Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
245 AM EDT Thu Oct 15 2026
Day 1
Valid 12Z Thu Oct 15 2026 - 12Z Fri Oct 16 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF WEST TEXAS...

The setup for Thursday into early Friday morning continues to trend
towards a very active period across portions of the Southern Plains
as a cold front drives south with the aid of a strengthening
surface ridge emanating out Canada. Complex longwave evolution
will generate quite a strong surface response with high pressure
nosing out of western Canada, eventually strengthening into a 1040+
mb high centering over Montana by later this afternoon. This will
finally push the front bisecting the Plains through the Ohio Valley
southward creating a focused area of low-level convergence as it
interacts with rich theta_E air positioned over the Southern Plains
of OK/TX. Current surface analysis maintains our ridge across the
Lower Mississippi Valley with a prevailing south to southwest fetch
out of the adjacent Gulf, leading to a fairly pronounced deep
layer moisture source across much of the Lone Star state and the
eastern half of OK. PWATs centered over west TX up through OK
remain very much elevated with the 00z RAOB's out of both KOUN and
KMAF indicating PWAT anomalies encroaching on +2 to +3 standard
deviations when accounting for climatology. This is also well above
the 90th percentile with the NAEFS outputs signaling closer to the
upper 97-99th percentile when adjusting for seasonal climo, so the
environmental conditioning is more than favorable for prospects of
heavy rainfall in any convective regimes.

Streaming mid- level vorticity within the western flank of our
ridge over the Southeast CONUS will continue for at least another
24 hours before the general pattern, both at the surface and aloft,
finally shifts and the threat for significant convective coverage
and associated impacts diminishes across the region. Classic low-
level convergence regime with the front will allow for the standard
continuation of convection over the Southern Plains the first part
of Thursday with the eventual decay in the magnitude for a short
time late-morning into the afternoon. By the mid to late-afternoon
time frame, we'll begin seeing our front take a dive south as it
begins feeling the pressure gradient pattern building over the
Plains and Northern Rockies thanks to our maturing high out of the
Canadian Prairies. By the following evening (Thursday night), the
nocturnal LLJ will respond ahead of the approaching boundary
leading to enhanced low to mid-level convergence from the eastern
Permian Basin down through the adjacent Concho Valley, into the Big
Bend and Lower Trans Pecos. The further south the setup, the more
prolonged the heavy convective regime will last creating a
cumulative effect of all the heavy rain occurring during the
period.

A noteworthy precipitation gradient can be seen within the ensemble
means with heavy QPF signatures over the Big Bend to Lower Trans
Pecos with a gradient decline as you move northward. Areal average
QPF between 3-5" with locally higher amounts are anticipated along
and south of I-10, mainly east of the Davis Mountains with the
maxima centered over the Lower Pecos River basin between Sanderson
to north of Del Rio. 00z HREF/REFS neighborhood probabilities
continue to pinpoint 70-100% exceedance probs for >3" with even a
pocket of 50-80% for >5" positioned over Terrell county in the Big
Bend up through portions of the Lower Concho Valley. This is the
area where the convective pattern will linger the longest before
the eventual frontal progression pushes the front through the area,
but it's also the area with the greatest instability and deep layer
moisture presence when assessing raw PWAT indices being forecast.

Considering such a robust signal, the previous MDT risk forecast is
still very much in play with only minor modifications to the risk
itself from the previous issuance. Continuity and the enhanced
probabilities maintain a favorable prospect for widespread flash
flooding across the aforementioned areas with even a threat for
areas north around the central Concho Valley, including the San
Angelo area and surrounds. The SLGT risk extends further north into
southern OK with the initial convective threat carrying over from
the morning hours and some overlap in the afternoon on initiation
before the front finally pushes through the air and dry air
advection in wake of the front puts an end to the threat. DFW metro
will be right on the edge of seeing more appreciable rainfall, but
current progs are the worst stays just outside the metroplex this
period. Will be something to monitor moving forward, but the area
remains in the MRGL encompassing the outskirts of the main axis of
heavier precip and associated SLGT risk.

Kleebauer


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt