519
FXUS21 KWNC 191739
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 19 2026

SYNOPSIS: Mid-level high pressure is expected to bring an elevated risk of
extreme heat to a large parts of the southern, central and western contiguous
U.S. (CONUS). Brief weakening is possible, but conditions may reintensify
later, so the potential hazard covers all of week-2. 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, but hazardous rainfall amounts are not expected unless
moisture from a potential tropical cyclone streams in. One or more tropical
cyclones might also impact Hawaii, raising the potential for heavy
precipitation and gusty winds. Meanwhile, a wavering frontal boundary near the
southeastern CONUS supports a heavy precipitation risk there until the middle
of week-2.

HAZARDS

Moderate risk of extreme heat for much of the Great Plains and adjacent parts
of the Mississippi Valley, the southern High Plains, and the Desert Southwest,
Mon-Wed, Jul 27-29.

Slight risk of extreme heat for the southern California Valley, the Southwest,
parts of the Intermountain West, much of the Rockies, the Plains and adjacent
Mississippi Valley, the Gulf Coast, and the adjacent Southeast, Mon-Sun, Jul
27-Aug 2.

Slight risk of heavy precipitation for the central Gulf Coast, part of the
South Atlantic region, and the eastern Carolinas, Mon-Thu, Jul 27-30.

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

DETAILED SUMMARY

FOR WEDNESDAY JULY 22 - SUNDAY JULY 26:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY JULY 27 - SUNDAY AUGUST 02: Heading into the start of week-2, models
are in good agreement featuring an amplified 500-hPa ridging over the Interior
West and High Plains bookended by a pair of mid-level troughs, one over the
northeastern Pacific and the other overspreading much of eastern North America.
Both troughs are a little more persistent than indicated by yesterday`s models,
but still weaken considerably or dissipate by the end of week-2. Over time, the
European ensemble (ECENS), GEFS, and Canadian ensemble (CMCE) means show the
ridge essentially persisting there throughout week-2. The location of maximum
500-hPa heights may drift, and the strength may wax and wane somewhat, but
these changes are expected to be subtle and inherently difficult to specify
during the week-2 period, and the ridge remains relatively amplified throughout
the period. The anomalous ridge is expected to take on a somewhat positive tilt
over the last half of the period, with its axis eventually stretching northward
from the Four Corners toward the Northern Plains. 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 the
northwestern and most of the eastern CONUS.



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 27-29, with coverage expanded
to include more of the northern Lower Mississippi Valley, but trimmed slightly
away from parts of southern New Mexico and the South Atlantic Coast. These
adjustments are based mainly on the expected mid-level pattern evolution and
internal heat index tools, which depict nontrivial chances for heat index
values exceeding 110 deg F as far north as southeastern South Dakota and
adjacent Iowa. The best chances for this extreme heat stretches from southern
Kansas through much of Oklahoma and into adjacent Texas early week-2. Deep
South Texas and part of the Desert Southwest also 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. The moderate risk covers
the first few days of week-2, ending as the evolution of the mid-level ridge
becomes less certain. Surrounding the moderate risk area, a large slight risk
of extreme heat remains posted, although the area was trimmed slightly on the
southeastern and northwestern tiers to account for the slightly stronger and
more persistent mid-level troughs expected to affect these areas. Anomalously
high SSTs in the waters adjacent to the Gulf and South Atlantic coasts are
expected to contribute to heat and humidity there. The ECENS and GEFS
Probabilistic Extreme Tools (PETs) are not as robust with the odds for extreme
heat as might be expected, but are slightly more confident early in the period
than yesterday. Both now display portions of the Plains with a greater than 40
percent chance for high temperatures above the 85th climatological percentile
during the first few days of week-2, although the ECENS remains displaced
slightly farther east. The GEFS PET also shows similar odds for portions of the
Four Corners region. One factor possibly muting the PETs extreme heat
likelihoods is the expected unusually high dew points east of the Rockies. This
would elevate the heat index values, whereas the PETs only reflect actual
temperatures.



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 despite uncertainty
in the precipitation forecast during the 6- to 14-day period (Jul 25-Aug 2).
The anticipated heat is expected to overwhelm any short-lived relief that may
occur.



This 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.



A wavering frontal boundary is likely to set up near the central Gulf and South
Atlantic coastal regions in conjunction with the mid-level troughing favored
over the eastern U.S. This set-up brings a slight risk of heavy precipitation
to parts of the central Gulf Coast, South Atlantic region, and eastern
Carolinas. Ensemble output shows the mean position of this feature to be a
little farther east and south than yesterday, a trend that continued from the
prior day, but most tools indicate the possibility that surface waves of low
pressure along the front could push the front farther west periodically.
Therefore, the slight risk of heavy precipitation is again reduced in scope
relative to yesterday, and is valid Jul 27-30. Continuous heavy precipitation
does not appear likely. The raw ensemble output and a preponderance of the PETs
show slightly increased chances (less than 30 percent) for three-day
precipitation amounts to exceed the 85th climatological percentile and 1 inch
total. Despite the relatively nondescript solutions shown by much of the
guidance, the position and persistence of the quasi-stationary front and
abundant low-level moisture have the potential to induce scattered heavy
rainfall at times.

FORECASTER: Rich Tinker

$$