Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
427 AM EDT Mon Aug 31 2026
Day 2
Valid 12Z Tue Sep 01 2026 - 12Z Wed Sep 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE UPPER
TEXAS COAST AND FAR SOUTHWEST LOUISIANA...

...Central Gulf Coast...

Guidance varies in timing and intensity however there is consensus
for Invest AL97 to move onshore the upper Texas coast on Tuesday
morning bringing an increasing threat for heavy rainfall. Several
inches of rain may materialize given PW values greater than 2.25
inches and an increasing low level flow to intensify ascent across
this region. A Slight Risk was maintained although shifted to
reflect the latest guidance and WPC QPF placement.

...Portions of the Southwest...

The multiday, heavy rainfall event over the Southwest/West will
drastically reduce coverage and intensity during this period in
response to the mid-level trough moves onshore the California
coast. This will lead to height falls well into the Southern
Rockies and Central Plains. This not only will shift the favorable
corridor for ascent, but also push the greatest moisture anomalies
farther east and out of the Southwest. For portions of Arizona, New
Mexico and souther Colorado a modest threat will continue for this
period although cell motion will likely be more progressive in
nature thus limiting the threat for flash flooding. A Marginal Risk
remains in effect.

...Great Lakes to New England...

Multiple mid-level disturbances will track through the flow from
the Great Lakes to the Northeast and in tandem with a stationary
frontal boundary draped over the region, will bolster ascent. The
resulting lift will act upon PWs pooled south of the boundary that
will approach 2" (+1.5 sigma) to support fast moving thunderstorms
(0-6km mean winds 25-35 kts) but that will contain 1+"/hr rain
rates. The latest suite of guidance suggests multiple rounds of
convection on Tuesday due to the weak mid-level impulses, and as
bulk shear climbs to 30-40 kts, repeating rounds of convective
clusters could produce as much as 3" of rain. A Marginal Risk area
remains in effect for this region. Should models trend higher with
amounts/repeating rounds cause the heaviest rain to fall atop the
more vulnerable soils around the Tri-State area of Connecticut, New
York and New Jersey, an upgrade to a Slight risk may be needed.

...Gulf Coast and Florida...

Persistent easterly flow across the Florida Peninsula will once
again supply tropical PWs around 2.25" to the region to support
scattered afternoon convection. This setup should allow for a rapid
expansion of thunderstorms on the westward advancing sea breeze
before pinning storms along the western/Gulf side of the Peninsula
later in the aftn. While coverage is a but uncertain, a weak mid-
level impulse progged to move across the area may act to enhanced
diurnal activity, and with rainfall rates likely reaching 2-3"/hr
at times, this could produce excessive rainfall within urban areas
of the Sun coast therefore the Marginal Risk area was maintained.

Campbell/Weiss


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