Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
750 PM EDT Thu May 2 2024
Day 2
Valid 12Z Fri May 03 2024 - 12Z Sat May 04 2024

...THERE IS SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
TEXAS AND LOUISIANA COAST AND THERE IS A MARGINAL RISK OF
EXCESSIVE RAINFALL FOR MUCH OF TEXAS, THE LOWER MISSISSIPPI VALLEY,
TENNESSEE VALLEY, CENTRAL PLAINS, AND THE PACIFIC NORTHWEST...

...Southern Plains and Southeast...

21z update... A copious amount of rain (at least 8 to 12 inches)
has fallen over parts of southeast Texas Thursday morning with more
heavy rain to pass through for the remainder of the day 1 period
and into the day 2 period. This very water-logged part of the
region will be very sensitive to any additional precipitation. A
Slight Risk was raised for this period to cover the most sensitive
locations with the expected additional rain over the region, which
spans from southeast Texas, across southern Louisiana and clips the
extreme southwest edge of Mississippi.

Campbell

A trio of areas extending from the southern plains through the
Southeast US will draw attention for the period. The primary area
of focus will reside in the Lower Mississippi Valley where some
guidance is now suggesting the development of convection upstream
within the axis of an approach cold front, developing upscale and
maneuvering through the ArklaTex into LA by the beginning of the
forecast period. Locally heavy rains would be a certainty if this
evolution occurred and will need to be monitored closely with
regards to timing and magnitude

...Northeast...

Showers are expected to move through parts of the Appalachian and
western portions of the Northeast as a warm front lifts through the
region. Hi-res guidance suggests there will be several hours where
the thunderstorms will be be capable of producing hourly rainfall
rates up to 2/2.25 inches/hour, particularly across western New
York, western Pennsylvania and northern West Virginia. 3-hr FFG
values across this part of the country are as low as 1.5 inches so
there will be an increased threat for excessive rainfall and local
flooding concerns. A Marginal Risk area was raised from western New
York to central West Virginia.

Campbell

...Central Plains...

A fairly robust mid-level perturbation will eject east-southeast
out of WY/CO with convection initiating over the Front Range,
eventually congealing into a MCS as it migrates eastward through
southern NE into KS. Models are in agreement of at least some
modest QPF with 1-2" scattered across the aforementioned areas and
QPF maxima running upwards of 3" at this time. Current QPF maxima
is within the vicinity of southern NE into northern KS, but the
expectation is for multiple pockets of higher QPF embedded within
the complex as it moves to the southeast. As of now, the system
looks to remain progressive, but will monitor closely as we
approach the event in question to see if we can hone in on any
specific area for potential upgrades, or maintain continuity.

...Pacific Northwest...

21Z update... QPF trended a bit further south along the northern
California coast so in turn the Marginal Risk area was expanded a
smidgen southward to reflect this trend.

Campbell

A relatively weak IVT pulse will enter coastal OR and northwest CA
by the second half of the period with locally heavy rainfall
expected through Saturday morning. IVT index is running at an "AR
1" which signals a weaker atmospheric river event, but one that can
still produce modest rainfall totals to the coastal plain. Ensemble
trends have come up a bit from previous forecasts with QPF running
between 1.5-2.5 over the span of 12 hrs (00-12z Saturday), with a
bit more as we head into D3. As a result, kept continuity with the
MRGL risk from previous forecast package.

Kleebauer