371 
FXUS21 KWNC 041727
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 04 2026

SYNOPSIS: Strengthening mid-level high pressure over the Four Corners occurring 
near the peak of summer brings the risk of extreme heat for much of the 
western, central, and southeastern Contiguous U.S. (CONUS) throughout week-2.

HAZARDS

Moderate risk of extreme heat for much of the Great Basin, Desert Southwest, 
and Southern Plains, as well as portions of the Lower Mississippi Valley and 
Central Plains, Sun-Wed, Jul 12-15.

Slight risk of extreme heat for much of the western and central CONUS, as well 
as the Gulf Coast, southern Georgia, and the eastern Carolinas, Sun-Sat, Jul 
12-18.

DETAILED SUMMARY

FOR TUESDAY JULY 07 - SATURDAY JULY 11: 
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR SUNDAY JULY 12 - SATURDAY JULY 18: Multiple model ensembles depict 
anomalous mid-level ridging building quickly over the Four Corners early in 
week-2, with 500-hPa heights reaching a maximum near 600-dm by day-10 (Jul 13) 
with a closed 594-dm contour covering most of the southwestern CONUS and 
remaining quite amplified through the end of week-2. This pattern is highly 
favorable for above-normal temperatures across the Lower 48, and when occurring 
near the peak of summer brings a widespread risk of extreme heat, particularly 
for the western CONUS. Generally southerly flow off the Gulf of America is 
favored to boost dewpoints across the Plains and eastern U.S., resulting in 
potentially hazardous heat index values for most of the rest of the country. 
Above-normal temperatures are also favored for the Great Lakes, Ohio Valley, 
and Northeast U.S., but a weak yet persistent trough depicted over Hudson Bay 
is likely to keep maximum temperatures and heat indices below hazardous 
criteria for these areas.



The potential for extreme heat is supported by a variety of forecast tools. The 
Probabilistic Extremes Tools (PETs) from the GEFS and ECMWF both indicate a 40% 
chance of maximum temperatures to exceed the 85th climatological percentile for 
portions of the Great Basin early in week-2 and at least a 20% chance for all 
but the northeastern portion of the CONUS throughout the forecast period. The 
GEFS is more bullish, initially indicating a 60% chance over the Great Basin, 
and generally larger coverage of 40% chances through the middle of week-2. The 
uncalibrated extreme heat tool shows widespread 60% or greater chances of 
either maximum temperature or heat index to exceed the 95th percentile at some 
point during the week-2 period, as well as heat wave onset to occur early in 
week-2 and have a duration lasting at least 3 days. Going with best model 
consensus, a moderate risk of extreme heat is posted for much of the Great 
Basin, Desert Southwest, and Southern Plains, as well as portions of the Lower 
Mississippi Valley and Central Plains, valid Jul 12-15. A slight risk of 
extreme heat is also posted for all but northernmost portions of the Great 
Plains, as well as the Middle Mississippi Valley, the Gulf Coast, southern 
Georgia, and the eastern Carolinas covering all of week-2.



The intense heat over the Desert Southwest is likely to induce the development 
of a surface thermal low pressure, kicking off the southwestern monsoon season. 
Dynamical models are depicting the potential initiation of monsoon convection 
later in week-2, although there is significant disagreement with regard to 
timing and intensity of any emerging monsoon activity so no associated hazards 
are issued at this time. Nonetheless, isolated heavy rainfall is possible 
across the southern Great Basin and this region is prone to flash flooding with 
relatively small precipitation accumulations. Monsoonal thunderstorms can also 
produce dry lightning, resulting in increased wildfire risk.

FORECASTER: Danny Barandiaran 

$$