FOUS30 KWBC 220821
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Mon Sep 22 2025

Day 1
Valid 12Z Mon Sep 22 2025 - 12Z Tue Sep 23 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTH
CENTRAL KANSAS INTO NORTH CENTRAL OKLAHOMA...

...Central to Southern Plains...
The latest model suite is in better agreement with the evolution 
of the amplifying upper trof across the Northern to Central Rockies
day 1 and the downstream outbreak of organized convection along 
and to the north of the path of the associated surface low moving 
west to east from the TX Panhandle into western OK. A slight risk 
area was added for the potential for organized convection along and
to the north of this low, across areas of south-central KS into 
north-central OK where the low level southerly flow will be
strengthening and the corresponding 850-700 mb moisture flux
becoming anomalous, upwards to 2 to 3 standard deviations above 
the mean by the end of the day 1 period. The neighborhood 
probabilities are high in both the HREF and RRFS for 1 and 2"+ 
amounts across these areas. Additionally, both the HREF and RRFS 
show a defined area of probabilities exceeding the 3 hourly FFG 
values in the 0000-1200 UTC Tuesday time frame as the potentially 
organized convection presses east southeastward. 

...Mid to Lower Mississippi Valley into the Ohio Valley...
A broad marginal risk area was maintained in association with height
falls pushing east northeastward from the Mid Mississippi Valley 
through the Ohio Valley. Well defined large scale lift in an axis 
of above average PW values, 1 to 1.5+ standard deviations above the
mean, will support the likelihood of widespread moderate to heavy
precipitation in an axis from northern AR, far southeast MO, far 
southeast IL, western to central KY, much of IN and OH. At the 
moment the convection across these areas may be fairly progressive.
This and very low relative soil moistures, much of the area in 
moderate to severe drought, will keep the risk level at marginal 
for the time being. While the HREF and RRFS neighborhood 
probabilities are fairly high for 1 and 2"+ amounts day 1, the HREF
and RRFS probabilities for 3 hour rainfall exceeding FFG values 
remains very low, reflecting the antecedent very dry conditions. 

...Southwest...
The closed low off the Southern CA coast is expected to move 
little during the upcoming day 1 period. The right entrance region
of the jet streak to the east of this closed low will push 
eastward, but continue to support uvvs enhancement in the above 
average PW axis, 1 to 3 standard deviations above the mean, that 
will remain in place across Southern CA into the Southwest. 
Additional scattered convection across these areas will support 
localized heavy amounts and isolated runoff issues. No changes were
made to the previous marginal risk area.

Oravec


Day 2
Valid 12Z Tue Sep 23 2025 - 12Z Wed Sep 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHERN
MISSOURI, NORTHERN ARKANSAS, NORTHEAST OKLAHOMA AND SOUTHEAST KANSAS...

The strengthening 850-700 mb moisture flux late day 1 over the
Southern Plains will remain anomalous day 2 as surface low 
pressure continues to push eastward from the Southern Plains toward
the Lower Mississippi Valley. 850-700 mb moisture flux anomalies 
are forecast to remain in the 2 to 3+ standard deviation above the 
mean level. This will support the likelihood for the continuation 
of the day 1 organized convection over the Southern Plains, pushing
eastward into the Lower Arkansas Valley and toward the Mid to Lower
MS Valley. There are differences with the track of the primary
surface low, resulting in north to south spread with respect to
where the max precip axis will be. WPC is favoring the more
southern qpf axes solutions, with the max axis depicted from far
eastern OK, northern OK/far southern MO into western TN. This is a
slight southward trend from previous forecasts, reflecting a
southward trend in qpf guidance. Changes to the previous slight and
25% areas were to follow the slight southward qpf axis trend,
pushing them approximately 40-60 miles farther to the south.  

...Coastal Central California... 
There is good model agreement with the nearly stationary closed 
low off the Southern CA coast day 1 beginning to slowly move back 
to the north on day 2 toward the Central CA coast. This slow north
movement will also allow for a northward expansion of the 
anomalous PW values over Southern CA into coastal Central CA, with
values as high as 3-4 standard deviations above the mean. With good
model agreement on the closed low track day 2, there is also good
agreement on potential for areal average moderate precip totals,
with potential for locally heavier amount along the Central CA
coast. Isolated runoff issues are possible, especially over any burn scars.

Oravec


Day 3
Valid 12Z Wed Sep 24 2025 - 12Z Thu Sep 25 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE
TENNESSEE AND OHIO VALLEY REGIONS...

The mid to upper level trof moving east from the Southern Plains
day 2 will amplify day 3 as it pushes into the Lower MS Valley.
Anomalous PW and 850-700 moisture flux values will stretch across a
large area from the Lower MS Valley, and into the TN & OH Valley, 
Central Appalachians and the Mid-Atlantic. Model consensus is for a
broad region of moderate to heavy precip in this anomalous PW and 
850-700 mb moisture flux axis. There is a typical amount of qpf 
spread for a day 3 time period. WPC is leaning more toward the 
multi model ensemble qpf mean axis/NBM axis to drive our qpf and 
excessive rainfall axis. While a large portion of the day 3 QPF and
ERO axes are currently in moderate to severe drought, there may be
overlap in qpf areas from day 3 and day 1 over the TN and OH 
Valley regions and overlap between the day 2 and day 3 qpf axes 
across the Lower MS Valley into the TN Valley, which will likely 
increase soil saturations and increase stream flows. The previous 
slight risk area was trimmed on the western edge by approximately 
75-100 miles across far southeast MO, southern IL and southern IN 
to better fit the latest QPF. 

...Central California...
The slow moving closed low approaching the central CA coast late
day 2 will continue to push slowly eastward day 3 and push inland
by early Thursday morning. Similar to the day 2 period, an axis of
anomalous PW values, 2 to 3 standard deviations above the mean,
will persist to the east northeast of the closed low across
Central CA. Scattered convection in this anomalous PW axis will
support locally heavy rains across Central CA and isolated runoff
issues, especially across burn scar regions. Only some small
changes made to the previous marginal risk area, trimming it
westward across western NV.

...Far southeast Arizona into New Mexico...
No changes of note made to the previous marginal risk area across
this region. Scattered convection possible, with localized heavy
rain and isolated runoff issues, especially in burn scar regions.

Oravec
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