Hydrologic Outlook issued February 21 at 3:24PM PST by NWS Pendleton OR

ESFPDT

Synopsis: Rain and high mountain snow from and multiple systems this
weekend and early next week will lead to rising water levels on area
streams and rivers. Rainfall amounts of 2 to 5 inches are expected
in the Cascades and 1 to 3 inches in the eastern Oregon mountains.
In addition, temperatures will be rising to the 40s and lower 50s in
the mountains which will lead to snow melt adding even more water to
area rivers and streams. The National Water Model is highlighting
high water on numerous smaller streams and creeks, but streamflow
amounts are generally only slightly higher than high water
thresholds.

What: Precipitation fed by an atmospheric river and snow melt due to
warmer temperatures this weekend into early next week will lead to
rises on area creeks, streams and rivers. Rivers are low enough so
that most rivers will remain below bankfull. However, the Walla
Walla River at Touchet and the Naches River at Cliffdell are
expected to exceed bankfull late Sunday night before receding Monday
and Tuesday. Another concern will be rapid rises on smaller streams
and creeks due to heavier downpours and snowmelt. This could lead to
debris flows on recent burn scars and over steep terrain.

The Walla Walla River at Touchet has a 44 percent chance of
exceeding bankfull but less than a 5 percent chance of reaching
minor flood stage. It is expected to reach bankfull late Sunday
evening and remain there through Tuesday morning.

The Naches River at Cliffdell has a 29 percent chance of exceeding
bankfull but less than a 5 percent chance of reaching minor flood
stage. It is expected to reach bankfull late Sunday evening and
remain there until dropping below bankfull Monday afternoon.

The Klickitat River at Pitt is forecast remain below bankfull, but
model probabilities give it a 13 percent chance of rising above
bankfull and a 9 percent chance of reaching minor flood stage. All
other river forecast points have a less than a 10 percent chance of
exceeding bankfull.

When: Rain will begin tonight and continue through Monday with the
heaviest rain expected Saturday night and Sunday.

Where: The Upper and Lower East Slopes of the Washington and Oregon
Cascades, The Simcoe Highlands, The Northern and Southern Blue
Mountains, The Blue Mountain Foothills of Washington and Oregon,
Wallowa County and the Grande Ronde Valley.

This Hydrologic Outlook will be updated as needed due to changing
conditions.