066
FOUS30 KWBC 070828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Sun Jul 7 2024

Day 1
Valid 12Z Sun Jul 07 2024 - 12Z Mon Jul 08 2024

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
COASTAL TEXAS...

...Coastal Texas and Louisiana...

The latest (3Z) NHC forecast track for Beryl has Beryl positioned
just offshore the mid-Texas coast with it making landfall prior to
12Z Monday (please see the NHC website for the
latest information). Outer bands will wrap into the coast from South Texas
up along the coast into far southwestern Louisiana, though the bulk
of its precipitation shield will lie in the Day 2 period. There is
some suggestions that Beryl may intensify just before moving
onshore which should boost the accompanied wind gusts and rain. A
Moderate was introduced roughly from Rockport to Freeport an points
north since Beryl is expected to be onshore within the period. The
Slight and Marginal Risk areas were shifted eastward given the
forecast trend. Future adjustments in the track of Beryl may shift
the ERO areas a bit, depending on its evolution in the next 24-36
hours.

...Southern and Central Plains...

Organized convection is likely over portions of Kansas and Oklahoma
Sunday and through the overnight hours. The latest hi-res guidance
continue to have impressive model QPF agreement/signal; thus,
forecast confidence is above average with this event.
Interestingly the pattern appears to favor a rather progressive
convective complex... and PWs are not forecast to be overly high
either. The impressive QPF from the models, while somewhat
surprising, is likely indicative of the very strong mid/upper level
forcing and low level frontal convergence in play.

The moisture plume ahead of Beryl may be reaching this part of the
country during this period which could act to enhance rainfall
efficiency. A Slight risk area with higher but sub- Moderate
probabilities within that outline covers of Oklahoma, southeast
Kansas and northern portions of Texas. The apparent
progressiveness of convection keeps the risk from going
higher...but will need to continue to monitor. It has also been dry
lately in much of the region, which can increase the flash flood
threat due to hydrophobic soils. Regardless, with 12Z HREF
neighborhood probabilities of >2"/hr rainfall rates ~10-30% for
several hours Sunday afternoon and early evening.

...Southeast...

A stalled frontal boundary across the region will be the focus for convection
which will maintain an isolated threat for flash flooding
concerns. PWs will remain above the climatological 90th percentile,
and layered IVT suggest we may see some mid/upper level moisture
connection to Beryl. The intrusion of tropical moisture may help
bolster rainfall efficiency in what will already be a favorable
environment for heavy rainfall rates. A Marginal remains in effect
for a majority of the Southeast region for this period.

Campbell/Fracasso

Day 2
Valid 12Z Mon Jul 08 2024 - 12Z Tue Jul 09 2024

...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF EASTERN TEXAS...

The National Hurricane Center has Beryl tracking north/northeast
through eastern Texas. The guidance continues to suggest a fairly
compact storm, therefore the QPF swath is expected to be relatively
narrow and oriented N-S along and slightly east of the storm track.
WPC has areal average QPF ranging from 3 to 7 inches with isolated
maximums in the double digits. Given the adjustment to the NHC
storm track and the new WPC QPF, the inherited risk areas were all
shifted as follows. The Moderate Risk spans from Port Lavaca to
east of Galveston Bay and northward into southwest Arkansas. The
Slight Risk spans from San Antonio Bay to west of Vermilion Bay
and northward into central Arkansas. The Marginal Risk spans from
east of Corpus Christi to Atchafalaya Bay and from the Texas
Panhandle to Southern Missouri, tied to the frontal boundary to the
north. Note that the placements of the Excessive Risk areas will
largely be dependent on the NHC track so stay tuned for future
adjustments.

...Southeast...

Convection in proximity to the lingering frontal boundary will
persist across the Southeast; therefore maintained the Marginal
Risk area. Recent rains have increased soil saturation levels and
with additional showers and thunderstorms expected the threat for
isolated flooding concerns will remain elevated for this part of
the country, despite the lower QPF signal in the guidance. Will
gain more insight once we move into the CAM window, and also with
better clarity on the speed of recurvature of Beryl.

Fracasso/Campbell


Day 3
Valid 12Z Tue Jul 09 2024 - 12Z Wed Jul 10 2024

...Mississippi Valley and Midwest...

Beryl is expected to quickly phase with an upper trough and
surface front to the north, which lead to a significant change from
the previous forecast. These features should lead to the potential
for heavy rain causing flash flooding concerns over some areas
from eastern Texas northeastward through Wednesday. At this time,
the higher QPF amounts focus over northwest Arkansas to central
Illinois with the highest over the Ozarks. Areal averages are
expected to be around 2 to 5 inches with local maximums upwards of
8 inches. A Slight Risk extends from northwest Arkansas to central
Illinois. A Marginal Risk stretches from the central Gulf Coast
northward to northern Illinois and southern Michigan. Again, an
future adjustments will likely be dependent on the latest NHC track
for Beryl.

...Southwest...

Some moisture may feed into the Southwest and southern Colorado in
a monsoonal pattern. A Marginal Risk was maintained for most of New
Mexico, southeast Arizona and south-central Colorado for this
period considering sensitivities due to burn scars and areas that
have seen ample rainfall recently.

...Southeast...

Given the abundant moisture over the region and some model are
signaling for locally heavy rainfall, especially for eastern
portions of Florida. General consensus suggests 1 to 2 inches
although local maximums of 3 to 4+ inches will certainly possible.
A Marginal Risk remain in effect for portions of central/northern
Florida and southeast Georgia.

...Northeast...

Interaction of moisture ahead of Beryl and a front settling over
the Mid-Atlantic/southern New England may favor heavy rainfall
potential over this region. Some focus of the convective rain
ahead of the front(s) and sufficient instability for heavy rain
rates in the northern Mid-Atlantic to Northeast favor of a
Marginal Risk.

Campbell

Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt