Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Tue Jul 14 2026
Day 2
Valid 12Z Wed Jul 15 2026 - 12Z Thu Jul 16 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE EDWARDS PLATEAU, CENTRAL RIO GRANDE VALLEY, AND HILL COUNTRY...

...Texas...

Convective cluster across the Edwards Plateau and neighboring RGV
and Hill Country will likely lead to the development of an MCV
and/or a more consolidated mid-level disturbance in the region that
will remain relatively stagnant in terms of its general motion
leading to a repeat of the same pattern that will plague the area
during the D1 period. This repeating evolution of convection is a
worst- case scenario where another round of heavy rainfall will
transpire and overlap areas that will be impacted significantly the
period prior. Multi- model consensus is basically on top of each
other in the placement of the next wave of heavy rains in the
region with additional totals of 3+ inches increasingly likely
during the D2 time frame. NBM mean QPF totals for the 48hr period
are >5" around the area of Del Rio and neighboring portions of the
Edwards Plateau. Moving towards the 75th and 90th percentile
forecasts, NBM jumps significantly into 6" and 8", respectively for
each data point. Widespread 3-6" totals are likely in the 2-day
period, but it is within the realm of possibility that additional
rainfall on D2 will push totals in areas above 10 inches, a
threshold that likely spell major flash flooding and hydrologic
impacts that will encroach more severe levels compared to the
normal scenarios from the past.

The setup continues to show great consistency within the latest
ensemble and deterministic outputs which does add value to the
forecast as this provides greater confidence in a high level event
brewing as we step through the D2 period. The previous MDT risk was
generally maintained with just some minor adjustments on the
eastern and southern flank of the risk. This period, and the event
in question will need to be monitored for a potential upgrade to a
High Risk which will likely occur once we see how the initial
evolution is transpiring. No matter the case, life-threatening
flash flooding and significant hydrologic concerns are increasingly
likely for the D2 period with the heaviest rainfall likely to occur
in the initial start of the D2 and after 00z Thursday when the
nocturnal LLJ initiates and provides a fresh low-level moisture
injection and enhanced convergence within the proximity of any
lingering disturbance. A high-end MDT risk remains in effect for
those areas referenced above with a broader MDT extension out into
Hill Country and over into the Lower Trans Pecos to Big Bend.

...Mogollon Rim into Central Arizona...

Broad upper ridge centered over the Northern U.S. will continue to
provide significant moisture advection into the interior west
leading to scattered convective signals from the Canadian border
down into the Desert Southwest with flash flood concerns in those
more susceptible areas out west. Increased confidence in a locally
favorable convective maxima has allowed for not only a continuation
of the previous SLGT risk positioned across the Mogollon Rim in AZ,
but also an expansion further northwest and north, including the
addition of Flagstaff proper. 00z HREF at the end of its temporal
range signaled widespread thunderstorm genesis over the terrain
after 20z Wednesday with some formidable heavy rain cores likely to
materialize out of the initiation. Modest neighborhood
probabilities for >1" of rainfall exist in the small window between
18-00z Wed/Thu with the highest probs situated in that terrain area
between Phoenix and Flagstaff within the Mogollon Rim across
central AZ. In coordination with the local Flagstaff WFO, have
expanded the previous SLGT risk forecast to areas northwest of
Flagstaff within the western periphery of the Mogollon Rim, as well
as a further north expansion to include Flagstaff proper given the
recent trends in guidance, and the premise of urbanization factors
providing more suitable ground conditions for flash flood
prospects.

...Lower Mississippi Valley into Southeast...

Our meandering upper level disturbance will continue to churn over
the Southern U.S. with sights on the Lower Mississippi Valley by
Wednesday afternoon. Models are within close proximity of each
other on the positioning of the disturbance with the centroid of
the circulation likely to be focused somewhere over Arkansas and
the southwest corner of TN. Elevated moisture and general diurnal
destabilization across the Lower Mississippi and Southeastern U.S.
will lead to another round of slow-moving thunderstorms capable of
producing locally heavy rainfall with rates of 2-3"/hr likely in
those stronger cell cores. The setup is not as prolific within the
QPF means compared to the previous few periods, so the threat
remains within the MRGL risk threshold. However, will continue to
monitor trends closely as we move forward in time as the chance for
a targeted upgrade, likely underneath the upper level disturbance,
is plausible.

Kleebauer


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt