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FOUS30 KWBC 040830
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
330 AM EST Sun Jan 4 2026

Day 1
Valid 12Z Sun Jan 04 2026 - 12Z Mon Jan 05 2026

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

Precipitation is expected to increase in coverage and intensity
Sunday morning across northern to central California as the next
batch of shortwave energy rotates through the mean west coast trof
and inland across central CA. PW values and 850-700 mb moisture
flux are expected to increase Sunday associated with this next
batch of shortwave energy. This will support locally heavy precip=20
totals along much of the California coast Ranges and into the=20
upslope of the Sierra. Hourly rainfall rates in the .25-.50" range
possible along the central CA coast and into the upslope of the=20
northern Sierra. A small slight risk area was maintained in the=20
upslope of the northern Sierra where model consensus is for=20
potential of additional 1 to 2" of rain. The HREF probabilities of=20
3 hr precip exceeding 3 hr FFG values shows an area of 15-30%=20
probabilities sinking southward along the upslope of the northern=20
Sierra Sunday where the slight risk area is drawn. Overall, no=20
changes of note made to the previous outlook for the upcoming day 1
period.


Oravec

Day 2
Valid 12Z Mon Jan 05 2026 - 12Z Tue Jan 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG THE CENTRAL
TO NORTHERN CALIFORNIA COAST AND NORTHERN CALIFORNIA...


There are large scale differences developing day 2 with the
amplification of a closed low in the base of the mean trof off the
Central to Southern CA coast. The NAM and GFS are showing a more
southwest solution compared to the EC, CMC and UKMET. This farther
southwest solution is resulting in a trend of less precip along=20
the central CA coast to the south of San Francisco and into the
Northern Sierra in the GFS and NAM as the low level flow has a
much weaker onshore component compared to the EC, CMC and UKMET.=20
Models often struggle with closed formation downstream of=20
flattening upper ridges with overall low confidence at the moment.
The latest WPC qpf did trend towards less precip across the central
CA Coast Range and over the Northern Sierra, but not as dry as the
GFS and NAM. Subsequently, the previous marginal risk area was
decreased in size. There may be additional changes needed to the
risk area with future model cycles, depending how the evolution of
the closing off mid to upper level center evolves.=20=20

Oravec


Day 3
Valid 12Z Tue Jan 06 2026 - 12Z Wed Jan 07 2026

...THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS
LESS THAN 5 Percent...

Oravec


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!8mdlQ6Il-CroIS5Ass09nzhnMQs-r4IorTFtYaCBOrhZ=
_ALmEFbAEu6-IoGfRlTCViCccYl00L7c3K_1TGV2cdLDEAE$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!8mdlQ6Il-CroIS5Ass09nzhnMQs-r4IorTFtYaCBOrhZ=
_ALmEFbAEu6-IoGfRlTCViCccYl00L7c3K_1TGV2YKunWD8$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!8mdlQ6Il-CroIS5Ass09nzhnMQs-r4IorTFtYaCBOrhZ=
_ALmEFbAEu6-IoGfRlTCViCccYl00L7c3K_1TGV2GOxX1No$=20

=3D =3D =3D
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