770
AGUS74 KWCO 111507
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT TUE JUN 11 2024

.Synopsis...
River flooding continues in East Texas... Flash and urban flooding possible
in Florida... Snowmelt-induced rises across California, Intermountain West,
and Rockies... Potential for isolated flooding impacts in the Upper Midwest
and Upper Great Lakes...Heavy rainfall next week along the Central Gulf
Coast...

.Discussion...

.East Texas...
Moderate to major river flooding is ongoing and forecast across the Sabine,
Trinity, and Neches river basins. Crests are expected late this week as the
flood wave routes downstream. Little to no precipitation through day 6
(Sun) should allow for unimpeded recessions across the area.

.Florida...
Flash and urban flooding, some locally considerable in urban areas, is
possible this week as ongoing heavy rainfall through day 4 (Fri) brings 5 -
10" totals to central and southern FL, including the Keys. Locally higher
7-day totals, with totals greater than 15" possible, are anticipated in
southwest FL. Outside of urban areas, the soil column remains very dry due
to ongoing drought conditions and regions of karst topography will help
store water underground. Streamflow are low indicating there is ample
storage capacity, at least initially. Despite this, flooding is likely
given the slow-moving and prolonged nature of the rain, which will lead to
rapid accumulations. The National Water Model (NWM) Short Range Forecast is
signaling increasing probabilities for high water and rapid-onset flooding,
adding to confidence for flooding impacts. The greatest risk for flooding
impacts will be in urban areas, particularly Sarasota, Fort Myers, and
Naples and poorly drained areas. Impacts will largely be dependent on
rainfall intensity.

.California, Intermountain West, and Rockies...
Ongoing warming temperatures and snowmelt paired with periods of scattered
rainfall will continue to promote increased runoff across much of the
Intermountain West, northern/central Rockies, and the Sierra Nevada this
week. Isolated minor river flooding is ongoing, and area streams, creeks,
and rivers will continue to see rises.

.Upper Midwest and Upper Great Lakes...
Moderate to locally heavy rainfall days 2 - 3 (Wed - Thu), and again on day
5 (Sat), is forecast across the region, increasing the potential for
isolated flooding impacts. Both forcings of the NWM Medium Range Forecast
(MRF) are signaling the potential for rapid-onset flooding in SD, NE, IA
and southern MN, however the GFS-forced NWM indicates more widespread
responses. Regarding the overall magnitude of the streamflow responses, the
MRF High Flow Magnitude Forecast is generally suggesting only modest rises,
with annual exceedance probabilities for streamflow near 50%. Regarding
antecedent conditions, streamflows are normal to above normal (USGS) and
soils are on the wetter side. The region also has ongoing flooding,
particularly on the Mississippi River, Rock River, Little Sioux River, and
South Fork Crow River. Isolated flooding impacts associated with this
rainfall is possible.

.Central Gulf Coast...
Heavy rainfall is forecast days 6 - 7 (Sun - Mon) bringing with it
potential for flooding impacts. Antecedent conditions along the coast are
wet and streamflows are above climatological normals, particularly in
Eastern TX and LA. The NWM MRF is beginning to signal isolated responses,
particularly in southern MS. However, confidence regarding the magnitude
and placements of potential impacts is low due to the extended nature of
the event and variability in model guidance.

//Ayala

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