Subj : HVYRAIN: Excessive Rainfa
To   : All
From : Mike Powell
Date : Sun Jan 28 2024 09:42:00

FOUS30 KWBC 280811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
311 AM EST Sun Jan 28 2024

Day 1
Valid 12Z Sun Jan 28 2024 - 12Z Mon Jan 29 2024

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

Churchill


Day 2
Valid 12Z Mon Jan 29 2024 - 12Z Tue Jan 30 2024

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

Churchill

Day 3
Valid 12Z Tue Jan 30 2024 - 12Z Wed Jan 31 2024

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF COASTAL NORTHWESTERN CALIFORNIA AND FAR SOUTHWESTERN OREGON...

By the last half of Day 3 (i.e. from Tuesday late afternoon into
the overnight) the most direct landfall from a relatively strong
atmospheric river may occur, bringing some of the heaviest long
duration totals into the Pacific Northwest region. The
northwestern CA into far southwestern OR appears to have the best
chances for localized accumulations of 1-3" in association with
the idealized wind vectors into the upslope terrain, but the
differing deterministic and ensemble solutions suggest that this
occurring prior to 12z on the 31st is far from a sure thing (with
the ECMWF being the slowest and therefore driest solution, while
the CMC is fastest and heaviest). The GFS is the compromise
solution and is well represented in the WPC QPF, calling for those
1-3" localized amounts. The greater threat for more widespread
longer duration flooding looks to occur into Day 4, though a
faster solution could warrant an expansion of the Marginal (or
perhaps even a targeted upgrade to Slight) in subsequent updates. 

Churchill
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