FOUS30 KWBC 120805
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Fri Sep 12 2025

Day 1
Valid 12Z Fri Sep 12 2025 - 12Z Sat Sep 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH FLORIDA, SOUTHWESTERN COLORADO THROUGH CENTRAL NEW MEXICO,
AND THE NORTHERN PLAINS...

...South Florida...
Stationary front persists over far South Florida today with the
positive moisture anomaly focused over the Miami metro with the
eastern coast likely to get more slow moving heavy thunderstorms 
in the light mean layer flow. The Slight Risk is shrunk to be 
closer to the Miami-Palm Beach metro area with the Marginal Risk 
still extending up the east coast nearly to Jacksonville.

...New Mexico and Colorado...
The positively tilted upper level trough from an upper low over
northern NV will pivot to neutral tilt this afternoon. Therefore,
expect a more south to north oriented axis of heavy rainfall, 
stretching from south-central New Mexico to across much of western
Colorado. Moisture from the Pacific will also be drawn northward 
into eastern Arizona and western New Mexico with PW anomalies of
+1.5 to 2 sigma, resulting in a rather large QPF footprint.
Diurnal convection is the main focus at play today, though 
guidance continues to suggest repeating rains over southeast AZ and
southern NM into the overnight. The Slight Risk is maintained over
southwest CO and central NM. 

...Northern Rockies onto the Northern Plains...
The upper low center shifts north to MT by late tonight. Notable
activity ahead of the low/trough looks to focus over the western
Dakotas into eastern MT per 00Z CAM consensus where a Slight Risk 
has been raised. PW anomalies of 1 to 2 sigma remain over northern
ID/western MT where the Marginal Risk is maintained.

...Upper Midwest...
Ongoing activity over eastern ND and northern MN should shift
southeast by 12Z and track to northern WI. Then diurnally driven
convection looks to cross a similar path. Given the advance of
moisture over the upper ridge axis extending over eastern IA, it
was worth adding a Marginal Risk to northern MN/WI and the western
U.P. of MI. 


Jackson


Day 2
Valid 12Z Sat Sep 13 2025 - 12Z Sun Sep 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM WESTERN KANSAS
TO FAR WESTERN TEXAS, THE MIAMI METRO, AND WESTERN NORTH DAKOTA...

...Central High Plains through Southern Rockies...
The upper level trough over the Intermountain West becomes 
negatively tilted on Saturday with the monsoonal moisture axis over
NM during the day shifting to the southern High Plains overnight. 
The position of this trough will enhance the low level jet on the
High Plains Saturday night and draw deeper Gulf moisture north 
over the Panhandles and eastern New Mexico and through western 
Kansas. This will encourage diurnally developing lines of storms 
from New Mexico terrain to press eastward onto the High Plains.
Given the +2 sigma PW anomalies and overall slow storm motion, the
Slight Risk area was expanded a bit over western KS and down into
far western Texas. 

...South Florida...
The front will push south from Florida during the day Saturday with
anomalous moisture lingering in the morning over the Miami metro
where A Slight Risk persists. The Slight Risk still looks generous
given the decreasing moisture profile through the day, but is
maintained for now.

...Northern Plains...
The upper low center over central MT will allow the focus for
heavy convection to shift north a bit from Friday with both morning
and diurnal max activity looking to focus on western ND. Given good
overlap in heavier precip among available CAMs and the EC-AIFS, a
Slight Risk is raised over western ND. Pivoting of the low without
much lateral movement is expected, prolonged heavy rainfall is
possible with.

Jackson


Day 3
Valid 12Z Sun Sep 14 2025 - 12Z Mon Sep 15 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE DAKOTAS...

...Central and Northern Plains...
Negatively-tilted trough axis lifting up the central Plains Sunday
should provide a narrow focus to convective development over the
western or central Dakotas. This activity will be heavy given PW
anomalies of +3 sigma persist over this area. Further development
is expected from central KS up through the Dakotas where a generous
Marginal Risk remains in effect.

Jackson
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