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FOUS30 KWBC 020828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EST Fri Jan 2 2026

Day 1
Valid 12Z Fri Jan 02 2026 - 12Z Sat Jan 03 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
CALIFORNIA COAST NORTHWARD INTO NORTHERN CALIFORNIA...

No major model disagreements with the eastward push of the strong
mid to upper level low off the northern California coast day 1. The
low level southerly flow will strengthen Friday along and ahead of
the associated frontal boundary pushing toward the central to
northern California coast. While PW values are only 1 to 1.5
standard deviations above the mean, the 850-700 mb moisture flux
values are more anomalous, 2-3+ standard deviations above the mean.
Precip should increase in intensity along the northern CA coast
after 0000 UTC Sat, and spread south into coastal central CA in the
0600-1200 UTC time frame. The frontal boundary is expected to be
fairly progressive, limiting very heavy rainfall totals. HREF and
RRFS neighborhood probabilities for .50"+ hourly amounts are=20
generally less than 30%, with a few localized 60%+ probabilities=20
along the central CA coast range to the south of Monterey, and=20
across the northern Sierra. Areal average 1 to 1.5" amounts=20
expected along the central to northern CA coast and 1.5-2" in the=20
northern Sierra with isolated heavier totals of 2.5-3"+ possible.=20
No significant changes made to the previous marginal risk, with=20
localized runoff issues possible where soils remain fairly=20
saturated from recent rains, especially across northern CA.=20

Oravec


Day 2
Valid 12Z Sat Jan 03 2026 - 12Z Sun Jan 04 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
NORTHERN SIERRA AND SOUTHERN CALIFORNIA...

The axis of anomalous 850-700 mb moisture flux values...2 to 4
standard deviations above the mean...along and ahead of the inland
moving frontal boundary at the end of the day 1 period will impact
the upslope areas of the northern Sierra and spread through the=20
Transverse Ranges of Southern California day 2. The primary change=20
from the previous outlook was to add a small slight risk area in=20
the upslope area of the Northern Sierra. HREF neighborhood=20
probabilities for .50"+ hourly rainfall amounts are fairly=20
high...50%+ at the beginning of the day 2 period and again in the=20
2100 UTC Sat to 0000 UTC Sun period. This will result in day 2=20
rainfall totals of 2-4"+ in a region of fairly saturated soils from
recent heavy rains. No changes of note made to the previous slight
risk area over Southern CA in the vicinity of the Transverse=20
Range. The south southwesterly low level flow will have a=20
significant upslope component into the Transverse Ranges during=20
the first half of day 2. This is reflected in both the HREF and=20
RRFS .50"+ hourly probabilities which are high, 50-80%+ during this
period. Localized runoff issues are possible where soils remain=20
fairly saturated from recent heavy rains.=20

Oravec


Day 3
Valid 12Z Sun Jan 04 2026 - 12Z Mon Jan 05 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG THE
CALIFORNIA COAST AND IN THE UPSLOPE OF THE SIERRA...

Additional shortwave energy expected to rotate through the mean
trof position along the West coast and inland across California day
3. This will support a continued wet showery pattern with=20
additional moderate to locally heavy precip totals along much of=20
the California coast Ranges and into the upslope of the Sierra. A=20
broad marginal risk area was maintained from the previous outlook=20
this period with changes mostly to better fit the latest model and
WPC qpf. The slight risk area over Southern California in the=20
vicinity of the Transverse Range was removed given consensus of=20
additional moderate totals.=20

Oravec


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!6qGK_rzOvB2ObWzsCoW9b0hamTvc3eTTLJ8qgPwGHzdy=
qM7ohG0mtttFSXbdszmiRVjCKYvr5bdlM1RlBaSRc_vy2ys$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!6qGK_rzOvB2ObWzsCoW9b0hamTvc3eTTLJ8qgPwGHzdy=
qM7ohG0mtttFSXbdszmiRVjCKYvr5bdlM1RlBaSR40ZN9co$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!6qGK_rzOvB2ObWzsCoW9b0hamTvc3eTTLJ8qgPwGHzdy=
qM7ohG0mtttFSXbdszmiRVjCKYvr5bdlM1RlBaSRp49gFxA$=20

=3D =3D =3D
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