FOUS30 KWBC 130849
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Sat Sep 13 2025

Day 1
Valid 12Z Sat Sep 13 2025 - 12Z Sun Sep 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR EASTERN NEW 
MEXICO INTO FAR WEST TEXAS AS WELL AS FOR WESTERN NORTH DAKOTA...

...Central High Plains through Southern Rockies/West TX...

Upper trough over the Great Basin this morning will continue 
slowly eastward and take on a negative tilt, with a continued 
influx of moisture (PW anomalies +2 sigma) into the Southern 
Rockies and points northward. As the trough axis crosses the Four 
Corners region around 00Z tonight, LLJ increase will support 
convection over eastern NM late afternoon that will push into West 
Texas in the evening. Storms may have enough forward speed to limit
flash flooding potential, but 00Z CAMs continue to show potential 
for 1-4" amounts. Focused the Slight Risk outline further from the 
previous shifts to the best ensemble agreement. 

...Northern Plains...

Southerly flow through the column will maintain a surge of 
moisture (PW anomalies +3 sigma / 1.50" into the Northern Plains 
as weaker shortwaves race northward ahead of the main upper low 
over MT. Recent CAM guidance still shows some east-west 
displacement of heaver north-to-south QPF maxima, owing to small 
differences in shortwave/sfc boundary interactions and any morning 
convection. Maintained the Slight Risk outline over western ND but 
the eventual QPE footprint will likely be much narrower. 

...Northeastern Illinois and surrounding areas...

Shortwave diving southeastward out of Wisconsin this morning at 
the nose of a jet streak will help organize a small area of at 
least modest rainfall around the Chicagoland area that continues 
SSE-ward this afternoon. Some 00Z CAM guidance remains rather 
bullish with 2-3" amounts which may be enough to cause some urban 
runoff issues. 

...South Florida...

Frontal boundary will remain just to the southeast of Florida, but
precipitable water values will start the day around 2 inches. 
Drier air will slowly work southeastward through the entirety of 
the Peninsula by the end of the day, and have targeted the Marginal
Risk outline to around the urban areas between Palm Beach and Miami.

Fracasso


Day 2
Valid 12Z Sun Sep 14 2025 - 12Z Mon Sep 15 2025

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

...Central and Northern Plains...

Upper trough exiting the Rockies will split off its southern 
portion into an upper low over western Nebraska midday Sunday, with
southerly flow continuing across the Northern Plains (and ample 
moisture -- PW anomalies still +2 to +3 sigma). This mid-level low 
will lift northward and act as a focus for convergence toward the 
nose of the sfc- based instability gradient just to the east. 
Storms may repeat over the same area as D1, with the potential for 
another 1-2"+ of rain. Maintained the Slight Risk outline here with
a broader Marginal Risk extending to the south where the guidance 
shows potential for 2-4" of rainfall, but over areas with higher 
FFG values (esp. the Sand Hills). 

Fracasso


Day 3
Valid 12Z Mon Sep 15 2025 - 12Z Tue Sep 16 2025

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

Fracasso
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