140
AGUS74 KWCO 191517
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL NWS National Water
Center - Tuscaloosa AL 1015 AM CDT THU SEP 19 2024

.Synopsis...
Urban flooding possible in Southern Florida... Isolated flash
flooding and  ongoing river flooding and coastal flooding across the
Carolinas... Coastal  flooding across the Mid-Atlantic... Rainfall
for the Central Plains this  weekend... Receding flows across
Central Montana...

.Discussion...

.Southern Florida...
Heavy rainfall is forecast in southern Florida today and tomorrow,
and  associated urban flooding is possible. The extensive urban
nature of this  region will be at highest risk of flash flooding,
with flooding of roads  and ponding of water possible. Additionally,
with already saturated  grounds, slow moving storms may generate
flash flooding. Impacts will  largely be dependent on storm motion
and rainfall rates.

.Carolinas...
There is potential for isolated flash flooding impacts through the
day  today associated with scattered convection. The NWM SRF is
signaling  potential for rapid-onset flooding, particularly across
eastern North  Carolina, though associated Annual Exceedance
Probabilities, forced by the  NWM 18-Hour Maximum High Flow
Magnitude Forecast, are generally not less  than 50%, decreasing
confidence that flows will be impactful.

Isolated river flooding will continue across the Coastal Plain of
the  Carolinas (Pee Dee, Cape Fear/NE Cape Fear, Neuse, Contentnea)
into this  weekend in response to the recent tropical rainfall.
Additionally,  minor-to-moderate coastal flooding at high tide is
possible through day 3  (Sat) from Savannah, GA to Duck, NC.

.Mid-Atlantic...
Minor-to-moderate coastal flooding at high tide continues to be
possible  through tomorrow from the Chesapeake Bay to Long Island
Sound. This could  continue into the weekend. Check with your local
NWS office for more  information related to coastal flooding impacts.

.Central Plains...
Potentially heavy rainfall (totals up to 3") this weekend may bring
an  isolated flash flooding threat to the region. Dry antecedent
conditions  will likely mitigate the majority of flooding impacts,
with abnormally dry  to moderate drought conditions in place (USDM)
throughout the region. The  NASA GRACE-Based Root Zone Soil Moisture
Drought Indicator is signaling a  wetness percentile of less than 10
throughout much of the area adding to  confidence that much of this
rainfall will likely be beneficial. However,  isolated areas of
lowland flooding or urban flash flooding cannot be ruled  out in
areas of heavier rainfall.

.Central Montana...
Over the past 48 hours, much of Central Montana received 2 - 4",
locally 5"  (48 hr, MRMS) and water will continue to route
downstream unimpeded  resulting in elevated flows. Small stream
flooding in low lying areas  remains possible through the morning
today.

//Ayala

$$