Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
845 PM EDT Fri Jul 31 2026
Day 2
Valid 12Z Sat Aug 01 2026 - 12Z Sun Aug 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE THE UPPER
MIDWEST TO THE GULF COAST AND THE SOUTHERN HIGH PLAINS...

...Upper Midwest...
A potent and unseasonably deep low pressure system (ensemble mean
forecast MSLP values below the minimum CFSR climatological) will
continue to pivot across the Upper Midwest as its parent mid/upper
low digs and deepens over the region. Ahead of the system, strong
low-level south and southwesterly flow will advect deep Gulf
moisture (PWs 2-2.25 inches/150-175% of normal) northward. Combined
with impressive dynamics, large scale ascent, and sufficient
instability, the threat of convectively driven heavy rain is
expected to continue into Day 2/Saturday, especially within the
pivoting comma head due north of the low track across parts of
Illinois and Indiana. There, the 12Z HREF/RRFS guidance is
highlighting the potential for significant QPF, with notable
probabilities of exceeding 3"/24 hrs (60-80%) and 5"/24 hrs
(25-50%). As a result, the existing SLGT risk can be considered an
enhanced SLGT from east-central Illinois to northwest Indiana.
Elsewhere across the Ohio and Tennessee Valleys, only cosmetic
adjustments were made to the SLGT and MRGL risks.


...Parts of the Southeast to the Gulf Coast...
A mid/upper impulse embedded within northwesterly flow on the
southern periphery of the deepening low over the Upper Midwest will
dive into the Southeast before slowing down near the Florida
Panhandle during the Day on Saturday. Anomalously high PWs of
2.25-2.75 inches (125-150% of normal) along with 1000-2000+ J/kg of
MUCAPE will support numerous clusters of slow-moving showers and
thunderstorms containing intense rainfall rates. The 12Z HREF/RRFS
show fairly widespread probabilities of 40-90% for QPF greater than
3"/24 hours and 20-60% for greater than 5"/24 hours across parts
of the Southeast, especially for portions of Georgia and the
Florida Panhandle. Given this increased signal for potentially
significant rainfall, the SLGT risk was expanded southward to
include southwest Alabama, southern Georgia, and most of the
Florida Panhandle.


...Southern Rockies/High Plains to the Texas Hill Country...
Monsoonal moisture and instability interacting with upslope flow
and a southward progressing cold front will support scattered
showers and thunderstorms from the southern Rockies and High Plains
to the Texas Hill Country on Day 2/Saturday. This activity will
have the potential to produce heavy rainfall rates in excess of 1"
per hour, leading to isolated and scattered instances of flash
flooding. 12Z HREF/RRFS probabilities for QPF greater than 3"/24
hours are 20-50% and mostly concentrated across the southern High
Plains of New Mexico. The existing SLGT risk covering that area
looked on track so minimal changes were made. However, the
HREF/RRFS is also beginning to highlight the Texas Hill Country
with a 10-40% chance for QPF greater than 3"/24 hours. Also notable
are the very low but non-zero probabilities for greater than 5"/24
hrs (5-10%). As a result, the MRGL risk was expanded eastward from
far western Texas with this update, and a future upgrade to a SLGT
risk can't be ruled out.

Miller


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt