Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
423 PM EDT Fri Oct 11 2024

Day 1
Valid 16Z Fri Oct 11 2024 - 12Z Sat Oct 12 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Easterly low level flow will bring showery conditions to the
central and southeast Atlantic coast of FL from this afternoon into
tonight. 12Z soundings showed precipitable water values at or below
1.5 inches that resulted in limited instability. That...combined
with a relative lack of organization shown currently on satellite
or in the short-range hi-resolution guidance...suggests that
rainfall rates or totals are not likely to reach levels of concern
for flash flooding. Thus we will continue to carry no risk area in
the ERO.

Bann

Day 2
Valid 12Z Sat Oct 12 2024 - 12Z Sun Oct 13 2024

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER FLORIDA KEYS INTO THE SOUTHEAST FLORIDA URBAN CORRIDOR...

Moisture and instability return northward into southern Florida 
Saturday into Saturday night, with PWs increasing towards 2.25" and
CAPE over 1000 j/kg. Meanwhile a weak wave moving into the eastern
Gulf of Mexico may result in an uptick in low level flow and
convergence. Thus expect we should gradually see an uptick in
convective coverage this weekend over the Keys into south FL.

The overall synoptic pattern still looks to favor slow moving
convective cells along and near the coastal convergence axis give
easterly low level flow and westerly upper level winds. Timing
remains a bit uncertain. Even though the better convective
coverage may end up more over the Keys this period (where flash
flooding is harder to come by) the 12Z suite of model guidance
still suggests the increasing moisture and instability poses at
least a conditional threat of localized flash flooding Saturday
into Saturday night into the more urban areas of southeast FL. If
deep convection does indeed develop then urban flash flooding is
possible from the upper Keys into southeast FL.

Bann

Day 3
Valid 12Z Sun Oct 13 2024 - 12Z Mon Oct 14 2024

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER FLORIDA KEYS INTO THE SOUTHEAST FLORIDA URBAN CORRIDOR...

The risk on day 3 is a continuation of the threat on day 2 over
Southeast Florida. The overall thermodynamic ingredients remain
the same, however there is a chance that forcing will be stronger
by Sunday. Still some timing and positional differences amongst the
guidance, but the general consensus is for a weak wave to move
across FL Sunday, which should both result in a subtle uptick in
mid/upper forcing and locally enhance lower level convergence.

The 12Z suite pf numerical guidance still pointed to a somewhat
greater chance of loosely organized convective clusters Sunday
into Sunday night...and with wind fields still supporting slow
moving cells...the risk of isolated urban flash flooding is still
possible but not enough to upgrade beyond a Marginal risk area at
this point. Will continue to monitor trends.

Chenard


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