontal system
favors increased chances of heavy precipitation across portions of the
southeastern U.S. and Mid-Atlantic.

HAZARDS

Slight risk of extreme heat across portions of the Southern Plains and Lower
Mississippi Valley, Tue-Mon, Jul 8-14.

Slight risk of extreme heat across portions of Interior California, the Pacific
Northwest, Great Basin, and Northern Rockies, Tue-Mon, Jul 8-14.

Slight risk of heavy precipitation across portions of the Southwest, Central
and Southern Rockies, and Central Great Basin, Tue-Mon, Jul 8-14.

Slight risk of heavy precipitation across portions of the Lower Mississippi and
Tennessee Valleys, Southern Appalachians, Mid-Atlantic, and Southeast, Tue-Sat,
Jul 8-12.

Flooding possible across portions of Arizona and New Mexico.

DETAILED SUMMARY

FOR THURSDAY JULY 03 - MONDAY JULY 07:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR TUESDAY JULY 08 - MONDAY JULY 14: Mid-level ridging is predicted to amplify
while slowly retrograding into the western CONUS during week-2. The 0z ECENS
continues to depict a 597-dm ridge axis across the Four Corners early in the
period, with +60 meter positive height anomalies extending over much of the
Northwest. The 0z GEFS and CMCE are slightly less amplified compared to the
ECENS but depict the same general evolution. At the surface, this translates to
increasing chances for above-normal temperatures over much of the West. The
initial focus for elevated extreme heat potential is favored across the
Northwest, and then expanding southward through the California Central Valley
by the middle of the period based on the progression of 20 percent or greater
probabilities for temperatures exceeding the 85th climatological percentile in
the GEFS and ECENS Probabilistic Extremes Tools (PETs). A slight risk of
extreme heat is posted across portions of Interior California, the Pacific
Northwest, Great Basin, and Northern Rockies for all of week-2. Predicted
temperatures based on the uncalibrated ECENS and GEFS range from the mid-90s
deg F across the northern Great Basin to possibly above 105 deg F across the
California Central Valley. While even hotter temperatures are possible across
the Desert Southwest, this region is excluded from the slight risk due higher
extreme heat thresholds and additional uncertainty regarding the monsoon
potentially leading to relatively cooler temperatures.



Above-normal temperatures also remain forecast across portions of the Southern
Plains and Lower Mississippi Valley with forecast highs generally in the upper
90s to possibly the low 100s deg F across central Texas. Elevated humidity is
likely to boost heat index values by several degrees further increasing the
risk for extreme heat. The calibrated skill weighted heat tool depicts
probabilities of 20-40 percent for heat index values exceeding the 95th
climatological percentile across the region, with some areas potentially having
heat index values above 110 deg F. As a result of these enhanced signals, the
slight risk for extreme heat is posted for all of week-2 across portions of the
Southern Plains and Lower Mississippi Valley.



An active monsoon pattern remains forecast across the Southwest due to
favorable ridge axis placement across the Four Corners, combined with continued
tropical cyclone activity across the East Pacific. However, the ECENS PET is
much more robust with the precipitation signal compared to its GEFS
counterpart, and therefore, only a slight risk for heavy precipitation is
posted for the entire period. Due to locally heavy precipitation received over
portions of New Mexico, any additional precipitation during week-2 is likely to
worsen saturated ground conditions and possibly trigger additional flooding in
the region. A flooding possible hazard remains issued, and also includes many
parts of Arizona where locally heavy precipitation may also trigger flash
flooding and debris flows near recently burned areas. In addition to flash
flooding, thunderstorm impacts may include lightning, gusty winds and blowing
dust. However, in spite of these potentially adverse but localized impacts,
some areas experiencing moderate to exceptional drought conditions and
wildfires will benefit from the enhanced rainfall.



Across the Ohio Valley and Mid-Atlantic, seasonably warm temperatures are
forecast beginning later in week-1 into the outset of week-2. However, it is
marginal in terms of whether or not extreme heat thresholds will be reached
during this time given that it will be closer to the expected hottest time of
year climatologically. Temperatures are forecast to moderate by the middle of
the period as troughing builds across the East, with the 0z ECENS depicting
negative mid-level height anomalies developing across the Ohio Valley and Great
Lakes during the second half of the period. A slow moving or stalled frontal
system favors elevated chances of heavy precipitation across portions of the
Eastern Seaboard and the Gulf Coast. Both the GEFS and ECENS PETs depict some
areas having at least a 20 percent chance 3-day precipitation totals exceed the
85th climatological percentile and 1-inch early in the period, with the ECENS
PET continuing the elevated chances later into week-2. Therefore, a slight risk
of heavy precipitation is posted across portions of the Lower Mississippi and
Tennessee Valleys, Southern Appalachians, Mid-Atlantic, and Southeast, Jul 8-12.



Shortwave troughing forecast to move across the Gulf of Alaska favors a
breakdown of ridging predicted during week-1. Following very warm temperatures
across northern Alaska in week-1, temperatures are likely to moderate going
into week-2. While above-normal precipitation is favored across much of
southern and eastern Alaska, precipitation amounts are not forecast to reach
hazards thresholds.

FORECASTER: Thomas Collow

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