FOUS30 KWBC 071554 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1154 AM EDT Tue Apr 7 2026 Day 1 Valid 16Z 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... 16Z Update: Weak shortwave trough across the eastern Gulf will migrate through the Peninsula over the course of the afternoon and early evening with a surface low progged just off the eastern FL coast. Combination of deep layer moisture established across the southern half of the Peninsula on the order of +1 to +2 deviations above climo along with the aided ascent provided by the shortwave and surface low alignment will create an environment favorable for locally heavy rainfall along the eastern FL coast. There will likely be a dual QPF maxima positioned near the Space Coast (Daytona Beach to Cape Canaveral), as well as a second positioned from West Palm Beach down to the Miami metro as noted via the latest CAMs output and associated hi-res ensemble. The area across the Space Coast will see the benefit of some RER jet dynamics and prevailing east-northeast flow coupled between the sprawling high across the northeastern CONUS and the surface reflection off the southeastern FL coast. Current radar indicates some modest frictional convergence in proximity to the Cape Canaveral area which has been well-forecast over the last series of HRRR/RRFS runs. 12z HREF neighborhood probabilities for >3" are running between 60-80% between the area from Daytona Beach down to just north of Melbourne, but only limited probs for >2" on the EAS fields which signals more localized maxima compared to a larger heavy rain footprint and broader flash flood potential. That said, this area is still recovering from being impacted yesterday, so the threat for flash flooding is a little higher than normal within any stronger cells. The SLGT risk remains in place over this area down through the east-central portion of the coast to account for this threat. Further south across southeastern FL, a frontal boundary is analyzed from Fort Myers through West Palm Beach with a weak shortwave progression over the western Gulf making headway into the Peninsula. The combination of the surface reflection and added ascent and shear pattern from the mid-level disturbance will likely induce an area of convective development over the Everglades later this afternoon, migrating eastward into the southeastern metro corridor providing instances of scattered heavy rain areas that could enhance flash flood prospects within the urban zones. Rates from cells just off the coast this morning were able to reach between 3-5"/hr already with the environment in place which lends credence to those pockets of potentially heavy rainfall that could spur up flash flooding in a short period of time. HREF neighborhood probs for >3" are between 60-90% over the corridor from West Palm down to Miami with the maximum likely over eastern Broward to northern Miami-Dade. This makes sense given the positioning of the boundary bisecting these areas which could be a focal point for convection to develop and align before pivoting off the FL coast. The SLGT risk from previous forecast was unchanged given the above. Kleebauer 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