FOUS30 KWBC 150811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Wed Jul 15 2026

Day 1 Valid 12Z Wed Jul 15 2026 - 12Z Thu Jul 16 2026

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

...Texas...

Current satellite and radar composite depict a defined low to mid-
level circulation situated over the Edwards Plateau into the
neighboring Hill Country along and north of US90 to the west of San
Antonio. Heavy rainfall continues within the confines of the
disturbance with rainfall rates generally between 2-3"/hr in the
stronger cores nestled within the meandering complex. Recent CAMs
have been struggling with the handling of this feature with the
latest 00z suite running too quiet in terms of the current
convective coverage and what was being forecast. This effect left
some of the current probability fields on the conservative side
compared to the past runs, but even still, the results are formidable.

850mb UA analysis indicates a ~25kt LLJ centered over the southern
Hill Country with the nose of the jet protruding into the Edwards
Plateau. Expectation for the maturation of the LLJ will be
generally similar to last night where an expected redevelopment of
convection will ensue over the Rio Grande Valley and points west,
overlapping many of the areas that were recently impacted by
considerable rainfall in the past 12-24 hrs. This stems from the
LLJ influence and the overall convergence scheme being exacerbated
by both the MCV and the positioning of a surface trough analyzed in
the area. Despite the lower confidence in the full CAMs output,
the QPF totals being disseminated in the hi-res are still
incredibly concerning and the story is validated through the HREF
neighborhood and EAS prob fields all the same. HREF blended mean
QPF depicts widespread 3-6" of rainfall with locally up to 8"
across the Edwards Plateau, RGV, and Hill Country to the southeast
of I-10. This is also just the mean QPF depiction as a few
deterministic members are amplifying further with 10+ inch
forecasts showing up over portion of the Edwards Plateau and lower
Concho Valley. One of the biggest trends has been the uptick in the
signal across Crockett County and points southeast into Hill
Country where model consensus shows the highest threat for
significant rainfall totals >5". Neighborhood probabilities for the

5" threshold are running between 40-70% in this general area for

the period with the >8" threshold solidly between 30-50% for the
same region. Historical precedence for these types of
probabilistic outputs points to a significant event with life-
threatening characteristics increasingly favorable across the areas
hardest hit. Couple the expected additional rainfall with
widespread 6+ inch totals that already occurred in the region and
you have a recipe for high level impacts and major hydrologic
concerns through a broad area.

The previous forecast High Risk remains valid and the risk
inherited was maintained with some small adjustments around the
northern periphery of the risk area, expanding more into the Lower
Concho Valley across Crockett County. The eastern extent is still
situated west of I-35 with the Hill Country to RGV the most
prominent focus for significant, life-threatening flash flood
prospects. MDT risk extends a bit further north towards San Angelo,
but still remains south of the population center. This is a close
setup for the area, so will be monitoring closely to see if the
more appreciable rainfall can make it that far north to provide
more locally significant impacts to the Central Concho Valley.
Heavy rain threat will also exist out towards the Big Bend into the
Lower Trans Pecos, especially the following evening, but that area
is more fluid as the behavior of the MCV will be integral to the
western extent of the heaviest rainfall. The High Risk location is
where confidence is high on the three major characteristics for the
setup: high intensity rates between 2-4"/hr, overlapping heavy
rainfall over areas previously impacted, and consensus within the
CAMs on where redevelopment is likely, validated by the HREF
probability fields. This setup will need to be monitored very
closely and for everyone to heed all watches and warnings due to
the gravity of the setup.

...Central Arizona into the Interior West...

So far models remain consistent on the broad upper ridge centered
over the Northern U.S. continuing 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.
The signal for heaviest rainfall continues to be situated within
the proximity of the terrain across Central AZ where CAMs depict a
broad convective initiation after 19z centered within a defined
theta_E ridge positioned from southeastern AZ up through the
Mogollon Rim. 00z HREF neighborhood probabilities are generally
robust for at least 1" of rainfall across the terrain between
Phoenix to Flagstaff with probabilities between 60-80% showing up
over the higher terrain located within the Mogollon Rim.
Neighborhood 2" probs are relatively modest between 30-50% for the
same area, a signal sufficient enough to maintain the previously
inherited SLGT risk with only some minor adjustments on the
southeast flank of the risk. Prevailing upper level flow is still
likely to lead to precip moving southwest off the terrain and
towards the adjacent valley in south-central AZ, so the prospects
for flash flooding near Phoenix are higher than in recent periods,
but still generally favored for a MRGL risk.

Outside AZ, scattered thunderstorms are likely to materialize
within the Great Basin up into the ranges of northwest WY into
southern MT due to a continued elevated deep layer moisture
advection regime bisecting the area for another few periods. The
main concern will be flash flood threats in any urban settings and
those more susceptible slot canyons across UT and northern AZ north
of I-40. A broad MRGL risk extends north through the above areas
with isolated to widely scattered flash flood prospects expected
for these domains.

...Lower Mississippi Valley into Southeast...

