343
FOUS30 KWBC 121349 AAA
QPFERD

Excessive Rainfall Discussion...UPDATED
NWS Weather Prediction Center College Park MD
949 AM EDT Wed Jun 12 2024

Day 1
Valid 1343Z Wed Jun 12 2024 - 12Z Thu Jun 13 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN
FLORIDA AND CENTRAL TEXAS...

...1350z Special Update...

A prominent shortwave continues to slowly maneuver over central TX
with ongoing convection north of Austin up towards Killeen down
through Jarrell and adjacent areas. Rates have been generally
between 1.5-2.5"/hr with some sporadic 3"/hr amounts at times in
specific cells. Totals will run generally 1-3" under the focused
area with maxima around 5" for locations that see multiple cells
move overhead. Flash flooding is ongoing in multiple areas in the
above corridor leading to confidence in higher flash flooding risks
allowing for an intermediate upgrade to a SLGT risk across portions
of central TX.

Kleebauer


...Previous Discussion...

...Southern Florida...

Bands of heavy showers have set up to the east of a weak low
positioned offshore the Tampa Bay region and has been yielding
rainfall rates of 1 to 2 hours. This convection and intensity is
expected to persist into the morning hours. Areal averages of 1 to
3 inches will be common for central and southeast portions of the
the peninsula while the southwest side will be much wetter with 3
to 8 inches forecast. Isolated higher amounts may be possible
between Tampa Bay and the Everglades. A Slight Risk covers from
Tampa Bay to Melbourne to points south and a Marginal Risk area
spans from central Florida and encompasses the Slight Risk.

...Texas...

Showers and thunderstorms will focus across central/eastern Texas
where the best lift and instability aligns with the pooled Gulf
moisture. Local rainfall totals likely within the 1-2 inch range
with maxes closer to 3 inches. While amounts are on the lower end
the recent rains will have increased soil saturation thus lowering
the amount of rain needed to become problematic. The Marginal Risk
was maintained for an isolated threat for flooding concerns for
portions of central and eastern Texas toward the Mid and Upper
Coast.

...Upper Mississippi Valley...

Showers and thunderstorms will move through the Northern Plains and
Upper Mississippi Valley ahead of an advancing cold front. PW
values of 1.5 inches over much of the north-central part of the
country will help boost rainfall efficiency and amounts, potentially
spreading 1 to 3 inches over the sensitive area and may lead to
isolated areas of flooding. The Marginal Risk area remains in
effect for portions of Minnesota, Wisconsin and Iowa.

Campbell


Day 2
Valid 12Z Thu Jun 13 2024 - 12Z Fri Jun 14 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN
FLORIDA...

...Florida...

Heavy rains near and south of a stalled front will persist adding
an additional 1 to 4 inches of rain to the already wet state. The
risk for flooding will remain elevated therefore maintained the Slight
Risk from Tampa Bay to Melbourne metros and south to the Keys and
the Marginal Risk area for central Florida.

...Midwest...

The central Midwest will see the pattern evolve upstream to
overhead by Thursday afternoon and evening with a shortwave
progression bisecting the region along with a cold front moving
through on the base of a low moving through the northern Great
Lakes in to Ontario. PW values around 1.25 inches will still be
enough to help boost rainfall rates across the Midwest. Areal
averages of 1 to 3 inches will be possible across this part of the
country where recent rains have left soils nearly saturated. Rain
may become excessive and lead to isolated instances flooding. The
inherited Marginal Risk remains in good order and covers eastern
Iowa/Missouri to southwest Michigan and northern Indiana.

Campbell


Day 3
Valid 12Z Fri Jun 14 2024 - 12Z Sat Jun 15 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN
FLORIDA...

...South Florida...

The frontal boundary will begin to sink south as a cold front
through central Florida during this period. Meanwhile tropical
moisture will persist across the state while now moving up the
eastern Seaboard. Guidance suggests this period to be less wet than
the last few days however the areal averages for southern and
central Florida are less than 2 inches. Given the multi-day heavy
rain event the threat for excessive rainfall and flooding concerns
will remain elevated for this period, therefore a Slight Risk
continues for South Florida and a Marginal Risk for central
Florida.

...Rockies and Plains...

Anomalous moisture over much of the Rockies and adjacent Plains
will migrate eastward with time as a low pressure system exits
into the High Plains. Some higher QPF is expected near the higher
terrain of northeast New Mexico and eastern Colorado. Much Nebraska
and the surrounding area will have be near or north of the warm
front and could easily pick up 1 to 3 inches of rainfall. A vast
majority of this region has 3-hr FFG near 1.5/2 inches however
there are very isolated locations as low as 0.25 inch. A Marginal
Risk is in effect from northeast New Mexico to Iowa/Minnesota/South
Dakota.

...New England...

The shortwave and associated cold front will sweep through the
Great Lakes region and lift through the Northeast during this
period. Showers and thunderstorms are expected to spread much of
the Northeast however focusing the higher QPF values across
southern New England where tropical moisture will be advecting
northward into the region. Guidance does show variance on the
location and the max value but consensus seems to favor southern
New Hampshire/Maine where FFG is as low as 1.5/2 inches at this
time. Isolated instances of flooding may arise. A Marginal Risk
spans from southeast New York to Downeast Maine.


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