FOUS30 KWBC 110836
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
336 AM EST Tue Feb 11 2025

Day 1
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...

Few changes needed to the old Day 2 ERO as it propagates into the
Day1 period. Main focus for heavy rainfall and the potential for
excessive rainfall will be along and ahead of a cold front
associated with a developing synoptic scale low pressure system
within a broad/fairly flat flow pattern. Inclusion of more CAM
guidance supports the idea of higher intensity rainfall extending 
as far west as eastern Texas...a tendency we often see convection 
get organized farther southwest than expected in events like this, 
and there is growing QPF signal in the 12z ECMWF, UKMET and Gem Reg
over this area. The Slight risk area extended northeastward where 
there is a bit of instability that develops later in the period but
looks to be lacking initially. At expect the flash flood risk to 
pick up more over this area as we head into day 2.

Bann


Day 2
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH...

...Tennessee Valley into the Mid-South...

The prolonged heavy rainfall event will continue om Wednesday into
Wednesday night over the Southeast. The extended duration of this 
event will lead to storm total rainfall into the 3-5" range, with 
locally higher totals possible. As stronger forcing ejects eastward
on Wednesday, an increase in the low level jet should aid in both 
increasing moisture convergence and advecting instability
northward. The best overlap of ingredients that has the potential
for excessive rainfall looks to be over parts of AL/GA into far
southwest Tennessee. This is approximately the same area as the
previous Day 3 outlook...and given no major shifts in the synoptic
pattern saw little reason to make too many changes.

...California Coast...
The plume of moisture from the Pacific Ocean towards the end of Day
2 will start to bring rain to the coastal areas during the Day 3
period...beginning in northern and central portions of California
on Wednesday that propagates southward on Wednesday night and 
early Thursday. Present indications are that the axis of the
Atmospheric River and the associated heaviest amounts remain off 
shore or right along the coastal terrain...but a general uptick in
amounts was noted over the past 24 hours in this area.

Bann


Day 3
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE 
SOUTHERN CALIFORNIA COAST...

There is a Moderate Risk of excessive rainfall over portions of the
Southern California coast embedded within a broader Slight risk of
excessive rainfall covering much of the central and southern 
California coast. An atmospheric river is expected to skirt the 
coast as it makes its way south and east. The primary concern is
for damaging flooding and debris flow from the numerous fresh burn
scars in the region given the 24-hour QPF in the 1.5 to 3.5 inch 
range...with potentially localized higher amounts. In 
addition...the area is highly urbanized and an environment in which
much of the rainfall will turn immediately to runoff. Farther 
north...the Slight risk was extended into portions of the 
Sacramento Valley and San Joaquin Valley...where QPF is not 
expected to be as great but the conditions have been wetter and 
soils are more saturated than soils farther south.

Bann

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