FOUS30 KWBC 140751
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
351 AM EDT Wed Oct 14 2026

Day 1
Valid 12Z Wed Oct 14 2026 - 12Z Thu Oct 15 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF OKLAHOMA INTO THE RED RIVER VALLEY OF TEXAS...

Current upper level setup is shifting into a classic longwave
pattern suitable for widespread convective impacts and heavy rain
potential from southwest TX up through the Plains, arcing back into
the Mid-Mississippi and Ohio Valleys. Deep upper low (ULL)
positioned over the interior west will slowly pivot eastward,
maintaining a persistent diffluent pattern centered downstream of
the Rockies leading to multiple rounds of convection and flash
flood prospects over the Central and Southern Plains. At the
surface, multiple surface lows are analyzed over the CO Front Range
back into the Four Corners with another set of weaker lows aligned
within a quasi-stationary front extending from the Plains into the
Ohio Valley. The whole setup is in flux with the slow evolution of
the longwave trough over the west, but we'll finally see some
progression of the frontal waves, and front in general, as we move
into the second half of the D1 period as another key component in
the setup makes its presence known further north.

WV satellite over the Northern CONUS into Canada notes a digging
shortwave trough migrating southeast out of the Canadian Prairies
that will continue to dig south and strengthen as it merges with a
mid-level vorticity maxima streaming northeast out of the Plains
involved in the current convective regime this evening. The
shortwave to the north will amplify and create a pronounced
meridional regime that will act as a pivotal piece to the surface
reflection as a surface high will slide south out of western Canada
and strengthen rapidly thanks to the general upper level
amplification. This will take our "stalemate" currently analyzed
over the Plains and give it the push necessary to finally press the
quasi-stationary front southward, turning the front into a textbook
cold front on the leading edge of the surface ridge to the north.
This combined with convergent flow around the western periphery of
a ridge centered over the Lower Mississippi Valley will lead to a
significant rainfall threat across portions of Southern Plains,
especially into OK and the Red River basin between OK/TX.

00z HREF this evening was noteworthy with regards to more
substantial prospects for flash flooding given the probabilistic
output, as well as the appreciable HREF mean QPF distribution
across the Southern Plains. The frontal progression will make the
area of southwest to central OK as the primary axis for heavy
convection as convergent flow in-of the front, along with PWAT
anomalies bordering and/or exceeding record levels to date will
provide a sufficient environment capable for producing heavy
rainfall with efficient warm rain processes capable for more
significant totals in the region. Latest CAMs and global
deterministic signals are robust with multiple pieces of guidance
now indicating widespread areas of 3-5" of rain with maxima upwards
of 8" according to low-end probabilities within the ensemble for
exceeding the 8 inch threshold (15-25%). The greatest probabilities
for exceeding all three of the 3/5/8 inch thresholds are positioned
over central OK with the OKC metro as a notable data point in the
middle of the elevated prob fields. Considering the alignment of
the front and the multi-round evolution of convection during the
period, this has merit considering the front will likely not be out
of the area until late in the forecast cycle, and perhaps even
bleeding into the new D2 time frame as the fight between the ridge
axis over the Southeast and the strengthening surface high to the
north will clash with the eventual winner being the high over the
north moving into Thursday. LLJ upwards of 40kts is anticipated
over the Southern High Plains into OK which only adds to the setup
as the shear component will allow for merging cells and larger
convective clusters to materialize and hold together for extended
periods before fading as they move northeast with the mean flow.
This will be the main cause for such a widespread significant
rainfall across the region in this period.

Heavy rainfall will also be plausible over the Southern High Plains
of TX, as well as over the Ohio Valley with the former being the
more prominent for heavy rain prospects thanks to deeper moisture
flux and ample instability positioned around the western flank of
the Southeast ridge. The Ohio Valley threat is due to the migration
of mid-level energy out of the Plains within the confines of the
quasi-stationary front which will delineate the more appreciable
deep layer moisture along and south of the boundary with a slow
filtering of drier from the north as a weaker ridge moves over the
Great Lakes. Areas from the TX Big Bend up through the Permian
Basin and Caprock could see localized amounts of 2-4" which would
certainly cause issues within any urbanized zones and areas with
several low-water crossings that are littered over the area. Areas
in the Ohio Valley are generally more in the 1-3" range for totals,
but a few stronger cells over places near the Ohio River may see
locally higher amounts which could result in flash flood potential.

