646
FXUS21 KWNC 231812
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 23 2025

SYNOPSIS: There are continued model indications for developing mid-level low
pressure over eastern North America, supporting cooler temperatures and
lowering the risk for extreme heat across many parts of the central and eastern
Contiguous U.S. (CONUS).  Potentially stalled frontal activity favored over the
southeastern CONUS supports an increased risk for heavy precipitation over the
Gulf states and into the mid-Atlantic. Associated with mid-level high (low)
pressure favored over the Great Plains (West Coast), periods of elevated winds
are possible over the western CONUS, as well as heavy precipitation over parts
of the lower Four Corners and Great Plains.

HAZARDS

Slight risk of extreme heat for parts of the Great Plains, Mississippi,
Tennessee and Ohio Valleys, Southeast, and the lower Mid-Atlantic, Thu-Fri, Jul
31-Aug 1.

Slight risk of heavy precipitation for parts of the Lower Mississippi Valley,
Southeast, and Mid-Atlantic, Fri-Mon, Aug 1-4.

Slight risk of heavy precipitation across many parts of the Great Plains and
Mississippi Valley, Thu-Mon, Jul 31-Aug 4.

Slight risk of heavy precipitation for parts of the Desert Southwest, Thu-Mon,
Jul 31-Aug 4.

Slight risk of high winds for many parts of the western CONUS, Thu-Mon, Jul
31-Aug 4.

DETAILED SUMMARY

FOR SATURDAY JULY 26 - WEDNESDAY JULY 30:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY JULY 31 - WEDNESDAY AUGUST 06: Over the past few days, dynamical
models continue to advertise a strengthening 500-hPa anomalous ridge center
over central Canada, with more amplified troughing downstream over southeastern
Canada and into the northeastern CONUS. The prevailing northwesterly flow tied
to this trending mid-level pattern is expected to bring cooler summertime
temperatures, and likely keep any widespread extreme heat risks at bay over
many parts of the central and eastern CONUS later next week and into the first
weekend of August. One exception remains the southcentral and southeastern
CONUS where both raw and calibrated temperature tools maintain elevated odds
for above normal temperatures early in the period.  However, the latest ECMWF
and GEFS Probabilistic Extremes Tools (PETs) differ on the location of greatest
heat signals, with the former (latter) favoring a more easterly (westerly)
solution across the southern tier. Given uncertainty associated with the extent
of the mean surface high pressure behind an advancing frontal boundary over
this part of the country, a moderate risk of extreme heat is discontinued in
the updated outlook.  However, a slight risk remains posted and valid through
Aug 1 where PETs show at least 20% chances for daytime temperatures exceeding
the 85th percentile, as temperatures could be slow to moderate.  Later in the
period, there is model support in the ensembles for anomalous ridging
redeveloping across the Interior West. The GEFS indicates a modest warming
response in its PET, though the ECMWF remains largely free of any heat signals
beyond day 10 (Aug 2) throughout the CONUS. As a result, no additional
temperature hazards are included in the outlook, but the potential for renewed
heat will continue to be monitored this week.



Tied to the aforementioned frontal boundary, raw model guidance suggests that
this surface feature may stall over the southeastern CONUS and bring repeated
chances for heavy precipitation along for the Gulf States and into the
Mid-Atlantic through the middle of week-2.  The PETs are in fair agreement with
this potential, indicating increased chances for 3-day amounts exceeding the
85th percentile with the highest amounts focused along the coastal Carolinas,
Delmarva region and just offshore. Notably, the uncalibrated ECMWF shows >40%
chances for amounts exceeding an inch, supportive of a moderate risk
designation for heavy precipitation. However, in deference to the drier GEFS, a
slight risk remains issued (Aug 1-4) and is expanded westward to include the
central and eastern Gulf states in the outlook.  Consistent with recent
rainfall events with this synoptic setup, additional surface low formation
remains possible along a stalled frontal boundary, which could gain tropical
characteristics should any development occur offshore. Probabilistic tropical
cyclone genesis tools are weak with this realization, but this potential will
continue to be monitored.



Along the northern periphery of the mean 500-hPa ridge over the central CONUS,
episodic shower and thunderstorm activity may bring locally heavy precipitation
amounts across the Great Plains and parts of the Mississippi Valley. This
potential remains supported in the PETs through the middle of week-2, with
model consistency indicating higher chances for amounts exceeding an inch into
the Central Plains. Therefore, a slight risk of heavy precipitation remains
issued and is expanded southward to include more of the lower Missouri River
basin in the outlook.



Upstream across the West, there is better model support for enhanced onshore
flow with mid-tropspheric moisture overspreading the western CONUS associated
with deeper troughing extending from the eastern Pacific into the West Coast.
This is well reflected in the PETs, which indicate 20-60% chances for 3-day
amounts exceeding the 85th percentile across portions of the Northern
Intermountain, Rockies, and Great Basin, but amounts are not expected to exceed
hazard criteria.  Periods of elevated winds are however a concern at or near
the base of the mean troughing aloft, and a slight risk of high winds is posted
(Jul 31 to Aug 4) for much of the western CONUS where PETs show increased
signals for wind speeds exceeding the 85th percentile. The combination of
elevated wind speeds, low humidity and high temperatures increases the risk for
wildfire activity across parts of the West.



Over the southwestern CONUS, the combination of deeper troughing in the West,
as well as a renewed potential for tropical cyclone activity favored in the
eastern Pacific, supports increased chances for above-normal and possibly heavy
precipitation in the lower Four Corners.  While the GEFS is comparably drier
than the ECMWF, a slight risk of heavy precipitation is issued over parts of
Arizona and New Mexico (Jul -31-Aug 4) based on a wet trend in the tools,
increased chances for 3-day amounts exceeding the 85th percentile, along with
higher chances for elevated dewpoint temperatures in the Desert Southwest.



No hazards are issued over Alaska. Although amplified troughing is favored over
the Gulf of Alaska to promote increased winds and enhanced precipitation
amounts over the Southeast, tools indicate amounts remaining below hazard
thresholds.

FORECASTER: Nick Novella

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