FOUS30 KWBC 020830
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Mon Sep 2 2024

Day 1
Valid 12Z Mon Sep 02 2024 - 12Z Tue Sep 03 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE HILL COUNTRY/CENTRAL TEXAS AND ALONG THE TEXAS GULF COAST...

...Texas...

An upper level trough with a mid-level vort will be advancing into
western Texas during this period. Meanwhile a surface low hugging
the South Texas Coast will maintain easterly flow from the Gulf
allowing PW values of 2+ inches to pool over much of the state. The
latest guidance continues to depict areal averages of 1 to 5 inches
of QPF across the Hill Country into east-central Texas and along
much of the Texas coastline. Recent rainfall has increased soil
saturation across the state thus lowering FFGs. The hi-res guidance
is showing training of slow moving convection capable of 1 to 2.5 
inches/hour rain rates which could easily lead to scattered areas
of excessive rainfall and localized flash flooding. A Slight Risk
areas remains in effect for west-central and central Texas.
Additionally, a Slight Risk was added for the coastline today where
storms will be producing rates of 1 to 3 inches/hour.  

...Carolinas...

A cold front sinking through the Mid-Atlantic region will continue
to move showers and thunderstorms southward over the Carolinas
today. Guidance keeps the bulk of the QPF offshore during this
period where there are better dynamics in place however there will
still be an isolated threat for localized excessive rainfall and
flooding. A Marginal Risk area was maintained for eastern portions
of the Carolinas.

Campbell


Day 2
Valid 12Z Tue Sep 03 2024 - 12Z Wed Sep 04 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL TEXAS...

...Texas...

The mid-level vort is expected to exit the region although 
precipitable water values will remain high (+1 to +2 sigma 
initially, then decreasing late Tuesday). A large portion of the 
flooding potential will be contingent on a verified forecast from 
Day 1/Monday, as Monday will have the heavier rain/stronger storms 
of the two days. However, even the lesser amounts of rain expected 
Tuesday should still cause flooding issues in the area with a 
widespread 1 to 1.5 inches forecast with locally higher amounts. A
Slight Risk remains in effect for central portions of the state.

The heaviest rains in the state are expected to be along the Gulf
Coast from Galveston south and west through Corpus Christi. Locally
heavy rains to 2 inches per hour will be possible. For now the
greatest flooding threat remains confined to any urban areas, but
should Monday's rains overperform here then a Slight may be needed
for the hardest hit areas with future updates.

...Idaho/Montana...

A potent shortwave trough will interact with up to 2 sigma above 
normal atmospheric moisture on Tuesday. PW values rising to near 1
inch will support storms capable of heavy rain that may produce 
isolated flash flooding should the storms impact particularly flood
sensitive or more urban areas.

Campbell/Wegman


Day 3
Valid 12Z Wed Sep 04 2024 - 12Z Thu Sep 05 2024

...Gulf Coast and Lower Mississippi Valley...

The influx of anomalous Gulf Moisture will persist all across the 
southern tier states while the upper trough and vort exits the 
plains and into the Mississippi Valley. The surface front will 
continue to be draped west to east across the South continuing to 
provide focus for showers and thunderstorms across the region. 
During the late afternoon and evening hours there will be an 
intensification of instability and forcing to boost rainfall rates 
across the Lower Mississippi Valley, particularly over Louisiana, 
western Mississippi and southeast Arkansas. Most of the guidance 
are suggesting that 1 to 3 inches will concentrate over this part 
of the region thus increasing the risk for excessive rainfall and 
local flooding potential. There is the potential for a few 
locations for local maximums to exceed 6 inches near northern
Louisiana/Arkansas. Onshore flow across southeast Louisiana and 
southern Mississippi could yield 1 to 4 inches as well. A Slight 
Risk area was raised for parts of Louisiana, Mississippi and 
Arkansas.

Campbell

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