FOUS30 KWBC 100822
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Tue Mar 10 2026

Day 1
Valid 12Z Tue Mar 10 2026 - 12Z Wed Mar 11 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF 
THE SOUTHERN AND WESTERN PLAINS AND OVER PARTS OF THE SOUTHERN GREAT LAKES...

The signal for potentially two heavy precip axes persists in the
guidance..in the very favorable coupled jet entrance/exit regions 
expected between the southern stream closed low moving into the 
Southern Plains and the northern stream jet across Mid Mississippi 
Valley and the Midwest region. 

Gulf moisture gets drawn northward over parts of the central U.S.
from Texas into the central portion of the Mid-Mississippi Valley
during the day. There has been a trend in the model guidance over
the past 24 hours for the core of the higher precipitable water
values to get shunted more eastward than northeastward...resulting
in lower model QPF despite the upper support and mid-level
mesoscale forcing remaining favorable. Consequently...trimmed the
Slight Risk area to cover only portions of Illinois and Indiana
where QPF exceeded an inch and which overlapped areas that
experienced moderate to heavy rainfall a few days ago and have
suppressed flash flood guidance.  

The better instability...and associated higher rainfall 
rates...still look to be over portions of Texas into southeast of 
Oklahoma as flow aloft becomes increasingly difluent in response to
an approaching upper low. .Mixed layer CAPE values of 1500 to
around 2500 J per kg develop ahead of the low where precipitable 
water values will have risen into the 1.25 to 1.5 inch range 
resulting in the potential for 1+ inch per hour rates. The axis of
model QPF and WPC deterministic QPF align well with modestly- 
lowered flash flood guidance from rainfall several days ago.

Bann


Day 2
Valid 12Z Wed Mar 11 2026 - 12Z Thu Mar 12 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE 
SOUTHERN US...

The upper low over the southern states will continue to translate
eastward on Wednesday. The upper support will be weakening as the
system weakens/fills with time. Model run to run consistency has
been poor and another round of changes were made this cycle. The
changes included introduction of a Slight Risk over parts of
eastern Texas and western Louisiana where model QPF exceeded two
inches. In addition...there was some overlap between locally heavy
rainfall a couple of days ago and the QPF.

...Pacific Northwest...
Persistent on-shore flow of deep moisture into parts of coastal
Washington and northern Oregon should result in occasional moderate
rainfall...mainly in the west face of the coastal ranges. Amounts
on the order of 2.5 inches to 3.5 inches in 24 hours is forecast
which could result in isolated flooding ot run off problems in
areas of poor drainage.

Bann


Day 3 
Valid 12Z Thu Mar 12 2026 - 12Z Fri Mar 13 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHWEST UNITED STATES...

...Pacific Northwest...
On-shore flow of deep moisture into parts of coastal Washington 
and northern Oregon persists into the Day 3 period that results in
occasional moderate to locally heavy rainfall continuing along the
coastal ranges. An additional 1 to 3 inches in 24 hours are 
possible...which could result in isolated flooding ot run off 
problems in areas of poor drainage.

Bann
$$
--- SBBSecho 3.28-Linux
 * Origin: Capitol City Online (618:250/10)