188
FXUS21 KWNC 201913
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 20 2026

SYNOPSIS: Persistent mid-level high pressure is expected to bring an elevated
risk of extreme heat to a large portion of the contiguous U.S. (CONUS) from the
Ohio and Tennessee Valleys and Southeast westward to the West. Hot weather and
near or below normal rainfall bring an increased risk of rapid onset drought to
part of the northern Great Plains. In the West, the monsoonal circulation may
be periodically robust with localized enhanced rainfall, but due to high
uncertainty no associated precipitation hazard is designated at this time. One
or more tropical cyclones might also impact Hawaii, raising the potential for
heavy precipitation and gusty winds. Meanwhile, development of a surface low
east of the Appalachians and associated wavering frontal boundary across the
southeastern CONUS and southern Mid-Atlantic supports a heavy precipitation
risk for these regions until the middle of week-2. A tight pressure gradient
from surface high pressure over the Northeast Pacific and adjacent low pressure
over California may support episodic high winds across coastal parts of
southwest Oregon and northern California.

HAZARDS

Moderate risk of extreme heat for much of the Great Plains and adjacent parts
of the Mississippi Valley, and the Southwest, Tue-Thu, Jul 28-30.

Slight risk of extreme heat for many parts of the Gulf Coast and Florida, Ohio
and Tennessee, and Mississippi Valleys, Great Plains, Central and Southern
Rockies, Great Basin, Southwest, and California Valley, Tue-Mon, Jul 28-Aug 3.

Slight risk of heavy precipitation for the central Gulf Coast, part of the
South Atlantic region, and the eastern Carolinas, Tue-Thu, Jul 28-30.

Slight risk of high winds for coastal portions of southwestern Oregon and
northern California, Tue-Sun, Jul 28-Aug 2.

Rapid onset drought (ROD) possible for part of the northern Great Plains.

DETAILED SUMMARY

FOR THURSDAY JULY 23 - MONDAY JULY 27:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR TUESDAY JULY 28 - MONDAY AUGUST 03: Models continue to be in good agreement
featuring a persistent amplified 500-hPa ridging over the western and central
CONUS and troughing across the northwestern and northeastern regions. Ridging
is generally more amplified across the models compared to yesterday, centered
over the Four Corners region and expanding westward with time. This feature
favors an increased risk of extreme heat across large parts of the western,
central, and southern CONUS. Both northwest and northeast of this broad area,
stagnant mid-level troughs are expected to slowly weaken but remain essentially
stationary through the period, likely keeping extreme heat out of these regions.



Underneath the ridging aloft, an elevated potential for heat risk continues to
be supported by a number of temperature and heat tools across many parts of the
southern, western, and central CONUS. Higher than normal dewpoints are also
favored east of the Rockies due to a long fetch of Gulf moisture near the
surface, increasing dew points and helping to drive up heat index values there.
A moderate risk of extreme heat is posted for Jul 28-30, with coverage expanded
to include more of Arizona and the Great Plains. These adjustments are based
mainly on increased heat signals primarily in the GEFS Probabilistic Extreme
Tool (PET). The ECENS PET probabilities may be lower due to forecast potential
for localized heavy rainfall across the Four Corners due to the Southwest
Monsoon. Deep South Texas and part of the Desert Southwest have significant
chances for heat index values or absolute temperatures to top 110 deg F, but
this is not as unusual there as it is in the locations farther north.
Surrounding the moderate risk area, a large slight risk of extreme heat remains
posted throughout week-2, with slight expansion eastward into parts of the
Great Lakes region and Ohio Valley. Anomalously high SSTs in the waters
adjacent to the Gulf and South Atlantic coasts are expected to contribute to
heat and humidity east of the Rockies. According to the National Blend of
Models (NBM), southern portions of the heat risk area such as the Southwest,
Southern Plains, Lower MIssissippi Valley and Florida may experience near or
record breaking high nighttime temperatures in the upper 70s to low 80s, which
would provide little overnight relief. In general the ECENS PET is not as
robust with the odds for extreme heat compared to the GEFS across the West but
has increased probabilities for heat across the Southern Plains and Lower
Mississippi Valley.



Meanwhile, antecedent dryness, anomalous warmth and dryness during week-1, and
the potential for extreme heat during week-2 support an enhanced risk of Rapid
Onset Drought (ROD) across portions of the Northern Plains. The anticipated
heat is expected to overwhelm any short-lived relief that may occur.



Week-2 is expected to be an active period of tropical activity in the eastern
Pacific. More than one tropical cyclone is expected, and models have
consistently shown at least one of these systems moving far enough toward the
central Pacific to threaten Hawaii with heavy rain and high winds. Please refer
to the National Hurricane Center (NHC) for the latest tropical developments.



Despite the strong mid-level ridge favored across the western CONUS, the
forecast position of the ridge center does not support an extreme advection of
monsoonal moisture into the region, although model forecasts and the PETs today
show slightly higher likelihood than yesterday. In addition, it is possible
that one or more of the tropical cyclones expected in the eastern Pacific could
track northward and contribute to a surge of tropical moisture into the region,
which would significantly enhance rainfall amounts. Raw model output and the
PETs aren`t sufficiently robust to support any slight heavy precipitation risk
from being posted, but with the tools trending wetter and the potential for
tropical moisture incursion, the situation will need to be closely monitored.



Multiple models indicate possible surface low pressure initially over the Ohio
Valley redeveloping east of the Appalachians by the beginning of week-2 with an
associated wavering frontal boundary forming near the central Gulf and South
Atlantic coastal regions in conjunction with the mid-level troughing favored
over the eastern U.S. This pattern supports slight risk of heavy precipitation
to parts of the central Gulf Coast, South Atlantic region, and eastern
Carolinas, Jul 28-30. There is uncertainty about how much rainfall occurs over
the land versus offshore, thus only a slight risk is designated. There is
currently limited threat of flooding across the eastern Carolinas designated
for week-1, thus heavy rainfall could support localized flooding. The ECENS PET
and uncalibrated ensemble output is more favorable of heavy rainfall occurring
over land compared to the GEFS, indicating at least a 20% chance of 3-day
rainfall exceeding the 85th percentile climatologically and one inch.



Across the West, surface high pressure over the northeastern Pacific and
adjacent surface low pressure over California and the Great Basin may support a
tight pressure gradient across parts of the West Coast. Thus a slight risk of
high winds is highlighted for coastal portions of  southwestern Oregon and
northern California, Jul 28-Aug 2.

FORECASTER: Melissa Ou

$$