FOUS30 KWBC 041552
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1152 AM EDT Sat Apr 4 2026

Day 1
Valid 16Z Sat Apr 04 2026 - 12Z Sun Apr 05 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE ARKLATEX/LOWER MISSISSIPPI VALLEY AND A PORTION OF THE OHIO
VALLEY INTO WESTERN PENNSYLVANIA...

...South-Central Texas into ArkLaTex...

Cold front position is currently analyzed just to the east of the
DFW metro with heavy rain migrating into northeast TX and the
ArkLaTex. Expect this area to be a focal point this afternoon as
frontal convergence and a modestly unstable environment will aid
in some heavier rainfall coverage with totals between 2-4"
expected. Upstream trends in precip magnitude signal this range to
be pretty consistent with some localized flash flooding occurring
where heavy rain persists for 2+ hours. Right now the best spot is
across the area stretching from Texarkana to Tyler where models
have been consistent with a band of heavier precip leading to
precip totals >3" in areas. Antecedent conditions initially are
very dry, so this will curb some of the threat upfront, but
persistent heavy rainfall could still spur up some flash flood
prospects, especially inside the urban areas along I-30 and I-20.

Further southwest into hillier terrain of south-central TX along
I-35, consensus has grown for a round of heavy thunderstorms to
impact areas from Waco down to just north of San Antonio. PWATs
running around the 99th percentile climatologically, as noted by
the latest 12z RAOB from KFWD with a similar environment situated
across much of east TX should be sufficient for efficient rainfall
rates between 2-3"/hr at peak intensity. This is highlighted well
within the 12z HREF hourly probs of >2"/hr running between 20-35%
within the I-35 corridor extending from Waco, south. This area is
notoriously more flashy due to the topographic composition and
sprawling urbanization factors lined up across the interstate
domain. It will not take much to cause some local issues with
flash flooding in any strong cells that materialize. The SLGT risk
was expanded south given the above, and in conjunction with
coordination from the local WFO's out of Houston and Austin/San
Antonio as it encompasses portions of their respective CWA's.

...Lower Mississippi Valley...

The SLGT risk over MS/LA was generally maintained with the only
viable change being the addition of the risk introduced into the
New Orleans metro. This area has a split in CAMs on whether heavy
thunderstorm activity encroaches the area from the south as
prevailing southerly flow within the confluent pattern between the
front to the west and sprawling surface ridge to the east should
keep a moist, unstable airmass in place for the entirety of the
period. If any convection makes it to the area, it has the
potential to pack a punch as the environmental conditions provide
the opportunity for a quick 2-4" of rainfall as indicated by
moderate to high neighborhood probabilities within the latest HREF
(40-70%) for exceeding 2" of rain this period. The region further
north along the Mississippi, including the Jackson area are still
expected to see the greatest threat for heavy convection later this
evening as the axis of confluence and stronger forcing will combine
to bring a period of heavy rainfall prior to the frontal passage.
Considering the high EAS and neighborhood probabilities for >1" and
>2" respectively, there was no reason to deviate from the previous
forecast.

...Ohio Valley into Western Pennsylvania...

A wavy quasi-stationary front positioned from IL to PA will be a
focal point for convective development later today with a cold
front approach from the west as a primary surface low lifts
northeast through the Great Lakes. The area along I-76 in Ohio and
points southeast to Pittsburgh have some of the lower FFG's in the
country currently, all of which due to previous days of impact that
led to scattered flash flood issuances and moderate river flooding
in the vicinity. A well-defined axis of confluent flow across the
Mid Atlantic to Ohio Valley will allow for the prospects of
scattered convection capable of localized flash flooding,
especially in the corridor that has been heavily impacted in recent
days. The overall output from the hi-res isn't necessarily
impressive, but multiple CAMs do try to drop a quick inch or two
within that domain that's more sensitive to any additional
rainfall. The setup is conducive for these concerns, so despite the
modest probs indicated within the HREF neighborhood prob fields,
the antecedent conditions combined with those probabilities was
enough to maintain the SLGT risk from previous forecast, and expand
a bit further east to include the Pittsburgh metro and surrounds.

Kleebauer


Day 2
Valid 12Z Sun Apr 05 2026 - 12Z Mon Apr 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTH TEXAS ON SUNDAY...

Much like model runs over the past day or two...the suite of
numerical guidance from 04/00Z has continued to trend a bit faster
with the arrival of a cold front from the north. This adds to the
concern that moisture and instability will be swept out of the area
very early in the Day 2 period...if not before the period begins at
12Z on Sunday. Spaghetti plots of QPF continue to show enough
members with post-frontal amounts in the 1 inch to 2 inch range to
keep the Marginal in place...but the area continued to be
increasing confined to coastal areas and the deep south portion of
Texas.

Bann

Day 3
Valid 12Z Mon Apr 06 2026 - 12Z Tue Apr 07 2026

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

Bann


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