122
FXUS21 KWNC 181841
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 18 2026

SYNOPSIS: A developing area of mid-level low pressure over the eastern U.S. and
potentially stalled frontal activity over the Gulf and western Atlantic
increases the risk of heavy precipitation for portions of Florida. Enhanced
atmospheric moisture associated with tropical activity in the eastern Pacific
supports a heavy precipitation risk over the Four Corners later next week, with
a lingering threat of heavy precipitation with possible flooding in the region
early in week-2.

HAZARDS

Slight risk of heavy precipitation for portions of the Southeast, Sat-Fri, Sep
26-Oct 2.

Slight risk of heavy precipitation for parts of the Southwest, southern
Rockies, and Southern High Plains, Sat, Sep 26.

Flooding possible for portions of the Four Corners region.

DETAILED SUMMARY

FOR MONDAY SEPTEMBER 21 - FRIDAY SEPTEMBER 25:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR SATURDAY SEPTEMBER 26 - FRIDAY OCTOBER 02: Towards the end of next week and
into the following weekend, dynamical models remain in general agreement
featuring strong mid-level ridging overspreading much of central North America,
bookended by a pair of troughs over the eastern Pacific and eastern U.S. As the
western mean trough weakens, the troughing over the eastern U.S. remains
favored to become more amplified with its axis deepening along the Eastern
Seaboard early in week-2. As a result, cooler and drier conditions are expected
for much of the eastern CONUS downstream of the ridge axis, with more unsettled
weather ahead of the trough axis. Relative to yesterday, the ECMWF and GEFS
ensembles depict a deeper trough and a more southeastern positioned mean
frontal boundary, which looks to push the highest precipitation amounts further
offshore across the Gulf and western Atlantic. However, as the anomalous ridge
center upstream progresses to the east of the Hudson Bay later in week-2,
ensembles show the anomalous troughing retrograding over the Southeast,
potentially bringing a renewed risk of heavy precipitation for coastal parts of
the Gulf and lower Eastern Seaboard later in September. Upstream, rising
mid-level heights over the southwestern CONUS supports the development of drier
conditions over the Four Corners, however multiple tools continue to show a
lingering likelihood for enhanced moisture advection and locally heavy
precipitation.



Even with the mean frontal boundary favored further south early in week-2,
there continues to be an increased risk of heavy precipitation. Both the GEFS
and ECMWF Probabilistic Extreme Tools (PETs) show at least 20% chances of 3-day
amounts exceeding the 85th percentile and 1 inch mainly across the Florida
peninsula. Based on daily mean surface analyses in the ensembles, the boundary
is favored to stall, but looks to possibly retreat northward across the Gulf
where surface low development remains possible along the boundary later in the
period. This is supported by the aforementioned retrogression of the troughing
aloft, and increasing precipitation amounts over the eastern Gulf, Florida, and
the western Atlantic in the tools. Therefore, a slight risk of heavy
precipitation remains posted with its coverage now mainly limited to Florida
and remains valid for all of week-2 to capture the persistence of frontal
activity.  Based on the PETs, periods of elevated winds are possible early in
week-2, however wind speeds look to remain below hazard criteria onshore.  Due
to antecedent dryness and drought conditions being registered within the
highlighted slight risk area, any enhanced precipitation may prove to be
beneficial in alleviating dry soils, though local, urban flooding is also
possible should any heavy precipitation be realized. The heavy precipitation
risk is also supported by observed Sea Surface Temperatures (SSTs) and
precipitable water analyses which are currently registering in the highest
climatological percentiles within the Gulf. Should any surface low develop,
there is also the potential for the low to acquire tropical characteristics
during the period.



Upstream, a slight risk of heavy precipitation remains posted over the Four
Corners and into parts of the High Plains and remains valid Sep 26 based on
enhanced precipitable water content that is favored to persist into week-2.
There is better model support for the bulk of the enhanced atmospheric moisture
contributing from favored TC activity in the Eastern Pacific. The National
Hurricane Center (NHC) continues to monitor an area located to the south of
Mexico with 80% chances of formation during the next week (as of 11am PDT),
where ensembles generally favor the disturbance taking more of a northward
track near the Gulf of California supportive of a surge event later next week.
Given the continued indications of potentially heavy precipitation throughout
the Four Corners during the next week or so, a flooding possible hazard remains
posted. Due to the highest week-1 rainfall accumulations becoming more focused
over the eastern Four Corners with amounts exceeding 2-3 inches in many areas,
the flooding possible coverage is adjusted to remove (include) parts of Arizona
and Utah (New Mexico). This region is prone to flash flooding and caution
should be exercised near canyons and creek beds.



As much of the enhanced atmospheric moisture shifts northward along the western
periphery of the ridge axis, PETs have grown wetter across the higher
elevations of the West and the Northern Plains with 20-30% chances of 3-day
amounts exceeding the 85th percentile. However, tools depict low daily amounts
with low chances for 3-day totals exceeding an inch, precluding any additional
precipitation related hazards.



Underneath the amplified ridge axis favored, above-normal temperatures are
predominately favored for much of the CONUS with the strongest temperature
anomalies featured over many parts of the Interior West, Great Plains, and
Mississippi Valley. Although daytime temperatures look to fall in the highest
climatological percentiles based on the PETs, no corresponding temperature
related hazards are posted. Actual daytime maximums are expected to remain
below hazard criteria due to decreasing sun angles in the autumn, as the
anomalously warm temperatures are also not anticipated to adversely impact
ground conditions.



Due to above-normal precipitation forecast for much of Alaska, isolated
flooding is possible across parts of the western and central Mainland where
many areas have consistently registered above-normal since this summer. More
mid-level troughing is also favored to develop across the northeastern Pacific
later in week-2, promoting more surface low development in the Gulf of Alaska.
While there is some support in the GEFS PET for 3-day amounts exceeding the
85th percentile with pockets in the southern Mainland and Southeast exceeding 3
inches, the ECMWF features a considerably drier solution, and no precipitation
related hazards are issued.



In addition to the aforementioned watch area for TC development in the eastern
Pacific, the NHC is also monitoring a pair of low pressure areas with 80% and
40% chances of development during the next week. The latter, lower likelihood
watch area is located in the Central Pacific and is associated with the
remnants of Tropical Depression 15. Any additional precipitation related to
this disturbance nearing Hawaii may worsen already saturated grounds, following
the impacts associated with TCs Lowell, Moke, and Lala this season.

FORECASTER: Nick Novella

$$