Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
822 PM EDT Tue Apr 7 2026

Day 1
Valid 01Z Wed Apr 08 2026 - 12Z Wed Apr 08 2026

The excessive rainfall risks were removed from Florida given the
nocturnal downward trends in activity and instability. The upper
trough axis has also shifted east of the Peninsula, removing some
forcing. Localized heavy precip is likely overnight as abundant
moisture and some low level boundaries persist up near Daytona and
near Palm Beach. CAM guidance continues to indicate a diurnal ramp
up in heavy rain coverage over the eastern side of the FL
peninsula tomorrow where a Slight Risk remains in effect.

Jackson


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

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE EASTERN FLORIDA PENINSULA...

20Z Update: A persistent pattern of northeasterly flow into the
eastern FL Peninsula along with a quasi-stationary front bisecting
portions of the state will lead to another round of scattered
convective activity capable of localized flash flooding. The best
chance for this to occur will be across the urban settings along
the I-95 corridor stretching from Daytona Beach down to the Miami
metro with the latest HREF blended mean QPF generally heaviest near
the Treasure Coast. This is coincident with the alignment of the
stationary front where convergence would be maximized in the
vicinity of the front allowing storms to anchor and provide a more
prolonged heavy rain scenario when storms develop. Other prospects
for heavy rain will likely be along the immediate coast due to
frictional convergence spurred by the prevailing northeasterly
surface flow coupled with a moderate effective shear layer between
30-40kts out of the southwest. This setup is relatively favorable
for anchored storms along the immediately coastal plain, especially
when accompanied by at least modest instability, which is forecast
via a 500-1500 J/kg MUCAPE during Wednesday afternoon.

Areal neighborhood probabilities for >3" remains very similar to
today's output (50-80%) up and down a majority of the eastern FL
Peninsula with a targeted area situated across the Treasure Coast
and immediate Miami metro corridor. Some of the deterministic CAMs
outputs are fairly robust with 5-8" of rainfall in some areas that
see the prolonged convective anchoring that occurs within proximity
to the aforementioned front which at least signals a ceiling
outcome (10th percentile maxima) for the setup. PWATs will remain
above normal around 1-2 standard deviations above normal over the
southern half of FL which would be sufficient for those heavier
cores to materialize when convection occurs. Considering some
overlap over the past few days, especially the current D1 of a SLGT
risk, and in coordination with the Miami and Melbourne WFO's,
another SLGT risk was introduced for the new D2 update to account
for the threat.

Kleebauer


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
CENTRAL PLAINS AND MIDWEST...

20Z Update: The general synoptic pattern across the Central CONUS
remains consistent on a run-to-run basis as locally heavy rainfall
from Kansas to points east-northeast through Northern IL will allow
for a threat of isolated flash flooding on Thursday night into
Friday morning. A weak shortwave ejecting out of the Central
Rockies will intersect a slow-moving cold front propagating out of
the Upper Midwest and Northern Plains creating a focused axis of
ascent along and just ahead of the front as it migrates through the
Plains and Central Midwest. Areal QPF average of 1-3" is forecast
within vicinity of the front with much of the rain occurring in a
window between 00-12z Friday, a lot of the setup stemming from the
introduction of a modest nocturnal LLJ enticing convergence along
the front. The magnitude of rainfall and antecedent soil moisture
anomalies pin this into the traditional MRGL risk threshold, in
agreement with the latest CSU First Guess Fields.

Kleebauer

..Previous Discussion..

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