942
AGUS74 KWCO 191527
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT FRI JUL 19 2024

.Synopsis...
Flash and urban flooding in the Eastern Carolinas, South-Central Texas,
Lower Mississippi Valley, ArkLaTex and Southeast... Monsoon activity
increases this week in the Southwest... Ongoing river flooding in the
Midwest and Great Lakes... Flooding possible in Puerto Rico...

.Discussion...

.Eastern Carolinas...
The threat for flash and urban flooding associated with moderate to locally
heavy rainfall will continue into early next week. Yesterday`s rainfall
saturated top layer soils (>70% 0 - 10 cm RSM, NASA SPoRT) increasing the
likelihood that additional heavy rains will lead to rapid runoff and
localized flooding impacts. Flooding impacts will primarily be a concern in
urban areas and areas of poor drainage, with small stream responses being
more dependent on training storms. This is further backed by below normal
flows on streams and absent NWM MRF high flow signals providing additional
confidence of ample in-channel storage.

.Southwest...
Increasing coverage and intensity of monsoon rains could lead to flash
flooding along arroyos and complex terrain, along with urban flooding,
particularly in NM, western AZ, and southern CO where the heaviest rainfall
is forecast. Slow moving convection may cause flash flooding issues,
especially over vulnerable areas like burn scars, dry washes, and slot
canyons.  Localized heavy rainfall of 2 - 4" remains possible into next
week for this region. This will likely increase the threat for locally
significant impacts in these areas, as intense rainfall on recently burned
hydrophobic soils will intensify runoff conditions.

.Lower Mississippi Valley, ArkLaTex and Southeast...
Moderate to locally heavy rainfall continues to be possible into next week,
bringing localized flash and urban flooding impacts. These factors will
likely lead to rapid stream rises and pluvial flooding of typical flood
prone or low-lying areas. Regions include TX, LA, AR, MS, and AL.
Antecedent conditions are generally on the drier side, less than 55% with
local areas closer to 75% (0 - 10 cm, NASA SPoRT), suggesting confidence in
primarily urban impacts. Though impacts will be mostly dependent on
rainfall rates and potential training.

.South-Central Texas...
Flash and urban flooding will be possible as an active rainfall pattern
begins early next week. Areas that receive repeated days of rainfall will
be most vulnerable to flooding impacts, as slow moving and efficient
rainfall saturates soils. The GFS-forced National Water Model (NWM) Medium
Range Forecast is generally more aggressive than the NBM-forced NWM,  and
is signaling scattered potential for rapid-onset flooding days 4 -5 mostly
in central Texas. Responses from the NBM-forced NWM are generally more
subdued.

.Midwest and Great Lakes...
Scattered minor to isolated moderate and major river flooding is ongoing
and forecast, primarily in portions of eastern IL, northern IN, and
southern WI. Majority of these rivers have crested, and with no significant
rainfall expected through the weekend, flows will continue to route and
recede unimpeded.

.Puerto Rico...
Isolated urban and small stream flooding impacts are possible associated
with heavy rainfall today and tomorrow. Rainfall has left soils on the
northwestern and eastern portions of the island saturated (NASA SPoRT).
This is also where the heaviest rainfall is forecast the next few days.

//Ayala

$$