FOUS30 KWBC 190811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Fri Sep 19 2025

Day 1
Valid 12Z Fri Sep 19 2025 - 12Z Sat Sep 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE
CENTRAL SIERRA NEVADA...

...California/Great Basin...

Remnant energy from Mario will continue to lift north across
California and become sheared by an upstream low over the Pacific,
with some energy wrapping back offshore, while the remainder 
moves east into the Great Basin. This energy, along with highly 
anomalous moisture (+4 std dev above normal), is expected to 
continue to produce showers and storms early in the period across 
parts of California, including the Sierra Nevada. While forecast amounts
have trended down, there is still some signal for locally heavy 
rain to continue early in the period across portions of the central
Sierra Nevada. A small Slight Risk was maintained, mostly for the 
initial 6-hours, where the HREF shows higher probabilities for 
additional amounts exceeding an inch. By the afternoon, as the mid 
level energy and greater moisture anomalies move east, expect the 
greater chance for heavier rain to begin to focus over central 
Nevada, where the HREF is showing a broader footprint of high 
probabilities for amounts over an inch.

...Southwest...

Expect widespread coverage of showers and storms today, as moisture
from Mario bolsters PWs across the region. The general consensus of
the CAMs show greater coverage across eastern Arizona and western
New Mexico during the afternoon, before storms move southeast into
southeastern New Mexico and West Texas by this evening. Storm 
motions are expected to generally progressive, limiting the threat 
for widespread heavy amounts and flooding. However, there is some 
signal for backbuilding and training, which could raise at least 
isolated runoff concerns. HREF neighborhood probabilities for
amounts exceeding an inch are above 50 percent within much of the
Marginal Risk area.

...Upper Mississippi Valley/Midwest to the Lower Missouri Valley...

A mid-to-upper level low/negatively-tilted upper trough will
continue to move slowly east from the northern Plains into the 
upper Mississippi Valley this period. While not expected to be a 
widespread heavy rainfall event, south-to-north training storms 
ahead of the associated occluded front, may produce locally heavy 
amounts and isolated flooding from northern Illinois back across 
the upper Mississippi Valley. The HREF shows widespread high
probabilities for amounts exceeding an inch across this region, 
with some localized high probabilities for amounts over two inches.

Meanwhile, shortwave energy diving southeast out of the northern
High Plains, is expected to produce a secondary area of organized
amounts, with some locally heavy amounts possible from 
southeastern Nebraska into southwestern Iowa and northwestern 
Missouri this evening into the overnight. Here also, the HREF is
showing high probabilities for amounts over an inch, with heavier
amounts possible.

...Central Plains...

Energy moving through the base of the previously noted upper
trough, interacting with deepening moisture along a strengthening
low level jet is expected produce showers and storms developing 
and dropping southeast across Kansas, with locally heavy amounts 
possible by this evening. HREF probabilities indicate localized
amounts of an inch or more are likely, with heavier amounts
possible.

Pereira


Day 2
Valid 12Z Sat Sep 20 2025 - 12Z Sun Sep 21 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHEASTERN KANSAS AND NORTHEASTERN OKLAHOMA THROUGH THE OZARKS...

Storms developing late in the previous period across Kansas may
continue, producing locally heavy amounts across portions of the 
Ozark Region Sunday morning. Redevelopment is possible back to the
west later in the day as shortwave energy emanating from the west
moves into the region and interacts with deepening moisture
afforded by strengthening southerly flow.

Pereira


Day 3
Valid 12Z Sun Sep 21 2025 - 12Z Mon Sep 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND FROM THE OZARKS THROUGH THE MID MISSISSIPPI VALLEY...

...The Southwest...

An upper low off of the California coast will drift southeast,
supporting the return of deeper moisture spreading north across
Arizona and western New Mexico on Sunday. With PW anomalies
increasing to 2-3 standard deviations above normal, numerous showers
and storms, producing locally heavy rainfall amounts and isolated 
flooding concerns, can be expected.

...Ozarks through the Mid Mississippi Valley...

A broad upper trough will drift slowly east from the Plains into
the Mississippi Valley this period. A series of mid level
shortwaves lifting along the leading edge of the trough,
interacting an axis of deeper moisture is expected to produce showers
and storms with periods of heavy rainfall possible.

Pereira
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