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FOUS30 KWBC 071913
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Tue Oct 7 2025

Day 1
Valid 16Z Tue Oct 07 2025 - 12Z Wed Oct 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
KENTUCKY, NORTHERN TENNESSEE, THE OHIO VALLEY, AND NEW MEXICO...

...16Z Update...

The slight risk over the Midwest was removed from the Upper Ohio
Valley, in coordination with PBZ. The marginal risk was expanded to
account for lingering potential in eastern Ohio/western PA. The
overall synoptic pattern continues to signal a progressive cold
front pushing through the Upper Ohio Valley/Northeast this evening,
while a slower propagation is expected through the Lower Ohio
Valley. Anomalous, 99th percentile, PWATs are forecast for the
slight risk area this afternoon, with 3" in 24 hours neighborhood
exceedance probabilities between 20-35%.

The risk areas in New Mexico were expanded slightly based on the
latest CAM trends, and the marginal risk over southeastern Florida
was removed in coordination with MFL.

Kebede

...Previous Discussion...

...Mid-South through the Upper Ohio Valley and Central
Appalachians...

A weak mid-level vorticity maxima (currently over far northeastern
Arkansas) will trek east-northeastward across Kentucky through
most of the day. This feature will likely maintain at least some of
its organization given persistent convection near and east of its
center and sufficient downstream instability. Areas of 1-3 inch
rainfall totals are expected with this feature, and an uptick in
convective coverage should occur later today as surface heating
promotes destabilization within a moist airmass downstream of the
feature. Slow cell movement and localized training/backbuilding are
both expected to prompt areas of excessive runoff through the
forecast period especially within the Slight Risk area.

Later today, height falls from a larger scale trough centered over
Hudson Bay will aid in additional convection along a front that
will sweep through the region. Storms may redevelop across Kentucky
and Tennessee, although the degree of coverage will be heavily
modulated by the degree of lingering instability behind the initial
wave of daytime convection expected across those areas. A pool of
at least 1.5 inch PW values should remain - supporting heavy
rainfall with any lingering convection through the evening hours.

Additional convection is expected along the aforementioned cold
front across New York State and western New England. Storm motions
should be relatively fast (30+ knots), limiting any heavy rainfall
to any localized areas of training that can materialize.
Additionally, antecedent dryness/drought should limit excessive
runoff potential. A Marginal risk extends to western Pennsylvania
and vicinity - although this risk seems a bit too isolated farther
northward to include or expand in any probabilities at this time.

...New Mexico...

A southwestward moving cold front will stall close to the higher
terrain across central New Mexico today through tonight. Upslope
flow behind this front and weak mid/upper waves traversing the
state will both initiate deep convection within a sufficiently
moist airmass (0.7-1.25 inch PW) for heavy rainfall. Storm motions
across northern portions of the state may be quick enough to limit
rainfall, yielding a mostly isolated flash flood threat in areas
that are sensitive (i.e., burn scars, low-lying areas). Central and
southern portions of the state should experience slower storm
motions and perhaps multiple rounds of convection from afternoon
through the overnight hours. Given increase in convective coverage
and potential for local 3+ inch rainfall totals occurring
perilously close to sensitive areas/burn scars, a Slight Risk was
introduced with the expectation of at least a few instances of
excessive runoff given the scenario.

Cook

Day 2
Valid 12Z Wed Oct 08 2025 - 12Z Thu Oct 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF NEW MEXICO AND EASTERN ARIZONA...

...2030 Update...

The marginal risk area over the Four Corners region was pulled back
from the AZ-MX border and tightened up elsewhere based on 12z hires
guidance and FFGs. Mid-level vorticity embedded within an expanding
ridge will lift through the southwestern U.S. and interact with
anomalous moisture/instability all beneath a 55-70 kts jet. Some
parts of northwestern New Mexico could receive between 0.5-0.8
inches of rain by Thursday morning. A mitigating factor for an
upgrade were that EAS exceedance probabilities of at least 1" were
below 15% across the marginal risk area.

Kebede

...Previous Discussion...

Some continuation of heavy rainfall potential will exist across New
Mexico during the early morning hours of the D2/Wed forecast
period. During the day, an increase in insolation/destabilization
should promote development of isolated to scattered thunderstorms
initially along terrain/ridgelines near the Arizona/New Mexico
border and across the southern Rockies. Storms will drift
slowly/erratically while producing brief heavy rainfall. Typical
low spots/sensitive areas will experience a flash flood threat with
this activity. Coverage of flash flood potential should be sparse
enough to warrant continuation of a Marginal Risk and associated
probabilities.

Cook

Day 3
Valid 12Z Thu Oct 09 2025 - 12Z Fri Oct 10 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS A LARGE
PART OF THE SOUTHWEST AND SOUTHEASTERN FLORIDA...

...2030z Update...

The marginal risk in the Southwest was expanded farther into the
Four Corners/Intermountain West, in coordination with FGZ. 1-1.5"
PWATs will represent maximum precipitable water for this time of
year over much of Arizona and southern Utah. 12z GEFS and CMCE
24-hour qpf exceedance probabilities of 1" are between 15-20% over
parts of northern and central Arizona, where 3-hour rates don`t
eclipse 0.65".

Elsewhere, the marginal over southeastern Florida was trimmed a
bit on the northern edge based on the latest guidance.

Kebede

...Previous Discussion...

...Southwest...

Models are consistent in depicting a dramatic increase in
atmospheric moisture content across the Colorado River Valley from
both Hurricane Priscilla and the Gulf of California. Widespread
1-1.75 inch PW values are expected by midday Thursday. This
moisture will combine with deep southwesterly steering flow and
weak mid-level waves aloft to produce several areas of
precipitation throughout the forecast period (including the
overnight and early morning hours). A close inspection of point
forecast soundings from model data casts some doubt on the extent
of instability developing within the moist axis due to widespread
cloud cover. Any daytime destabilization within the region will
likely lead to stronger convection and an increased risk of flash
flooding. Trends in instability will be monitored for possible
upgrades in parts of the Marginal Risk area in later outlooks.

...Southeastern Florida...

Models depict a few areas of convection developing very close to
urbanized areas of southeastern Florida during peak heating hours.
Point forecast soundings across the area depict typically
moist/unstable profiles (2+ inch PW values), though wind fields are
very weak, suggesting slow/erratic cell movement and mergers. Spots
of 1-3 inch/hr rain rates could materialize, supporting an urban
flash flood risk across the area.

Cook


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt