756
AGUS74 KWCO 281522
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT FRI JUN 28 2024

.Synopsis...
Additional rounds of rainfall in the Upper and Middle Mississippi Valley...
Flash flooding possible in the Four Corners region, and Northeast...
Snowmelt induced flooding continues in Alaska... Rain increases across
Puerto Rico/USVI early-to-mid next week...

.Discussion...

.Upper and Middle Mississippi Valley...
Widespread moderate to major river flooding is ongoing across far southeast
SD, southern MN, and northern IA. Record flooding is ongoing along the
Minnesota and Des Moines rivers. Moderate rainfall today may slow
recessions, with little increase to current river flow expected. After
today, there will be a break in the rainfall through the weekend, allowing
for flows to route/recede unimpeded.

Rain returns to the forecast on day 4 (Mon) across MN and northern IA. This
area will have some time to recover from ongoing impacts before this next
event but will need to be monitored closely, given the vulnerable
antecedent conditions. The National Water Model (NWM) Medium Range Forecast
(MRF) (NBM and GFS forced) are indicating potential for widespread new and
renewed river rises early next week in response to this rainfall, however
the magnitude of response is still uncertain.

.Four Corners...
Daily scattered thunderstorms will bring the potential of isolated flash
and urban flooding to parts of NM, AZ, and western CO. Regions that receive
multiple rounds of rainfall are more susceptible to flooding impacts as
soils reach saturation. The highest flood threat is in areas with recent
burn scars, slot canyons, dry washes, and regions where training and more
persistent storms occur.

.Northeast...
Moderate to heavy rainfall on days 2 into 3 (Sat into Sun) will bring the
potential for isolated flash and urban flooding to portions of the
Adirondacks and northern New England. Soils are generally moist, with room
for infiltration (50 - 65% RSM, 0 - 10 cm NASA SPoRT). Though there is
available infiltration capacity, training moderate rain could overwhelm
soils, increasing the chance of flooding, especially in areas of complex
terrain. Decreased QPF into the latest GFS-forced NWM MRF has resulted in a
reduction of signals over this area with only a few lower order streams
within the region forecast to hit AEPs of 20% or less, suggesting that the
potential for elevated flows on area streams is low.

.Alaska...
Warming temperatures continue to cause snow and ice melt at high
elevations, leading to rivers running high in areas across Southcentral AK.
Minor flooding on the Chilkat River near Klukwan continues through at least
the weekend, with ample snow available to melt. Also, high water continues
on the Nuyakuk River near Dillingham, Klutina River at Copper Center, and
Alsek River above Bates River.

.Puerto Rico/USVI...
Moderate to heavy rainfall early-to-mid next week will bring the potential
for flooding across the islands. Many stream flows across the region are
normal to above normal for both the year and day, suggesting soil capacity
is nearing saturation. This will increase flooding concerns, and trends in
forecast rainfall amounts will need to closely be monitored heading into
the weekend.

//GKendrick



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