Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jan 12 2023 08:29:41

FOUS30 KWBC 120829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EST Thu Jan 12 2023

Day 1
Valid 12Z Thu Jan 12 2023 - 12Z Fri Jan 13 2023

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN CALIFORNIA COAST...

Models have have continued to shift slightly farther north and
west with the plume of heaviest rainfall through today and
tonight, so the Slight and Marginal Risk areas in northern CA were
shifted and trimmed a little bit more with this update. That said,
all rain that falls in the Slight and Marginal Risk areas of CA
will be falling on very saturated soils, so nearly all of it is
expected to run off, contributing to continued elevated flash
flooding concerns, especially over burn scars and poor drainage
areas. Amounts of 1-2" are generally expected, but with the
gradient so close to the coast amounts of 2-4" could easily in the
Slight Risk area with a small shift to the east (best represented
by the 00z ARW). The combination of the atmospheric river (AR)
aligning more parallel to the coast and being farther offshore
should mean fewer extremely high measurements in the coastal
mountains, as those totals are more likely when the AR is aligned
more orthogonal to the coast. The Olympic Mountains, however, are
aligned to soak up more rainfall on a nearly due southerly flow,
so multiple inches of rain are possible. Fortunately it's been
less wet than areas further south into CA, so widespread flash
flooding issues are not expected at this time (especially given
that rates here should generally remain below 0.5"/hr).

Churchill/Wegman



Day 2

The Day 2 outlook will be updated by 0830Z.


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!4_A21XuwEbeQLl5k0PvCjOcNNLz1JRIg5ePHMyCg8R29=
FxBtJQs7pf5ajFKcgkaHFPvAblausU-nIPUSqTkwlDSQHIg$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!4_A21XuwEbeQLl5k0PvCjOcNNLz1JRIg5ePHMyCg8R29=
FxBtJQs7pf5ajFKcgkaHFPvAblausU-nIPUSqTkwEmh4yzY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!4_A21XuwEbeQLl5k0PvCjOcNNLz1JRIg5ePHMyCg8R29=
FxBtJQs7pf5ajFKcgkaHFPvAblausU-nIPUSqTkwhShmuUY$=20


$$



=3D =3D =3D
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