Our meandering upper level disturbance continues to churn over the
Southeastern U.S. with the center of circulation analyzed over
northern MS according to UA analysis and a defined cyclonic
character via the latest WV satellite imagery. Expectations are
for this slow-moving disturbance to drift to the west-northwest
with sights on the Lower Mississippi Valley by later this afternoon
as the HREF 700-500mb analysis pins the circulation crossing into
southwestern AR later this morning, drifting towards the center of
the state by the middle of the afternoon. 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, and the area FFG's across AR are much higher compared to
points further east where multiple days of rainfall compromised the
top soil layer enough to warrant greater impacts with any
convective episodes. Given the aforementioned variables, the threat
remains within the MRGL risk threshold with little change from the
inherited forecast. We will continue to monitor closely on any
potential targeted upgrades over the region.

Kleebauer


Day 2 Valid 12Z Thu Jul 16 2026 - 12Z Fri Jul 17 2026

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

...Texas...

Convection will continue across the Edwards Plateau and surrounds
for at least one more period as the regional pattern maintains a
persistence in its evolution with yet another round of convection
lingering through the morning from the previous period, and one
last round of nocturnal convection anticipated the evening of
Thursday into early Friday morning. The past few iterations of the
CAMs and global deterministic are coming into better alignment on
how they have the event across TX playing out with a strengthening
signal for heavy rainfall in-of the Central RGV up through the
Concho Valley and slipping into the southeastern Permian Basin.
Ensemble means have exhibited a crescendo in the depicted areal
average QPF leading to generally robust totals bordering between
2-4", locally higher in the hardest hit locations. Considering the
nature of anticipated compromised soils and ongoing flooding across
portions of the RGV and Edwards Plateau, very little additional
rainfall would cause a myriad of problems, including an
exacerbation of any remnant flood waters, especially if impacted by
additional heavy rainfall >1"/hr as noted via the very low FFG's
already in place across the region.

The previous MDT risk was maintained and even expanded a bit
eastward through more of the Hill Country over into the Edwards
Plateau with emphasis on Val Verde county extending up to the
neighboring counties to the north, including the I-10 stretch in
central Crockett county. This is the area of greatest concern for
the setup in D2 leading to a high-end MDT risk forecast centered
over this corridor. Rainfall totals in a narrow tongue could breach
6" locally as asserted by a few of the deterministic outputs which
makes sense considering the incredibly moist environment in place.
This period will be monitored very closely and its susceptible to
larger scale changes as the setup evolves as the handling of the
MCV and the placement of the quasi- stationary front and any
surface trough axis' in the area will be foci for heavy convection.
Heavy rain will enhance life- threatening flash flooding to
portions of the region for yet another period before the setup
finally looks to break heading into D3.

...Southwest U.S into the Great Basin...

Another round of afternoon and evening convection will transpire
across the Southwest CONUS into the Great Basin on Thursday with
the threat carrying into the early morning periods of Friday in
some locations. Models are keen on a more robust moisture advection
pulse and general instability axis across the Desert Southwest on
Thursday with a broad axis of heavy rain prospects from the
southern border all the way north into southern UT. Hi-res ensemble
and several global deterministic outputs remain very bullish on
the threat in and around the slot canyons of southern UT, along the
Mogollon Rim, and down towards the terrain embedded within
Cochise, Santa Cruz, and Pima counties. Areal average of 1-2" is
forecast for the region along the southern border with 1-1.5"
forecast across the Mogollon Rim and southern UT. Considering the
environment maturing closer to 1000-2000 J/kg MUCAPE over much of
AZ into southern UT/NV, instability and anomalous moisture within
the 90-99th percentile of climatology across the region will
produce more widespread heavy rain prospects leading to scattered
flash flood occurrences in those more susceptible locations in the
terrain. There is even some opportunity for thunderstorm genesis
off several outflows that could impact some of the larger urban
corridors within AZ, including the Phoenix metro as the environment
favors this type of potential. A broad SLGT risk was maintained
for much of AZ into southern UT with the eastern extent out towards
the NM/AZ border into the immediate Four Corners, outlining the
mean QPF closer to 0.5" from recent forecast.

...Mid-Mississippi Valley...

Remnant mid-level disturbance will slowly pivot across AR into MO
by Thursday maintaining a consistent posture of targeted mid-level
ascent and favoring greater convective coverage under the weak
circulation. The pattern is less favorable for more widespread
heavy rain prospects, especially those that would warrant more
considerable attention and a higher risk like in previous days.
Nonetheless, the signal is still there for isolated flash flood
potential within portions of the Ozarks up through the mid-
Mississippi region near St. Louis. HREF mean QPF shows a general
max near the IL/MO border near and north of St. Louis. Expecting
this signal to settle somewhere near this area given the favorable
2+ inch PWATs centered over the area. The previous MRGL was
expanded north to match the trends in guidance.

Kleebauer
$$

--- Scorpio BBS
* Origin: capitolcityonlinet.net * KY, USA (618:250/10)