890
FXUS21 KWNC 081915
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 08 2026

SYNOPSIS: Model ensembles continue to favor anomalous mid-level high pressure
across the southern and central Contiguous U.S. (CONUS) and above normal
temperatures across much of the Lower 48, although the risk of extreme heat is
diminishing as we move into the second half of September. An unseasonably cool
Canadian air mass is forecast to move into the northcentral and northeastern
states, providing a taste of early fall weather. A potential surge of moisture
from the Gulf of California may result in heavy precipitation over portions of
the Desert Southwest and Great Basin. Antecedent dryness, combined with little
precipitation favored over the next two weeks supports a Rapid Onset Drought
(ROD) risk for portions of the Central and Southern Plains, Lower and Middle
Mississippi, Ohio and Tennessee Valleys. However, significant precipitation is
predicted to occur over eastern Kansas and southern Missouri during this
two-week period.

HAZARDS

Slight risk of much below normal temperatures for parts of the northcentral and
northeastern CONUS, Wed-Sun, Sep 16-20.

Slight risk of heavy precipitation from the Four Corners region northeastward
into Nebraska, Wed-Fri, Sep 16-18.

Flooding possible for portions of the Desert Southwest and Great Basin.

Rapid Onset Drought (ROD) risk for portions of the Central and Southern Plains
and the Middle and Lower Mississippi, Tennessee, and Ohio Valleys.

DETAILED SUMMARY

FOR FRIDAY SEPTEMBER 11 - TUESDAY SEPTEMBER 15:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR WEDNESDAY SEPTEMBER 16 - TUESDAY SEPTEMBER 22: Dynamical model guidance
remains in good agreement regarding elevated chances for mid-level ridging and
positive 500-hPa height anomalies persisting from the Southwest and the Rocky
Mountain states eastward across the Central and Eastern CONUS early in week-2.
Heights are forecast to rise across the northwestern CONUS as the period
progresses, due to an expanding mid-level ridge centered near Southeast Alaska.
These ridges lend themselves to continued elevated chances for above normal
temperatures for most of the western and southern CONUS. The model ensembles
forecast falling mid-tropospheric heights and surface temperatures over a broad
region that encompasses the area (approximately) from the Northern High Plains
eastward to the Great Lakes and Northeast. South of this region, support for
extreme heat hazards continues to dwindle. The Probabilistic Extremes Tools
(PETs) show very little potential for maximum temperatures to exceed the 95th
climatological percentile (the favored threshold during shoulder seasons), and
daily ensemble calculated heat indices no longer show much signal above 105F.
However, temperatures are likely to remain well above normal for parts of Texas
and the Gulf Coast region. Those sensitive to heat should continue to exercise
caution.



Early in week-2, an unseasonably cool air mass is predicted to overspread
portions of the northcentral and northeastern CONUS. The GEFS and ECENS PETs
forecast overnight low temperatures near or below 40 deg F for much of these
northern states, with some of the coolest locations approaching freezing.
Therefore, according to these model ensembles, most areas have a greater
likelihood of getting frost rather than a freeze. Much below normal
temperatures are posted across the Dakotas, northern Minnesota, and far
northern portions of New York state and New England, Sep 16-20. Uncalibrated
temperature tools favor slightly milder overnight temperatures. In either case,
outlying areas of frost appear to be more likely than a 32-degree freeze for
most areas.



Model ensembles indicate a mid-level trough near the West Coast early in
week-2. This may combine with enhanced moisture from the Gulf of California due
to tropical activity over the Eastern Pacific to generate heavy precipitation
over the Four Corners region. Uncalibrated probabilities from the GEFS and
ECENS both indicate at least a 20% chance of 3-day precipitation totals to
exceed half an inch (with little signal for 1-inch) over the region into the
middle of the forecast period. Similarly, both model PETs (especially the
ECENS) indicate at least a 20% chance of 3-day precipitation to exceed the 85th
climatological percentile for days 8-10 (Sep 16-18). Therefore, a slight risk
of heavy precipitation is posted for Sep 16-18 across most of the Four Corners
region, spreading northeastward into Nebraska. Additionally, given the
continued indications of potential heavy precipitation, a flooding possible
hazard remains posted for portions of the Four Corners region during the week-2
period. This region is prone to flash flooding and caution should be exercised
near canyons and creek beds, and additional rainfall may hamper recovery
efforts from recent flooding in the Grand Canyon.



A Rapid Onset Drought (ROD) risk remains designated for parts of the Southern
Plains and Lower Mississippi Valley and adjacent portions of the Central
Plains, Ohio, Tennessee and Middle Mississippi Valleys, and Southeast U.S. This
area has seen 20-40% of normal precipitation and deficits of 1-2 inches over
the past 30 days. Above normal temperatures are forecast for this region over
the next two weeks increasing evapotranspiration rates into the third week of
September. The best chance for any significant precipitation is across southern
Missouri and eastern Kansas near a mean baroclinic zone.

FORECASTER: Anthony Artusa

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