Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Oct 31 2023 15:32:16

FOUS30 KWBC 311532
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1131 AM EDT Tue Oct 31 2023

Day 1
Valid 16Z Tue Oct 31 2023 - 12Z Wed Nov 01 2023

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.=20
=20
Campbell/Kleebauer


Day 2
Valid 12Z Wed Nov 01 2023 - 12Z Thu Nov 02 2023

....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR MUCH OF
WASHINGTON STATE FROM THE CASCADES WEST...

An atmospheric river will be making its way inland during this
period, bringing beneficial moisture to western parts of Oregon
while moderate-to-heavy rainfall for northwest Oregon and western
Washington. Much of coastal Oregon and the Willamette Valley are
experiencing lower than normal river levels, so the start of this
first atmospheric river will largely be absorbed into the soil.
Recent burn scars scattered about the Washington Cascades will
increase the threat for localized flooding concerns with this
anomalous plume of moisture. PW values of 1.5 inches will be
nearly double the normal for early November by 00Z then another
surge brings it to being tripled the average. The Marginal Risk
area that was already in effect had minor adjustments made to
reflect the latest trend in model guidance and WPC QPF.

Campbell


Day 3
Valid 12Z Thu Nov 02 2023 - 12Z Fri Nov 03 2023

....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN
WASHINGTON AND NORTHWEST OREGON...

The focus of the highest rainfall will shift to the Cascades as
the atmospheric river surges further inland to the Intermountain
West while amounts along the coastline somewhat decreases.
Rainfall from the previous day will likely have increased soil
saturation thus maintaining an elevated threat for excessive
rainfall and localized flash flooding. Western Oregon will likely
begin to have localized flooding concerns after reaching/exceeding
beneficial amounts. The latest guidance depicts areal averages of
2 to 3 inches along the Cascades and 1 to 2 inches along the
coastline. A Marginal Risk area covers much of the same locations
highlighted in the Day 2 Marginal with a southern expansion along
the Oregon Coast and Oregon Cascades.

Campbell


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!-F_Duf0vxGAUT9MmLrnYIyWAK0mSIrwiEEKX5BFfTbeM=
pBQOoO7MsLHmWGmXx2KiIbD2H9G6J5JTYGS9uVPmhYU9LGg$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!-F_Duf0vxGAUT9MmLrnYIyWAK0mSIrwiEEKX5BFfTbeM=
pBQOoO7MsLHmWGmXx2KiIbD2H9G6J5JTYGS9uVPmnXuZrTw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!-F_Duf0vxGAUT9MmLrnYIyWAK0mSIrwiEEKX5BFfTbeM=
pBQOoO7MsLHmWGmXx2KiIbD2H9G6J5JTYGS9uVPmbKDSlzw$=20


$$



=3D =3D =3D
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