874
AGUS74 KWCO 231522
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT SUN JUN 23 2024

.Synopsis...
Additional rounds of rainfall in the Northern Plains, Upper Midwest, Upper
Great Lakes and the Ohio Valley... Flash flooding possible in the Four
Corners region and Northeast...Snow-melt induced flooding in Alaska...

.Discussion...

.Northern Plains, Upper Midwest , Upper Great Lakes and the Ohio Valley...
Additional rounds of rainfall continue early next week through the end of
the week bringing the potential for flash, urban and small stream flooding.
Any rainfall lingering today and on day 2 (Mon) will be on the lighter side
and is expected to have minimal hydrologic impacts while days 3, 5 and 6
will be the heaviest (Tue, Thu, Fri). Widespread moderate to major river
flooding is ongoing and expected across southeast SD, southern MN, and
northern IA into next week. Record forecasts are ongoing and/or forecast
for many rivers seen over the same areas. Soil conditions are saturated in
areas of southeastern SD, northern IA, southern MN and central WI  (0 - 100
cm, 75 - 90% RSM, NASA SPoRT) given that widespread rainfall amounts of 3 -
10" (MRMS) have fallen over the past 72 hours. Streamflows are running much
above normal for all days of the year, suggesting limited to no storage
capacity to store additional rainfall and any remaining soil capacity will
likely be overwhelmed. Each additional round of rainfall will serve to
further compound the flood potential. The National Water Model (NWM) Medium
Range Forecast (MRF) continues to highlight much of the same region that
has just seen past rainfall including areas of SD, MN, IA, and WI as well
as portions of MI. Rapid-onset flooding probabilities are near 25 - 50% in
these areas with corresponding annual-exceedance probabilities (AEPs) near
50% Given these conditions, any given rainfall may delay recessions and may
potentially cause some renewed rises.

.Four Corners...
Moisture continues to remain in place over the region through the rest of
the week, specifically in areas of NM and AZ, bringing locally heavy
rainfall and the potential for flash flooding with days 4 - 5 (Wed - Thu)
likely being the biggest threat. Areas that received past rainfall may
continue to see a threat of flash flooding and excessive runoff. The flood
threat is highest in areas on recent burn scars, slot canyons, dry washes
and where training is likely to occur.

.Northeast...
Moderate to heavy rainfall continues to impact the region bringing the
potential for localized flash flooding, especially in areas where training
has occurred and in primarily urban areas today through day 2 (Mon) and
then again on day 4 and 7 (Wed and Sat). Soils are near normal (60 - 75%, 0
- 10 cm, NASA SPoRT) and near to below mean annual streamflows (USGS)
suggesting there is still sufficient infiltration capacity overall to
capture runoff. These factors will help to mitigate any widespread
hydrologic responses and limit the threat to urban, low-lying, and poor
drainage areas.

.Alaska...
Warming temperatures continue to cause snow and ice melt at high
elevations, leading to rivers running high in areas across Southcentral
Alaska. Minor flooding on the Chilkat River near Klukwan continues as well
as high water on the Nuyakuk River near Dillingham. The Skwentna and Yentna
Rivers will also likely have high water with out-of-bank conditions by day
2 (Mon).

//Kirkpatrick



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