FOUS30 KWBC 070828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Tue Apr 7 2026

Day 1
Valid 12Z Tue Apr 07 2026 - 12Z Wed Apr 08 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE ATLANTIC SIDE OF THE FLORIDA PENINSULA TODAY...

Introduced a Slight Risk area across the Atlantic side of the
peninsula in an environment conducive of focusing and sustaining
locally heavy rainfall amounts and rainfall rates into the evening
hours. There had been showers and some thunderstorms on Monday
afternoon and evening...but the approach of a mid and upper level
feature helped increase coverage of light to moderate rainfall in
the overnight hours prior to the start of the Day 1 period at
07/12Z. Thinking is that this will help prime the soils enough to
slow the intake a bit of additional rain later today.

Additional showers and thunderstorms should develop during the day
along a slow moving cold front making its way southward in an
atmosphere with precipitable water approaching 1.75 inches. That
should support some downpours anywhere along the central or
southern peninsula on the Atlantic side. Additionally...there looks
to be a period of renewed moisture infusion by strengthening
easterly winds off the Atlantic following frontal passage which
enhances the potential for flooding.

The 00Z runs of the HREF and RRFS both maintain 10 to 20 percent
neighborhood probabilities of 3 inches of rain in 3 hours (broadly
speaking) from Cape Canaveral to Miami until 08/00Z and roughly the
same range for 24 hour amounts exceeding 5 inches. Despite the
disagreement shown by HREF and RRFS exactly as to where the highest
probabilities occur...the presence of ingredients along a corridor
that has stretches of surfaces impervious to water because of
urbanization supported an upgrade.

Bann

Day 2
Valid 12Z Wed Apr 08 2026 - 12Z Thu Apr 09 2026

...THERE IS A Marginal RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE EASTERN FLORIDA PENINSULA ON WEDNESDAY...

The 07/00Z suite of numerical guidance lingered additional rainfall
into the Day 2 as a quasi stationary front remains present. Even
so...the guidance maintained focus mainly along the eastern
coastline as having an elevated threat for urban flash flooding
concerns. There were a few nudges based on the latest guidance but
the overall changes did not reflect a fundamental change in
forecast reasoning. The QPF did not normally suggest a Slight
risk...but the need for one will be revisited based on how much
rain falls and where it falls today and tonight.

Bann

Day 3
Valid 12Z Thu Apr 09 2026 - 12Z Fri Apr 10 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
NORTHERN/CENTRAL PLAINS...

There is a growing consensus among the models for heavy to
excessive rainfall threat shaping up on Thursday given
strengthening return flow from the Gulf region encounters the
leading edge of colder air coming out of Canada and the northern
US. Precipitable water values between 0.8 and 1.0 inches and CAPE
values in excess of 1500 J per kg will encounter the
front...resulting in storms that could result in heavy to
potentially excessive rainfall Thursday into Thursday night/early
Friday.

Bann


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