In coordination with the local Norman, OK WFO, a Moderate Risk of
excessive rainfall was added to the new D1 period with emphasis on
areas from southwestern OK and the Red River basin up through
central OK and into the Tulsa metro area. This aligns with the
greatest probabilities for greater than both 3 and 5 inch
thresholds within both the HREF and REFS outputs this evening.
Despite some antecedent drier conditions, the record breaking
environment in terms of PWATs and repeating axis of convection
would be sufficient for locally significant flash flood potential,
especially into the OKC metro where flash flooding concerns are
highest. The SLGT risk from the previous forecast still extends
from southwest TX up through the Mid-Mississippi and Ohio Valleys
with an eastern inflection over the Central Appalachian front in WV
where the threat for 1-2"/hr rainfall in the period has trended up
over the past few model cycles, indicative of the environmental
conditions in place.

Kleebauer
 

Day 2
Valid 12Z Thu Oct 15 2026 - 12Z Fri Oct 16 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
WEST TEXAS INTO OKLAHOMA...

Complex upper level evolution across the northern half of the CONUS
will lead to our first strong cold front of the season being
propelled rapidly to the south Thursday evening as diurnal mixing
ceases near sunset and the front faces little resistance on its
push southward. The upper level setup over the Southeast CONUS will
still be in position to provide a continued draw of rich theta_E
air out of the Gulf into the Southern Plains ahead of the front
meaning the convergence signature and prospects for heavy rainfall
will continue for those along and ahead of the front.

The greatest potential for heavy rain will exist over the Southern
High Plains into southwestern TX as they will be the last places to
see the frontal passage at any point in the forecast period with
areas of the Big Bend and Lower Trans Pecos likely to not see the
front until perhaps after the D2 time frame. General instability
maximum and PWAT anomalies up near +3 standard deviations correlate
to heavy thunderstorm prospects over the Southern High Plains with
a corridor of significant rainfall potential from the Western
Rolling Hills of TX, through the Permian Basin and Concho Valley,
down into the Big Bend area and over into the terrain of southwest
TX. Some added isentropic ascent will lead to prolonged periods of
heavy rain, even after the front passes until a more robust dry air
advection regime takes shape beyond the current D3.

Ensembles continue to trend towards an area of appreciable rainfall,
especially south of the Pecos River in west TX where the greatest
instability axis is located, along with substantially high PWATs
running between 1.5-2", a signal that would easily encroach on the
95-99th percentile according to the latest NAEFS and ECENS
climatological percentiles. Forecast total remain prolific for this
area of the CONUS with guidance inferring on a broad area of at
least 2-4", locally higher, across portions of west TX with the max
focused over the Stockton Plateau towards the RGV within the Big
Bend. This setup resembles some of the more prominent heavy rain
depictions for west TX as the combination of pre-frontal convection
and then prolonged isentropically forced precipitation will
account for a cumulative effect, leading to such a robust QPF depiction.

This is trending towards a formidable setup for this area of the
CONUS with a high- end SLGT remaining the forecast over the above
areas. There is a potential for an upgrade in the risk further as
the the progged cold front will play a significant role in the
potential, thus will need to evaluate any timing differences in the
latitudinal push of the front itself. For now, a pretty high
likelihood of at least scattered flash flood prospects within the
Stockton Plateau to Big Bend area with outside chances for more
appreciable flash flooding in the areas of both Midland/Odessa over
into San Angelo. The previous SLGT was adjusted a bit further
north to encompass southern OK to account for lingering flash flood
chances beyond the main impacts from the now D1.

Kleebauer
 

Day 3
Valid 12Z Fri Oct 16 2026 - 12Z Sat Oct 17 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Kleebauer
 

Day 4 and Day 5
Valid 12Z Sat Oct 17 2026 - 12Z Mon Oct 19 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS
PARTS OF EAST-CENTRAL AND SOUTHEAST FLORIDA SATURDAY AND SUNDAY...

A well defined cold front is expected to press southward Saturday
across central to south Florida, becoming stationary across South
FLorida on Sunday. Low level east northeasterly flow will
strengthen into the east coast Florida in the wake of this front on
Saturday and remain strong through Sunday. PW values in this
strengthening low level east northeasterly flow are expected to
remain above average, 1.5 to 2+ standard deviations above the mean.
Strong boundary layer convergence maxima likely along the east
central coast of Florida. This will support potential for locally
heavy rains from well defined rain bands that may train for a
period both Saturday and Sunday, with isolated runoff issues
possible along the east central coast of Florida, especially in
urbanized regions.

Oravec
$$
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