535
FXUS21 KWNC 261811
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 26 2025

SYNOPSIS: Tied to an active North American monsoon circulation heading into
July, as well as a potential influx of tropical moisture from the eastern
Pacific, there are elevated chances for above-normal and locally heavy
precipitation over the southwestern contiguous U.S. (CONUS). Any heavy
precipitation may trigger localized flooding and exacerbate saturated ground
conditions across the lower Four Corners during week-2. Mid-level high pressure
favored over the Gulf of America is expected to bring above-normal summertime
temperatures with possible extreme heat conditions for portions of the
south-central CONUS during the period.

HAZARDS

Moderate risk of heavy precipitation for parts of the Desert Southwest, Fri,
Jul 4.

Slight risk of heavy precipitation for parts of the Desert Southwest, Rockies,
and Great Basin, Fri-Thu, Jul 4-10.

Slight risk of extreme heat over parts of the Southern Plains and Lower
Mississippi Valley, Sat-Tue, Jul 5-8.

Slight risk of high winds along most of the immediate West Coast, Fri-Tue, Jul
4-8.

Flooding possible over portions of Arizona and New Mexico.

DETAILED SUMMARY

FOR SUNDAY JUNE 29 - THURSDAY JULY 03:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY JULY 04 - THURSDAY JULY 10: By late next week, dynamical models
continue to advertise a weakness in subtropical ridging over the southwestern
CONUS and western Mexico. Based on the orientation of the mid-level ridge axis
and the 700-hPa flow pattern, a healthy North American monsoon circulation
remains favored heading into July, where there continues to be elevated chances
for above-normal and potentially heavy precipitation affecting the southwestern
CONUS. Moreover, added tropical moisture from the eastern Pacific is also
expected to be a key player, as guidance continues to favor Gulf Surge activity
in the Desert Southwest associated with the passage of a tropical low (Invest
95E) near the Gulf of California. The National Hurricane Center continues to
favor high chances (80%) of formation with this disturbance in the next seven
days. The advection of additional tropospheric moisture is supported by the
confluence of positive precipitable water anomalies over the Four Corners, as
well as in the raw and calibrated precipitation tools, with some of the highest
totals beginning to time off into week-1. This is reflected in the GEFS and
ECMWF Probabilistic Extremes Tools (PETs) which indicate a slight reduction of
the wet signals for days 8 through 10 (Jul 4-6) over the southwestern CONUS
compared to yesterday. As a result, the high risk of heavy precipitation is
discontinued in today`s outlook, however a corresponding moderate risk area
remains posted and valid for Jul 4, where there are 30-60% chances for amounts
exceeding the 85th percentile in the PETs, with 20-30% chances for amounts
exceeding a half an inch in the uncalibrated ECMWF early in week-2. A broader
slight risk area for heavy precipitation also remains issued for the entirety
of week-2 based on favored persistence of enhanced moisture in the region,
which could trigger additional thunderstorm activity and locally heavy rainfall
later in the 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 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 impacts, some areas experiencing moderate to exceptional
drought conditions and wildfires will benefit from the enhanced rainfall.



As much of the enhanced tropospheric moisture looks to overspread the Interior
West and enter the Great Plains, there is also the potential for increased and
possibly heavy precipitation for the central CONUS. The ECMWF favors surface
low formation in the lee of the Rockies, with increased chances for 3-day
amounts exceeding the 85th percentile and 1 inch from the Central Plains to the
Great Lakes early in week-2. However, the GEFS and Canadian are absent of this
synoptic forcing, with little to no support for heavy precipitation in their
raw or calibrated tools. As a result of these differences, no corresponding
precipitation hazard is issued but this potential will continue to be
monitored. Across the southeastern CONUS, models depict the passage of a
frontal boundary late in week-1 that looks to stall by early week-2 becoming a
focal point for enhanced precipitation. Since yesterday, both raw and
calibrated tools have become less supportive of a heavy precipitation risk
along the coastal Southeast and Mid-Atlantic, with the highest amounts now
depicted offshore, and the corresponding slight risk of heavy precipitation is
removed in the updated outlook.



Over the northwestern CONUS, much of the 500-hPa ridging predicted late in
week-1 is favored to deamplify by the outset week-2, resulting in a moderation
of summertime temperatures mainly over the Northern Intermountain and Northern
Plains. While the GEFS PET maintains some residual signals for temperatures
exceeding the 85th percentile for this part of the country, the slight risk of
extreme heat is removed in the updated outlook.  Downstream, the GEFS and ECMWF
remain at odds with one another in regards to the evolution of a longwave
trough over eastern Canada, resulting in uncertainty in regards to the
potential for a renewed heat risk mainly across parts of the central and
eastern CONUS. However, both ensembles continue to signal a strengthening of
the subtropical ridge east of the Rockies, where the GEFS and ECWMF PETs
continue to highlight increased chances for maximum daytime temperature
exceeding the 85th percentile over the Southern Plains and Lower Mississippi
Valley. Therefore, a slight risk of extreme heat is posted (Jul 5-8) and is
expanded to include portions of the central Gulf Coast due to increased warm
signals in the ECMWF PET. It is worth noting that sea surface temperatures in
the Gulf of America remain well above average and nearly record breaking for
this time of year, which would reinforce the anomalously warm temperatures
favored across the south-central and southeastern CONUS.



Surface high pressure over the northeastern Pacific adjacent to mean surface
low pressure over the Interior West may lead to tight pressure gradients along
much of the West Coast. This may be enhanced by the aforementioned heat
potential favored early in the period, which would likely lower surface
pressure. As a result, a slight risk of high winds remains posted along most of
the immediate West Coast Jul 4-8 where PETs also indicate increased chances for
wind speeds exceeding the 85th percentile.



Numerous wildfires have developed across Alaska and additional fire activity is
expected to continue with above-normal temperatures predominately favored over
the Mainland during week-2. The smoke generated by these fires is forecast to
meander around the state during the period, following low-level wind currents.
As a result, periods of very poor air quality and low visibility may occur.

FORECASTER: Nick Novella

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