Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
835 PM EDT Thu Jul 25 2024
Day 1
Valid 01Z Fri Jul 26 2024 - 12Z Fri Jul 26 2024

...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL FOR THE MIDDLE
AND UPPER TEXAS COAST...

A Moderate Risk for excessive rainfall has been maintained for
this update for much of the Middle and Upper TX Coast, while being
downgraded for the portions of southwestern LA. Heavy rainfall has
come to an end for the bulk of the region (and surroundings), but
the expectation is for refiring of convection once again late
tonight along the coast (where SB CAPE ranges from 1000-2500 J/kg
with precipitable water values of 2.0-2.2 inches, which are near
the 90th percentile). A positively-tilted longwave trough remains
anchored just to the west (over TX), allowing for DPVA from the
southwest (at least partially derived from prior convection over
the terrain of northeastern Mexico). This locked pattern is tending
to result in reinitiation of convection during the overnight
hours, and hi- res guidance once again depicts this potential
tonight (with 18z HREF 40-km neighborhood probabilities for 5"
exceedance of 20-30%). With 1-4" of rainfall (and locally higher)
over the past 24 hours alone, the area remains sensitive
hydrologically (with USGS gauges indicating above normal to near
record streamflows). Some models indicate intense convection
developing farther inland as well (to as far north as College
Station), and a Slight Risk has been maintained in these areas.

Otherwise, a Slight Risk was maintained for portions of the
Carolinas and adjacent portions of eastern GA, where heavy rainfall
is still ongoing (though will likely wane with loss of daytime
heating). A broader Marginal Risk was maintained across the
Southeast, where localized downpours may continue in the presence
of widespread tropical moisture (with a large area of 1.8"+ PWATs).
A Marginal Risk has also been maintained across much of the
Southwest and Intermountain West, where monsoonal convection will
gradually wane with the loss of daytime heating.

Churchill


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt