Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jan 18 2024 08:12:56

FOUS30 KWBC 180812
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
311 AM EST Thu Jan 18 2024

Day 1
Valid 12Z Thu Jan 18 2024 - 12Z Fri Jan 19 2024

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF WESTERN WASHINGTON AND NORTHWEST OREGON...

A Marginal Risk was maintained across portions of the Olympic
Peninsula southward into northwestern Oregon, where moderate to
heavy rainfall, along with snow melt in some areas may lead to
excessive runoff.  Guidance shows precipitation spreading north
with a well-defined warm front lifting across the region today.=20
GFS and ECMWF IVT indicate significant moisture transport into the
region beginning later this morning.  Model consensus shows 1-2
inches, with locally heavier amounts across the region.  The
heaviest amounts are expected along the southern slopes of the
Olympics, where upslope flow is likely to bolster amounts.  This
along with rising snow levels and low-level snow melt may raise
the threat for isolated excessive runoff.

Pereira


Day 2
Valid 12Z Fri Jan 19 2024 - 12Z Sat Jan 20 2024

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
NORTHERN CALIFORNIA...

Guidance continues to show a well-defined mid-level shortwave and
its associated frontal system moving into Northern California by
early Saturday.  As noted in the previous discussion, the need for
a Marginal Risk remains borderline with guidance showing the
associated IVT plume steadily weakening as it moves onshore.  In
addition, the 00Z model cycle is overall slower to develop heavier
amounts and areal averages have generally come down in this latest
run, especially for the more inland areas.  However, there remains
some spread with some models including the ECMWF/CMC and their
ensemble means still showing some potential for locally heavy
amounts, especially along the coast north of SF Bay.  This is
where the models continue to indicate some of the stronger forcing
and deeper moisture will coincide, especially late in the period.=20
Therefore, given the wet antecedent conditions and at least some
potential for localized heavier amounts, opted to maintain a
Marginal Risk from SF Bay northward into the Northern Coast
Ranges.

Pereira

Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!46eIeU3EvG1XvVlGht2MHdEDH5ahBLvsKeaK_XL-BLKM=
OPXWVa5IFuE9CzqUQFjj2a8lgfM4CI2QjxymXK0mZa-l450$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!46eIeU3EvG1XvVlGht2MHdEDH5ahBLvsKeaK_XL-BLKM=
OPXWVa5IFuE9CzqUQFjj2a8lgfM4CI2QjxymXK0mkP6eRVY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!46eIeU3EvG1XvVlGht2MHdEDH5ahBLvsKeaK_XL-BLKM=
OPXWVa5IFuE9CzqUQFjj2a8lgfM4CI2QjxymXK0muXwamm0$=20


$$



=3D =3D =3D
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